Meanwhile, the sensing performance and sensing mechanism of the sensors are discussed. The improved experimental schemes are raised and the critical research directions of graphene/metal-oxide sensors in the future are proposed.Owing to the excellent sensitivity to gases, metal-oxide semiconductors (MOS) are widely used as materials for gas sensing. Usually, MOS gas sensors have some common shortages, such as relatively poor selectivity and high operating temperature. Graphene has drawn much attention as a gas sensing material in recent years because it can even work at room temperature, which reduces power consumption. However, the low sensitivity and long recovery time of the graphene-based sensors limit its further development. The combination of metal-oxide semiconductors and graphene may significantly improve the sensing performance, especially the selectivity and response/recovery rate at room temperature. In this review, we have summarized the latest progress of graphene/metal-oxide gas sensors for the detection of NO The ele2. The sensor showed high sensitivity to NO2 at low concentrations. In another work, Hu et al. [3 with an ultra-fast response time of 1.4 s at room temperature. The sensors based on rGO exhibited a rapid and high response to target gas at room temperature. However, these sensors show a common shortage. Since the binding force between graphene and gas molecules is van der Waals force or even covalent bonds [The mass production of single-layered graphene is difficult. Another problem is that pristine graphene does not have a bandgap, which means it is not suitable for semiconductor gas sensors . Graphenu et al.  fabricatnt bonds , the recnt bonds –20.2), titanium dioxide (TiO2), zinc oxide (ZnO), copper oxide (CuO), tungsten oxide (WO3), indium oxide (In2O3), ferric oxide (Fe2O3) and cobalt oxide (Co3O4) are important materials for gas sensors [2−. With the increase of temperature, O2− is transformed into O−. When the temperature is above 397 °C, the oxygen anions are converted into O2−. The reaction equations are as follows:Metal-oxide semiconductors (MOS), including tin oxide . In general, people should not be exposed to an environment with more than 35 ppm NH3 for more than 15 min or an environment with more than 10 ppm CO for more than 10 min. Also, people should not be exposed to workplaces with more than 0.08 ppm formaldehyde for more than 30 min according to World Health Organization [There are many kinds of toxic gases from industrial processes and car emissions around us, such as NOnization . Therefonization . Compare2–rGO sensor [2 and rGO formed p–n heterojunctions. The enhancement mechanism of the p–n heterojunction is shown in Ec and Ev are the energies of conduction band and valence band of the two components, respectively, while the Fermi level energy (Ef) is between these two bands. It can be seen from 2, meaning that electrons transfer from rGO to SnO2 in the heterojunctions. The Schottky barrier is only 0.2 eV due to the changed Fermi level of the composite structure after achieving a dynamic balance of the electron flow, indicating that the electrons are able to pass through the energy barrier. In summary, the SnO2–rGO sensor allow for the transition of electrons even at room temperature because of its low Schottky barrier. When exposed to air at room temperature, oxygen molecules obtain electrons from n-type SnO2–rGO hybrids to form O2−. The electron depletion layers generated on the interfaces of SnO2 grains and rGO sheets owing to the loss of electrons and the resistance is the initial resistance of the sensor. The initial resistance of SnO2-rGO sensor is much lower than that of a SnO2 sensor since because of the high conductivity of rGO, indicating that variations of resistance can be detected at room temperature. Moreover, the electron depletion layers in the SnO2–rGO sensor where the electrons are constantly moving between SnO2 and rGO are wider than those in a SnO2 sensor. When exposed to reducing gases , the gas molecules act as electron donors to SnO2–rGO so that the resistance of composite sensor decreases dramatically, leading to high sensitivity and rapid response.Reduced graphene oxide (rGO), which plays the role of a p-type semiconductor, can form heterojunctions when forming composites with most metal-oxide semiconductors. In the example of a SnOO sensor , SnO2 anIsotypical p–p homojunctions are formed when rGO forms composites with most p-type metal-oxide semiconductors. The enhancement mechanism of p–p homojunctions is similar to that of p–n heterojunctions. However, p–n junctions cause the recombination of charge carriers with a decreased amount of charge carriers, while p–p junctions lead to spatially separated charge carriers with an unchanged amount of charge carriers. The following summarizes the parameters of several room-temperature gas sensors based on rGO/metal oxides, which exhibit enhanced sensing performance mainly due to the formation of heterojunctions.3 with ultra-fast response/recovery times of 78 s/188 s, which was much better than that of a pure rGO sensor (low response and endless recovery time). The composite sensor with the optimal amount of GO (1.5 mL) was highly sensitive to low concentrations of NH3 and responded dramatically, which could be ascribed to the p–n heterojunctions formed between ZnO and rGO. However, the influence of humidity on the sensor response was not negligible due to the residual oxygen (high hydrophilicity) on rGO and the active sites (oxygen vacancies) on ZnO. Chen and co-workers [2–rGO sensor, which was synthesized via growing SnO2 nanorods on a GO surface, showed a response of 1.3 to 200 ppm NH3 with instant response/recovery times of only 8 s/13 s at room temperature. The rapid response and particularly the ultra-fast recovery were extremely inspiring because the recovery time of sensors based on rGO is usually long at room temperature. As a comparison, the pure SnO2 sensor is only able to work at 160 °C. The outstanding sensing performance was accounted for by the p–n heterojunctions according to the explanation of the authors. NH3 adsorbed on rGO has a smaller adsorption energy than other gases. Strong hydrogen bonds were formed between hydrogen atoms (NH3) and the residual oxygen atoms on rGO, facilitating the interaction of NH3 with rGO. Thus the selectivity to NH3 was good. The authors found that water molecules affected the sensor at low humidity levels. However, the response of the composite sensor increased with increasing humidity at high humidity levels. At low humidity levels, ammonia and water molecules competed for adsorption, which reduces the sensing performance of NH3. As humidity levels increased, ammonia adsorbed on the surface of sensor by dissolving into water, leading to the higher response. This is quite different from the usual opinion that sensitivity will decrease at high humidity levels.Tai et al.  deposite-workers  demonstrEg1 (1.2 eV) is not equal to Eg2 (0.4 eV) [3 was not as well as that of a pure ZnO sensor, the ZnO–rGO sensor exhibited rapid response/recovery times with a detection limit of 50 ppb while the pure ZnO sensor was unrecoverable at room temperature. The authors stated that the p–p junctions constituted ZnO and rGO reduced the response/recovery times dramatically. An interesting phenomenon found by the authors was that the pure ZnO sensor showed characteristics of a p-type semiconductor during the test. Two reasons were given for this. One was that a little carbon and nitrogen might be doped into ZnO due to the addition of graphite and nitrogen gas protection during the carbothermal reduction (1150 °C). Another was the formation of Schottky barriers between ZnO and the metal electrodes, which caused ZnO to exhibit p-type semiconductor properties. The gas-sensing performance parameters of the abovementioned sensors for reducing gases based on metal oxides and rGO enhanced by the formation of semiconductor interfaces are listed in Zhang et al.  synthesi(0.4 eV) –51. The (0.4 eV)  mixed Zn2–rGO sensor as an example [2 and rGO formed p–n heterojunctions during the recombination process. The Fermi level of SnO2 is higher than that of rGO since the work function of SnO2 (4.55 eV) is lower than that of rGO (4.75 eV). As a result, electrons transfer from SnO2 to the conduction band of rGO, not only leading to the bending of the energy bands but also forming potential barriers at the interfaces between SnO2 and rGO. When exposed to air at room temperature, oxygen molecules form O2− by obtaining electrons from p-type SnO2–rGO hybrids. Thus, hole accumulation layers and potential barriers are generated at the interfaces of SnO2–rGO hybrids. There are wider hole accumulation layers and higher potential barriers in SnO2–rGO than in pristine SnO2 owing to the existence of the immanent potential barrier and the imprisoned electrons in rGO. When exposed to an oxidizing gas (NO2), which has a high electron affinity, the electrons are continuously captured from SnO2–rGO hybrids, leading to wider hole accumulation layers and increased potential barriers. Consequently, the resistance of composite sensor decreased sharply, leading to high sensitivity and rapid response time. The reaction equations are as follows:Similarly, taking a SnO example , as disp example , SnO2 an2 and the response/recovery times were only 25 s/15 s with good stability at room temperature. As a comparison, the response of the ZnO sensor was 6.2 and the response time was over 150 s under the same conditions. The pure rGO sensor only showed a response of 1.2 and a recovery time up to 58 s. The effect of humidity on this sensor was also tested. It was found that the sensor was relatively stable to different humidity levels. The authors ascribed the enhanced sensing properties to both the p–n heterojunctions and the increased carrier concentrations. Specifically, the addition of rGO increased carrier concentrations and provided conductive pathways, which favored the transfer of electrons. The CeO2–rGO sensor reported by Jiang et al. [2 sensing performance of CeO2–rGO sensor. Zhang et al. [3)3·9H2O solution, then synthesized α-Fe2O3–rGO hybrids via hydrothermal method. During the process of testing, the authors found that the doping amount of graphene significantly affected the sensing properties of the α-Fe2O3–rGO sensor. The α-Fe2O3–rGO sensor with the optimal doping amount of 12.2% showed the highest sensitivity and rapid response time to NO2 at room temperature. In addition, the sensor exhibited excellent selectivity to NO2 because other interference gases required high operating temperatures to react with the surface of this sensor. As a comparison, the pure α-Fe2O3 sensor does not work at room temperature. The formation of p–n heterojunctions was an important factor for the exceptional sensing performance. There were two different depletion layers and potential barriers in the composites due to the heterojunctions, one at the α-Fe2O3 grain boundaries and another at the interfaces of α-Fe2O3 and rGO. It appeared clear that O2 adsorption on the α-Fe2O3 grain boundaries modified the width of the α-Fe2O3 depletion layer, which conversely altered the width of depletion layer at the α-Fe2O3 and rGO interfaces leading to higher sensitivity. In addition, the periodic exposure of the α-Fe2O3–rGO sensor to 0.1 ppm NO2 indicated that the process of response was repeatable. However, a drift of the baseline was easily noted, which usually appears in room-temperature sensors, and further optimization is needed to control the drift. In another work, p–p junctions were accounted for the outstanding sensitivity to NO2 of Co3O4–rGO sensors at room temperature [In an early work, Liu et al.  stated tg et al.  added GOperature .2 nanoparticles were grown on S-rGO sheets to prepare SnO2–S-rGO hybrids. The