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A linear free‐energy correlation in the low‐energy tandem mass spectra of protonated tripeptides Gly–Gly–Xxx
Author(s) -
Morgan Daniel G.,
Bursey Maurice M.
Publication year - 1994
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210290705
Subject(s) - tripeptide , protonation , chemistry , substituent , stereochemistry , ion , residue (chemistry) , peptide , proton affinity , crystallography , organic chemistry , biochemistry
The backbone cleavages of protonated tripeptide ions of the series Gly—Gly—Xxx, where Xxx Gly, Ala, Val, d ‐Leu, l ‐Leu, Ile, Phe, Tyr, Trp, Pro, Met and Glu, were studied in a hybrid tandem mass spectrometer. C ‐Terminal y ‐type ions and N ‐terminal a ‐ and b ‐type ions were noted. A linear relationship between log ( y 1 / b 2 ) and the proton affinity of the C ‐terminal amino acid substituents was found: as the proton affinity of the C ‐terminal residue increases, the fraction of y 1 ion formation increases. When the C ‐terminal substituent was more basic than Trp, the b 2 ion was not observed. It is likely that the site of protonation changes from peptide bond to side‐chain for just these residues, Lys, His and Arg.