Date: Thu, 16 Jan 1997 12:17:28 -0600
Message-Id: <v01530512af051ed86881@[128.252.197.88]>
To: abrfhyp@cco.caltech.edu
From: rskubish@pharmdec.wustl.edu (Richard Skubish)
Subject: peptide synthesis -18 mass
>Date: Fri, 23 Aug 1996 14:48:43 -0700 (PDT)
>Mime-Version: 1.0
>Old-To: RIFLEMAN@uthscsa.edu, Recipients of ABRF List <abrf@aecom.yu.edu>
>From: Gary Hathaway <hathaway@cco.caltech.edu>
>Subject: Re: peptide synthesis -18 mass
>To: Recipients of ABRF List <abrf@aecom.yu.edu>
>Sender: Association of Biomolecular Resource Facilities
><abrf-request@aecom.yu.edu>
>Precedence: bulk
>
>At 1:59 PM -0500 8/23/96, RIFLEMAN@uthscsa.edu wrote:
>>A problem for the weekend:
>>>We have synthesized a peptide which comes out to be 2 major peaks: The
>>>correct >Mass and the -18 mass.
>>>The peptide does have an asp-gly which could go to succinimide, and then back
>>to asp and isoasp.
>>>It also has several sers that can go to dehydroalanine and several
>>>tyrosines.
>>Is it possible for tyrosine to go to dehydrophenylalanine? How common is it
>>to get any one of these alternatives, and is there another alternative for -18
>>mass?
>>>The -l0 peak seems to be pretty stable. Does anyone know how stable the
>>>above
>>3 alternatives are? In other words, could we count on the concentration to be
>>stable in an assay? On the sequencer?
>>
>>Peggy,
> I rather doubt that the problem is the loss of water from tyrosine, a more
>likely possibility is that during workup you formed an ester e.g.
>trifluoroacetyl ester which being a good leaving group gave you the
>dehydroalanine derivative. To test this hyposthesis, you might try using a
>good nucleophile like DTT, or betamercaptoethanol and repeat the mass
>analysis to see if a new peak emerges with the new predicted mass.
>
>--------------------------------------------------
>Gary M. Hathaway, Director
>PPMAL - Protein/Peptide Micro Analytical Laboratory
>California Institute of Technology
>139-74, Division of Biology
>Pasadena, CA 91125
>
>http://www.caltech.edu/~ppmal
>email Gary: hathawayg@starbase1.caltech.edu
>email facility: ppmal@caltech.edu
>phone: lab (818) 395-6388 or office (818) 395-2769
>FAX (818) 449-3414
>-------------------------------------------------
>
Richard Skubish
rskubish@pharmdec.wustl.edu
314-362-0283
Washington University Medical School
Box 8103 - PNACL
660 S. Euclid
St. Louis, MO 63110