title: Plastic bottle

text: There is ongoing concern as to the use of plastics in consumer food packaging solutions, environmental impact of the disposal of these products, as well as concerns regarding consumer safety. Karin Michaels, Associate Professor at Harvard Medical School, suggests that toxins leaching from plastics might be related to disorders in humans such as endocrine disruption. Aluminum and cyanide were found as trace elements in the examined samples but they are considered to be toxic elements according to the United States food and drug administration FDA. In the United States, plastic water bottles are regulated by the FDA which also inspects and samples bottled water plants periodically. Plastic water bottle plants hold a low priority for inspection due to a continuously good safety record. In the past, the FDA maintained that there was a lack of human data showing plastics pose health problems. However, in January 2010, the FDA reversed its opinion saying they now have concerns about health risks. An article published on 6 November 2017 in Water Research reported on the content of microplastics in mineral waters packed in plastic or glass bottles, or beverage cartons. In 2018, research conducted by Sherri Mason from the State University of New York in Fredonia revealed the presence of polypropylene, polystyrene, nylon and polyethylene terephthalate microparticles in plastic bottles. Polypropylene was hereby found to be the most common polymeric material (54%) and nylon the second most abundant (16%) polymeric material. The study also mentioned that polypropylene and polyethylene are polymers that are often used to make plastic bottle caps. Also, 4% of retrieved plastic particles were found to have signatures of industrial lubricants coating the polymer. The research was reviewed by Andrew Mayes of the University of East Anglia (UEA) School of Chemistry The European Food Safety Authority suggested most microplastics are excreted by the body, however the UN Food and Agriculture Organization warned that it is possible that the smallest particles (< 1.5 μm) could enter the bloodstream and organs, via the intestinal wall.


title: Plastic bottle

text: Plastic bottles are marked at their base with the resin identification code to indicate the material used.


title: Plastic bottle

text: Product labels are attached with adhesive or are shrunk to fit. In-mould labelling is a process of building the label into the bottle during molding.


title: Plastic bottle

text: An accordion bottle or collapsible bottle is a plastic bottle designed to store darkroom chemicals or any other chemical that is highly susceptible to oxidation. They work by being able to squeeze down to remove excess air from the bottle to extend the life of the product. An alternate benefit is minimizing storage, transportation, or disposal space when the bottle is empty or as the content is being dispersed, for example with water bottles used by hikers. Collapsing can also keep foods fresher.


title: Plastic bottle

text: Bottles, used for storing carbonated water and soft drinks, has an uneven bottom for stability reasons. The technology was developed and patented by Lithuanian Domas Adomaitis in 1971.


title: Villains (Queens of the Stone Age album)

text: Villains is the seventh studio album by American rock band Queens of the Stone Age, released on August 25, 2017 through Matador. The album was announced on June 14, with a teaser trailer taking the form of a comedy skit featuring the band performing a polygraph test with Liam Lynch. The first single, "The Way You Used to Do", was released the following day along with the announcement of a world tour. "Villains" is the first Queens of the Stone Age album to not feature any special guest musicians, the second to not feature Mark Lanegan, and the first to feature Jon Theodore as full time member of the band.


text: The album received widely positive reviews and performed well commercially, topping "Billboard"s Top Alternative Albums and Top Rock Albums charts. At the 2018 Grammy Awards ceremony, it was nominated for Best Rock Album, losing to The War on Drugs' "A Deeper Understanding".


text: Several of the songs from the album were previewed in some form prior to its release. The album's final track, "Villains of Circumstance", was first premiered by Josh Homme in 2014 at an acoustic concert for James Lavelle's Meltdown Festival, while "The Evil Has Landed" was performed by the band during their first gig of 2017 on June 22 at The Rapids Theatre in Niagara Falls, New York. "The Evil Has Landed" was released as a single on August 10, 2017. In addition to this, several snippets of songs have been featured in teaser trailers released online in promotion of the album, including a short clip of the album's opening track, "Feet Don't Fail Me", as well as an a cappella from the intro to the same song.


text: The album has been described as "a little looser and more uptempo than their last release "...Like Clockwork" and "more carefree". Homme cites his interest in dancing, working with Mark Ronson, and Ronson's collaboration with Bruno Mars "Uptown Funk" for the direction of the album. Kory Grow of "Rolling Stone" notes, "While the guitars still have the limber crunch of Queens albums past, they're playing around easy-breezy disco beats and chilly synths on songs like "Feet Don't Fail Me" and "Un-Reborn Again."" The song "Un-Reborn Again" was seen as a nod to T. Rex by critics, with the lyrics "Scaredy nose Jack/ Scaredy nose Jack/ Knowing nothing about nothing" echoing T. Rex's "Telegram Sam" with the lines "Golden Nose Slim/ Golden Nose Slim/ I knows where you’ve been", a T. Rex influence that Homme mentioned during the promotion of the album.


text: The cover art for "Villains" was designed by graphic artist Boneface, who designed the artwork for Queens of the Stone Age's previous album, "...Like Clockwork." It was the first time that the band had returned to an artist to request artwork on a subsequent album. In an interview with the Juxtapoz magazine, Boneface talked about returning to create a cover for the album and his working relationship with Josh Homme. In the article he stated that, "Returning was honestly a pretty daunting task. People seemed to like all the artwork I did for the last album, so I felt I had something to live up to. Also, the fact that QOTSA tend to use a different artist for each album cover made it kind of special that they decided to use me again. I think Josh likened our relationship to Hunter S. Thompson and Ralph Steadman in the initial rallying call. So after I’d decided to plunge back into the QOTSA jacuzzi, I started work the way I usually do, just trying to create something cool. I did a bunch of preliminary drawings before I’d heard any new songs or we’d even talk about the album, and one of those sketches actually ended up being the basis for the album cover." Each band member was given their own artwork, with Homme's on the front cover, and the rest of the band members on the back. An alternate vinyl cover that was released exclusively through independent record stores had a light blue tint over the image, gave Josh Homme a bloody nose, and the devil behind Homme giving two middle fingers.


text: In the "Billboard" charting week of September 3, 2017, "Villains" was the No. 3 album on the "Billboard" 200 upon its first week of release, selling 73,000 equivalent units, and 69,000 in traditional album sales. It was also the best selling album of the week, starting at No. 1 on the Top Album Sales chart.


text: "Villains" received widespread acclaim from music critics. At Metacritic, which assigns a normalized rating out of 100 to reviews from mainstream critics, the album has an average score of 81 based on 30 reviews, indicating 'universal acclaim'.


text: Giving the album four out of five, AllMusic editor Stephen Thomas Erlewine claimed that "At this stage, Queens of the Stone Age don't have many new tricks in their bag, but their consummate skill -- accentuated by the fact that this is the first QOTSA album that features just the band alone, not even augmented by Mark Lanegan -- means they know when to ratchet up the tempo, when to slide into a mechanical grind, and when to sharpen hooks so they puncture cleanly. All that makes Villains a dark joy, a record that offers visceral pleasure in its winking menace." In his review for "Rolling Stone", Will Hermes wrote, ""Queens of the Stone Age" always sounded like the best glam-band name ever, and while Josh Homme's free-ranging heavy rock hypnotists were never quite that, they come as close as ever on "Villains"."


text: In a more reserved review for "Pitchfork", contributor Zoe Camp concluded that, ""Villains" isn’t always so smooth and several sections fall flat, like the staccato-spiked funk that surfaces midway through “The Evil Has Landed” or the melodically static refrains on “Fortress.” Nevertheless, the stalled moments don't detract from the fun of the ride. Queens’ final destination is what matters—and a beeline into the unknown sure beats another go at the merry-go-round. Villains reaffirms what makes this band so special to begin with: their willingness to blow up the status quo as established by their riff-rock brethren, and even themselves."


text: Amongst the most critical reviews was an article by Will Butler for "Under the Radar". In the review, Butler claimed "It'll be of concern to Queens purists that "Villains" pulls from sounds that expired a decade ago and beyond. Dwelling on better times of a bygone era is a fundamental pillar of escapism, but it's disconcerting when one of the most uncompromising, forward-thinking bands in the rock pantheon leans so heavily on what worked in the past that they forget that the onus is on them to innovate."


title: Perfect game (bowling)

text: A perfect game is the highest score possible in a game of bowling, achieved by scoring a strike in every frame. In bowling games that use 10 pins, such as ten-pin bowling, candlepin bowling, and duckpin bowling, the highest possible score is 300, achieved by bowling 12 strikes in a row in a traditional single game: one strike in each of the first nine frames, and three more in the tenth frame.


title: Perfect game (bowling)

text: In five-pin bowling, the highest possible score is 450, as a strike is worth 15 pins. It is rare to bowl or witness one. The Canadian Five Pin Bowlers Association approves from 10 to 40 perfect games per year.


title: Perfect game (bowling)

text: Before a is recognized by the certifying body of the league or tournament, a series of tests are conducted by the local or regional bowling association. First, the bowler and league (or tournament) must be in good standing with the organization. In earlier years, the bowling ball(s) used in the scoring was taken for testing (hardness, weighting, and other aspects that would otherwise break the organization's regulations). Also, the lanes used in the scoring were shut down after the last game of the day was completed. The official then used a tape reader to test the oil condition, to make sure it met the organization's regulations. The data was then sent to the certifying body, and the score received a certification decision a few days to a few weeks later.


title: Perfect game (bowling)

text: There are cases where the tests do not meet regulation, and therefore the score is not recognized by the organization. However, the score still counts towards the league or tournament statistics. Modern recognition is much easier; lanes are no longer shut down, balls are no longer taken and inspected. The lanes are inspected once a year, and the ball's make and serial number (USBC only requires that the ball have an engraved serial number, they do not need the actual number) are taken by a league/tournament official and reported to the certifying organization.


