1- The tryptophan is being oxidized by oxidizing agents presents in your
solvents. To solve this, add DTT to the solvents (all of them, it doesn't
cause by products);
2- The conversion flask dry-down time is too long, causing tryptophan to be
degraded due to the absence of an acid condition. To solve this, optimize the
conversion flask dry-down time according to the user manual.
I hope this help!
Suzanne Perry-Riehm wrote:
>
> I have a peptide sequence in which the tryptophan is "missing" in the
> cycle where it should have appeared. The original sample was a protein
> digested
> after R&A with endo LYS-C. The peptides were separated on a PE ABI173A
> and the peptide peak sequenced with standard gas-phase Edman Chemistry. I
> do visualize a small peak that co-elutes with PRO. The client assures me
> that this does have a TRP in this position and the rest of the sequence
> matches up 100%.
>
> Any help in this matter?
Best regards,
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Prof. Ricardo B. Cunha Brasilia - DF - Brasil
mailto:rbcunha@unb.br
http://www.geocities.com/Athens/Acropolis/5221
Instituto de Quimica - UnB
http://www.unb.br/ie/qui/
Centro Brasileiro de Servicos e Pesquisas em Proteinas - UnB
http://www.unb.br/cbsp/CBSP.html
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