Date: Wed, 22 Jan 1997 09:33:20 -0600
Message-Id: <v01530502af0ce15b0c34@[128.252.197.88]>
To: abrfhyp@cco.caltech.edu
From: rskubish@pharmdec.wustl.edu (Richard Skubish)
Subject: cyclization of dissulfide peptide
>Date: Fri, 06 Dec 1996 08:29:16 -0500
>From: "Tom Haas Ph.D." <haast@cesmtp.ccf.org>
>Old-To: abrf@aecom.yu.edu, fmf+@pitt.edu
>Subject: cyclization of dissulfide peptide -Reply
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>
>Frances,
>
>I've used the Ekathiox resin from sigma (cat# E-6394) to
>cyclize 8 peptides in the last few months. All couplings went
>to > 99% with no dimer formation. I've do the couplings for
>5-6 hrs in: 0.1-0.5% acetic acid, 0-50% ACN or 0.1-0.5%
>acetic acid, 20-50% DMF.
>
>I found that if you purified your peptide using a TFA buffered
>system, you should first neutralize the peptide with NaOH to
>pH 5.5-7 and then add the acetic acid. With the TFA-peptide
>salt, the pH is to low (< 3, even with acetic acid), and you
>only get about 50-80% cyclization.
>
>Good luck.
>
>Tom
>
>
>--------------------------------------------------------
>Frances M Finn <fmf+@pitt.edu>
>Dear All,
>
> We have recently been requested to make and cyclize
>the following peptide PCSAHDHRCLQKY-amide. We have
>tried both the DMSO and the ferricyanide procedures
>described by ABI which have worked well with other
>sequences. With this peptide we get approximately 5%
>cyclization and nothing that we have tried, including acylation
>of the N-terminal amino group before deblocking and cleaving
>has improved the yield. The peptide is being synthesized via
>the F-moc method. Incidentally the crude material shows 99%
>the correct molecular ion for the structure containing
>a completely deblocked peptide with (probably) two cysteines.
>I am not really positive that the two cys's are reduced but
>reducing them before cyclization has no imporved the
>situation.
>
>Does anyone have information that might be of help here?
Richard Skubish
rskubish@pharmdec.wustl.edu
314-362-0283
Washington University Medical School
Box 8103 - PNACL
660 S. Euclid
St. Louis, MO 63110