title: Perfect game (bowling)

text: In league or tournament play, a certified 300 game is usually commemorated with a ring. Subsequent league 300s are denoted by setting "chips" or precious stones into the ring, so that skilled bowlers do not have to wear several rings. The United States Bowling Congress (USBC) offers a "multiple" 300 ring for an additional fee that features the number of approved 300 games for that bowler surrounded by stones. The ring can be returned to have the number changed as the bowler rolls additional perfect games.


title: Perfect game (bowling)

text: In casual or "open" play, a 300 game is not recognized officially by any certifying, professional, or other organization, but may be honored by other means within the bowling center, such as a plaque, trophy, "wall of fame" photo, or other prize.


title: Perfect game (bowling)

text: A handful of 300 games have been broadcast on live TV. Grazio Castellano of Brooklyn, New York was the first to roll a on live television. This occurred on October 4, 1953, during an Eastern All-Star league session in Newark, New Jersey. (Castellano is a member of the United States Bowling Congress Hall of Fame.) A more recent example came in October 2006, when England's Paul Moor became the first man to register a score of 300 in the Weber Cup (the first 300 on live British television), the annual Europe versus America team challenge event. Australian Jason Belmonte became the first bowler to ever roll a 300 game in the televised finals of the World Tenpin Masters, defeating Moor in the 2007 event. Tommy Jones had shot a perfect game in each Weber Cup from 2007 to 2009. Shota Kawazoe has rolled back-to-back 300 games on live Japanese television.


title: Perfect game (bowling)

text: A bowler that bowls a perfect game on a televised PBA Tour event receives a $10,000 bonus, although the PBA and/or its sponsors have occasionally offered as much as a $1 million bonus for a player that bowls a 300 game in selected televised events. Through June 2022, there have been 34 televised 300 games in title events on the PBA Tour, and two more on the Senior PBA Tour. The first 300 game in a televised PBA event was rolled by Jack Biondolillo in the opening match of the 1967 Firestone Tournament of Champions finals (broadcast by ABC). This was also the first "nationally" televised broadcast of a perfect game. The most recent perfect games in a U.S. telecast of a PBA Tour event happened in the PBA Tour Finals, on June 5, 2022, on CBS Sports Network, when Kyle Troup (Group A Stepladder Semifinals, second game vs Kris Prather) and Jason Belmonte (PBA Tour Finals, first game vs Dom Barrett) both rolled the 33rd and 34th 300 games on the same day respectively. It was the first time that the accomplishment happened twice in the same day at a televised event.


title: Perfect game (bowling)

text: Sean Rash rolled the PBA's 23rd and 25th 300 games to become the first player with multiple televised perfect games in PBA Tour stops. Canadian François Lavoie, having previously bowled the PBA Tour's 26th televised 300 game, joined Rash when he bowled the Tour's 29th in 2020. Chris Via rolled two 300 games, making him the third member of this exclusive club. (Via is the only player of the three to roll both of his 300 games in the same season.) Mika Koivuniemi narrowly missed (As well as becoming the first to do so) joining this exclusive club. Having rolled the PBA's 17th televised perfect game in 2003, Mika shot a 299 game in the semifinals of the 2011 PBA Tournament of Champions. Belmonte's 2022 PBA Tour Finals championship match 1 300 game made him the fourth (21st in 2012 and 34th in 2022).


title: Perfect game (bowling)

text: Two other players have shot multiple 300 games on U.S. television, though one or both games were not rolled in an official PBA title event. In 2009, Wes Malott rolled two 300 games in an ESPN broadcast of the King of Bowling series. Though this event featured PBA players, it was not an official PBA Tour event. Ryan Shafer, who earlier in his career rolled the PBA's 19th televised 300 in a PBA Tour event, threw his second televised 300 game in a singles match at the Geico PBA Team Shootout, a made-for-TV event broadcast on ESPN, July 2, 2011. PBA Hall of Famer Chris Barnes, who rolled the PBA's 22nd televised 300 game, has also rolled live perfect games on European television (2014 QubicaAMF World Cup) and Japanese television (2015 PBA-DHC Japan Invitational).


title: Perfect game (bowling)

text: Female bowlers have also achieved perfection in front of a television audience. Ritsuko Nakayama of the Japan Professional Bowling Association became the first female to score a perfect game in front of a national television audience, doing so in Japan on August 21, 1970. Michelle Feldman of the Professional Women's Bowling Association (PWBA) became the first female to score a 300 on American national television, when she accomplished the feat in a 1997 Prime Sports broadcast. Cara Honeychurch, Liz Johnson and Dasha Kovalova have also bowled 300 games in PWBA events on American TV. Urara Himeji, Wendy Macpherson and Takiko Naganawa have rolled 300 games on Japanese national television – all during JPBA events.


title: Perfect game (bowling)

text: The following is a list of all perfect 300 games in nationally televised PBA Tour title events (PBA Hall of Famers marked with an asterisk; major tournaments in bold text):


title: Perfect game (bowling)

text: Andy Varipapa, a standout bowler from the 1930s and 1940s, joked about a being twelve strikes in a row spanning two games. Hence, such a result is named after the veteran bowler.


title: Perfect game (bowling)

text: 75-year-old Will June, grandfather of Cato June, became the oldest player to bowl consecutive perfect games on August 31, 2010.


title: Perfect game (bowling)

text: A "900 series", a three-game set with scores adding up to 900, is a more difficult feat to achieve than bowling a single perfect game because it requires more consistency and careful attention to the subtle changes in the lane conditions from game to game. The first six 900 series reported, starting with PBA Hall of Famer Glenn Allison's in 1982, were all rejected by the USBC for various reasons – mostly due to nonconforming lane conditions. Finally, in 1997, an officially certified 900 series was bowled by collegiate bowler Jeremey Sonnenfeld, rolled at Sun Valley Lanes in Lincoln, Nebraska. It was the first 900 series approved by the USBC. Twelve perfect series were bowled in the ten-year period 1997–2008, and six were bowled in the two years 2009–2010. As of June 25, 2022, the USBC lists a total of 40 officially certified 900 series by 39 different bowlers, with Robert Mushtare the only person to roll more than one.


title: Perfect game (bowling)

text: The concept of a perfect bowling game has been regularly used in fiction for either suspenseful or comedic effect.


title: Zero-energy building

text: A Zero Energy Building (ZEB), also known as a Net Zero Energy (NZE) building, is a building with net zero energy consumption, meaning the total amount of energy used by the building on an annual basis is equal to the amount of renewable energy created on the site or in other definitions by renewable energy sources offsite, using technology such as heat pumps, high efficiency windows and insulation, and solar panels.


title: Zero-energy building

text: The goal is that these buildings contribute less overall greenhouse gas to the atmosphere during operations than similar non-ZNE buildings. They do at times consume non-renewable energy and produce greenhouse gases, but at other times reduce energy consumption and greenhouse gas production elsewhere by the same amount. The development of zero-energy buildings is encouraged by the desire to have less of an impact on the environment, and by tax breaks and savings on energy costs that make zero-energy buildings financially viable.


title: Zero-energy building

text: Terminology tends to vary between countries, agencies, cities, towns and reports, so a general knowledge of this concept and its various employments is essential for a versatile understanding of clean energy and renewables. The IEA and European Union most commonly use Net Zero Energy, with "zero net" mainly used in the USA. A similar concept approved and implemented by the European Union and other agreeing countries is nearly Zero Energy Building (nZEB), with the goal of having all new buildings in the region under nZEB standards by 2020.


title: Zero-energy building

text: Typical code-compliant buildings consume 40% of the total fossil fuel energy in the US and European Union and are significant contributors of greenhouse gases. To combat such high energy usage, more and more buildings are starting to implement the carbon neutrality principle, which is viewed as a means to reduce carbon emissions and reduce dependence on fossil fuels. Although zero-energy buildings remain limited, even in developed countries, they are gaining importance and popularity.


title: Zero-energy building

text: Most zero-energy buildings use the electrical grid for energy storage but some are independent of the grid and some include energy storage onsite. The buildings are called "energy-plus buildings" or in some cases "low energy houses". These buildings produce energy onsite using renewable technology like solar and wind, while reducing the overall use of energy with highly efficient lightning and heating, ventilation and air conditioning (HVAC) technologies. The zero-energy goal is becoming more practical as the costs of alternative energy technologies decrease and the costs of traditional fossil fuels increase.


title: Zero-energy building

text: The development of modern zero-energy buildings became possible largely through the progress made in new energy and construction technologies and techniques. These include highly insulating spray-foam insulation, high-efficiency solar panels, high-efficiency heat pumps and highly insulating, low emissivity, triple and quadruple-glazed windows. These innovations have also been significantly improved by academic research, which collects precise energy performance data on traditional and experimental buildings and provides performance parameters for advanced computer models to predict the efficacy of engineering designs.


title: Zero-energy building

text: Zero-energy buildings can be part of a smart grid. Some advantages of these buildings are as follows:


title: Zero-energy building

text: Although the net zero concept is applicable to a wide range of resources, water and waste, energy is usually the first resource to be targeted because:


title: Zero-energy building

text: The introduction of zero-energy buildings makes buildings more energy efficient and reduces the rate of carbon emissions once the building is in operation; however, there is still a lot of pollution associated with a building's embodied carbon. Embodied carbon is the carbon emitted in the making and transportation of a building's materials and construction of the structure itself; it is responsible for 11% of global GHG emissions and 28% of global building sector emissions. The importance of embodied carbon will grow as it will begin to account for the greater portion of a building's carbon emissions. In some newer, energy efficient buildings, embodied carbon has risen to 47% of the building's lifetime emissions. Focusiong on embodied carbon is part of optimizing construction for climate impact and zero carbon emissions requires slightly different considerations from optimizing only for energy efficiency.


title: Zero-energy building

text: A 2019 study found that between 2020 and 2030, reducing upfront carbon emissions and switching to clean or renewable energy is more important than increasing building efficiency because "building a highly energy efficient structure can actually produce more greenhouse gas than a basic code compliant one if carbon-intensive materials are used." The study stated that because "Net-zero energy codes will not significantly reduce emissions in time, policy makers and regulators must aim for true net zero carbon buildings, not net zero energy buildings."