SnO2–S-rGO sensor exhibited exceptional sensitivity to NO2 with a detection limit of 450 ppb at room temperature. The sensor also showed good repeatability and was not affected by water molecules. In contrast, a sensor based on S-rGO showed high sensitivity to NO2, but its response/recovery times were long (more than a few minutes). A gas sensor based on SnO2–rGO [2 in their previous study, but it could only work at 50–55 °C. The authors ascribed the better sensing performance of the SnO2–S–rGO sensor to the following factors: The addition of sulfonic acid enhances the dispersibility of rGO. At same time, the conductivity of S-rGO is better than that of rGO. Most importantly, the p–n heterojunctions between S-rGO and SnO2 lead to the good sensing properties. Because noble metals offer exceptional catalytic activity, the same group [2–rGO ternary hybrids by reducing AgNO3 on the dispersion of SnO2–rGO, and the sensing properties were tested at room temperature. The authors demonstrated that the response and recovery of this sensor were much faster than that of SnO2–rGO sensor, which could only work at 50–55 °C. The doping of Ag nanoparticles not only improved the electron transfer rate of the sensor, but also increased the number of active sites on the surface of the sensor. Moreover, the introduction of Ag nanoparticles reduced the Schottky barrier of the ternary composites so that those electrons with lower energy were able to cross the energy barrier at room temperature. Thus the sensor can work near room temperature. The most important reason for the excellent NO2 sensing performance of the ternary composite sensor was still the p–n heterojunctions. The gas-sensing performance parameters of the abovementioned NO2 sensors based on metal oxides and rGO enhanced by the formation of semiconductor interfaces are listed in Liu et al.  preparedSnO2–rGO  also exh2 nanoparticles prevent graphene from agglomerating, which in turn leads to a high specific surface area. Graphene enhances the conductivity of the composite materials, enabling the composite sensors to achieve a high response at low operating temperatures. Moreover, the introduction of graphene provides more adsorption sites at the surface of the composite so that the response can be significantly improved.By changing morphology and structure of the sensor materials, one can obtain large specific surface area, more conductive pathways and more active sites, which significantly improve sensing performance of the sensor. As shown in 2 at room temperature, while the pure rGO sensor only exhibited 7.7% response under the same conditions. Apart from the conductive 3D network channels provided by rGO, the large specific surface area of the composite sensor also contributed to the high response. Liu et al. [2, GO, sodium acetate and sodium citrate in an autoclave. Different from other drying processes, the hybrids were obtained through freeze-drying to keep the 3D structure. ZnO nanoparticles were well wrapped in graphene sheets, while the graphene sheets were well dispersed in the hybrids. The ZnO–rGO sensor exhibited 8% response to 50 ppm NO2 with rather rapid response/recovery times (132 s/164 s) while the pure rGO sensor showed a response of 6.4% with longer response/recovery times (149 s/243 s) at room temperature. The sensor showed exceptional selectivity to NO2. Other gases, such as C3H6O, CH3(CH2)3OH, CH3OH and H2, were not able to react with the oxygen ions that adsorbed on the surface of this composite sensor at low operating temperatures. NO2 is a strongly electron-withdrawing molecule that enhanced the electron-withdrawing ability of oxygen functional groups through its electron-deficient N atom interacting with active sites on rGO. In addition, the authors did an interesting comparative experiment with the ZnO–rGO sensor, a pure rGO sensor and a sensor fabricated by physically mixing ZnO and graphene dispersions. The last sensor exhibited the worst gas-sensing performance to NO2 due to the agglomeration of graphene sheets and ZnO particles. Similarly, this group [2 nanoparticles, synthesized via the method mentioned above, exhibited a higher response to NO2 and faster response/recovery times than a 2D SnO2–graphene sensor, fabricated by the same method without freeze-drying process.ZnO is widely used as a typical wide-bandgap (3.37 eV) metal-oxide gas sensor material. However, the problem with ZnO gas sensors is their poor selectivity . Li et au et al.  developeis group  demonstr2), as a wide-bandgap semiconductor, has been widely used as photocatalyst, and in solar cells and gas sensors [3 sensor using rGO decorated with TiO2 nanocrystals. There were two different morphologies in these sensing materials: rGO either laid on the surface of TiO2 nanoparticles, partly wrapping them, or made “bridges” at the interface between two nanoparticles. Due to the “bridges” existing between TiO2 nanoparticles, the initial resistance of TiO2–rGO sensor was greatly reduced, indicating that the sensor was able to work at room temperature. The partly “wrapping” microstructure enhanced the number of adsorption sites. Moreover, the TiO2–rGO sensor showed a better selectivity to NH3 than the pure rGO sensor owing to the acidic surface of TiO2 preferentially adsorbing primarily NH3. Ye et al. [2–rGO sensor, fabricated via depositing GO and TiO2 nanoparticles on IDEs and then heating them for reduction, showed a 1.5-times higher response than a rGO sensor at room temperature. In contrast, a pure TiO2 sensor did not respond to NH3 at room temperature, which proved that the introduction of graphene reduced the operating temperature of the TiO2 sensor. The same group [3 room-temperature sensor based on TiO2–rGO hybrids, synthesized by a hydrothermal method, exhibited a two-times higher response and a much shorter response time than the TiO2–rGO sensor fabricated by direct deposition as mentioned above. Apart from the porous and undulating graphene sheets due to the introduction of TiO2 nanoparticles, the mellow and regular TiO2 nanoparticles also contributed to the improvement of the gas-sensing performance. However, the stability was poor because the composite sensor was sensitive to water molecules. Further optimization is needed to control the influence of humidity on the sensors.Titanium dioxide  hybrids fabricated via hydrothermal synthesis using GO and SnCl2 as precursors exhibited a 3D nanostructure with high specific surface area (94.9 m2/g). During the hydrothermal process, GO served as a template to promote the preferential growth of SnO2 nanoparticles and prevented SnO2 nanoparticles from agglomeration. The response of the composite sensor to NH3 at 10 ppm was 5.09% and the response/recovery time was less than 1 min at room temperature, whereas the sensor based on SnO2 did not respond to NH3 and the sensor based on GN showed a response of only 2.7 % at room temperature. The authors claimed that the introduction of GN not only increased the specific surface area, but also improved the conductivity of the sensor at room temperature. Bo et al. [2 nanoparticles on the VG networks. The SnO2–VG room-temperature sensor was capable of detecting as low as 20 ppb of formaldehyde and showed a response of 4.6% to 5 ppm formaldehyde, which was three-times higher than that of the graphene sensor. Compared with normal graphene sheets, the specific surface area of vertical graphene sheets is extremely increased. The SnO2 nanoparticles on the VG sheets with the 3D structure provided numerous adsorption sites for target gas molecules.SnOof gases –77, so tn et al.  demonstro et al.  grew ver3)3 to develop In2O3–rGO hybrids through a facile one-step microwave-assisted hydrothermal method. The response of the In2O3–rGO sensor to 5 ppm NO2 was 37.81% with excellent stability and selectivity at room temperature. It should be noted that graphene improved the conductivity of the sensing materials, while the addition of In2O3 nanocubes prevented rGO sheets from re-accumulation, as shown in 2O nanorods–rGO hybrids obtained after annealing showed a porous structure with a high surface area to volume ratio. The porous structure promoted the diffusion of gases, improving the reaction of gases with oxygen species on the surface of the hybrid material. The Cu2O–rGO composites exhibited exceptional catalytic activity and acted as high-efficiency catalysts for the reduction of oxygen molecules, leading to an excellent response. This room-temperature sensor exhibited a linear response to the concentration of NH3 with rapid response/recovery times. The gas-sensing performance parameters of the abovementioned graphene/metal-oxide gas sensors enhanced by improved morphology and structure are listed in Apart from the abovementioned common MOS, some other MOS also have exceptional sensing properties after mixing with graphene. Yang et al.  added a In the past years, some scholars have found that excellent sensing properties can also be achieved when MOS are directly mixed with pristine graphene. The formation of heterojunctions is improper to explain this phenomenon since pristine graphene is a conducting material. Also, the morphology and structure of the composite sensor have not been altered through the introduction of graphene. Another strengthening mechanism, namely a synergetic coupling effect between graphene and metal oxides, is proposed. In detail, the enhanced sensing performance is accounted for by chemical bonds between graphene and metal oxides. Many XPS studies have claimed that there indeed exist chemical bonds between metal oxides and graphene.3, a transition-metal oxide semiconductor is widely used as a gas sensor because of its small bandgap (2.585 eV) and its physical and chemical stability [2 sensor based on WO3 nanospheres wrapped in graphene sheets, prepared by a simple sol–gel technique, showed a linear response to low concentrations of NO2, while the pure WO3 and graphene sensors did not respond to NO2 at room temperature. The authors claimed that the reason for room-temperature sensing of the composite sensor was the effective charge transfer between graphene and WO3 nanospheres by chemical bonds. The research group confirmed that there existed C–O–W chemical bonds between WO3 and graphene by Raman and XPS measurements. The proposed sensing mechanism is shown in 2 molecules, the gas molecules adsorbed on WO3 nanospheres cause the energy band to bend upward via obtaining electrons from WO3 and move the Fermi level of WO3 from the conduction band to the valence band. The reactions mentioned above shift the work function of WO3 [3 and graphene. Because of the continuous loss of electrons of WO3, electrons are transferred from the graphene sheets to WO3 through chemical bonds to maintain the adsorption. The chemical bonds are considered as electrons bridges during the response, which improved the sensing performance of the graphene–WO3 sensor. In addition, the excellent conductivity of graphene may also enhance the response because graphene offers conductive pathways that enhanced the efficiency of charge-carrier transfer in the composites. Zhang et al. [3O4–graphene gas sensor through a traditional hydrothermal method. The XPS results certified that Co–O–C bonds were formed at the interfaces of Co3O4 and graphene. The Co cations in Co3O4 were strongly attracted by the oxygen anions in the oxygen functional groups of the graphene. Consequently, the centers of Co3+ and Co2+ served as additional active adsorption sites for NO2. At the same time, the electrons transferred from graphene to Co3O4 through the Co–O–C bonds lead to an additional increase of the width of hole accumulation layers, leading to a high sensitivity at room temperature. In another work, Feng et al. [3O4 nanocrystals by using electrospinning. The Co3O4–rGO room-temperature sensor