guy - 16-6-2007 at 14:59
Gelatin contains a fair amount of glycine and proline. Is there a way to separate them?
From wiki:
"The approximate amino acid composition of gelatin is: glycine 21 %, proline 12 %, hydroxyproline 12 %, glutamic acid 10 %, alanine 9 %, arginine 8%,
aspartic acid 6 %, lysine 4 %, serine 4 %, leucine 3 %, valine 2 %, phenylalanine 2 %, threonine 2 %, isoleucine 1 %,hydroxylysine 1 %, methionine and
histidine <1% and tyrosine < 0.5 % "
12AX7 - 16-6-2007 at 16:19
Off hand, it should start with hydrolysis/saponification. Then you might acidify and isolate the free molecules, or acidify double and get the salts.
I get the feeling crystallization would be annoying though... I don't suppose these can be distilled? I'd say chromatography, but that tends to be
insanely tedious...
Tim
not_important - 16-6-2007 at 18:30
I believe acid hydrolysis is more commonly used, except when you're after tryptophan, as alkaline hydrolysis causes more racemization. The alphatic
neutral amino acids are extractable from neutral solution (where they exist as the free amino acids) by butyl alcohol.
I'd start by reading these
http://www.biochemj.org/bj/027/1838/0271838.pdf
http://www.biochemj.org/bj/061/0177/0610177.pdf
http://www.biochemj.org/bj/018/1070/0181070.pdf
or alternatively
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=12...
(has the full process sketched out)
http://www.jbc.org/cgi/reprint/227/2/871.pdf
http://links.jstor.org/sici?sici=0950-1193(19250501)98%3A687%3C58%3ATIOAPO%3E2.0.CO%3B2-M
[Edited on 17-6-2007 by not_important]
guy - 16-6-2007 at 18:42
Ah the copper picrate route seems pretty good. A solution of picrate salt is safe right?
not_important - 16-6-2007 at 18:51
The barium carbamate sound good, too, especially for a preliminary separation.
12AX7 - 16-6-2007 at 20:41
Incidentially, according to the pKa's, most (if not all) amino acids should have the carboxylic proton hanging out with the amine, right? Is that in
solution, or solid as well? And if so, why isn't it ever drawn as such?
Tim
not_important - 16-6-2007 at 21:55
See here http://www.biologydaily.com/biology/Amino_acid or here http://www.sdsc.edu/pb/edu/pharm207/2/lec2.html or http://www.biocrawler.com/w/images/c/c5/Amino_acids_2.png
While you're correct in regards to amino acids in solution by themselves, consider where they show up. In proteins they're mostly as amides, which
may have free carboxylic and amino groups tied up as salts, but they're not on the same amino acid. And often the free acids in a bottle appear as
their acid salts. For most purposes the overall structure is more important than shwoing the internal salt form, which is usually illustrated in a
generic form.
I'd assume that the ionic form persists in the solid state, but assigning ownership of the hydrogen ion may be more difficult in that case, the
carboxylic acid group of a neighboring molecule could approach an amino group more closely that the amino group's own acid function.