title: Zero-energy building

text: One way to reduced embodied carbon is by using low-carbon materials for construction such as straw, wood, linoleum, or cedar. For materials like concrete and steel, options to reduce embodied emissions do exist, however, these are unlikely to be available at large scale in the short-term. In conclusion, it has been determined that the optimal design point for greenhouse gas reduction appeared to be at four story multifamily buildings of low-carbon materials, such as those listed above, which could be a template for low-carbon emitting structures.


title: Zero-energy building

text: Despite sharing the name "zero net energy", there are several definitions of what the term means in practice, with a particular difference in usage between North America and Europe.


title: Zero-energy building

text: The most cost-effective steps toward a reduction in a building's energy consumption usually occur during the design process. To achieve efficient energy use, zero energy design departs significantly from conventional construction practice. Successful zero energy building designers typically combine time tested passive solar, or artificial/fake conditioning, principles that work with the on-site assets. Sunlight and solar heat, prevailing breezes, and the cool of the earth below a building, can provide daylighting and stable indoor temperatures with minimum mechanical means. ZEBs are normally optimized to use passive solar heat gain and shading, combined with thermal mass to stabilize diurnal temperature variations throughout the day, and in most climates are superinsulated. All the technologies needed to create zero energy buildings are available off-the-shelf today.


title: Zero-energy building

text: Sophisticated 3-D building energy simulation tools are available to model how a building will perform with a range of design variables such as building orientation (relative to the daily and seasonal position of the sun), window and door type and placement, overhang depth, insulation type and values of the building elements, air tightness (weatherization), the efficiency of heating, cooling, lighting and other equipment, as well as local climate. These simulations help the designers predict how the building will perform before it is built, and enable them to model the economic and financial implications on building cost benefit analysis, or even more appropriate – life-cycle assessment.


title: Zero-energy building

text: Zero-energy buildings are built with significant energy-saving features. The heating and cooling loads are lowered by using high-efficiency equipment (such as heat pumps rather than furnaces. Heat pumps are about four times as efficient as furnaces) added insulation (especially in the attic and in the basement of houses), high-efficiency windows (such as low emissivity, triple-glazed windows), draft-proofing, high efficiency appliances (particularly modern high-efficiency refrigerators), high-efficiency LED lighting, passive solar gain in winter and passive shading in the summer, natural ventilation, and other techniques. These features vary depending on climate zones in which the construction occurs. Water heating loads can be lowered by using water conservation fixtures, heat recovery units on waste water, and by using solar water heating, and high-efficiency water heating equipment. In addition, daylighting with skylights or solartubes can provide 100% of daytime illumination within the home. Nighttime illumination is typically done with fluorescent and LED lighting that use 1/3 or less power than incandescent lights, without adding unwanted heat. And miscellaneous electric loads can be lessened by choosing efficient appliances and minimizing phantom loads or standby power. Other techniques to reach net zero (dependent on climate) are Earth sheltered building principles, superinsulation walls using straw-bale construction, pre-fabricated building panels and roof elements plus exterior landscaping for seasonal shading.


title: Zero-energy building

text: Once the energy use of the building has been minimized it can be possible to generate all that energy on site using roof-mounted solar panels. See examples of zero net energy houses here.


title: Zero-energy building

text: Zero-energy buildings are often designed to make dual use of energy including that from white goods. For example, using refrigerator exhaust to heat domestic water, ventilation air and shower drain heat exchangers, office machines and computer servers, and body heat to heat the building. These buildings make use of heat energy that conventional buildings may exhaust outside. They may use heat recovery ventilation, hot water heat recycling, combined heat and power, and absorption chiller units.


title: Zero-energy building

text: ZEBs harvest available energy to meet their electricity and heating or cooling needs. By far the most common way to harvest energy is to use roof-mounted solar photovoltaic panels that turn the sun's light into electricity. Energy can also be harvested with solar thermal collectors (which use the sun's heat to heat water for the building). Heat pumps can also harvest heat and cool from the air (air-sourced) or ground near the building (ground-sourced otherwise known as geothermal). Technically, heat pumps move heat rather than harvest it, but the overall effect in terms of reduced energy use and reduced carbon footprint is similar. In the case of individual houses, various microgeneration technologies may be used to provide heat and electricity to the building, using solar cells or wind turbines for electricity, and biofuels or solar thermal collectors linked to a seasonal thermal energy storage (STES) for space heating. An STES can also be used for summer cooling by storing the cold of winter underground. To cope with fluctuations in demand, zero energy buildings are frequently connected to the electricity grid, export electricity to the grid when there is a surplus, and drawing electricity when not enough electricity is being produced. Other buildings may be fully autonomous.


title: Zero-energy building

text: Energy harvesting is most often more effective in regards to cost and resource utilization when done on a local but combined scale, for example a group of houses, cohousing, local district or village rather than an individual house basis. An energy benefit of such localized energy harvesting is the virtual elimination of electrical transmission and electricity distribution losses. On-site energy harvesting such as with roof top mounted solar panels eliminates these transmission losses entirely. Energy harvesting in commercial and industrial applications should benefit from the topography of each location. However, a site that is free of shade can generate large amounts of solar powered electricity from the building's roof and almost any site can use geothermal or air-sourced heat pumps. The production of goods under net zero fossil energy consumption requires locations of geothermal, microhydro, solar, and wind resources to sustain the concept.


title: Zero-energy building

text: Zero-energy neighborhoods, such as the BedZED development in the United Kingdom, and those that are spreading rapidly in California and China, may use distributed generation schemes. This may in some cases include district heating, community chilled water, shared wind turbines, etc. There are current plans to use ZEB technologies to build entire off-the-grid or net zero energy use cities.


title: Zero-energy building

text: One of the key areas of debate in zero energy building design is over the balance between energy conservation and the distributed point-of-use harvesting of renewable energy (solar energy, wind energy and thermal energy). Most zero energy homes use a combination of these strategies.


title: Zero-energy building

text: As a result of significant government subsidies for photovoltaic solar electric systems, wind turbines, etc., there are those who suggest that a ZEB is a conventional house with distributed renewable energy harvesting technologies. Entire additions of such homes have appeared in locations where photovoltaic (PV) subsidies are significant, but many so called "Zero Energy Homes" still have utility bills. This type of energy harvesting without added energy conservation may not be cost effective with the current price of electricity generated with photovoltaic equipment, depending on the local price of power company electricity. The cost, energy and carbon-footprint savings from conservation (e.g., added insulation, triple-glazed windows and heat pumps) compared to those from on-site energy generation (e.g., solar panels) have been published for an upgrade to an existing house here.


title: Zero-energy building

text: Since the 1980s, passive solar building design and passive house have demonstrated heating energy consumption reductions of 70% to 90% in many locations, without active energy harvesting. For new builds, and with expert design, this can be accomplished with little additional construction cost for materials over a conventional building. Very few industry experts have the skills or experience to fully capture benefits of the passive design. Such passive solar designs are much more cost-effective than adding expensive photovoltaic panels on the roof of a conventional inefficient building. A few kilowatt-hours of photovoltaic panels (costing the equivalent of about US$2-3 dollars per annual kWh production) may only reduce external energy requirements by 15% to 30%. A high seasonal energy efficiency ratio 14 conventional air conditioner requires over 7 kW of photovoltaic electricity while it is operating, and that does not include enough for off-the-grid night-time operation. Passive cooling, and superior system engineering techniques, can reduce the air conditioning requirement by 70% to 90%. Photovoltaic-generated electricity becomes more cost-effective when the overall demand for electricity is lower.


title: Zero-energy building

text: Companies in Germany and the Netherlands offer rapid climate retrofit packages for existing buildings, which add a custom designed shell of insulation to the outside of a building, along with upgrades for more sustainable energy use, such as heat pumps. Similar pilot projects are underway in the US.


title: Zero-energy building

text: The energy used in a building can vary greatly depending on the behavior of its occupants. The acceptance of what is considered comfortable varies widely. Studies of identical homes have shown dramatic differences in energy use in a variety of climates. An average widely accepted ratio of highest to lowest energy consumer in identical homes is about 3, with some identical homes using up to 20 times as much heating energy as the others. Occupant behavior can vary from differences in setting and programming thermostats, varying levels of illumination and hot water use, window and shading system operation and the amount of miscellaneous electric devices or plug loads used.


title: Zero-energy building

text: Utility companies are typically legally responsible for maintaining the electrical infrastructure that brings power to our cities, neighborhoods, and individual buildings. Utility companies typically own this infrastructure up to the property line of an individual parcel, and in some cases own electrical infrastructure on private land as well.


title: Zero-energy building

text: In the US utilities have expressed concern that the use of Net Metering for ZNE projects threatens the utilities base revenue, which in turn impacts their ability to maintain and service the portion of the electrical grid that they are responsible for. Utilities have expressed concern that states that maintain Net Metering laws may saddle non-ZNE homes with higher utility costs, as those homeowners would be responsible for paying for grid maintenance while ZNE home owners would theoretically pay nothing if they do achieve ZNE status. This creates potential equity issues, as currently, the burden would appear to fall on lower-income households. A possible solution to this issue is to create a minimum base charge for all homes connected to the utility grid, which would force ZNE home owners to pay for grid services independently of their electrical use.


title: Zero-energy building

text: Additional concerns are that local distribution as well as larger transmission grids have not been designed to convey electricity in two directions, which may be necessary as higher levels of distributed energy generation come on line. Overcoming this barrier could require extensive upgrades to the electrical grid, however, as of 2010, this is not believed to be a major problem until renewable generation reaches much higher levels of penetration.


title: Zero-energy building

text: Wide acceptance of zero-energy building technology may require more government incentives or building code regulations, the development of recognized standards, or significant increases in the cost of conventional energy.