showed excellent sensitivity to low concentrations of NH3, an ultrafast response time of only 4 s with exceptional selectivity to NH3. The authors claimed that the introduction of rGO exhibiting a strong attraction to NH3 played a crucial role in improving the sensitivity and selectivity. However, the most important factor was that the chemical bonds (C–O–Co) formed between rGO and Co3O4, which facilitated the electrons transfer at the interfaces of rGO and Co3O4.WOtability –89. In atability  reportedn of WO3  to be adg et al.  fabricatg et al.  develope2 and graphene. The response of the SnO–graphene sensor to 50 ppm NH3 reached 21% with fast response/recovery times of only 15 s/30 s at room temperature. The most encouraging result was that the sensor could maintain its excellent response for more than one year. The authors demonstrated that the formation of C–O–Sn chemical bonds, confirmed by XPS results, was responsible for the superior performance of the SnO–graphene sensor. Zhang et al. [2 than a pure NiO sensor. The authors also ascribed the enhanced sensor sensitivity to the Ni–O–C bonds formed at the interfaces of NiO nanoparticles and graphene sheets. The NO2 molecules capture electrons from the surface of NiO nanoparticles when the sensor is exposed to NO2. More and more electrons are transferred from graphene to NiO by Ni–O–C bonds because of the lower Fermi level of NiO, increasing the sensitivity and response rate of the NiO–graphene sensor. However, the sensitivity of the NiO–graphene sensor was not as good as that of the pure NiO sensor at low concentrations of NO2 (0.25–1 ppm). In order to enhance the sensitivity of this sensor, the authors [2 to the NiO–graphene hybrids (p-type) to form p–n heterojunctions and found that the sensitivity of the SnO2–NiO–graphene sensor was about 10-times that of the NiO–graphene sensor. The authors claimed that the low adsorption energy of NO2 on the surface of SnO2 and the formation of p–n heterojunctions contributed to the exceptional sensitivity. The gas-sensing performance parameters of the abovementioned metal oxide–graphene gas sensors enhanced by a synergetic coupling effect are listed in Kumar and co-workers  fabricatg et al.  fabricat authors  added n-2–rGO fabricated by Zhang et al. [In this review article, the progress of room-temperature graphene/metal-oxide gas sensors has been summarized. The introduction of graphene or its derivatives greatly improves the sensitivity and reduces the operating temperature of MOS gas sensors. The advances in the field of graphene/metal-oxide gas sensors over the past few years have greatly broadened the research directions of gas sensors. However, the achievements reported in this article are still in the stage of basic research and require a lot of effort to put these researches into practical use. The main bottleneck is that the gas sensors are susceptible to environmental humidity 4783,87,96.g et al.  showed aA small number of these composite sensors seem to exhibit the phenomenon of resistance-baseline drift, which is due to the formation of chemical bonds during the adsorption of gas molecules at the material surface, resulting in slow or even impossible recovery. Some researchers have stated that the recovery time can be reduced by heating or irradiating with UV light. Unfortunately, the measures will damage the structure of rGO films and increase the cost. Another point we have to mention is that the sensors based on metal oxides and graphene exhibit complicated sensing mechanisms owing to the additional reactions between gas molecules and various sensing materials.Future works should focus on the following aspects: The most important thing is to simulate the influence of humidity on the sensor performance in a real environment and study the mechanism of humidity influence. A hydrophobic coating can be applied to the surface of the sensor to reduce the effects of humidity. Regarding the synthesis, it is important to quantify and control the effect of hydrothermal or solvothermal parameters on the micromorphology of hybrids. An important way to enhance the selectivity of composite sensors is mixing or doping with other phases . Similarly, the recovery time can be reduced by surface functionalization of graphene/metal-oxide hybrids with specific functional molecules such as boron or nitrogen. In addition, more effort should be dedicated to the detection of more environmental gases, especially VOCs. Last but not least, the influence of baseline drift in resistance can be eliminated by defining a new method, which calculates the response values by using the resistance value after each response cycle.


Group I catalytic introns have been found in bacterial, viral, organellar, and some eukaryotic genomes, but not in archaea. All known archaeal introns are bulge-helix-bulge (BHB) introns, with the exception of a few group II introns. It has been proposed that BHB introns arose from extinct group I intron ancestors, much like eukaryotic spliceosomal introns are thought to have descended from group II introns. However, group I introns have little sequence conservation, making them difficult to detect with standard sequence similarity searches. Taking advantage of recent improvements in a computational homology search method that accounts for both conserved sequence and RNA secondary structure, we have identified 39 group I introns in a wide range of archaeal phyla, including examples of group I introns and BHB introns in the same host gene. Group I introns are canonical examples of catalytic RNAs ,2. They et al.  which returned 591 443 sequences comprised of 6 710 959 751 total nucleotides.--anytrunc which can improve performance on truncated or interrupted sequences, such as group I introns interrupted by embedded HEGs. Hits with an E-value ≤0.01 were kept, and overlapping hits were removed, keeping the hit with the lowest E-value. Highly similar hits were removed such that no two remaining hits were more than 97% identical given their alignment to the CM.Infernal v1.1.2  was usedE-value threshold of ≤10−3.Homing endonuclease gene (HEG) homologs were detected by translating each of the 39 introns in all six frames and searching all ORFS ≥20aa against Pfam 31.0  using th--rfam, which accelerates searches by enforcing strict sequence-based filters.Large subunit (LSU) and small subunit (SSU) rRNA sequences were identified using cmsearch in all sequences with an IB4 or IA3 hit using the Rfam 13.0  archaealTo check that host LSU and SSU rRNA sequences were archaeal in origin, we scored each rRNA sequence with the domain-specific Rfam covariance models LSU_rRNA_archaea, LSU_rRNA_bacteria, and LSU_rRNA_eukarya  or the corresponding SSU models  and checked that the highest-scoring alignment was to the archaeal profile. This is only suitable as a coarse-grained check; similarity scores to multiple alignment profiles are a crude substitute for phylogenetic classification on trees.Taxonomic classification of 25 SSU rRNAs identified on the same contigs as the introns was done on the RDPClassifier web server  using tret al.  and further subdivided into fourteen subtypes  based on variation in conserved consensus secondary structure ,51. No set al.  and usedet al. , lightlyThe quantity and diversity of known archaeal genome sequence has grown rapidly recently, due to metagenomic studies of uncultivated archaea ,36–44, iE-value , the estimated number of false positives at that score threshold. After removing overlapping hits and keeping the hit with the lowest E-value, there were no significant hits at a threshold of E < 0.01 for ten subtypes and the RF00028 model. IA2 and IC3 searches found three and two significant hits, respectively, but upon examination, we were unsure whether these were truly in archaeal sequences, as opposed to misannotated or contaminating bacterial or phage DNA, and we did not consider these further.We searched this archaeal sequence data with each of the 14 group I subtype CMs and with the Rfam Intron_gp1 model. Most of the 15 searches take less than 30 minutes on four CPU cores. The IA1 and IC3 subtype alignments include large HEG insertions, and these larger queries take 1–4 h. The Infernal search program, cmsearch, assigns log-odds probability scores to RNA secondary structure alignments and ranks putative hits by a measure of the statistical significance, the E-value of 0.01 or less, after we removed overlapping, lower scoring hits. We examined these hits and removed 25 that corresponded to redundant identical sequences in the archaeal database; seven where the sequence record does not contain a complete intron; three where we were not confident that the sequence folded into a complete group I consensus structure; and four where we were not confident that the host gene is an archaeal sequence. Because introns may contain nonconserved insertions including HEGs, a single intron may be identified by Infernal in more than one local alignment piece. After assigning the remaining hits to single introns, we identified a total of 39 nonredundant, full length putative group I introns, 27 IB4s and 12 IA3s. Most were identified by at least one strongly significant hit; 30 of the 39 have at least one hit of E < 10−10. Table The IB4 and IA3 CM searches found a total of 95 significant hits with an We looked at three other lines of evidence, independent of Infernal similarity scores, that provide additional support for a conclusion that these are group I introns.E. coli coordinate numbering  and P7 is aligned only as primary sequence. Identifying a P7 helix, other secondary structure elements typical of group I introns, and additional base pairs that extend Infernal-predicted consensus helices provide more confidence in the predicted introns. We manually identified a P7 helix in all 39 predicted introns . We manuThe 39 introns are found in 31 different GenBank sequences annotated as archaeal, all of which were obtained by metagenomic environmental sampling. Because GenBank annotation can be unreliable, especially for the phylogenetic source of sequences obtained in metagenomic samples, we also checked that each host rRNA gene sequence scored higher for archaeal SSU and LSU rRNA Rfam consensus models than to bacterial or eukaryotic models. An example of a sequence that failed this check is an LSU rRNA in GenBank MBAA01000200.1, a 4.7 kb contig that was binned into a Lokiarchaeota genome assembly, but appears to be bacterial. We had already named two introns from this contig (IA3.13 and IB4.16) before removing them from our analysis, which is why they are missing in Table We asked whether group I introns are broadly distributed across the archaeal phylogeny, or if they only occur in some particular clade. Specific phylum assignments are annotated in 25 of the 31 GenBank records. Both because of the unreliability of these annotations, and also because the taxonomy of archaeal phyla has been expanding ,35,52, wet al. (Various sources say that group I introns have not been identified in archaea before ,12,55. Het al.  referredet al. .Infernal searches are convenient but not strictly necessary to find these introns. BLAST searches can also identify significant similarities between some of these archaeal intron sequences and some known group I introns in bacteria and eukarya. One reason they have been missed in previous archaeal genome annotations may be that a few informative similarities would be hard to spot amidst a long list of BLAST hits to rRNA and HEG sequences.The failure to identify group I introns in archaea has previously been attributed to their having evolved into BHB introns and gone extinct . It remaDevelopment of CM-based RNA similarity search methods was originally motivated by a desire to search for group I introns , but untSupplementary DataClick here for additional data file.


