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Improved peptide detection with matrix‐assisted laser desorption/ionization mass spectrometry by trimethylation of amino groups
Author(s) -
Stewart N. A.,
Pham V. T.,
Choma C. T.,
Kaplan H.
Publication year - 2002
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.726
Subject(s) - chemistry , peptide , mass spectrometry , matrix assisted laser desorption/ionization , protein mass spectrometry , amino acid , chromatography , desorption , analytical chemistry (journal) , tandem mass spectrometry , organic chemistry , biochemistry , adsorption
Trimethyl α‐amino derivatives of peptides (penta to deca) with a permanent positive charge on their α‐amino groups were prepared by in vacuo reaction with iodomethane and subjected to matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS). Compared to the unmodified peptide, the signal intensity of the trimethyl α‐amino derivative in MALDI‐MS is increased by at least an order of magnitude. Similarly, an octapeptide with a trimethylated ϵ‐amino group derived from the solitary lysine residue of the B‐chain of insulin also shows the same relative increase in signal intensity. Another advantage of the in vacuo methylation procedure is that trimethylation of a peptide amino group can be carried out readily with a combination of isotopes 13 CH 3 I and 12 CH 3 I or CD 3 I and CH 3 I, yielding a doublet signal either 3 or 9 units apart, respectively. The presence or absence of such a doublet signal can be used as a criterion to discriminate between peptide and non‐peptide signals in the mass spectrum. Copyright © 2002 John Wiley & Sons, Ltd.