livingdeadbeat

Hi,

In a test in our a-level class we had to use gelatine because we didn't have proline. We used acid hydrolysis to break down the polymer, which i believe has glycine and proline in it in roughly equal measures.

Then we added ninhydrin, which produced a yellowish colour. Now i know why proline doesn't produce the purple colour, but what i don't get is how come this works? Because Glycine is a primary amino and its also present in gelatine, so surely when we performed acid hydrolysis the result would be equal (roughly) amounts of proline and glycine. How come the glycine didn't react as well and turn the solution purple?

Thanks for any help.

Ok dude, thanks alot for your help

That's right. One molecule of amino acid has to react with two molecules of ninhydrin to form a highly conjugated chromophore that gives the purple color. Proline cannot de-aminate to allow the second molecule of ninhydrin to react. As you stated, proline's amino group is stuck in a pyrrolidine ring.

Cool thanks. But why does it turn brownish yellow?

Hi everyone,

Another question. In writing about ninhydrin and amino acids that form the subunits of proteins i was wondering what it is that makes proline produce a brownish colour?

From what i've read i think the purple that it usually gives with primary amino groups is due to the ninhydrin reacting with the N in the amine. I'm guessing, cos proline has a ring structure that makes the anime a secondary the N isn't available for it to reaction and form the purple...

Is the above correct and what makes it go brown?

Thanks for any help

As defined by wikipedia, "Anime is commonly defined as animation originating in Japan." Anime generally utilizes a specific style of drawing, which is poked fun at in this bit of internet pop culture: http://www.homestarr...sbemail57.html. Many examples of actual anime cartoons with which to satisfy your curiosity are available online, through a simple google search.

 

An amine refers to some derivative of ammonia and takes into account the entire structure. For example, it would be possible to call the amino acid glycine "carboxymethylamine." You treat the basic structure of the molecule as being an ammonia derivative and list the "added" carboxymethyl substituent.

 

When speaking of a part of a molecule (referred to as a moiety), the term amino is used instead. Using the same example, you could call glycine aminoacetic acid. When using this naming convention, the base structure is the acetic acid skeleton and the amino group is the "added" part.

 

This wikipedia excerpt should clear up up confusion: http://en.wikipedia....aining_nitrogen

 

As for more examples, you could rename trimethylamine as N,N-dimethylaminomethane. Your confusion is largely just a nomenclature issue.

Ah all makes sense now! Thanks alot for taking the time to explain that.

Haha you wouldn't believe how many times i've typo'd amine through this assignment.

Hi forum,

I have ,probably, a very simple question for you lot to answer but i can't find an explanation i understand well enough on the net.

I've just started biology at college and i'm writing about amino acids. Through research in my "Life" book i see that they have two functional groups, one being animo.

Then looking online i see lots of sites talking about amines, which seem to also be NH with the no of H dependant on if they are primary or secondary etc. ?

I'm confused with the difference between amines and amino groups. Could someone please explain this to me.

Thanks alot.