title: Zero-energy building

text: The Google photovoltaic campus and the Microsoft 480-kilowatt photovoltaic campus relied on US Federal, and especially California, subsidies and financial incentives. California is now providing US$3.2 billion in subsidies for residential-and-commercial near-zero-energy buildings. The details of other American states' renewable energy subsidies (up to US$5.00 per watt) can be found in the Database of State Incentives for Renewables and Efficiency. The Florida Solar Energy Center has a slide presentation on recent progress in this area.


title: Zero-energy building

text: The World Business Council for Sustainable Development has launched a major initiative to support the development of ZEB. Led by the CEO of United Technologies and the Chairman of Lafarge, the organization has both the support of large global companies and the expertise to mobilize the corporate world and governmental support to make ZEB a reality. Their first report, a survey of key players in real estate and construction, indicates that the costs of building green are overestimated by 300 percent. Survey respondents estimated that greenhouse gas emissions by buildings are 19 percent of the worldwide total, in contrast to the actual value of roughly 40 percent.


title: Zero-energy building

text: Those who commissioned construction of passive houses and zero-energy homes (over the last three decades) were essential to iterative, incremental, cutting-edge, technology innovations. Much has been learned from many significant successes, and a few expensive failures.


title: Zero-energy building

text: The zero-energy building concept has been a progressive evolution from other low-energy building designs. Among these, the Canadian R-2000 and the German passive house standards have been internationally influential. Collaborative government demonstration projects, such as the superinsulated Saskatchewan House, and the International Energy Agency's "Task 13", have also played their part.


title: Zero-energy building

text: The US National Renewable Energy Laboratory (NREL) published a report called Net-Zero Energy Buildings: A Classification System Based on Renewable Energy Supply Options. This is the first report to lay out a full spectrum classification system for Net Zero/Renewable Energy buildings that includes the full spectrum of Clean Energy sources, both on site and off site. This classification system identifies the following four main categories of Net Zero Energy Buildings/Sites/Campuses:


title: Zero-energy building

text: Applying this US Government Net Zero classification system means that every building can become net nero with the right combination of the key net zero technologies - PV (solar), GHP (geothermal heating and cooling, thermal batteries), EE (energy efficiency), sometimes wind, and electric batteries. A graphical exposé of the scale of impact of applying these NREL guidelines for net zero can be seen in the graphic at Net Zero Foundation titled "Net Zero Effect on U.S. Total Energy Use" showing a possible 39% US total fossil fuel use reduction by changing US residential and commercial buildings to net zero, 37% savings if we still use natural gas for cooking at the same level.


title: Zero-energy building

text: Many well known universities have professed to want to completely convert their energy systems off of fossil fuels. Capitalizing on the continuing developments in both photovoltaics and geothermal heat pump technologies, and in the advancing electric battery field, complete conversion to a carbon free energy solution is becoming easier. Large scale hydroelectric has been around since before 1900. An example of such a project is in the Net Zero Foundation's proposal at MIT to take that campus completely off fossil fuel use. This proposal shows the coming application of Net Zero Energy Buildings technologies at the District Energy scale.


title: Zero-energy building

text: The goal of green building and sustainable architecture is to use resources more efficiently and reduce a building's negative impact on the environment. Zero energy buildings achieve one key goal of exporting as much renewable energy as it uses over the course of year; reducing greenhouse gas emissions. ZEB goals need to be defined and set, as they are critical to the design process. Zero energy buildings may or may not be considered "green" in all areas, such as reducing waste, using recycled building materials, etc. However, zero energy, or net-zero buildings do tend to have a much lower ecological impact over the life of the building compared with other "green" buildings that require imported energy and/or fossil fuel to be habitable and meet the needs of occupants.


title: Zero-energy building

text: Both terms, zero energy buildings and green buildings, have similarities and differences. "Green" buildings often focus on operational energy, and disregard the embodied carbon footprint from construction. According to the IPCC, embodied carbon will make up half of the total carbon emissions between now[2020] and 2050. On the other hand, zero energy buildings are specifically designed to produce enough energy from renewable energy sources to meet its own consumption requirements, and green buildings can be generally defined as a building that reduces negative impacts or positively impacts our natural environment [1-NEWUSDE]. There are several factors that must be considered before a building is determined to be a green building. Building a green building must include an efficient use of utilities such as water and energy, use of renewable energy, use of recycling and reusing practices to reduce waste, provide proper indoor air quality, use of ethically sourced and non-toxic materials, use of a design that allows the building to adapt to changing environmental climates, and aspects of the design, construction, and operational process that address the environment and quality of life of its occupants. The term green building can also be used to refer to the practice of green building which includes being resource efficient from its design, to its construction, to its operational processes, and ultimately to its deconstruction. The practice of green building differs slightly from zero energy buildings because it considers all environmental impacts such as use of materials and water pollution for example, whereas the scope of zero energy buildings only includes the buildings energy consumption and ability to produce an equal amount, or more, of energy from renewable energy sources.


title: Zero-energy building

text: There are many unforeseen design challenges and site conditions required to efficiently meet the renewable energy needs of a building and its occupants, as much of this technology is new. Designers must apply holistic design principles, and take advantage of the free naturally occurring assets available, such as passive solar orientation, natural ventilation, daylighting, thermal mass, and night time cooling. Designers and engineers must also experiment with new materials and technological advances, striving for more affordable and efficient production.


title: Zero-energy building

text: With advances in ultra low U-value glazing a (nearly) zero heating building is proposed to supersede nearly-zero energy buildings in EU. The zero heating building reduces on the passive solar design and makes the building more opened to conventional architectural design. The zero heating building removes the need for seasonal / winter utility power reserve.


title: Zero-energy building

text: The annual specific heating demand for the zero-heating house should not exceed 3 kWh/ma. Zero heating building is simpler to design and to operate. For example: there is no need for modulated sun shading.


title: Zero-energy building

text: The two most common certifications for green building are Passive House, and LEED. The goal of Passive House is to be energy efficient and reduce the use of heating/cooling to below standard. LEED certification is more comprehensive in regards to energy use, a building is awarded credits as it demonstrates sustainable practices across a range of categories. Another certification that designates a building as a net zero energy building exists within the requirements of the Living Building Challenge (LBC) called the Net Zero Energy Building (NZEB) certification provided by the International Living Future Institute (ILFI). The designation was developed in November 2011 as the NZEB certification but was then simplified to the Zero Energy Building Certification in 2017. Included in the list of green building certifications, the BCA Green Mark rating system allows for the evaluation of buildings for their performance and impact on the environment


title: Zero-energy building

text: As a response to global warming and increasing greenhouse gas emissions, countries around the world have been gradually implementing different policies to tackle ZEB. Between 2008 and 2013, researchers from Australia, Austria, Belgium, Canada, Denmark, Finland, France, Germany, Italy, the Republic of Korea, New Zealand, Norway, Portugal, Singapore, Spain, Sweden, Switzerland, the United Kingdom and the US worked together in the joint research program called "Towards Net Zero Energy Solar Buildings". The program was created under the umbrella of International Energy Agency (IEA) Solar Heating and Cooling Program (SHC) Task 40 / Energy in Buildings and Communities (EBC, formerly ECBCS) Annex 52 with the intent of harmonizing international definition frameworks regarding net-zero and very low energy buildings by diving them into subtasks. In 2015, the Paris Agreement was created under the United Nations Framework Convention on Climate Change (UNFCC) with the intent of keeping the global temperature rise of the 21st century below 2 degrees Celsius and limiting temperature increase to 1.5 degrees Celsius by limiting greenhouse gas emissions. While there was no enforced compliance, 197 countries signed the international treaty which bound developed countries legally through a mutual cooperation where each party would update its INDC every five years and report annually to the COP. Due to the advantages of energy efficiency and carbon emission reduction, ZEBs are widely being implemented in many different countries as a solution to energy and environmental problems within the infrastructure sector.


title: Zero-energy building

text: In Australia, researchers have recently developed a new approach to the construction of visually-clear solar energy harvesting windows suitable for industrialization and applications in net-zero energy buildings. Industrial production of several prototype batches of solar windows has started in 2016.


title: Zero-energy building

text: Up to the December 2017, the State of Queensland has more than 30% of households with rooftop solar photovoltaic (PV) system. The average size of Australian rooftop solar PV system has exceeded 3.5 kW. In Brisbane, households with 6 kW rooftop PV system and reasonable energy rating, for example 5 or 6 stars for Australian National House Energy Rating, can achieve net zero total energy target or even positive energy.


title: Zero-energy building

text: In Belgium there is a project with the ambition to make the Belgian city Leuven climate-neutral in 2030.


title: Zero-energy building

text: In Brazil, the Ordinance No. 42, of February 24, 2021, approved the Inmetro Normative Instruction for the Classification of Energy Efficiency of Commercial, Service and Public Buildings (INI-C), which improves the Technical Quality Requirements for the Energy Efficiency Level of Commercial, Service and Public Buildings (RTQ-C), specifying the criteria and methods for classifying commercial, service and public buildings as to their energy efficiency. Annex D presents the procedures for determining the potential for local renewable energy generation and the assessment conditions for Near Zero Energy Buildings (NZEBs) and Positive Energy Buildings (PEBs).


title: Zero-energy building

text: With an estimated population of 1,439,323,776 people, China has become one of the world's leading contributor to greenhouse gas emissions due to its ongoing rapid urbanization. Even with the growing increase in building infrastructure, China has long been considered as a country where the overall energy demand has consistently grown less rapidly than the gross domestic product (GDP) of China. Since the late 1970s, China has been using half as much energy as it did in 1997, but due to its dense population and rapid growth of infrastructure, China has become the world's second largest energy consumer and is in a position to become the leading contributor to greenhouse gas emissions in the next century.


