Message-Id: <9701291408.AA05609@MIT.MIT.EDU>
Date: Wed, 29 Jan 97 09:10:03 EST
From: cook@mit.edu (richard f. cook)
Subject: PepSynth- Aspartimide formation
To: Recipients of ABRF List <abrf@aecom.yu.edu>
Haydn,
If you want to make this sequence again, in tBOC chemistry the
aspartimide formation is only a few percent if you use cyclohexyl
protection on the asp residues whenever asp is followed by S,T,A,G or N.
There are ABRF member companies that can cleave it for you (I believe
AnaSpec is one) if you don't have the HF cleavage/deprotection
apparatus.
Dick Cook
MIT
-----------------------------------------------
Hello ABRFers
We have recently synthesized the following sequence using Fastmoc
chemistry on
an ABI433A - ESQAYYDGRRSS. Our problem is that the final product
contains a
very high proportion (~45%) of the dehydrated Asp impurity. We are using
EDT,
thioanisole, water and TFA (1:2:2:35) for cleaving the peptide from the
resin.
Any suggestions as to how we can minimize this problem, which seems to
be
sequence related since other Asp-containing peptides we have made do not
contain the impurity, would be greatly appreciated.
Many thanks
Haydn Ball, PhD
Dept of Neurology,
UCSF
San Francisco
CA 94143-0518
hlb@prion.ucsf.edu
Tel (415) 476 6485