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Structural characterization of glycoporphyrins by electrospray tandem mass spectrometry
Author(s) -
Domingues M. R. M.,
Domingues P.,
Reis A.,
Ferrer Correia A. J.,
Tomé J. P. C.,
Tomé A. C.,
Neves M. G. P. M. S.,
Cavaleiro J. A. S.
Publication year - 2004
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.561
Subject(s) - chemistry , tandem mass spectrometry , fragmentation (computing) , electrospray , mass spectrometry , ion , electrospray ionization , residue (chemistry) , ether , stereochemistry , crystallography , chromatography , organic chemistry , computer science , operating system
Porphyrin derivatives having a galactose or a bis(isopropylidene)galactose structural unit, linked by ester or ether bonds, were characterized by electrospray tandem mass spectrometry (ES‐MS/MS). The electrospray mass spectra of these glycoporphyrins show the corresponding [M + H] + ions. For the glycoporphyrins with pyridyl substituents and those having a tetrafluorophenyl spacer, the doubly charged ions [M + 2H] 2+ were also observed in ES‐MS with high relative abundance. The fragmentation of both [M + H] + and [M + 2H] 2+ ions exhibited common fragmentation pathways for porphyrins with the same sugar residue, independently of the porphyrin structural unit and type of linkage. ES‐MS/MS of the [M + H] + ions of the galactose‐substituted porphyrins gave the fragment ions [M + H − C 2 H 4 O 2 ] + , [M + H − C 3 H 6 O 3 ] + , [M + H − C 4 H 8 O 4 ] + and [M + H − galactose residue] + . The fragmentation of the [M + 2H] 2+ ions of the porphyrins with galactose shows the common doubly charged fragment ions [porphyrin + H] 2+ , [M + 2H − C 2 H 4 O 2 ] 2+ , [M + 2H − C 4 H 8 O 4 ] 2+ , [M + 2H − galactose residue] 2+ and the singly charged fragment ions [M + H − C 3 H 6 O 3 ] + and [M + H − galactose residue] + . The fragmentation of the [M + H] + ions of glycoporphyrins with a protected galactosyl residue leads mainly to the ions [M + H − CO(CH 3 ) 2 ] + , [M + H − 2CO(CH 3 ) 2 ] + , [M + H − 2CO(CH 3 ) 2 − CO] + , [M + H − C 10 H 16 O 4 ] + and [M + H − protected galactose] + . The doubly charged ions [M + 2H] 2+ fragment to give the doubly charged ions [porphyrin + H] 2+ and the singly charged ions [M + H − protected galactose residue] + and [M + H − CO(CH 3 ) 2 ] + . For the porphyrins where the sugar structural unit is linked by an ester bond, [M + 2H] 2+ , ES‐MS/MS showed a major and typical fragmentation corresponding to combined loss of a sugar structural unit and further loss of water, leading to the ion [M + 2H − sugar residue − H 2 O] 2+ , independently of the structure of the sugar structural unit. These results show that ES‐MS/MS can be a powerful tool for the characterization of the sugar structural unit of glycoporphyrins, without the need for chemical hydrolysis. Copyright © 2004 John Wiley & Sons, Ltd.