Predicted MW Observed MW (ESI)
QYFYETK 978.1 977.4 (M+1 = 978.4)
My tryptic digest is adjusted to 1% TFA to quench the digestion. Over two days at 4C, about 15% of the peptide seems to convert to a peptide with a mass of 1922.1. m/e
Minor M+1 1923.1
Major M+2 961.5
This mass of 1922.1 is about 32-33 mass units less than twice the MW of the original peptide. Does anyone have any ideas about what's going on? I've considered dimerization with the loss of a couple of waters, but mechanisms or possible structures elude me!
Vernon
Vernon A. Shoup
QC, Regeneron Pharmaceuticals
Rensselaer, NY 12144
(518)488-6012
vernon.shoup@regpha.com