Marcus,
I have made homopolymers of leucine with lengths up to 15 residues. The
polyleu sequence is very difficult to work with, so be careful about
committing yourself to long polyleu sequences. I have found that I can
get decent purity of (leu)15 by using HATU, as Anita suggests. Because
there are no side-chain protecting groups in this sequence, I just use
95%TFA/5%water, and rotovap off the cocktail once I am finished cleaving.
Like Jane suggests, you should be able to precipitate the peptide by
cooling the flask in
dryice-methanol, and adding Et2O, also cooled in the methanol bath. I
haven't been able to find a suitable solvent for lyophization or HPLC
purification of this peptide, so a good synthesis is critical--you want to
have a satisfactory product after cleavage and precipitation.
Good luck!
g.
-- --
Gary Van Domselaar
Ph.D. Candidate, Associate Director,
Faculty of Pharmacy, Bioinformatics.org: The Open Lab
University of Alberta gary@bioinformatics.org
gary@penguin.pharmacy.ualberta.ca http://bioinformatics.org/gary
-- --
> >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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