title: Zero-energy building

text: Since 2010, Chinese government has been driven by the release of new national policies to increase ZEB design standards and has also laid out a series of incentives to increase ZEB projects in China. In November 2015, China's Ministry of Housing and Urban-Rural Development (MOHURD) released a technical guide regarding passive and low energy green residential buildings. This guide was aimed at improving energy efficiency in China's infrastructure and was also the first of its kind to be formally released as a guide for energy efficiency. Also, with rapid growth in ZEBs in the last three years, there is an estimated influx of ZEBs to be built in China by 2020 along with the existing ZEB projects that are already built.


title: Zero-energy building

text: As a response to the Paris Agreement in 2015, China stated that it set a target of reducing peak carbon emissions around 2030 while also aiming to lower carbon dioxide emissions by 60-65 percent from 2005 emissions per unit of GDP. In 2020, Chinese Communist Party leader Xi Jinping released a statement in his address to the UN General Assembly declaring that China would be carbon neutral by 2060 pushing forward climate change reforms. With more than 95 percent of China's energy originating from fuel sources that emit carbon dioxide, carbon neutrality in China will require an almost complete transition to fuel sources such as solar power, wind, hydro, or nuclear power. In order to achieve carbon neutrality, China's proposed energy quota policy will have to incorporate new monitoring and mechanisms that ensure accurate measurements of energy performance of buildings. Future research should investigate the different possible challenges that could come up due to implementation of ZEB policies in China.


title: Zero-energy building

text: Strategic Research Centre on Zero Energy Buildings was in 2009 established at Aalborg University by a grant from the Danish Council for Strategic Research (DSF), the Programme Commission for Sustainable Energy and Environment, and in cooperation with the Technical University of Denmark, Danish Technological Institute, The Danish Construction Association and some private companies. The purpose of the centre is through development of integrated, intelligent technologies for the buildings, which ensure considerable energy conservation and optimal application of renewable energy, to develop zero energy building concepts. In cooperation with the industry, the centre will create the necessary basis for a long-term sustainable development in the building sector.


title: Zero-energy building

text: India's first net zero building is Indira Paryavaran Bhawan, located in New Delhi, inaugurated in 2014. Features include passive solar building design and other green technologies. High-efficiency solar panels are proposed. It cools air from toilet exhaust using a thermal wheel in order to reduce load on its chiller system. It has many water conservation features.


title: Zero-energy building

text: In 2011, "Payesh" Energy House (PEH) or "Khaneh Payesh Niroo" by a collaboration of Fajr-e-Toseah Consultant Engineering Company and Vancouver Green Homes Ltd] under management of Payesh Energy Group (EPG) launched the first Net-Zero passive house in Iran. This concept makes the design and construction of PEH a sample model and standardized process for mass production by MAPSA.


title: Zero-energy building

text: Also, an example of the new generation of zero energy office buildings is the 24-story OIIC Office Tower, which is started in 2011, as the OIIC Company headquarters. It uses both modest energy efficiency, and a big distributed renewable energy generation from both solar and wind. It is managed by Rahgostar Naft Company in Tehran, Iran. The tower is receiving economic support from government subsidies that are now funding many significant fossil-fuel-free efforts.


title: Zero-energy building

text: In 2005, a private company launched the world's first standardised passive house in Ireland, this concept makes the design and construction of passive house a standardised process.


title: Zero-energy building

text: Conventional low energy construction techniques have been refined and modelled on the PHPP (Passive House Design Package) to create the standardised passive house.


title: Zero-energy building

text: Building offsite allows high precision techniques to be utilised and reduces the possibility of errors in construction.


title: Zero-energy building

text: In 2009 the same company started a project to use 23,000 liters of water in a seasonal storage tank, heated up by evacuated solar tubes throughout the year, with the aim to provide the house with enough heat throughout the winter months thus eliminating the need for any electrical heat to keep the house comfortably warm. The system is monitored and documented by a research team from The University of Ulster and the results will be included in part of a PhD thesis.


title: Zero-energy building

text: In 2012 Cork Institute of Technology started renovation work on its 1974 building stock to develop a net zero energy building retrofit. The exemplar project will become Ireland's first zero energy testbed offering a post-occupancy evaluation of actual building performance against design benchmarks.


title: Zero-energy building

text: The first zero energy building in Jamaica and the Caribbean opened at the Mona Campus of the University of the West Indies (UWI) in 2017. The 2300 square foot building was designed to inspire more sustainable and energy efficient buildings in the area.


title: Zero-energy building

text: After the April 2011 Fukushima earthquake followed by the up with Fukushima Daiichi nuclear disaster, Japan experienced severe power crisis that led to the awareness of the importance of energy conservation.


title: Zero-energy building

text: In 2012 Ministry of Economy, Trade and Industry, Ministry of Land, Infrastructure, Transport and Tourism and Ministry of the Environment (Japan) summarized the road map for Low-carbon Society which contains the goal of ZEH and ZEB to be standard of new construction in 2020.


title: Zero-energy building

text: The Mitsubishi Electric Corporation is underway with the construction of Japan's first zero energy office building, set to be completed in October, 2020 (as of September 2020). The SUSTIE ZEB test facility is located in Kamakura, Japan, to develop ZEB technology. With the net zero certification, the facility projects to reduce energy consumption by 103%.


title: Zero-energy building

text: Japan has made it a goal that all new houses be net zero energy by 2030. The developing company Sekisui House introduced their first net zero home in 2013, and is now planning Japan's first zero energy condominium in Nagoya City, it is a three-story building with 12 units. There are solar panels on the roof and fuel cells for each unit to provide backup power.


title: Zero-energy building

text: In October 2007, the Malaysia Energy Centre (PTM) successfully completed the development and construction of the PTM Zero Energy Office (ZEO) Building. The building has been designed to be a super-energy-efficient building using only 286 kWh/day. The renewable energy – photovoltaic combination is expected to result in a net zero energy requirement from the grid. The building is currently undergoing a fine tuning process by the local energy management team. Findings are expected to be published in a year.


title: Zero-energy building

text: In 2016, the Sustainable Energy Development Authority Malaysia (SEDA Malaysia) started a voluntary initiative called Low Carbon Building Facilitation Program. The purpose is to support the current low carbon cities program in Malaysia. Under the program, several project demonstration managed to reduce energy and carbon beyond 50% savings and some managed to save more than 75%. Continuous improvement of super energy efficient buildings with significant implementation of on-site renewable energy managed to make a few of them become nearly Zero Energy (nZEB) as well as Net Zero Energy Building (NZEB). In March 2018, SEDA Malaysia has started the Zero Energy Building Facilitation Program.


title: Zero-energy building

text: Malaysia also has its own sustainable building tool special for Low Carbon and zero energy building, called GreenPASS that been developed by the Construction Industry Development Board Malaysia (CIDB) in 2012, and currently being administered and promoted by SEDA Malaysia. GreenPASS official is called the Construction Industry Standard (CIS) 20:2012.


title: Zero-energy building

text: In September 2006, the Dutch headquarters of the World Wildlife Fund (WWF) in Zeist was opened. This earth-friendly building gives back more energy than it uses. All materials in the building were tested against strict requirements laid down by the WWF and the architect.


title: Zero-energy building

text: In February 2009, the Research Council of Norway assigned The Faculty of Architecture and Fine Art at the Norwegian University of Science and Technology to host the Research Centre on Zero Emission Buildings (ZEB), which is one of eight new national Centres for Environment-friendly Energy Research (FME). The main objective of the FME-centres is to contribute to the development of good technologies for environmentally friendly energy and to raise the level of Norwegian expertise in this area. In addition, they should help to generate new industrial activity and new jobs. Over the next eight years, the FME-Centre ZEB will develop competitive products and solutions for existing and new buildings that will lead to market penetration of zero emission buildings related to their production, operation and demolition.


title: Zero-energy building

text: Singapore unveiled a prominent development at the National University of Singapore that is a net-zero energy building. The building, called SDE4, is located within a group of three buildings in its School of Design and Environment (SDE). The design of the building achieved a Green Mark Platinum certification as it produces as much energy as it consumes with its solar panel covered rooftop and hybrid cooling system along with many integrated systems to achieve optimum energy efficiency. This development was the first new-build zero-energy building to come to fruition in Singapore, and the first zero-energy building at the NUS. The first retrofitted zero energy building to be developed in Singapore was a building at the Building and Construction Authority (BCA) academy by the Minister for National Development Mah Bow Tan at the inaugural Singapore Green Building Week on October 26, 2009. Singapore's Green Building Week (SGBW) promotes sustainable development and celebrates the achievements of successfully designed sustainable buildings.


title: Zero-energy building

text: A net-zero energy building unveiled more recently is the SMU Connexion (SMUC). It is the first net-zero energy building in the city that also utilizes mass engineered timber (MET). It is designed to meet the Building and Construction Authority (BCA) Green Mark Platinum certification and has been in operation since January 2020.


title: Zero-energy building

text: The Swiss MINERGIE-A-Eco label certifies zero energy buildings. The first building with this label, a single-family home, was completed in Mühleberg in 2011.


title: Zero-energy building

text: In December 2006, the government announced that by 2016 all new homes in England will be zero energy buildings. To encourage this, an exemption from Stamp Duty Land Tax is planned. In Wales the plan is for the standard to be met earlier in 2011, although it is looking more likely that the actual implementation date will be 2012. However, as a result of a unilateral change of policy published at the time of the March 2011 budget, a more limited policy is now planned which, it is estimated, will only mitigate two thirds of the emissions of a new home.


title: Zero-energy building

text: In January 2019 the Ministry of Housing Communities and Local Government simply defined 'Zero Energy' as 'just meets current building standards' neatly solving this problem.


