A study of b1+H2O and b1-ions in the product ion spectra of dipeptides containing N-terminal basic amino acid residues.
The product ion spectra of approximately 200 dipeptides were acquired under low-energy conditions using a triple quadrupole mass spectrometer. The spectra of dipeptides containing an N-terminal arginine (R), histidine (H), or lysine (K) were observed to yield a b(1) + H(2)O ion corresponding to the protonated basic amino acid. This was equivalent to the y(1)-ion in the corresponding C-terminal isomer. The formation of a b(1) + H(2)O ion was not a significant fragmentation channel in any dipeptides analyzed including those containing a C-terminal basic amino acid unless they also contained an N-terminal basic amino acid. Occurring simultaneously and under equal energy conditions an apparent b(1)-ion was formed, which has its corresponding C-terminal equivalent in the y(1)-H(2)O ion. Energy resolved mass spectrometry (ERMS), deuterium labeling, and accurate mass experiments as well as data reported were used to show the relationships between the b(1)+H(2)O and b(1)-ions in the dipeptides containing an N-terminal basic amino acid and the y(1) and y(1)-H(2)O ions in the corresponding C-terminal isomers.
Hiserodt
Richard D
RD
Research and Development, International Flavors and Fragrances Inc. (IFF), Union Beach, New Jersey 07735, USA. richard.hiserodt@iff.com
Brown
Sharon M
SM
Swijter
Dennis F H
DF
Hawkins
Nicole
N
Mussinan
Cynthia J
CJ
D001120:Arginine / Q000032:analysis; D004151:Dipeptides / Q000138:chemical synthesis / Q000737:chemistry*; D006639:Histidine / Q000032:analysis; D007536:Isomerism; D008239:Lysine / Q000032:analysis; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014867:Water / Q000737:chemistry
D004151:Dipeptides; D014867:Water; D006639:Histidine; D001120:Arginine; D008239:Lysine