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Electrospray tandem mass spectrometry of new porphyrin amino acid conjugates
Author(s) -
Serra V. Vaz,
Domingues M. R. M.,
Faustino M. A. F.,
Domingues P.,
Tomé J. P. C.,
Neves M. G. P. M. S.,
Tomé A. C.,
Cavaleiro J. A. S.,
FerrerCorreia A. J.
Publication year - 2005
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.2097
Subject(s) - chemistry , porphyrin , tandem mass spectrometry , moiety , protonation , fragmentation (computing) , electrospray ionization , mass spectrometry , electrospray , amide , photochemistry , stereochemistry , ion , medicinal chemistry , organic chemistry , chromatography , operating system , computer science
Porphyrin amino acid conjugates with one or two porphyrin units were analyzed by electrospray ionization tandem mass spectrometry (ESI‐MS/MS). The ESI‐MS spectra of all the porphyrins studied, obtained in positive ion mode, show the presence of the corresponding protonated molecule [M+H] + ; ESI‐MS spectra of diporphyrinyl compounds also show the doubly charged ions [M+2H] 2+ . The fragmentations of these ions induced by collision with argon were studied (ESI‐MS/MS). ESI‐MS/MS gives detailed structural information about the amino acids associated with the porphyrin. Cleavage of the bonds in the vicinity of the porphyrin moiety and those involving the side chain of amino acid residues gives structural information about this type of association. A fragmentation common to all derivatives corresponds to the cleavage of the phenylCO bond. The expected cleavage of the amide bond, that links the porphyrin to the amino acid moiety, is a minor fragmentation, which in some cases is even absent. The MS/MS spectra of the monoporphyrinyl derivatives show product ions characteristic of the amino acid linked to the porphyrin; the fragmentation also indicates when the amino acids has a terminal carboxylic group or a terminal ester group. The fragmentations of the diporphyrinyl compounds occur mainly by the cleavage of the spacer, leading, in the case of the doubly charged ions, to predominantly mono‐charged ions, indicating a preferential location of the two protons in separated porphyrinic units. Copyright © 2005 John Wiley & Sons, Ltd.