Dear Marcus,
(Leu)5 is a hydrophobic peptide. It is likely to be soluble in diethyl
ether. You will have to evaporate the ether, add glacial acetic acid to
extract the peptide into a suitable container such as a scintillation vial
and lyophilize.
Most likely you will get a gel instead of a powder.
To synthesize (Leu)10, I think it is better to do segment condensation of
Fmoc-(Leu)5-OH to the H-(leu)5-resin. If you decide to couple one amino acid
at a time, you may want to use HATU as the coupling agent to increase your
chance of success.
Anita Hong
AnaSpec, Inc.
2149 O'Toole Avenue, Suite F
San Jose, CA 95131
(408)452-5055 (phone)
(408)452-5059 (fax)
e-mail: service@anaspec.com
home-page: www.anaspec.com
............................................................................
........................
AnaSpec was recognized as a "Leader of the Pack"
in custom peptide synthesis by The Scientist.
............................................................................
........................
-----Original Message-----
From: Marcus Macht <Marcus.Macht@uni-koeln.de>
To: Recipients of ABRF List <abrf@aecom.yu.edu>
Date: Friday, October 06, 2000 6:02 AM
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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