Recipients of ABRF List@
<abrf@aecom.yu.edu>
Subject: RE: question about peptide synthesis
Date: Tue, 15 May 2001 09:41:51 -0400
MIME-Version: 1.0
X-Mailer: Internet Mail Service (5.5.2650.21)
Content-Type: text/plain;
charset="iso-8859-1"
To: Recipients of ABRF List <abrf@aecom.yu.edu>
Sender: Association of Biomolecular Resource Facilities <abrf-request@aecom.yu.edu>
Precedence: bulk
Errors-To: abrf-request@aecom.yu.edu
Wei-zhen,
Are you using Fmoc-Cys(Trt)-OH?
Notwithstanding Denis' excellent suggestions for how to proceed, it occurs
to me that your synthesis has probably crashed due to severe steric
hindrance of the threonine (which is branched on the beta carbon) versus the
N-terminal cysteine (which is blocked with a relatively humongous trityl
moiety). As Denis suggests, you can alleviate some steric problems by
reswelling your resin. And you probably have a fair amount of successful
coupling, already, even though your Kaiser is positive. So acetylation is
also not a bad idea.
But if you still get garbage, and you have to try, try again, I recommend
you use a different cysteine side chain blocking group, something nice and
small like Acm. Of course, you'll pay for that later, when you have to
deblock it. And you may find out that your overall yield and purity are
better with acetylation on the Trt cysteine synthesis. But it's nice to
have alternatives available.
Good luck.
Mark
-----Original Message-----
From: Wei-zhen Shen [mailto:shenw@ccf.org]
Sent: Monday, May 14, 2001 4:51 PM
To: Recipients of ABRF List
Subject: question about peptide synthesis
I have a question ragarding the peptide synthesis problem. One of my
investigator wants a 14 mer peptide (NH2-NTWTTCQSIAFPSK-COOH). When I tried
first time, the synthesis failed. Now second time the peptide has been
synthesized upto cys (CQSIAFPSK). The synthesis looks OK by checking the
coupling of cys but the coupling of next Thr, is still showing ninhydrin
positive color. I am using the Fmoc chemistry and tried using DIC as well
DIEA with HBTU. Any suggestion or tips will be helpful.
Wei-Zhen
This archive was generated by hypermail 2b29 : Wed Nov 21 2001 - 14:16:29 EST