Post-traumatic stress disorder (PTSD) has a profound contextual component, and has been demonstrated to alter future contextual learning. However, the mechanism by which a single traumatic event affects subsequent contextual experiences has not been isolated. Acetylcholine (ACh) is an important modulator of hippocampus-dependent learning such as contextual memory strength. Using Stress-Enhanced Fear Learning (SEFL), which models aspects of PTSD in rats, we tested whether muscarinic acetylcholine receptors (mAChR) in dorsal hippocampus (DH) are required during trauma for the effect of trauma on subsequent contextual fear learning. We infused scopolamine or vehicle into DH immediately before stress, and tested fear in both the trauma context and a novel context after a mild stressor. The results show that during learning, ACh acting on mAChR within the DH is required for sensitization of future contextual fear learning. However, this effect is selective for contextual learning, as this blockade leaves discrete cue sensitization intact. Rather than simply sensitizing the BLA, as previous studies have suggested, SEFL requires cholinergic signaling in DH for contextual sensitization. For fear to be adaptive, it must be titrated to the level of threat and relatively specific for threat-related stimuli. Both aspects of this fear responding are dysregulated in anxiety disorders such as post-traumatic stress disorder (PTSD), disorders where fear responses are enhanced and disrupt an individual’s normal functioning . Though Though the amygdala is likely to be the core structure in the stress circuit leading to PTSD, the hippocampus has also been shown to play an important role. MRI studies of PTSD patients frequently report substantial loss of gray matter in the hippocampus, though there is debate as to whether this is caused by the trauma or due to an underlying predisposition for diagnosis; in rodent studies, both circumstances have been observed . FurtherProper hippocampal functioning, particularly during contextual memory acquisition, depends upon cholinergic inputs originating from the medial septum in the basal forebrain cholinergic system. These inputs are critical for the formation of normal contextual associations, as blockade of muscarinic receptors by scopolamine in the hippocampus prevents contextual fear learning while leaving tone fear learning intact , and enhAnimal models of aspects of PTSD such as stress-enhanced fear learning (SEFL) have recapitulated many aspects of human PTSD symptomology, such as resistance to extinction therapy , and senThe relationship between cholinergic signaling during the trauma and manifestation of the SEFL phenotype is currently unknown. In our first experiment, we infuse scopolamine or aCSF vehicle into the dorsal hippocampus (DH) 1 h prior to SEFL, and demonstrate that scopolamine disrupts both trauma context memory formation and later sensitization of fear in a novel context. In our second experiment, we administer a tone-shock pairing instead of a context-shock pairing as the novel mild stressor, and demonstrate that scopolamine in DH does not block this sensitization, suggesting that cholinergic signaling in DH during trauma sensitizes future contextual learning, but not future learning about discrete stimuli. Finally, we provide evidence that these effects are not due to state-dependent effects of scopolamine administration, nor by blockade of consolidation, but are rather a consequence of blocking cholinergic-dependent contextual sensitization during a traumatic experience.ad libitum. Animals were handled daily (one-two min per rat) for at least 1 week prior to the start of all experimental procedures. The procedures used in this study were in accordance with policy set and approved by the Institutional Animal Care and Use Committee of the University of California, Los Angeles.A total of 64 naïve male Long-Evans rats, weighing 270–300 g  were individually housed and maintained on a 12-hour light/dark cycle with access to food and water One week after housing, rats received surgical implantation of two guide cannulae aimed at the dorsal hippocampus. DH cannulae placements are shown in ® to provide the context with a scent. Chambers were individually lit from above by white lights and cleaned with 50% Windex in between squads. Fans mounted above each chamber provided background noise (60 dB). The experimental room was brightly lit with overhead white light. Animals were transported to the context in squads of eight in their home cages, which were slid onto hanging racks mounted to a portable cart and covered with a white sheet or black sheet. All aspects of the context were altered to create a distinctive single shock context. This context was comprised of an alternating large small or height-staggered grid floor and a black plexiglass A-frame. The context light was off, the experimental room light was red, and chambers were cleaned and scented with a 7% acetic acid solution. Rats were transported to the context in groups of 4 in a black tub with individual dividers and bedding on the floor. Many aspects of the context were altered again for the cohort of rats that received tone conditioning and tone test in a separate, third context. This context consisted of a white plexiglass floor, white curving plexiglass rear wall in order to make the chamber shaped like a semicircle, context light off, red and white experimental chamber lights concurrently on, and cleaned with Pine Sol. Groups of four rats were transported to this context together in a large transparent plastic tub with blue pads on the floor. All chambers were cleaned with a 10% bleach solution following each day of behavioral testing.Behavioral training used a set of four identical fear conditioning chambers  equipped with a Med-Associates Video Freeze system. Individual boxes were enclosed in sound-attenuating chambers in an individual, dedicated experimental room. The SEFL context was comprised of chambers with aluminum sidewalls and a clear Plexiglas rear wall. The grid floor consisted of 16 stainless steel rods (4.8 mm thick) spaced 1.6 cm apart (center to center). Pans underlying each box were sprayed with a thin film of 50% WindexSEFL Context procedure is detailed in To assess cannulae placements, rats were anesthetized with isoflurane and decapitated. Brains were removed from the skull and placed in 10% formalin / 30% sucrose solution for 3 days prior to sectioning using a cryostat. Coronal sections (40 μm thick) were taken throughout the extent of the cannulae track and mounted on slides. Injection sites were reconstructed using bright field microscopy. Rats that had one or both cannulae or injector tracks outside the target structure were excluded from analysis .F = 22.53, p < 0.0001], Main effect of Shock Number , significant Interaction , Sidak’s multiple comparisons test, difference between vehicle and SCOP groups from PS1 (p < 0.01) through PS6 (p < 0.05), but no difference on subsequent trials (Naïve rats received an infusion of either scopolamine (SCOP) or vehicle (aCSF) into the dorsal hippocampus, and 1 h later experienced the 15-shock SEFL procedure or an equivalent context exposure with no stress . As ratst trials . These rF = 52.80, p < 0.0001), Drug main effect  = 17.68, p < 0.001), significant interaction between SEFL and Drug  = 14.71, p < 0.001); SCOP reduced fear in SEFL rats (p < 0.001) but not NS rats (p > 0.05)]. These findings suggest that cholinergic signaling in the DH, specifically at muscarinic receptors, is essential for the formation of a strong traumatic contextual memory.Though the effect of scopolamine infusion during trauma was mild, the effects on trauma memory recall were profound . While vWhile scopolamine is sufficient to disrupt the memory of a traumatic experience, it was unknown whether this temporary disruption would affect future fear learning to a novel contextual stimulus. Off drug, these rats were exposed to a novel context and given a single shock, and contextual freezing was measured the following day in the same context to test contextual sensitization.F = 32.37, p < 0.0001) and Drug  = 9.53, p < 0.01] and a significant interaction between SEFL and Drug ; SEFL rats who received scopolamine froze significantly less than those that received vehicle (p < 0.01).In vehicle rats, the prior stress enhanced subsequent fear learning to the new conditioning context, demonstrating the sensitizing nature of trauma to future fear learning . HoweverThis blockade of future contextual sensitization is not an obvious consequence of blocking traumatic memory formation, as many manipulations that disrupt this trauma memory have no effect on later contextual sensitization . Rather,Instead of a context-shock pairing, a cohort of rats received a single tone-shock pairing after the SEFL procedure. The following day, they were exposed to a novel context and the tone was played, in order to test sensitization to discrete stimuli .p > 0.05). Though some rats in the non-stressed scopolamine group had high initial freezing to the tone, which drove an interaction, the majority of non-stressed rats had very low responding to the tone . The disproportionate response of the SEFL groups continued in the period of time after the tone ended, while both non-stressed groups expressed normal levels of freezing . Though non-stressed vehicle rats did significantly increase freezing levels between the tone and post-tone periods (p < 0.05), freezing remained below both SEFL groups at that time point (p < 0.05). Together, these data suggest that scopolamine in DH does not block all consequences of the traumatic experience. Rather, it has a selective effect on future contextual sensitization.Despite the blockade of fear to the trauma context, scopolamine during trauma did not prevent future sensitization to discrete cues . Low basp > 0.05), suggesting that state-dependent effects are not the main mediator of the low levels of context fear seen in the scopolamine rats after SEFL.One potential mediator of the scopolamine disruption of freezing in the trauma context could be due to state-dependent effects, namely the incorporation of the mental attributes of experiencing scopolamine into the memory for the context. In order to test this, we subjected a subset of rats who had received scopolamine during SEFL to a second trauma test; this test occurred after an infusion of scopolamine . No signp > 0.05). Firstly, this test demonstrates that the reduced freezing levels seen during the sensitization test with pre-training scopolamine administration are not due to a prolonged duration of action of scopolamine, as post-training scopolamine did not disrupt freezing at that later time point. Secondly, this test is a conclusive demonstration that scopolamine in DH disrupts processes occurring during acquisition, but it does not exert its effects on trauma memory or later sensitization by blockade of memory consolidation.Scopolamine could exert its effects on both trauma memory formation and contextual sensitization by disrupting memory formation, by disrupting consolidation, or by a combination of the two. Indeed, scopolamine is known to disrupt both acquisition and consolidation of contextual memory . We testThe Stress-Enhanced Fear Learning (SEFL) procedure, in which an unpredictable 15-shock stressor is administered, generates a persistent sensitized state whereby novel mild stressors result in highly elevated levels of fear. This work extends the use of this model to study the role for cholinergic signaling during trauma on later sensitized responding, and demonstrates an important role for cholinergic signaling in DH for future contextual sensitization.Pre-training administration of scopolamine into DH prevented contextual fear memory formation for an intense, 15-shock stressor. Though cholinergic signaling in DH has long been known to facilitate contextual processing, this is the first demonstration that even intense trauma cannot overcome the blockade of memory formation by scopolamine.In addition to its role in contextual memory formation, this work has demonstrated a novel role for cholinergic signaling at muscarinic receptors in DH during a traumatic event for later contextual sensitization. Scopolamine administration into DH prior to the traumatic event blocked future contextual sensitization to a mild, single context-shock pairing in the absence of drug. The blockade of trauma memory formation is unlikely to be the mechanism for blocking this contextual sensitization for a number of reasons. The first is that blockade of