The ninhydrin reaction, one of the most important method of detecting amino acids, both technically and historically, has been conventionally used to detect their microgram amounts. When amino acids with a free alpha amino groups are treated with an excess of ninhydrin, they yield a purple colored product.
Update January 19: Amazon has increased the monthly price of Amazon Prime from $10.99 to $12.99 for those who opt for the month-to-month plan. However, the annual price remains untouched at $99 per year, which makes it the better option for avid Amazon shoppers.
In those nine years, meanwhile, Amazon also added Instant Video streaming to Prime and a handful of other perks. At the end of the day, members are only paying $20 more a year or about $1.66 more per month â pocket change. But this is the Internet, so some people were predictably peeved. If you're pondering if Amazing Prime is still right for you, you're not alone.