title: Zero-energy building

text: In the US, ZEB research is currently being supported by the US Department of Energy (DOE) Building America Program, including industry-based consortia and researcher organizations at the National Renewable Energy Laboratory (NREL), the Florida Solar Energy Center (FSEC), Lawrence Berkeley National Laboratory (LBNL), and Oak Ridge National Laboratory (ORNL). From fiscal year 2008 to 2012, DOE plans to award $40 million to four Building America teams, the Building Science Corporation; IBACOS; the Consortium of Advanced Residential Buildings; and the Building Industry Research Alliance, as well as a consortium of academic and building industry leaders. The funds will be used to develop net-zero-energy homes that consume 50% to 70% less energy than conventional homes.


title: Zero-energy building

text: DOE is also awarding $4.1 million to two regional building technology application centers that will accelerate the adoption of new and developing energy-efficient technologies. The two centers, located at the University of Central Florida and Washington State University, will serve 17 states, providing information and training on commercially available energy-efficient technologies.


title: Zero-energy building

text: The U.S. Energy Independence and Security Act of 2007 created 2008 through 2012 funding for a new solar air conditioning research and development program, which should soon demonstrate multiple new technology innovations and mass production economies of scale.


title: Zero-energy building

text: The 2008 Solar America Initiative funded research and development into future development of cost-effective Zero Energy Homes in the amount of $148 million in 2008.


title: Zero-energy building

text: By Executive Order 13514, U.S. President Barack Obama mandated that by 2015, 15% of existing Federal buildings conform to new energy efficiency standards and 100% of all new Federal buildings be Zero-Net-Energy by 2030.


title: Zero-energy building

text: In 2007, the philanthropic Siebel Foundation created the Energy Free Home Foundation. The goal was to offer $20 million in global incentive prizes to design and build a 2,000 square foot (186 square meter) three-bedroom, two bathroom home with (1) net-zero annual utility bills that also has (2) high market appeal, and (3) costs no more than a conventional home to construct.


title: Zero-energy building

text: The plan included funding to build the top ten entries at $250,000 each, a $10 million first prize, and then a total of 100 such homes to be built and sold to the public.


title: Zero-energy building

text: Beginning in 2009, Thomas Siebel made many presentations about his Energy Free Home Challenge. The Siebel Foundation Report stated that the Energy Free Home Challenge was "Launching in late 2009".


title: Zero-energy building

text: The Lawrence Berkeley National Laboratory at the University of California, Berkeley participated in writing the "Feasibility of Achieving Zero-Net-Energy, Zero-Net-Cost Homes" for the $20-million Energy Free Home Challenge.


title: Zero-energy building

text: If implemented, the Energy Free Home Challenge would have provided increased incentives for improved technology and consumer education about zero energy buildings coming in at the same cost as conventional housing.


title: Zero-energy building

text: The US Department of Energy Solar Decathlon is an international competition that challenges collegiate teams to design, build, and operate the most attractive, effective, and energy-efficient solar-powered house. Achieving zero net energy balance is a major focus of the competition.


title: Gimme Shelter (1970 film)

text: Gimme Shelter is a 1970 American documentary film directed by Albert and David Maysles and Charlotte Zwerin chronicling the last weeks of The Rolling Stones' 1969 US tour which culminated in the disastrous Altamont Free Concert. The film is named after "Gimme Shelter", the lead track from the group's 1969 album "Let It Bleed". "Gimme Shelter" was screened out of competition as the opening film of the 1971 Cannes Film Festival.


title: Gimme Shelter (1970 film)

text: This counterculture era documentary is associated with the Direct Cinema movement of the 1950s and 1960s. It was directed by the Maysles Brothers who are strong figures of the era, as well as Charlotte Zwerin. The movement revolves around the philosophy of being a "reactive" filmmaker, recording events as they unfold naturally and spontaneously rather than investigating the subject matter through documentary techniques such as interviews, reconstruction and voiceover.


title: Gimme Shelter (1970 film)

text: The film depicts some of the Madison Square Garden concert later featured on the 1970 live album, "Get Yer Ya-Ya's Out! The Rolling Stones in Concert", as well as Charlie Watts and a donkey filmed on the M6 motorway near Birmingham during a photography session for the album cover. It also shows the Stones at work in Muscle Shoals, Alabama recording "Brown Sugar" and "Wild Horses," and footage of Ike and Tina Turner opening for the Stones at their Madison Square Garden concert, to Mick Jagger's comment, "It's nice to have a chick occasionally."


title: Gimme Shelter (1970 film)

text: The Maysles brothers filmed the first concert of the tour at Madison Square Garden in New York City. After the concert, the Maysles brothers asked the Rolling Stones if they could film them on tour, and the band agreed.


title: Gimme Shelter (1970 film)

text: Much of the film chronicles the behind-the-scenes deal-making that took place to make the free Altamont concert happen, including much footage of well-known attorney Melvin Belli negotiating by telephone with the management of the Altamont Speedway. The movie also includes a playback of Hells Angels leader Ralph "Sonny" Barger's famous call-in to radio station KSAN's "day after" program about the concert, wherein he recalls, "They told me if I could sit on the edge of the stage so nobody could climb over me, I could drink beer until the show was over."


title: Gimme Shelter (1970 film)

text: The focus then turns to the 1969 concert itself at the Altamont Speedway, the security for which was provided by the Hells Angels (armed with pool cues). As the day progresses, with drug-taking and drinking by the Angels and members of the audience, the mood turns ugly. Fights break out during performances by The Flying Burrito Brothers and Jefferson Airplane; Grace Slick pleads with the crowd to settle down. When Mick Jagger arrives to the grounds via helicopter, he is punched in the face by an unruly fan while making his way to his trailer.


title: Gimme Shelter (1970 film)

text: At one point, Jefferson Airplane lead male singer Marty Balin is knocked out by a Hells Angel; Paul Kantner attempts to confront "the people who hit my lead singer" in response, announcing: "Hey, man, I'd like to mention that the Hells Angels just smashed Marty Balin in the face, and knocked him out for a bit. I'd like to thank you for that." Hells Angel "Sweet William" Fritsch, sitting on stage, grabs a microphone and replies: "You're talking to my people. Let me tell you what's happening. "You", man, you are what's happening!" Slick herself warns the Angels after they continue hitting people: "You don't hassle with anybody in particular. You gotta keep your bodies off each other unless you intend love. People get weird, and you need people like the Angels to keep people in line. But the Angels also— You know, you don't bust people in the head for nothing. So both sides are fucking up temporarily; let's not keep fucking up!" Jerry Garcia and Phil Lesh arrive, but The Grateful Dead opt not to play after learning of the incident with Balin from Santana drummer Michael Shrieve. (Santana and Crosby, Stills, Nash, and Young also performed at the concert but are not shown in the movie.)


title: Gimme Shelter (1970 film)

text: The Stones are shown appearing onstage that evening and perform "Sympathy for the Devil" as the tension continues to build. During the next song, "Under My Thumb," a member of the audience, 18-year-old Meredith Hunter, attempted, with other crowd members, to force his way onto the stage , and as a result was struck by the Hells Angels guarding the band. Hunter then drew a revolver before being attacked by Hells Angel Alan Passaro and was killed by at least six stab wounds. Hunter's stabbing was captured on film by at least one of the many camera operators filming the documentary, and appeared in the final cut of the film. According to Albert Maysles, the stabbing was filmed by Baird Bryant; other sources have also credited Eric Saarinen. The film sequence clearly shows the dark silhouette of a handgun in Hunter's hand against the crocheted vest of his girlfriend, Patty Bredehoft, as Passaro enters from the right, grabs and raises Hunter's gun hand, turns Hunter around, and stabs him at least twice in the back before pushing Hunter off camera.


title: Gimme Shelter (1970 film)

text: The credited camera operators for Altamont included a young George Lucas. At the concert, Lucas' camera jammed after shooting about of film. None of his footage was incorporated into the final cut.


title: Gimme Shelter (1970 film)

text: As of 2020, the film holds a score of 93% on Rotten Tomatoes based on 29 ratings, with an average rating of 9.17/10. The website's critical consensus reads "Equal parts essential and chilling, "Gimme Shelter" provides a spine-tingling look at how the Rolling Stones' music paralleled the end of the counterculture movement." In a 1971 review for "The Miami News", Susan Brink wrote that it was a "beautiful, honest film."


title: Ellen Ternan

text: Ellen Lawless Ternan (3 March 1839 – 25 April 1914), also known as Nelly Ternan or Nelly Wharton-Robinson, was an English actress known for association with the author Charles Dickens.


title: Ellen Ternan

text: Ellen Ternan was born in Rochester, Kent. She was the third of four children; she had a brother who died in infancy and two sisters named Maria and Frances (later the second wife of Thomas Adolphus Trollope, the brother of Anthony Trollope). Her parents, Thomas Lawless Ternan and Frances Eleanor Ternan (née Jarman), were both actors of some distinction.


title: Ellen Ternan

text: Ternan made her stage debut in Sheffield at the age of three, and she and her two sisters were presented as "infant phenomena". Ellen was considered the least theatrically gifted of the three sisters, but she worked extensively in the provinces, particularly after her father died in October 1846 in the Bethnal Green Insane Asylum.


title: Ellen Ternan

text: In 1857, she was spotted by Charles Dickens performing at London's Haymarket Theatre. He cast her, on the recommendation of his friend, actor and playwright Alfred Wigan, along with her mother and sister Maria, in three performances of "The Frozen Deep" by Wilkie Collins in Manchester in August 1857. It was not unusual for professional actresses to be invited to appear with amateur gentlemen; Mrs Ternan played a Scottish nurse; Maria, the heroine Clara; and Nelly (Ellen) took over the girl's part from Katey Dickens, Dickens's seventeen-year-old daughter.


title: Ellen Ternan

text: In mid-September 1857, Charles Dickens went with Wilkie Collins to Doncaster to see Ellen perform in "The Pet of the Petticoats" at the Theatre Royal, and wrote to John Forster that his relationship with his wife was disintegrating; 'Poor Catherine and I are not made for each other [-] What is now befalling I have seen steadily coming'.