trauma memory formation by blocking NMDA receptors, extinction of the trauma memory , and forThe mechanism by which scopolamine in DH disrupts this cholinergic-dependent sensitization was not a focus of this study, but some noted effects of scopolamine can be ruled out. For example, though scopolamine has been shown to affect consolidation processes, these effects are not sufficient to block contextual sensitization, as post-SEFL scopolamine infusion had no effect on later sensitization. Another noted effect of scopolamine, though after systemic administration, was an upregulation of M1 cholinergic receptors, alpha 7-containing nicotinic receptors, and NMDAR1 glutamate receptors in the DH , howeverMultiple mechanisms likely play a role in this cholinergic-dependent sensitization. During acute stress, ACh levels in DH become profoundly elevated  and co-vThough ACh has direct effects on hippocampal LTP, contextual sensitization may occur through other mechanisms, leading to a dissociation between the memory-impairing but sensitization-sparing effects of APV and the cholinergic effects on both processes. For example, muscarinic receptor activation on CA1 pyramidal cells altered spine morphology , while aThough scopolamine in DH blocks contextual sensitization, it does not block all consequences of the traumatic experience. With the known contribution of BLA GluR1 receptors and glucocorticoid signaling to the SEFL phenotype , it may In addition to the direct modulation of hippocampal processing, cholinergic blockade in DH may disrupt inter-regional communication necessary for future contextual sensitization after trauma. Scopolamine administered systemically disrupts resting state functional connectivity between mouse brain regions involved in memory , and thiAnxiety disorders such as PTSD may present with symptoms related to discrete stimulus sensitization, contextual sensitization, or both, however, the evidence that these symptoms may be produced by different patterns of neural activity was previously lacking. This study demonstrated for the first time a selective contribution of cholinergic signaling during trauma exposure to future contextual, rather than general, sensitized responding. For individuals who primarily overreact to unpleasant contexts, this dissociation could provide a basis for the development of specialized treatments. Even in the case where sensitized responding to contexts and discrete stimuli are both observed, pharmacological targeting of contextual circuitry could help to normalize responding to discrete stimuli, by facilitating improved discrimination between safe and unsafe contexts .This work highlights the important contribution of hippocampal signaling to the sensitization that occurs after an acute traumatic event and provides the first evidence that cholinergic signaling during the trauma may induce changes leading to enhanced contextual sensitization after trauma. Future work will endeavor to isolate the mechanism by which this signaling changes hippocampal processing and understand the contribution of cholinergic signaling during trauma to future anxiety states, hopefully leading to novel treatments for stress-induced sensitized states.All datasets generated for this study are included in the manuscript and/or the supplementary files.SH designed the experiments, performed surgeries, organized and ran behavioral experiments, analyzed results and was the primary writer of the manuscript. AH ran experiments and assisted with analysis and development of figures. LH and SS performed some surgeries and ran behavioral experiments. JL and AP ran behavioral experiments. MF assisted with design of experiments, analysis of data, and writing of the manuscript.MF is on the scientific advisory board of Neurovation, Inc. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Moreover, the existence of tall graphene nanowalls was found not to be beneficial to the protection as a consequence of their layered orientation. These correlations among the morphology, structure, and corrosion properties of graphene nanostructures were investigated in this study. Therefore, the enhanced corrosion resistance in selected cases suggests that the low-temperature CVD graphene under appropriate conditions would be able to protect metal substrates against corrosion.Chemical vapor deposition (CVD) graphene is reported to effectively prevent the penetration of outer factors and insulate the underneath metals, hence achieving an anticorrosion purpose. However, there is little knowledge about their characteristics and corresponding corrosion properties, especially for those prepared under different parameters at low temperatures. Using electron cyclotron resonance chemical vapor deposition (ECR-CVD), we can successfully prepare graphene nanostructures on copper (Cu) at temperatures lower than 600 °C. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and potentiodynamic polarization measurements were used to characterize these samples. In simulated seawater, i.e., 3.5 wt.% sodium chloride (NaCl) solution, the corrosion current density of one graphene-coated Cu fabricated at 400 °C can be 1.16 × 10 Their g in 2015 . It ment in 2015 . The rol in 2015 . Graphen2SO4 solution [On the other hand, graphene as an oxidation and corrosion resistive coating is of great interests recently ,28,29,30solution . Hsieh esolution . Miskovi2H2 at 600 °C for different times. On the other hand, electron cyclotron resonance chemical vapor deposition system , Hsinchu, Taiwan) was used for growing graphene films through flowing CH4 at different temperatures for 5 min. For film growth, the Cu foil (area: 2 cm × 2 cm) was used at the microwave power of 1200 W. The detailed rest process conditions and parameters were listed in Cu foils (30 cm × 150 cm × 0.00254 cm) were obtained from Alfa Aesar . Ag paste  and pipe sealant  were purchased for electrochemical measurements. A multi-sources electron cyclotron resonance chemical vapor deposition system , Hsinchu, Taiwan) was used for growing graphene films through flowing CFor material analyses, a field-emission scanning electron microscope  and an X-ray diffractometer  were adopted. In addition, the graphene films on the Cu substrate were checked by a micro-Raman spectrometer . Potentiodynamic polarization measurements were carried out by using a CHI potentiostat system  in a typical three-electrode setup with an Ag/AgCl reference electrode and a Pt wire counter electrode. For preparing the working electrode, the Cu wire was mounted on the backside of Cu substrates through silver paste, while the backside and surrounding sides were protected by pipe sealant. The drying conditions of the silver paste and pipe sealant are 80 °C for 3.5 h and 40 °C for 30 min, respectively. The electrolyte is 3.5 wt.% NaCl solution, and the sweeping potential range is between −0.8 and 0.6 V at the scan rate of 10 mV/s. All of the solutions were prepared with deionized water with a resistivity of more than 18 megohm/cm. We used CorrView software (version 2.6) to do data fitting in the Tafel plot in order to get the corrosion potential.2H2 flow, the surface texture seems not that clear, with few relatively large spots on gray surface. 4 flow, respectively. In the beginning, some rectangular stereostructures appear randomly at 350 °C, and gradually become larger through increasing temperatures, finally form the graphene nanowalls at 500 °C. In the later stages, even rose-like or flower-like structures start to stack and form big spheres under the influence of growth conditions. In general, graphene films grow for the most part in width, and not in height. While the film is thin, this coating appears flat. With a further increase in the amount of material in the film, it gets pinched and forms a texture. 2H2 flow. These large grain and good crystallinity would be attributed to the high growth temperature and better horizontal coverage. On the other hand, because the carbon ratio of C2H2 is higher than CH4, the C2H2 precursor could get more C2 radicals, which might be helpful for film deposition.−1 (D band), 1590 cm−1 (G band), 1620 cm−1 (D′ band), 2690 cm−1 (2D band), and 2950 cm−1 (D + G band). These peaks concur the existence of graphene films and nanowalls on Cu foil substrates that are observed in the above SEM and XRD analyses. First, the small 2D peaks imply multilayer graphene structure for all of the cases instead of a few-layer or even a single-layer structure. For the 2H2 flow, the growth time is the parameter that we controlled at the same temperature of 600 °C. The decreasing ID/IG ratios are 1.70, 1.60, and 1.47 as a result of the better crystallinity for long growth times. For the 4 flow, the growth temperatures are 350 °C, 400 °C, 450 °C, and 500 °C with the same time of 5 min. In D/IG ratios are 1.69, 0.87, 0.84 and 0.72 for the increasing growth temperatures. Here, the high G-band intensity at higher growth temperatures is due to the much superior sp2 crystallization of graphene nanostructures compared with that of 300 °C. Especially, there is a rapid transition from 350 °C to 400 °C, and the finally forming non-flat and porous graphene nanowalls at 500 °C.2H2, 5 min)-coated, and CVD graphene -coated Cu foils. The experiments were carried out ranging from −0.8 V to 0.6 V v.s. Ag/AgCl at the scan rate of 10 mV/s at room temperature. Originally, the corrosion potential for pure Cu foil is around −0.267 V. After adding good CVD graphene coatings, the corrosion potentials are shifted toward −0.2 V with several tens mV with relatively low corrosion activities. It depicts that the suitable CVD graphene coatings are able to improve the anticorrosion property under the appropriate growth conditions. corr) and corrosion potential (Ecorr) for the first scan. In addition, the scan numbers were raised 30 times in order to investigate the long-term stability. The corrosion current densities (jcorr) and corrosion potentials (Ecorr) for CVD graphene (C2H2)-coated Cu foils at different growth times and pure Cu foil were displayed in the left-hand side of corr of all of the CVD graphene (C2H2)-coated ones are lower than that of pure Cu foil. It is worthwhile to mention that the Ecorr for graphene  is closer to the positive side with lower jcorr, although it is relatively higher than those with shorter growth times. The right-hand side of corr and Ecorr for CVD graphene (CH4)-coated Cu foils at different growth temperatures and pure Cu foil, respectively. Despite the curve for 500 °C, all of the remaining jcorr are lower than that of pure Cu foil. However, the Ecorr for graphene -coated Cu foils are closed to the more negative potentials. This indicates that the appearance of vertical structures of graphene nanowalls might be fatal to the protection as a consequence of the fast diffusion channel against the horizontal surface. Among all of the growth conditions, the champion film is CVD graphene , and its jcorr and Ecorr are 1.16 × 10−5 A/cm2 and −0.219 V. Therefore, it is claimed that the protection graphene nanostructure can be successfully achieved at a relatively low temperature of 400 °C for 5 min in our system. 4, 500 °C)-coated Cu foils. Hence, basically the porous and high graphene nanowalls do not help the protection against corrosion in terms of morphology. In contrast, the surface with a low CVD growth temperature of 350 °C seems better. 2H2, 5 min) coating. This flatness is correlated with the relatively low jcorr and Ecorr on the more positive potential side. It indicates that the intermediate temperature CVD graphene with C2H2 as the carbon source can form the complete protection layer in a short growth time of five minutes, even suffering from multiple scans. Still, the corrosion will cause the surface oxidation confirmed by comparing the energy-dispersive x-ray spectroscopy (EDS) spectra  and graphene  coatings. However, after 10 scans, the Ecorr of pure Cu will shift to around −0.16 V, which could be a consequence of forming a passivation layer and thus be higher than those of all of the graphene-coated ones. spectra . Similarcorr and Ecorr closed to the more positive side of graphene-coated Cu can be achieved simultaneously for selected and optimal cases. More importantly, the lowest jcorr of graphene -coated Cu is one order of magnitude lower than that of the pure Cu. Meanwhile, its Ecorr of −0.219 V is 52 mV more positive than that of unmodified Cu. In contrast, the cases located outside the appropriate process window may suffer from non-uniform coverage, poor crystallinity, or porous nanowall structures, which also provide vertical diffusion pathway into the substrates. Our study suggests that the appropriate process and associated structures are essential to the development of graphene-based anticorrosion coatings through LTCVD.In conclusion, we have successfully demonstrated LTCVD graphene nanostructures with promising anticorrosion characteristics. The low j


