We have made peptides by fmoc chemistry that contain a disulfide bond and
an N-terminal cys using the approach you outlined, except that the internal
cysteines (those participating in the disulfide) were Trt protected and the
N-terminal cysteine was Acm protected. Following synthesis and cleavage
(the Trt groups come off), the peptides were air oxidized to form the
disulfide, followed by removal of the Acm protecting group from the
N-terminal cys.
There are a couple of good reviews on cys protecting groups and related
techniques:
Annis et al. Methods in Enzymology 289:198, 1997
Andreu et al.Methods in molecular biology 35:91, 1994
Latif
At 10:15 AM 5/15/98 -0400, you wrote:
>Dear ABRFers,
>
>We have received a request to synthesize a peptide and to make a peptide/KLH
>conjugate
>involving a short (15 residue), cyclic (disulfide bridge) peptide with an
>extra (3rd)
>Cysteine, at the N-terminus, for coupling to KLH. The N-term Cys was just
>added to the
>sequence to help in coupling to the carrier, as the presence of internal Glu
>and a couple of Lys residues (and absence of Tyr) in the sequence would
>probably
>eliminate alternative coupling schemes (coupling through an internal AA not
>an option).
>While it was suggested to us that we could pursue a scheme involving a
synthesis
>of peptide with 2 internal Cys(Acm) and free N-term Cys, coupling of this
>peptide
>to KLH and deblocking/oxidation of the conjugate, we would like to hear
>some opinions
>and suggestions from those of you who dealt with such or similar problems.
>
>Jan Lukszo
>Dr. Jan Lukszo
>Peptide Analysis and Synthesis
>NIH/NIAID/SBS
>Twinbrook II
>12441 Parklawn Drive
>Rockville, MD 20852
>phone:(301)496-3786
>fax:(301)480-2618
>E-Mail: lukszo@fcrfv2.ncifcrf.gov
>
>
----------------------------------------
A. Latif Kazim, Ph.D.
Biopolymer Facility
Science-4
Roswell Park Cancer Institute
Elm & Carlton Sts.
Buffalo, NY 14263
E-mail: kazim@sc3101.med.buffalo.edu
Phone: (716) 845-8923
Fax: (716) 845-7621