I'm used to use Maldi-tof as a MW quality control of the peptides I
synthesize. A couple of weeks ago, I synthesized an GM(O)G wich
MW=278. As I could not detect low MW in the Maldi I use, I asked a
friend to do it in a Electron Spray, and it showed the following
results:
1) 278.45; 279.09; 280.12
2) 298.75; 300.82; 301.04
3) 316.28; 317.03; 318.06
It looks for me that group 1 correspond to Na+ and group 2 =
K+. I'm used to see Na+ and K+ when I analyse Maldi spectra. Is it
common also to see them in ES?
Can I realy attribute the difference, I would say 298.75-
278.45=20.3 as the Sodium or I have to use the higher value of the
isotopes of group 2 minus the lower value of group 1 (301.04-
278.45=23.3)? Wich peak do I have to use to calculate the "real"
MW? (same question for the possible K+ peaks).
Thanks in advance,
Leo
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Leo Kei Iwai - Chemist
Dept of Biophysics
Escola Paulista de Medicina - EPM - UNIFESP
Lab of Transplantation Immunology
Instituto do Coracao - Incor - FMUSP
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