From: Jim Sparrow <jsparrow@athero.med.bcm.tmc.edu>
Subject: RE: PepSyn
Date: Wed, 08 Jan 97 11:41:00 C
To: Recipients of ABRF List <abrf@aecom.yu.edu>
Mark,
We have just published the following procedure modified from that of Hughes
and Leopold in the next issue of Peptide Research. It works as well as HF
to cleave and deprotect peptides in Boc/benzyl chemistry and should work
with your 4-methyl-benzyl-3-thio propionyl group.
TMSBr/TFA Resin Cleavage Procedure
One gram (1g) of peptidyl-resin is placed in a dry 100 ml round bottom
flask protected with a CaSO4 drying tube. The resin is stirred as 11.74 ml
of thioanisole and 0.2 ml of ethanedithiol are added followed by 50 ml of
trifluoroacetic acid. The cleavage mixture is cooled to -10 C with
stirring; 6.6 ml of trimethylsilylbromide is added and the stirring at -10 C
continued for 10 min. The flask is then transfer to a stirrer at room temp.
and connected to a N2 source. Stirring is continued for 2 1/2 hr. at room
temp under N2 and the flask protected from light with Al foil. The reaction
mixture is then filtered into a 250 ml r. b. flask and the flask, filterand
resin washed with 2 X 10 ml of TFA. The excess HBr is removed on the rotary
evaporator under house vacuum to prevent bumping and then the evaporator
transferred to the vacuum pump to remove the TFA at 35 C. The peptide is
precipitated with ether, filtered and washed with ether. The dry powder is
dissolved is water or 6 M GuHCl, 1 M Tris; the peptide can be desalted or
purified directly depending on whether the residual thioanisole/EDT
interfers with the HPLC separation.
For extended HPLC column life, we usually desalt our crude peptides on
BioGel P-2 in 0.1 M ammonium bicarbonate or 5% acetic acid depending on the
pI of the peptide. Jim Sparrow
-------------------------------------------------------
Dr. James T. Sparrow
Dept. of Medicine
Baylor College of Medicine
One Baylor Plaza
Houston, TX 77030
Phone: 713 798-4156
FAX: 713 798-4121
email: jsparrow@bcm.tmc.edu
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From: abrf-request
To: Recipients of ABRF List
Subject: PepSyn
Date: Tuesday, January 07, 1997 1:51PM
Two questions for the peptide chemists in the audience.
1. We wish to make a short peptide (7 residues) that contains an
N-terminal (3-thio)propionic acid residue. It will look like an
N-terminal Cys without its amino group. Using FastMoc chemistry on an ABI
430 synthesizer, I propose to add the thiopropionyl "residue" as its
4-methyl-benzyl-3-thio propionic acid derivative coupled using a normal
amino acid coupling cycle. Assuming this coupling should work, will the
4-methyl-benzyl protecting group be removed by TFA using typical FMOC
deprotection cocktails? This group has been used in t-Boc chemistry to
make peptides containing this group and is apparently readily removed
using HF. Alternatively, we could potentially use Trityl-thio-propionate,
the analog of Trityl-Cys that we currently use for our Cys derivatives
but this would require obtaining Trityl-3-thio-propionic acid.
2. Does anyone know of a source for Fmoc-homoarginine(Pmc)-OH?
(Pmc = pentamethylchroman-6-sulphonyl)
Many thanks in advance and New Year's greetings to all, especially the
"small angel" at the helm of this cyber ship.
\ml
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--
Mark O. Lively, Ph.D. Voice: 910-716-2969
Professor of Biochemistry Fax: 910-716-7671
Bowman Gray School of Medicine email: Lively@mgrp.bgsm.edu
Wake Forest University
Winston-Salem, NC 27157
Home page: http://www.bgsm.edu/molecular_genetics/
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