title: Ellen Ternan

text: Dickens was 45 years old when he met Ellen Ternan. She was 18 at the time, only slightly older than his daughter Katey. It is believed that Dickens began an affair with Ternan; however, the true nature of their relationship was kept secret from the general public. Ternan was clever, charming, a force of character, and interested in literature and the theatre. Dickens referred to Ternan as his "magic circle of one." According to what is known, matters came to a head in 1858 when Catherine Dickens opened a packet delivered by a London jeweller which contained a gold bracelet meant for Ternan, with a note written by her husband. Charles and Catherine Dickens separated that May, after 22 years of marriage.


title: Ellen Ternan

text: Ternan left the stage in 1860, and was financially supported by Dickens from that point onward. She sometimes travelled with him, which was the case in the event of the Staplehurst rail crash in Kent on 9 June 1865 as Dickens was travelling with Ternan and her mother back from a visit to France. Allegedly, he abandoned a plan to take her on his visit to America in 1867 for fear that their relationship would be publicized by the American press. She lived in houses he took under false names at Slough in Berkshire and later at Nunhead in Southwark. Although the truth of the issue has been highly speculated, Ternan may have given birth to a son by Dickens who died in infancy. There is little evidence pertaining to the nature of Charles Dickens and Ellen Ternan's relationship because neither Dickens, Ternan, nor Ternan's sisters left any account of the relationship, and most correspondence relevant to the relationship was destroyed. Dickens is thought by many scholars and commentators to have based several of his female characters on Ternan, including Estella in "Great Expectations", Bella Wilfer in "Our Mutual Friend" and Helena Landless in "The Mystery of Edwin Drood", and others may have been inspired by her, particularly Lucie Manette in "A Tale of Two Cities". Dickens left a legacy of £1,000 to Ternan in his will on his death in 1870, and sufficient income from a trust fund to ensure that she would never have to work again.


title: Ellen Ternan

text: In 1876, six years after Dickens's death, Ternan married George Wharton Robinson, an Oxford graduate, who was 12 years her junior and knew nothing of her close association with Dickens. She presented herself as 14 years younger (23 years old, rather than 37). The couple had a son, Geoffrey, and a daughter, Gladys, and ran a boys' school in Margate. Ternan's husband died in 1910, and she spent her last years in Southsea with her sister Frances. She died of cancer in Fulham, London and is buried in Highland Road Cemetery in Portsmouth, the city of Dickens's birth.


title: Ellen Ternan

text: The Dickens Fellowship and the surviving close family members of Charles Dickens maintained a facade of silence and denial about the affair from the time of Charles Dickens's death in 1870 until the death in December 1933 of his last surviving child, Sir Henry Fielding Dickens. Several Dickens researchers wrote about various aspects of the relationship between Ellen Ternan and Charles Dickens in the ensuing years, including Gladys Story in 1939, Ada Nisbet in 1952, Sir Felix Aylmer in 1959, and Katherine M Longley in 1985. Ellen Ternan was the subject of a bestselling biography by Claire Tomalin in 1990, which brought the relationship to a broader general audience. A summary of the story of the discovery of the relationship was published in 2012 by Professor Michael Slater.


title: Ellen Ternan

text: Some records relating to Ellen Ternan and her family are held by Senate House Library, University of London.


title: Ellen Ternan

text: Simon Gray's play about her life, "Little Nell", had its world premiere in 2007 at the Theatre Royal, Bath. It was directed by Sir Peter Hall and starred Louise Brealey as Ternan. The affair was featured in the docudramas "Dickens" (BBC, 2002) and "Dickens' Secret Lovers" (2008, Channel 4 – it was the main subject of this programme, presented by Charles Dance and with Ternan played by Amy Shiels and Dickens by David Haig). Ternan is also featured in the novel "Drood" by Dan Simmons.


title: Ellen Ternan

text: "The Invisible Woman" (2013) is a feature film adaptation of Tomalin's book about Ternan's relationship with Dickens. Ternan is played by Felicity Jones and Dickens by Ralph Fiennes. The 21-year age difference between the two actors is somewhat similar to the 27-year difference between Ternan and Dickens.


title: Active site

text: In biology and biochemistry, the active site is the region of an enzyme where substrate molecules bind and undergo a chemical reaction. The active site consists of amino acid residues that form temporary bonds with the substrate (binding site) and residues that catalyse a reaction of that substrate (catalytic site). Although the active site occupies only ~10–20% of the volume of an enzyme, it is the most important part as it directly catalyzes the chemical reaction. It usually consists of three to four amino acids, while other amino acids within the protein are required to maintain the tertiary structure of the enzymes.


title: Active site

text: Each active site is evolved to be optimised to bind a particular substrate and catalyse a particular reaction, resulting in high specificity. This specificity is determined by the arrangement of amino acids within the active site and the structure of the substrates. Sometimes enzymes also need to bind with some cofactors to fulfil their function. The active site is usually a groove or pocket of the enzyme which can be located in a deep tunnel within the enzyme, or between the interfaces of multimeric enzymes. An active site can catalyse a reaction repeatedly as residues are not altered at the end of the reaction (they may change during the reaction, but are regenerated by the end). This process is achieved by lowering the activation energy of the reaction, so more substrates have enough energy to undergo reaction.


title: Active site

text: Usually, an enzyme molecule has only two active sites, and the active sites fit with one specific type of substrate. An active site contains a binding site that binds the substrate and orients it for catalysis. The orientation of the substrate and the close proximity between it and the active site is so important that in some cases the enzyme can still function properly even though all other parts are mutated and lose function.


title: Active site

text: Initially, the interaction between the active site and the substrate is non-covalent and transient. There are four important types of interaction that hold the substrate in a defined orientation and form an enzyme-substrate complex (ES complex): hydrogen bonds, van der Waals interactions, hydrophobic interactions and electrostatic force interactions. The charge distribution on the substrate and active site must be complementary, which means all positive and negative charges must be cancelled out. Otherwise, there will be a repulsive force pushing them apart. The active site usually contains non-polar amino acids, although sometimes polar amino acids may also occur. The binding of substrate to the binding site requires at least three contact points in order to achieve stereo-, regio-, and enantioselectivity. For example, alcohol dehydrogenase which catalyses the transfer of a hydride ion from ethanol to NAD interacts with the substrate methyl group, hydroxyl group and the pro-"(R)" hydrogen that will be abstracted during the reaction.


title: Active site

text: In order to exert their function, enzymes need to assume their correct protein fold ("native fold") and tertiary structure. To maintain this defined three-dimensional structure, proteins rely on various types of interactions between their amino acid residues. If these interactions are interfered with, for example by extreme pH values, high temperature or high ion concentrations, this will cause the enzyme to denature and lose its catalytic activity.


title: Active site

text: A tighter fit between an active site and the substrate molecule is believed to increase the efficiency of a reaction. If the tightness between the active site of DNA polymerase and its substrate is increased, the fidelity, which means the correct rate of DNA replication will also increase. Most enzymes have deeply buried active sites, which can be accessed by a substrate via access channels.


title: Active site

text: There are three proposed models of how enzymes fit their specific substrate: the lock and key model, the induced fit model, and the conformational selection model. The latter two are not mutually exclusive: conformational selection can be followed by a change in the enzyme's shape. Additionally, a protein may not wholly follow either model. Amino acids at the binding site of ubiquitin generally follow the induced fit model, whereas the rest of the protein generally adheres to conformational selection. Factors such as temperature likely influences the pathway taken during binding, with higher temperatures predicted to increase the importance of conformational selection and decrease that of induced fit.


title: Active site

text: This concept was suggested by the 19th-century chemist Emil Fischer. He proposed that the active site and substrate are two stable structures that fit perfectly without any further modification, just like a key fits into a lock. If one substrate perfectly binds to its active site, the interactions between them will be strongest, resulting in high catalytic efficiency.


title: Active site

text: As time went by, limitations of this model started to appear. For example, the competitive enzyme inhibitor methylglucoside can bind tightly to the active site of 4-alpha-glucanotransferase and perfectly fits into it. However, 4-alpha-glucanotransferase is not active on methylglucoside and no glycosyl transfer occurs. The Lock and Key hypothesis cannot explain this, as it would predict a high efficiency of methylglucoside glycosyl transfer due to its tight binding. Apart from competitive inhibition, this theory cannot explain the mechanism of action of non-competitive inhibitors either, as they do not bind to the active site but nevertheless influence catalytic activity.


title: Active site

text: Daniel Koshland's theory of enzyme-substrate binding is that the active site and the binding portion of the substrate are not exactly complementary. The induced fit model is a development of the lock-and-key model and assumes that an active site is flexible and changes shape until the substrate is completely bound. This model is similar to a person wearing a glove: the glove changes shape to fit the hand. The enzyme initially has a conformation that attracts its substrate. Enzyme surface is flexible and only the correct catalyst can induce interaction leading to catalysis. Conformational changes may then occur as the substrate is bound. After the reaction products will move away from the enzyme and the active site returns to its initial shape. This hypothesis is supported by the observation that the entire protein domain could move several nanometers during catalysis. This movement of protein surface can create microenvironments that favour the catalysis.


title: Active site

text: This model suggests that enzymes exist in a variety of conformations, only some of which are capable of binding to a substrate. When a substrate is bound to the protein, the equilibrium in the conformational ensemble shifts towards those able to bind ligands (as enzymes with bound substrates are removed from the equilibrium between the free conformations).


title: Active site

text: Electrostatic interaction: In an aqueous environment, the oppositely charged groups in amino acid side chains within the active site and substrates attract each other, which is termed electrostatic interaction. For example, when a carboxylic acid (R-COOH) dissociates into RCOO and H ions, COO will attract positively charged groups such as protonated guanidine side chain of arginine.


title: Active site

text: Hydrogen bond: A hydrogen bond is a specific type of dipole-dipole interaction between a partially positive hydrogen atom and a partially negative electron donor that contain a pair of electrons such as oxygen, fluorine and nitrogen. The strength of hydrogen bond depends on the chemical nature and geometric arrangement of each group.


