AAA problem
Jacek_Mozdzanowski-1@sbphrd.com
Fri, 6 Nov 1998 08:15:55 -0500
In the late 80s Speicher reported (Protein Society Meeting poster?) the use
of DMSO for quantitative determination of cysteine in proteins/peptides.
The method is based on conversion of cysteine to cysteic acid. This
conversion happens during the gas phase hydrolysis with the use of HCl
which contains 4% DMSO. The method works great for cysteines, but affects
many other AA (Met being one of the most affected - oxidation). For that
reason I suspect that for the "regular" amino acid analysis any DMSO
present in the sample has to be completely removed prior to hydrolysis,
This may be a nontrivial task requiring vacumm drying and redrying of the
sample until all the DMSO is removed.
Jacek Mozdzanowski
Bioanalytical Sciences
SmithKline Beecham