We also observe a small peak preceding Pro in degradations (ABI
477A) through tryptophan
in both natural and synthetic peptides/proteins. This peak replaces Trp
altogether in samples that have been deliberately oxidized (e.g. with
hydrogen peroxide). The product appears to be 50-100 mass units larger than
PTH-Trp, but we're in the process of characterizing it further.
Henry Keutmann
Endocrine Unit, Mass. General Hospital
Boston MA 02114
617-726-3966
>
> Dear Suzanne,
>
> The presence of this small peak near Pro is a secondary product of
>PTH-Trp. In our Procise, using either gas or pulse liquid chemistry, we
>see this peak and always it is associated with the presence of TRP.
> I hope this info could be useful.
>
>Jose Cesar Rosa, Ph.D
>Centro de Quimica de Proteinas
>Faculdade de Medicina Ribeirao Preto
>Universidade de Sao Paulo
>Av. Bandeirantes, 3900
>14049-900 Ribeirao Preto, Brazil
>phone: 55-16-6331884
>fax: 55-16-6332119
>email: jcrosa@fmrp.usp.br
>
>
>
>On Wed, 7 Apr 1999, 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?
>>
>> Thanks,
>> Suzanne Perry-Riehm
>>
>> Suzanne C. Perry, Research Associate
>> NAPS Protein Service Laboratory
>> Biotechnology Department, University of British Columbia
>> CANADA
>> phone:(604)822-9662 Fax:(604)822-0676 email:perry@interchange.ubc.ca
>> Visit our web page at : www.biotech.ubc.ca/naps/napshome.htm
>