This is achieved by engineering the asymmetric electronic environment of the generated hot carriers on chemical vapor deposition grown large area nanopatterned monolayer graphene, which leads to a temperature gradient of 4.7 K across the device terminals for an incident power of 155 nW, thereby enhancing the photo-thermoelectric voltage by manifold compared to previous reports. The results presented outline a strategy for uncooled, tunable, and multispectral infrared detection.Due to the low photon energy, detection of infrared photons is challenging at room temperature. Thermoelectric effect offers an alternative mechanism bypassing material bandgap restriction. In this article, we demonstrate an asymmetric plasmon-induced hot-carrier Seebeck photodetection scheme at room temperature that exhibits a remarkable responsivity of 2900 VW Designing electronically asymmetric environment across monolayer graphene enhances the photo-thermoelectric effect and enables efficient infrared photodetection. Here, the authors report a photodetector based on CVD grown nano-patterned graphene with high responsivity of ~2900 V/W within 8–12 µm wavelength regime by Dirac plasmon-assisted hot carrier generation at room-temperature. It is known that upon illumination, the intrinsic carrier temperature of graphene increases by means of hot carrier generation that manifests as a Seebeck voltage (ΔV)7. Despite the proof-of-concept demonstrations, so far, due to the modest Seebeck coefficient of graphene ~100 µVK−1, it has not been possible to harness this effect as an effective approach that can rival contemporary technologies4.Two-dimensional (2D) materials, especially graphene has shown a lot of potential as a candidate material for infrared detection. An ultrafast (~ps) infrared detection process is to excite hot-carriers in absence of carrier-phonon scatteringT) of the charge carriers can be engineered with minimal effect on the lattice temperature in order to enhance Seebeck voltage generation for highly sensitive, spectrally tunable, fast infrared detection in the LWIR band at room temperature. The carrier temperature of graphene at a specific spectral range can be manipulated by the plasmonic excitation of Dirac fermions which can be controlled by electrostatic tuning of the Fermi level. In our recent work, spectrally tunable infrared absorption of ~60% in the LWIR was demonstrated for nanopatterned monolayer graphene coupled to an optical cavity8. At resonance, due to the strong confinement of electric field at the discrete nanoresonator edges, the electronic system of graphene heats up by means of boundary-assisted intraband Landau damping to generate hot-carriers9. Although the hot-carrier generation develops a change in conductance of graphene, the resultant photoresponse arising from ΔT is limited by the theoretical Seebeck coefficient of graphene. The key to an efficient photo-thermoelectric device is the generation of high temperature gradient which we demonstrate in our asymmetric plasmon-induced hot-carrier Seebeck photodetector. In the asymmetric device  of 1.1 × 109 Jones along with a fast response of ~100 ns.The motivation of the present work is to identify avenues on how the temperature gradient , but also maintains a comparable high detectivity of ~109 Jones.The two important parameters that determine a detector’s performance are (a) detectivity and (b) response time. The uncooled detector devices or bolometers working at room temperature are very slow with the response time of 12 arising from localized Dirac plasmon excitations associated with intraband transitions. As a result, a gradient is introduced into the charge carrier density of the graphene channel across the source-drain electrodes. This creates a temperature difference across the graphene channel that as we discuss later in details plays the key role in infrared detection mechanism. Based on the applied source-drain voltage (VSD), henceforth called bias voltage, and the gate voltage (VG), multiple electronic processes work in tandem or against each other that influence the detector response. The graphene channel width is chosen to be 10 µm which is comparable to the diffusion length of the charge carriers3. However, in order to enhance carrier collection, the graphene channel width is elongated to maintain an effective active area of 2000 µm2 as shown in Fig. 8, of period P = 600 nm and hole diameter D = 400 nm was chosen in the detector fabrication  detector design and the fundamental electronic processes involved are schematically shown in Fig. 14 that arises due to the residual impurities on the graphene surface. In addition, the Al2O3 gate dielectric is known to enhance p-type doping in graphene16  of different graphene devices as a function of Fermi energy is shown in Fig. 18 on graphene doped away from the charge neutrality point. It can also be noticed that with decrease in temperature, S diminishes  of the fabricated cavity-coupled graphene nanohole array absorber were measured using a Microscope-coupled Fourier transform infrared spectrometer (FTIR) . The light reflection from the absorber stack without patterned graphene, i.e. Si++ (100 μm)/Al2O3 (15 nm)/SU-8 (1.3 μm)/Al2O3 (50 nm)/gold (200 nm) was taken as the reference and the light absorption spectra was calculated as A = 1-R.Upon illumination with infrared light the electronic properties across the half-patterned graphene channel exhibit contrasting electronic behavior. When light is incident on the unpatterned section of the graphene channel coupled to an optical cavity, the light absorption is a modest ~3%, however in the patterned section, owing to Dirac LSP excitations, ~60% light is absorbed by way of strong confinement of electric field near the nanohole edges  in our case occur at energies lower than the optical phonon energy of graphene (200 meV)20 and far from that of the substrate (~105 meV)21, plasmon damping through the emission of optical phonon has negligible effect23. Therefore, the plausible pathway for the plasmon damping is by generation of hot carriers via edge scattering-assisted Landau damping24 and resistive loss due to electron-impurity and electron-acoustic phonon scatterings25.Once excited, the LSPs dissipate energy through various damping pathways like phonon emissionS1)17. Second, the half-patterned graphene channel can be treated as a region consisting of two series connected thermoelectric materials with different Seebeck coefficients  and patterned (S2) sections which drives the system further into thermoelectric imbalance. The different Seebeck coefficients of the two sides induce a directional photo-thermoelectric current accompanied by the bias current. The resulting potential gradient can be expressed as a function of the channel width, XL − XRXL and XR are the positions of the left and right contacts, respectively and Tcr is the local carrier temperature. Finally, the different carrier mobilities of the patterned and unpatterned sections of the channel lead to differential Joule heating during carrier transport, which further enhances the thermal gradient in the system by increasing the temperature-dependent Seebeck coefficients in the patterned and unpatterned regions.Multiple factors now contribute to the asymmetric environment within the graphene channel that determine the effective thermoelectric response of this complex system when irradiated with infrared light. First, there exists the photo-thermoelectric effect originating from the intrinsic Seebeck coefficient of graphene  where the patterned section has elevated temperature as can be observed in Fig. T across the channel yielded a photo-thermoelectric voltage VPTE of ~0.44 mV. During the simulation, the Fermi level of graphene was maintained at −0.85 eV, and a bias voltage VSD = 0.9 V was applied , a measurement strategy was employed that eliminated bolometric effects from the signal  Fig.  was doneT and VPTE obtained across the graphene channel. It is to be stressed that generation of such a high position-dependent ΔT at room temperature exceeds previously reported values by an order of magnitude4. A series of FEM simulations were performed to investigate the role of Fermi energy and bias voltage on the photo-thermoelectric effect  ΔT) which monotonically decreases with EF. Considering these competing effects, there is a trade-off where above a threshold Fermi energy (~−0.8 eV), the effect of enhanced ΔT on VPTE is negatively impacted by the lower Seebeck coefficient that results in a decrease in VPTE. Therefore, there is an optimum range of gate (VG) and bias voltage (VSD) for the best performance of the detector associated with maximum VPTE at a desired spectral wavelength which can be observed from Fig. Figure ect Fig. . It can D.C = VPTEPinc−1) for different bias voltages (VSD) and substrate temperatures (TS), where Pinc is the band limited incident IR power. The highest responsivity measured in the present work is 2.9 × 103 VW−1  curves were recorded at regular temperature intervals within the range of 80–320 K. As the temperature is decreased, the responsivity reduces as shown in Fig. 27. In the proposed device, the absorption of light is almost independent of temperature, in other words, the hot-carrier generation and subsequent development of ΔT remains unaffected by the temperature of the sample. However, the Seebeck coefficient of graphene decreases as the temperature is lowered  and the responsivity (NEP = Sn ℛ−1) of the detector for different substrate temperatures  is more than one order of magnitude lower than thermal photodetectors26 which establishes its superiority as an uncooled, room-temperature mid-IR photodetector. The specific detectivity (D*) is derived from the NEP and the detector active area (A) as D* at EF = −0.8 eV and VSD = 0.9 V is measured to be 1.1 × 109 Jones  is calculated by measuring the noise spectral density  assists the drift of the hot-carriers (holes) generated on the patterned section towards the drain (ground), whereas in the negative bias condition (source voltage: 0 V to −0.5 V), the flow of holes towards the drain (ground) is inhibited leading to diminished responsivity, as shown in Fig. To further elucidate the role of LSPs in hot carrier generation and how the proposed asymmetric design excels in creating a high responsivity detector, we compare the A.C photoresponse of three detectors that were fabricated with (i) half-patterned, (ii) full-patterned and (iii) unpatterned graphene channels, respectively. We postulate that for the unpatterned and full-patterned detectors, the photoresponse primarily arises from the bolometric effect. Furthermore, owing to the symmetric design of the unpatterned and full-patterned devices, it is expected that the polarity of bias voltage should not affect the photoresponse. In contrast, due to the asymmetric architecture of the half-patterned detector, a bias voltage in the direction of Δ6. Since light modulation by mechanical chopping was not a feasible technique for high-speed measurements, we adopted an alternate method to study the A.C photoresponse by electronic modulation of the source-drain bias  and is limited by the capacitance of the external circuitry36.The time response of the half-patterned detector was measured to quantify the operational bandwidth. Due to the ultrafast plasmonic excitation and charge transport in graphene, a fast photoresponse is expected37 was used to image a Pegasus and UCF logo printed on a substrate. The tunable response of the detector is evident from greyscale images shown in Fig. The proposed asymmetric graphene device is a multispectral gate tunable infrared detector. This opens up the possibility for making an uncooled multi-pixel infrared camera with performance comparable to the commercial cooled cameras. To demonstrate the real performance of the photodetector, a single-pixel imaging method  which is critical to the remarkable photoresponse. We identify various processes contributing to the photoresponse and present conclusive evidence that the fast (τres ~ 100 ns), high responsivity (2900 VW−1) and high D* ~ 1.1 × 109 Jones can be attributed to the photo-thermoelectric effect. The proposed frequency-tunable graphene detectors not only offer spectroscopic