Patrice Koehl koehl at
Wed Jan 25 04:29:02 EST 1995


	My wife has a 54 amino acid long peptide containing 12 cysteines.
Fully oxydised, the 12 cysteines are involved in 6 disulphide bridges. Though
the peptide contains 4 sites for trypsin, it does not cut it (which is not
too surprising, considering the stability the S-S bridges provide)
After full reduction, and alkylation of all free cysteines with vynil pyridine
(confirmed by MS), trypsin still does not cut the peptide. This is a little bit
more surprising, since the S-S bridge cannot form anymore. One hypothesis could
be that the vynil pyridine help forming a very stable hydrophobic core.
She has tried to add urea in order to unfold the peptide such that accessibility
for trypsin is easier, however it did not help. (Urea inhibits trypsin ?)
Any idea/references on how to "help" trypsin to cut this reduced, alkylated form ?
Thanks in advance for your help


Patrice Koehl
UPR 9003 du CNRS, ESBS			Tel (33) 88 65 53 89
Boulevard Sebastien Brant		Fax (33) 88 65 53 43
Illkirch Graffenstaden, France		e-mail : koehl at

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