Mass spectral study of Boc-carbo-beta3-peptides: differentiation of two pairs of positional and diastereomeric isomers

Journal of Mass Spectrometry : JMS
R SrikanthPalakodety Radha Krishna

Abstract

A mass spectral study of a series of new Boc-C-linked carbo-beta(3)-peptides prepared from C-linked carbo-beta(3)-amino acids (Caa) was carried out using liquid secondary ion mass spectrometry (LSIMS), electrospray ionization (ESI) and tandem mass spectrometry. Using the nomenclature of Roepstorff and Fohlman, the positive ion high- and low energy collision-induced dissociation (CID) of [M + H - Boc + H](+) ions of the peptides produce both N- and C-terminus ions, y(n) (+) and b(n) (+) ions, with high abundance and other ions of low abundance. Further, characteristic fragment ions of carbohydrate moiety are observed. In contrast to the CID of protonated peptide acids, the CID of [M - H](-) ions of the beta(3)-peptide acids do not give b(n)(-) ions and show abundant z(n)(-) and c(n) (-) ions which are insignificant in the former. Two pairs of positionally isomeric Boc-carbo-beta(3)-dipeptides were differentiated by the CID of [M + H](+) ions in LSIMS and ESIMS. The fragment ion [M + H - C(CH(3))(3) + H](+) formed from [M + H](+) by the loss of 2-methylprop-2-ene is relatively more abundant in the dipeptide Boc-NH-beta-hGly-Caa(S)-OCH(3) (14) containing the sugar moiety at the C-terminus whereas it is insignificant in Boc-NH-Caa(...Continue Reading

Citations

Nov 16, 2004·Rapid Communications in Mass Spectrometry : RCM·R SrikanthPalakodety Radha Krishna
Jul 1, 2005·Rapid Communications in Mass Spectrometry : RCM·R SrikanthPalakodety Radha Krishna
Aug 15, 2009·Rapid Communications in Mass Spectrometry : RCM·B RajuR Srinivas
Apr 9, 2009·Chemistry : a European Journal·Gangavaram V M SharmaHans-Jörg Hofmann
Jul 17, 2012·European Journal of Mass Spectrometry·M Vairamani, S Prabhakar
Nov 9, 2004·Journal of Mass Spectrometry : JMS
Oct 24, 2012·Organic & Biomolecular Chemistry·Gangavaram V M SharmaHans-Jörg Hofmann

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