detection but also pave the path towards dynamic multispectral imaging in the IR domain, which is lacking in the present IR imaging technologies.In conclusion, this work demonstrates outstanding room temperature photodetection using 2D monolayer graphene that is possible by the interplay between multiple physical phenomena: (i) tunable enhanced infrared absorption induced by localized Dirac plasmonic excitations, (ii) graphene mobility engineering, and (iii) excitation of asymmetric hot carriers and consequent electronic photo-thermoelectric effect. The asymmetric graphene channel design facilitates generation of high-temperature gradient (Δ++ (100 μm)/Al2O3 (8 nm) substrate. The source and drain contacts were fabricated by UV-lithography following by Ti/Au (3 nm/60 nm) deposition. The electron beam lithography (EBL) following by oxygen-plasma etching techniques was used to nanopattern the half side of transferred graphene with period P = 600 nm and diameter D = 400 nm.The large-scale monolayer graphene grown by chemical vapor deposition (CVD) method on copper foil was transferred on the SiVSD) was applied across the source-drain (SD) terminals and the resulting current I1 = I + ITE and I2 = –I + ITE were measured for applied voltage ± VSD, where I is the current generated by the bias voltage and ITE is the thermoelectric current (ITE = 0.5 × (I1 + I2)). This thermoelectric current was measured in dark (ITE-D) and in the presence of mid-IR light (ITE-L). Any contribution due to the photoconductive effect is expected to be independent of the polarity of applied bias voltage, which was thereby eliminated in the ITE-L calculation. Therefore, the photo-thermoelectric current and voltage can be calculated as IPTE = ITE-L − ITE-D and, VPTE = RGIPTE respectively (Supplementary Methods). The D.C responsivity (ℛD.C = VPTEPinc−1) was calculated by using the measured incident light power (Pinc), the gate-tunable graphene resistance (RG)  and the responsivity R = VPTEPinc−1. The built-in modules Electric Currents and Heat Transfer in Solids coupled with the multiphysics module Thermoelectric Effect were applied to predict the behavior of the detector.The COMSOL Multiphysics 5.3a software was used to simulate the performance of the detector. The overall goal of simulations was to find the time-dependent solution for the bias-dependent photo-thermoelectric current, which was further used to calculate the photo-thermoelectric voltage  and 20 µm long. The channel width of detector was 10 µm wide and 20 µm long, where half of the width of the graphene sheet was patterned, and the other half kept unpatterned. The gold terminals were 5 µm by 20 µm, and the thicknesses of graphene, gold contacts, aluminum oxide, and silicon were 0.5 nm, 50 nm, 8 nm, and 3 µm, respectively. Gold, Silicon, and Aluminum oxide materials were directly imported from COMSOL material library, while the experimentally measured parameters were used for graphene. The electrical conductivity and Seebeck coefficient were gate-dependent for graphene, measured experimentally for the patterned and unpatterned graphene, separately. The temperature-independent electrical conductivity was used for all materials to neglect the bolometric effects.V0 = 0 V. In order to add the contact resistance, the electrical contacts were introduced between gold and graphene. The heat flux was applied in the form of rectangular pulse of period 4 ms, which means for the first two milliseconds the heat flux was zero, corresponding to the dark state in the experiment. For the next two milliseconds, nonzero heat flux was applied on the patterned side of graphene using laser heating. A Gaussian beam with the spot size Rspot = 2 mm and the incident power Pinc = 153 nW was used. The absorbed heat flux depended on the absorption at different Fermi levels. The gate dependence of the light absorption was calculated by using the Lumerical FDTD software, which ranged from A = 34% at EF = −0.55 eV to A = 60% at EF = −1.0 eV for the patterned graphene (Supplementary Methods).The bias voltage was applied across the gold terminals; one side was set to ground, and the other at high potential. Except gold terminals and graphene, everything was considered electrically insulated. The current conservation boundary condition was applied for the whole geometry, and the initial values were set to T0 = 293.15 K, and the boundary condition open boundary was used across all the sides of the detector, except top and bottom surfaces which means the heat can flow inside or outside across the cross-sectional boundary depending on the ambient temperature. Thermal contacts were used between graphene, aluminum oxide, and silicon to control heat transfer in the vertical direction. The free tetrahedral mesh for gold and the free triangular mesh at the graphene surface were used, which were swept in vertical direction for the remaining geometry.The bottom side of the detector was kept at fixed temperature using the boundary condition in the software. The initial value of the temperature was set to −5 was used to measure the time-dependent thermoelectric voltage across the terminal for different Fermi energies. The dark and light thermoelectric voltages VTE,D and VTE,L were measured in absence and presence of the incident heat flux, respectively. The photo-thermoelectric voltage VPTE was then calculated by subtracting the dark from the light voltage, i.e. VPTE = VTE, L − VTE, D.The time-dependent solver with very low relative tolerance of 10Supplementary InformationDescription of Additional Supplementary FilesSupplementary Movie 1Supplementary Movie 2


Drosophila model mimicking key features of the TDP-43 autoregulatory feedback loop, we identified CG42724 as a genetic modulator of TDP-43 production in vivo. We found that CG42724 protein influences qualitatively and quantitatively the TDP-43 mRNA transcript pattern. CG42724 overexpression promotes the production of transcripts that can be efficiently released into the cytoplasm for protein translation. Importantly, we showed that TCERG1, the human homolog of the Drosophila CG42724 protein, also caused an increase of TDP-43 protein steady-state levels in mammalian cells. Therefore, our data suggest the possibility that targeting TCERG1 could be therapeutic in TDP-43 proteinopathies.TAR DNA-binding protein-43 (TDP-43) is a ubiquitously expressed DNA-/RNA-binding protein that has been linked to numerous aspects of the mRNA life cycle. Similar to many RNA-binding proteins, TDP-43 expression is tightly regulated through an autoregulatory negative feedback loop. Cell function and survival depend on the strict control of TDP-43 protein levels. TDP-43 has been identified as the major constituent of ubiquitin-positive inclusions in patients with Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Lobar Degeneration (FTLD). Several observations argue for a pathogenic role of elevated TDP-43 levels in these disorders. Modulation of the cycle of TDP-43 production might therefore provide a new therapeutic strategy. Using a The online version of this article (10.1186/s40478-018-0639-5) contains supplementary material, which is available to authorized users. TARDBP/TDP-43 gene in patients with FTLD/ALS -insertion line (UY5237) that significantly increased TDP-43 production , indicating that the human TDP-43 antibody did not recognize Drosophila proteins, including the Drosophila homolog TBPH. Normalization of the amount of TDP-43 proteins using the stain-free technology [P(UY)5237 element caused a drastic increase (~ 18-fold) of TDP-43 protein steady-state levels (p = 0.0001). In contrast, the P(UY)5237 element did not modify significantly FUS (p = 0.524)  . This assay is based on simultaneous PCR amplification of short fluorescent fragments and allows the comparative quantitative analysis of mRNA. We compared the levels of CG42724 transcripts in GMR-Gal4 > + and GMR-Gal4 > UY5237 Drosophila heads. We indeed observed a significant upregulation of the CG42724 transcripts  in GMR-Gal4 > UY5237 flies, compared to control flies    5237 element displayed no obvious external phenotype, compared to control flies  species  to prevent dissociation of putative HMW forms. Only a faint signal was detected in the insoluble urea fraction, indicating that TDP-43 species were mainly recovered as soluble forms in Drosophila. As expected, the expression of CG42724 increased the TDP-43 protein steady-state levels. TDP-43 proteins were detected as either full-length monomeric forms or HMW species, with TDP-43 proteins being the most prone to form aggregates in the presence of the UY5237 transgene. When samples were analysed in the presence of the reducing agent (+DTT), we observed a decrease of the HMW forms and, concomitantly, an increase of TDP-43 monomeric species, indicating that these complexes were indeed DTT-sensitive. Altogether, these data showed that CG42724-mediated increased expression of TDP-43 results in the appearance of TDP-43 HMW species and is associated with cellular toxicity in Drosophila retina.Interestingly, we also observed that TDPBR region contributes to the CG42724-mediated regulation of TDP-43 protein production using the UAS-TDP-43 construct (no TDPBR region) previously described in [UAS-TDP-43_TDPBR construct , overexpression of CG42724 caused only a 2-fold increase in TDP-43 protein steady-state levels (p = 0.0002)  gene .We first evaluated whether changes in CG42724 expression could affect the nucleocytoplasmic export of TDP-43 mRNAs. We performed cell fractionation   experiments. PCR products were amplified using a human TDP-43-specific primer  and a smaller one of ~ 800 bp (short isoform). The sequencing of these two major bands revealed that they corresponded to alternative transcripts of different sizes resulting from differential usage of polyadenylation sites. Note that we failed to characterize the intermediate band by sequencing , with a concomitant decrease of the long isoform   isoforms ratios of TDP-43 mRNA levels, whatever the experiments were performed using total mRNA or mRNA extracted from the cytoplasmic compartment. Quantification of the relative abundance of splice isoforms showed that the S/L ratio in the cytoplasmic compartment was significantly higher compared to that quantified in total mRNA   or not (GFP::TDP-43) to the TDPBR region, and compared their expression in HEK293 cells. As expected, introduction of the TDPBR sequence into the reporter construct resulted in a significant ~ 50% decrease (p = 0.0053) in the GFP::TDP-43 protein expression levels  . Together these results showed that the human TCERG1 protein can regulate TDP-43 protein production in mammalian cells, and that TCERG1-mediated regulation of TDP-43 production is also predominantly mediated by the TDPBR region.To validate these findings identified in els Fig. a, b. Co-78) Fig. a, c. In TDPBR [TDPBR sensor region includes low-affinity binding sites for TDP-43 and the polyadenylation site pA1, the most efficient polyadenylation site of the TDP-43 gene. In steady-state conditions, most TDP-43 production within cells comes from the transcript that uses the polyadenylation site pA1. Increase in TDP-43 nuclear levels results in an increased occupancy of the TDPBR that in turn suppresses usage of the pA1 site, resulting in elongation of transcripts beyond pA1. The elongated transcripts present an acceptor site for normally silent intron that contains the TDPBR region and the pA1 sequence. The exclusion of this intron forces the system to use suboptimal polyadenylation sites. The mRNAs using these alternative polyadenylation sites show an increased incidence of alternative splicing, and are partially retained in the nucleus and/or degraded.TDP-43 is a critical RNA-binding factor that has been shown to play a central role in RNA metabolism. Cell functions and survival depend on the strict control of TDP-43 protein levels. TDP-43 expression is tightly regulated through an autoregulatory negative feedback loop mediated by the binding of TDP-43 protein in a specific region of its mRNA 3’UTR called TDPBR , 42, 54.Drosophila model previously developed and characterized by our group [Drosophila transgenic model is based on the expression of the human TDP-43 cDNA under the control of the TDPBR sensor region. This TDP-43_TDPBR Drosophila model recapitulates key features of the self-regulatory process of the steady-state levels of TDP-43 proteins described previously in mammalian and cellular models, namely alternative splicing events, differential usage of polyadenylation sites, nuclear retention of the transcripts, and a