title: Active site

text: Van der Waals force: Van der Waals force is formed between oppositely charged groups due to transient uneven electron distribution in each group. If all electrons are concentrated at one pole of the group this end will be negative, while the other end will be positive. Although the individual force is weak, as the total number of interactions between the active site and substrate is massive the sum of them will be significant.


title: Active site

text: Hydrophobic interaction: Non-polar hydrophobic groups tend to aggregate together in the aqueous environment and try to leave from polar solvent. These hydrophobic groups usually have long carbon chain and do not react with water molecules. When dissolving in water a protein molecule will curl up into a ball-like shape, leaving hydrophilic groups in outside while hydrophobic groups are deeply buried within the centre.


title: Active site

text: Once the substrate is bound and oriented to the active site, catalysis can begin. The residues of the catalytic site are typically very close to the binding site, and some residues can have dual-roles in both binding and catalysis.


title: Active site

text: Catalytic residues of the site interact with the substrate to lower the activation energy of a reaction and thereby make it proceed faster. They do this by a number of different mechanisms including the approximation of the reactants, nucleophilic/electrophilic catalysis and acid/base catalysis. These mechanisms will be explained below.


title: Active site

text: During enzyme catalytic reaction, the substrate and active site are brought together in a close proximity. This approach has various purposes. Firstly, when substrates bind within the active site the effective concentration of it significantly increases than in solution. This means the number of substrate molecules involved in the reaction is also increased. This process also reduces the desolvation energy required for the reaction to occur. In solution substrate molecules are surrounded by solvent molecules and energy is required for enzyme molecules to replace them and contact with the substrate. Since bulk molecules can be excluded from the active site this energy output can be minimised. Next, the active site is designed to reorient the substrate to reduce the activation energy for the reaction to occur. The alignment of the substrate, after binding, is locked in a high energy state and can proceed to the next step. In addition, this binding is favoured by entropy as the energy cost associated with solution reaction is largely eliminated since solvent cannot enter active site. In the end, the active site may manipulate the Molecular orbital of the substrate into a suitable orientation to reduce activation energy.


title: Active site

text: The electrostatic states of substrate and active site must be complementary to each other. A polarized negatively charged amino acid side chain will repel uncharged substrate. But if the transition state involves the formation of an ion centre then the side chain will now produce a favourable interaction.


title: Active site

text: Many enzymes including serine protease, cysteine protease, protein kinase and phosphatase evolved to form transient covalent bonds between them and their substrates to lower the activation energy and allow the reaction to occur. This process can be divided into 2 steps: formation and breakdown. The former step is rate-limit step while the later step is needed to regenerate intact enzyme.


title: Active site

text: Nucleophilic catalysis: This process involves the donation of electrons from the enzyme's nucleophile to a substrate to form a covalent bond between them during the transition state. The strength of this interaction depends on two aspects.: the ability of the nucleophilic group to donate electrons and the electrophile to accept them. The former one is mainly affected by the basicity(the ability to donate electron pairs) of the species while the later one is in regard to its p"K". Both groups are also affected by their chemical properties such as polarizability, electronegativity and ionization potential. Amino acids that can form nucleophile including serine, cysteine, aspartate and glutamine.


title: Active site

text: Electrophilic catalysis: The mechanism behind this process is exactly same as nucleophilic catalysis except that now amino acids in active site act as electrophile while substrates are nucleophiles. This reaction usually requires cofactors as the amino acid side chains are not strong enough in attracting electrons.


title: Active site

text: Metal ions have multiple roles during the reaction. Firstly it can bind to negatively charged substrate groups so they will not repel electron pairs from active site's nucleophilic groups. It can attract negatively charged electrons to increase electrophilicity. It can also bridge between active site and substrate. At last, they may change the conformational structure of the substrate to favour reaction.


title: Active site

text: In some reactions, protons and hydroxide may directly act as acid and base in term of specific acid and specific base catalysis. But more often groups in substrate and active site act as Brønsted–Lowry acid and base. This is called general acid and general base theory. The easiest way to distinguish between them is to check whether the reaction rate is determined by the concentrations of the general acid and base. If the answer is yes then the reaction is the general type. Since most enzymes have an optimum pH of 6 to 7, the amino acids in the side chain usually have a p"K" of 4~10. Candidate include aspartate, glutamate, histidine, cysteine. These acids and bases can stabilise the nucleophile or electrophile formed during the catalysis by providing positive and negative charges.


title: Active site

text: Quantitative studies of enzymatic reactions often found that the acceleration of chemical reaction speed cannot be fully explained by existing theories like the approximation, acid/base catalysis and electrophile/nucleophile catalysis. And there is an obvious paradox: in reversible enzymatic reaction if the active site perfectly fits the substrates then the backward reaction will be slowed since products cannot fit perfectly into the active site. So conformational distortion was introduced and argues that both active site and substrate can undergo conformational changes to fit with each other all the time.


title: Active site

text: This theory is a little similar to the Lock and Key Theory, but at this time the active site is preprogrammed to bind perfectly to substrate in transition state rather than in ground state. The formation of transition state within the solution requires a large amount of energy to relocate solvent molecules and the reaction is slowed. So the active site can substitute solvent molecules and surround the substrates to minimize the counterproductive effect imposed by the solution. The presence of charged groups with the active site will attract substrates and ensure electrostatic complementarity.


title: Active site

text: The role of glutathione(GSH) is to remove accumulated reactive oxygen species which may damage cells. During this process, its thiol side chain is oxidised and two glutathione molecules are connected by a disulphide bond to form a dimer(GSSG). In order to regenerate glutathione the disulphide bond has to be broken, In human cells, this is done by glutathione reductase(GR).


title: Active site

text: Glutathione reductase is a dimer that contains two identical subunits. It requires one NADP and one FAD as the cofactors. The active site is located in the linkage between two subunits. The NADPH is involved in the generation of FADH-. In the active site, there are two cysteine residues besides the FAD cofactor and are used to break the disulphide bond during the catalytic reaction. NADPH is bound by three positively charged residues: Arg-218, His-219 and Arg-224.


title: Active site

text: The catalytic process starts when the FAD is reduced by NADPH to accept one electron and from FADH. It then attacks the disulphide bond formed between 2 cysteine residues, forming one SH bond and a single S group. This S group will act as a nucleophile to attack the disulphide bond in the oxidised glutathione(GSSG), breaking it and forming a cysteine-SG complex. The first SG anion is released and then receives one proton from adjacent SH group and from the first glutathione monomer. Next the adjacent S group attack disulphide bond in cysteine-SG complex and release the second SG anion. It receives one proton in solution and forms the second glutathione monomer.


title: Active site

text: Chymotrypsin is a serine endopeptidase that is present in pancreatic juice and helps the hydrolysis of proteins and peptide. It catalyzes the hydrolysis of peptide bonds in L-isomers of tyrosine, phenylalanine, and tryptophan. In the active site of this enzyme, three amino acid residues work together to form a catalytic triad which makes up the catalytic site. In chymotrypsin, these residues are Ser-195, His-57 and Asp-102.


title: Active site

text: The mechanism of chymotrypsin can be divided into two phases. First, Ser-195 nucleophilically attacks the peptide bond carbon in the substrate to form a tetrahedral intermediate. The nucleophilicity of Ser-195 is enhanced by His-57, which abstracts a proton from Ser-195 and is in turn stabilised by the negatively charged carboxylate group (RCOO) in Asp-102. Furthermore, the tetrahedral oxyanion intermediate generated in this step is stabilised by hydrogen bonds from Ser-195 and Gly-193.


title: Active site

text: In the second stage, the R'NH group is protonated by His-57 to form R'NH and leaves the intermediate, leaving behind the acylated Ser-195. His-57 then acts as a base again to abstract one proton from a water molecule. The resulting hydroxide anion nucleophilically attacks the acyl-enzyme complex to form a second tetrahedral oxyanion intermediate, which is once again stabilised by H bonds. In the end, Ser-195 leaves the tetrahedral intermediate, breaking the CO bond that connected the enzyme to the peptide substrate. A proton is transferred to Ser-195 through His-57, so that all three amino acid return to their initial state.


title: Active site

text: Substrate unbinding is influenced by various factors. Larger ligands generally stay in the active site longer, as do those with more rotatable bonds (although this may be a side effect of size). When the solvent is excluded from the active site, less flexible proteins result in longer residence times. More hydrogen bonds shielded from the solvent also decrease unbinding.


title: Active site

text: Enzymes can use cofactors as ‘helper molecules’. Coenzymes are referred to those non-protein molecules that bind with enzymes to help them fulfill their jobs. Mostly they are connected to the active site by non-covalent bonds such as hydrogen bond or hydrophobic interaction. But sometimes a covalent bond can also form between them. For example, the heme in cytochrome C is bound to the protein through thioester bond. In some occasions, coenzymes can leave enzymes after the reaction is finished. Otherwise, they permanently bind to the enzyme. Coenzyme is a broad concept which includes metal ions, various vitamins and ATP. If an enzyme needs coenzyme to work itself, it is called an apoenzyme. In fact, it alone cannot catalyze reactions properly. Only when its cofactor comes in and binds to the active site to form holoenzyme does it work properly.


title: Active site

text: One example of the coenzyme is Flavin. It contains a distinct conjugated isoalloxazine ring system. Flavin has multiple redox states and can be used in processes that involve the transfer of one or two electrons. It can act as an electron acceptor in reaction, like the oxidation of NAD to NADH, to accept two electrons and form 1,5-dihydroflavin. On the other hand, it can form semiquinone(free radical) by accepting one electron, and then converts to fully reduced form by the addition of an extra electron. This property allows it to be used in one electron oxidation process.


title: Active site

text: Inhibitors disrupt the interaction between enzyme and substrate, slowing down the rate of a reaction. There are different types of inhibitor, including both reversible and irreversible forms.