Sandie
What type of synthesis are you doing? tboc or FMOC?
What protecting groups are on your arginines?
Have you done N-terminal sequence analysis to verify that you do or do not
have an extra arginine in the sequence?
Deb McMillen
Institute of Molecular Biology
University of Oregon
Eugene OR
On Wed, 31 Jan 2001, Sandie Smith wrote:
> Dear pepsyn gurus
>
> I have just synthesized a peptide: GARRGKGR-NH2. By mass analysis I
> have two species,one is correct, the other has an extra Arg (+156).
> The incorrect one is about 70%. There was nothing to indicate an
> instrumental error. A Kaiser test indicated only that coupling was
> not as efficient at the RR cycles as the other cycles. This has
> happened one time before,two to three months ago, again involving a
> RR sequence. That time I had done a recouple after the first R. I
> redid the synthesis, without a recouple and got the correct mass
> only. I put it down to some unknown, never to be explained, problem,
> with the recouple. Now it's come up again. Please, does anyone have
> a solution to this puzzle?
>
> Thank you,
> Sandie
> Sandra S. Smith
> Research Associate
> Protein Microanalysis Facility
> Institute for Cellular and Molecular Biology
> MBB 1.420
> University of Texas, Austin, Texas 78712
>
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