decrease in steady-state mRNA levels.To identify genetic modulators of TDP-43 production in vivo, we used an autoregulatory TDP-43 ur group . This DrCG42724 Drosophila gene as a genetic modulator of TDP-43 production in vivo. We showed that CG42724 overexpression caused a drastic increase of TDP-43 protein steady-state levels, whereas CG42724 down-regulation resulted in a decrease of TDP-43 accumulation. The study of the underlying molecular mechanisms allowed us to highlight that the CG42724 protein influences both qualitatively and quantitatively the TDP-43_TDPBR mRNA transcripts pattern. We found that CG42724 overexpression promotes the inclusion of the TDPBR sensor region as well as the production of transcripts ending at the pA1 polyadenylation, isoforms that can be efficiently released into the cytoplasm for protein translation. Of course, additional mechanisms could also be involved. Notably, we observed that TCERG1 expression resulted in a slight increase of TDP-43 mRNA steady-state level, which could also contribute to the increase in TDP-43 protein accumulation. Importantly, this effect predominantly depends on the presence of the TDPBR region.In this study, we report the identification of the Drosophila CG42724 protein. The protein is composed of 1123 residues and contains three WW domains at its N-terminus followed by six FF domains at its C-terminus. The CG42724 protein was detected in affinity-purified Drosophila spliceosome [To date, very little is known about the iceosome . On the iceosome . InteresCG42724 gene encodes a homolog of the human TCERG1 (Transcription elongation regulator 1) gene. The CG42724 and TCERG1 proteins share 35% sequence identity and 48% sequence similarity. The highest homology is observed in the WW and FF domains. Importantly, our data suggest a significant degree of functional conservation between flies and mammals regarding the regulation of TDP-43 production. Indeed, we showed that similarly to CG42724, human TCERG1 overexpression also caused an increase of TDP-43 protein steady-state levels in mammalian cells.The TCERG1 knockdown [Bclx gene through the modulation the RNAPII transcription rate [TCERG1, previously named CA150, is a highly conserved human nuclear protein, localized at the interface of nuclear speckles and presumed nearby transcription sites , 60. TCEnockdown , 53. Basion rate .Interestingly, TCERG1 and TDP-43 proteins have been linked to common aspects of mRNA life cycle, namely transcription, pre-mRNA alternative splicing and polyadenylation site selection. Uncovering the mechanism of action of TCERG1 on TDP-43 production is complicated by their multifaceted functions, but also by the fact that RNAPII transcription, alternative splicing and alternative polyadenylation can be influenced reciprocally. All these processes are tightly coupled and coordinated.TDPBR region. We demonstrated previously that the negative regulatory activity of the TDPBR region is specifically dependent on TDP-43 expression [TDPBR region, possibly by competition through binding the same mRNA site. Indeed, even if TCERG1 has not been described as an RNA-binding protein, it has been shown that the protein associates in vitro with the Bcl-x pre-mRNA [We showed in this study that these processes of regulation predominantly depend on the presence of the pression , suggestpre-mRNA . Alternapre-mRNA , 63, 75.As a component of the splicing machinery, TCERG1 could also modulate the spliceosome assembly and activity. Consistent with this possibility, it has been shown that spliceosome assembly across the 3’UTR region induced by TDP-43 is a key event in the reduction of the amount of TDP-43 . The 3’UTDPBR sequence to the downstream region [TDPBR region could interfere with the recognition of pA1, forcing the use of suboptimal polyadenylation sites. As mentioned above, TCERG1 modulates the rate of RNAPII transcription by increasing its elongation rate [Otherwise, it has been shown that TDP-43 overexpression causes a rise in RNAPII density from the m region . Such a m region  and the m region , 40. Thuion rate . Therefoion rate . Thus, aTranscriptomic studies showed that TCERG1 is widely and highly expressed in the brain . Interestingly, TCERG1 has already been implicated in the pathogenesis of the neurodegenerative disorder Huntington’s disease (HD). TCERG1 interacts with the huntingtin (HTT) protein and has been associated with the morphological deposits related to the disease . TCERG1 Drosophila model that recapitulates key features of the TDP-43 auto-regulatory feedback loop, we have identified TCERG1 as a modulator of TDP-43 production in vivo. Further studies will be necessary to unravel the exact mechanisms through which TCERG1 modulates TDP-43 production. Nevertheless, regardless of underlying mechanisms, our data suggest the possibility that targeting TCERG1 could be therapeutic in TDP-43 proteinopathies.To conclude, using a Additional file 1:Figure S1. Schematic representation of the organization of the human TDP-43 gene. (TIF 282 kb)Additional file 2:The table lists the detailed genotypes of the flies used in this study. (DOC 64 kb)Additional file 3:The table lists the primers used in this study. (TIF 573 kb)Additional file 4:Figure S2. Quantification of CG42724 steady-state mRNA levels by RT-QMPSF. (A) Schematic representation of the CG42724 transcription unit, the relative location of RNAi target sites (green boxes) and the RT-QMPSF amplicon (red box). (B) Expression analyses of CG42724 mRNA transcript by RT-QMPSF. The single-stranded cDNA was PCR-amplified using one pair of primers spanning CG42724, yielding a 173 bp product, and a pair of primers spanning the reference gene Cyp1 (162 bp). The diagrams shown were obtained from GMR > + (control), GMR > UY5237 flies. The y-axis displays fluorescence in arbitrary units, and the x-axis indicates the size in bp. The electropherogram of the GMR > + (blue) and GMR > UY5237 (green) flies were superimposed by adjusting the peaks obtained for the control amplicon to the same level. (TIF 456 kb)Additional file 5:Figure S3. Light micrographs of new-born Drosophila adult eyes. Compared to control flies , expression of CG42724  or TDP-43_TDPBR  alone triggered no structural defects. Similarly, flies co-expressing CG42724 and TDP-43_TDPBR have no external phenotype. (TIF 25334 kb)Additional file 6:Figure S4. Homology TCERG1 and CG42724. Alignment of the human TCERG1 and Drosophila CG42724 proteins. TCERG1 and CG42724 share 35% sequence identity and 48% sequence similarity. The highest homology is observed in the WW domain (blue) and the FF domain (red). Alignment was performed using DRSC Integrative Ortholog Prediction Tool. (TIF 338 kb)Additional file 7:Figure S5. Quantification of TDP-43 steady-state mRNA levels by RT-QMPSF. (A) Schematic representation of the TDP-43 transcription unit and the relative location of the RT-QMPSF amplicons. (B) Expression analyses of TDP-43 mRNA transcripts by RT-QMPSF. This assay is based on simultaneous PCR amplification of short fluorescent fragments in a single tube. The single-stranded cDNA was PCR-amplified using: TDP-43F1/R1 yielding a 115 bp product, TDP-43F2/R2 that yielded fragments of 132 bp and CG42724 that produced an amplicon of 173 bp  and Cyp1 (162 bp) cDNAs were amplified as internal references. The number of cycles of amplification was determined by testing a range of cycle numbers in order to remain in the linear phase of the PCR. Fluorescent amplicons were separated on a genetic analyzer and the resulting fluorescent profiles were analyzed. The diagrams shown were obtained from GMR > + , GMR > TDP-43_TDPBR (red) or GMR > TDP-43_TDPBR, UY5237 (green) flies. The y-axis displays fluorescence in arbitrary units, and the x-axis indicates the size in bp. The electropherograms were superimposed by adjusting the peaks obtained for the control amplicons to the same level. (C) TDP-43 amplicons were amplified using a TDP-43-specific primer (F3) and an oligo-dT adapter primer (AUAP). The diagrams shown were obtained from GMR > + , GMR > TDP-43_TDPBR (red) or GMR > TDP-43_TDPBR, UY5237 (green) flies. Cyp1 cDNAs was amplified as internal reference. The electropherograms were superimposed by adjusting the peaks obtained for the control amplicons to the same level. Note that the “mis-alignement » of the longest pics is due to the imprecise sizing of the fragment > 1 kb. (TIF 1151 kb)Additional file 8:Figure S6.. Purity of subcellular fractions. Cytoplasmic/nuclear fractionation was performed on GMR > + (control), GMR-Gal4 > UAS-TDP-43_TDPBR or GMR-Gal4 > UAS-TDP-43_TDPBR, UY5237 transgenic flies. Nuclear (N) and cytoplasmic (C) fractions were qualified by performing Western blot experiments. Results shown are representative of 3 independent biological replicates. β-tubulin was used as a cytosolic marker, while histone H3 was used as a nuclear marker. Total protein was used as the loading control by Stain-free technology. (TIF 683 kb)


Whispering gallery mode (WGM) resonators are versatile high sensitivity sensors, but applications regularly suffer from elaborate and expensive manufacturing and read-out. We have realized a simple and inexpensive concept for an all-polymer WGM sensor. Here, we evaluate its performance for relative humidity measurements demonstrating a sensitivity of 47 pm/% RH. Our results show the sensor concepts’ promising potential for use in real-life applications and environments. Monitoring and measuring the relative humidity (RH) is an important factor in many chemical processes and industrial applications, for example in air quality management, food manufacturing or in metal processing and polymer synthesis . There iOptical techniques have the advantage of immunity against electrical and vibrational influences and offer interesting multiplexing capabilities, among others . Opticalpm/% RH) .R. Hence, changing one of these parameters will cause a resonance wavelength shift WGM-based sensors enable very long photon life times or high quality factors, respectively. This makes them ideal sensors for many applications, especially for biological and chemical sensing . Typicalshift Δλ :(1)Δλλ=Δ pm/% RH . The manAs a first step to overcome these issues, we developed an inexpensive, easy to handle, easy to manufacture and completely polymer-based sensor. The general setup of the WGM sensor concept was introduced earlier for the application of wavelength measurement . Using pAs outlined in the Introduction, the sensor concept was developed to rely on a simple scheme and to be easy to manufacture. The design is shown in The plate acts as an optical waveguide due to total internal reflection. Thus, an evanescent field is present at the surface of the plate. In this field, commercially available PMMA spheres  were placed with a random distribution and positions. Two different mean diameters, Germany) . At a paIn order to evaluate the sensor performance, the whole sensor was enclosed in an acrylic box, against environmental influences. To adjust the relative humidity, a Petri dish with a saturated salt solution was positioned inside the box together with the sensor . By usinh shifts .Before the sensor can be used for relative humidity measurements ,16, it nmera see . AfterwaIn each sphere, a variety of different modes is excited, so specific modes cannot be distinguished by the intensity measurements recorded with the sensor sketched in r(λ) ,16,17: for RH measurement showed promising results. For unfixed spheres, we achieved sensitivities of 47 esonator ). RatherEven though the sensor was not able to reliably measure humidity in the fixed sphere configuration, more favorable results may be achieved with an improved fixation layer, e.g., reduced coverage of the sphere surface by the fixation material and/or using a more elastic material. In view of the transfer of the sensor concept to real-life applications, it needs to be mentioned that in the experiments presented here, the temperature was constant over the whole trial period. In a real environment, this will, rather, not be the case. As temperature changes induce diameter changes, as well, the resonance pattern of the spheres will shift accordingly. Consequently, the two effects need to be separated in a humidity measurement. This can be realized in the future by making one part of the sensor array insensitive to humidity, for example by application of a protective layer. With this protected part, it would be possible to measure temperature variations simultaneously with the same sensor array in order to correct the evaluated humidity response for the actual temperature.