block pep
Conti Amedeo (conti@ch.unito.it)
Tue, 21 Apr 1998 13:46:55 +0200
Dear ABRFers
we have oxidized a 9KD protein containing 8 Cys (4 S-S) and digested with
Asp-N in Tris-HCl pH 8; separation of peptides by RP-HPLC in ACN/TFA was
quite good but all resulted N-terminally blocked except one starting with
Cys-Cys- that gave two cicles blank and then the right expected sequence;
MW of this peptide measured by ESI-MS was consistent with the presence of
one cystine residue.
Do you have any experience on which kind of blocking reaction could happen
to the N-terminal cysteine (cysteic acid)?
Thanks in advance
Amedeo Conti