Markus,
I'm not a specialist of peptides fragmentation, however I'm very familiar
with amino acid fragmentation and the -64 that you are mentioned is a
typical fragmentation (in medium-collision energies) of amino acids. The
[M+H-64]+ (of an amino acid) corresponds either to an elimination of a water
molecule from the immonium fragment [Im-H2O]+ and/or ot the formation of the
immonium ion from the fragment [M+H-H2O]+. It can be basically found to
amino acids that their residues can allow the loss of a water molecule (Ser,
Thr, Asp, Glu).
For ESI amino acid fragmentations you may see at: K. Petritis et al.
Parameter optimization for the analysis of underivatized protein amino acids
by liquid chromatography and ionspray tandem mass spectrometry, J.
Chromatogr. A, 896, (2000) 253-263.
If you are intresting in a pure mechanistic way for the formation of the
above fragmentation you can search for the articles of Yannik Hoppilliard
who worked a lot at this subject.
Hope that the above helped,
Kostas
***********************************************************************
Konstantinos PETRITIS
Institut de Chimie Organique et Analytique (ICOA), UMR-6005
University of Orleans, BP 6759, 45067, ORLEANS, CEDEX 2, France
Tel. +(33)-2-38-41-71-71, intern number 7777
Fax: +(33)-2-38-41-72-81
e-mail: konstantinos.petritis@univ-orleans.fr
http://www.univ-orleans.fr/SCIENCES/ICOA
----- Original Message -----
From: Markus Piotrowski <Markus.Piotrowski@ruhr-uni-bochum.de>
To: Recipients of ABRF List <abrf@aecom.yu.edu>
Sent: Monday, February 19, 2001 8:51 PM
Subject: MS/ProtSeq
> Dear All,
>
> I sequenced a peptide (mz 574, doubly charged) by ESI-Q-TOF-MS with the
> sequence: GQADTIGIAMR (Methionine oxidized)
>
> Interestingly, I can also read part of the sequence with peaks having a
> mass -64. Anyone heard about a loss of 64 during fragmentation of
> peptides?
>
> The centered spectrum is attached as simple text file.
>
> Markus
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