Re: cysteine deprotection
chris halkides (halkidesc@UNCWIL.EDU)
Thu, 15 Jul 1999 09:24:33 -0400
> A question for the peptide synthesis experts. We have a peptide with
>two cysteine residues, whose side chains are protected with an SBut group.
>The structure of the side chain therefore is CH2-S-S-But. So far we have
>been unsuccessful to selectively remove the SBut groups using two
>procedures that we found in the literature. One uses nBu3P in NMP/water
>(9:1) and the other uses nBu3P in 0.1M ammonium acetate, pH
>7.8/iso-propanol (1:1).
> Can anybody recommend a procedure that will deprotect the cysteines
>without affecting the other protecting groups in the peptide, which was
>synthesized using the Fmoc chemistry? Our ultimate goal is to modify the
>cysteine residues with palmitic acid moieties before we do the Tfa
>deprotection and peptide cleavage from the resin.
>
>Thanks,
>
>Chris (turck@itsa.ucsf.edu)
Hello Chris,
Bodanszky (Principles of Peptide Synthesis, Springer-Verlag) pp.
140-141 talks a little bit about this. He suggests thioglycol or
thioglycolic acid. Whitesides and collaborators (Techniques in protein
Chemistry, Volume 6) compare various dithiol compounds in the rate of
cleavage of disulfides at various pH values. They found that
dithiothreitol is relatively slow at pH 7 and suggest some alternatives
(which I have not tried).
Hope this helps.
Chris
Christopher Halkides
Dept. of Chemistry, UNCW
601 S. College Road
Wilmington, NC 28403-3297
(910) 962-7427