I did not make a peptide with Leucines only,but I tried to make a larger
one,which was the signal peptide of hCG beta.
At that time,I used to dilute the TFA,10-fold with water,and then extract
it with ether.This peptide,which was a 24-mer with
five Leu in a row,plus other hydrophobic amino acids,formed a wax at
interface of the two layers.All I needed to do was
to remove the liquid.The peptide,with many deletions,was then purified by
HPLC.The fun part was to keep it in solution.
Marcus Macht <Marcus.Macht@uni-koeln.de>@aecom.yu.edu> on 10/06/2000
06:38:02 AM
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cc:
Subject: PEPSYN: precipitation of (Leu)5?
Dear colleagues,
We are currently confronted with a precipitation problem in peptide
synthesis. For a customer we synthesized a Leu-pentamer. After cleavage
from the resin I acquired a MALDI spectrum of the raw product which showed
a mixture of the tetra- and pentamer (approx. 1:1). When we tried to
precipitate the peptide with diethylether after cleavage nothing happend.
We still have a nice clear solution even after storing it at -80ƒC over
night.
Does anybody of you have an idea about how to precipitate the peptide?
Would eventually addition of something more hydrophobic (e.g. pentane or
hexane) help or will this lead to a phase separation between the organic
phase and the TFA? Has anybody of you already tried to synthesize this
sequence and how did you circumvent the problem? Since the synthesis itself
of the sequence worked better than I expected, we will also try to sequence
(Leu)10 for the same customer. Does anybody have any experience with this
sequence as well? Should we maybe try to synthesize a pentamer, cleave of
halve of it, protect the free peptide with Fmoc-OSu and use this as
building block to finish the decamer?
Any hints are greatly appreciated! Thanks in advance.
Marcus Macht
********************************************************
Dr. Marcus Macht
University of Cologne
Centre for molecular medicine - Service laboratory
Joseph-Stelzmann-Str. 52
50931 Cologne, Germany
Tel.: +49 221 478-6995
Fax: +49 221 478-6977
e-mail: Marcus.Macht@uni-koeln.de
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