Amino acid analysis results

[John E. Fox]

In article <reedan-1909951419510001 at ppp8.global1.net>, reedan at globalone.net (Daniela Sciaky) says:
>
>We had a protein expressed in a pET vector with the his tag at the C
>terminus. Amino acid analysis shows that the amount of each amino acid is
>as expected for cysteine. We don't understand what would account for the
>lack of cysteines. Is cysteine particularly labile?
>
>Daniela

Yes Cys is often lost during hydrolysis, the recovery is very
variable.
The best way would be to convert the cys to cysteic acid and 
re-analyse.

John Fox