Dear Radhika,
The phenomena that you were seeing is often observed with peptide sequences
containing Pro-Pro. This is due to cis-trans isomerization of the Pro-Pro
bond. Try running your HPLC at elevated temperature (around 50 degree) and
you will see that the two peaks collapse to a single peak.
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
............................................................................
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AnaSpec was recognized as a "Leader of the Pack"
in custom peptide synthesis by The Scientist.
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-----Original Message-----
From: Radhika Krishnan <rkrishnan@smtplink.Coh.ORG>
To: Recipients of ABRF List <abrf@aecom.yu.edu>
Date: Thursday, January 20, 2000 2:03 PM
Subject: Pepsyn:Peculiar problem
>Hi Colleagues,
> I have benefitted a lot form the discussions that go on in this group ,
and
>would like to avail of your collective wisdom.
> I am faced with a peculiar problem with the synthesis of two peptides
that
>are designed to identify a immunological epitope. The sequences are as
follows,
>TTVYPPSSTAK and TVYPPSSTAK.
>I have synthesized these two sequences twice on the Pioneer with two
different
>batches of the acid Lys resin. My HPLC shows two peaks almost on the top of
each
>other. We tried purifying the major peak on a prep column, but analysis of
the
>"pure" peaks seem to indicate that nothing has changed. They look identical
to
>the crude HPLC. The mystery is that the MALDI of both the samples do not
>indicate anything untoward. The only peaks are that of the peptide.
> Is it possible that one of the amino acids might be a racemic mixture?
All
>my reagents are form PE Biosystems.
> Will AAA tell me anything if there were isomers.
> I have calibrated both my analytical and prep c18 columns.
>Thanks.
>Radhika.
>City of Hope, Duarte CA.
>
>
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