title: Characterization of cationic glycoporphyrins by electrospray tandem mass spectrometry.
abstract: Novel cationic porphyrin derivatives having a galactose or a bis(isopropylidene)galactose unit linked directly to a pyridine or to an aminophenyl group were characterized by electrospray tandem mass spectrometry (ESI-MS/MS). The electrospray mass spectra (ESI-MS) show the M(+) ions, since these porphyrins are already monocharged in solution. The fragmentation of these ions under ESI-MS/MS conditions was studied and it was found that elimination of the sugar residue as a radical (-163 or -243 Da) is a common fragmentation pathway. Loss of the sugar unit as a neutral fragment (-162 or -242 Da) and cross-ring fragmentations typical of glyco-derivatives are also observed for the pyridinium glycoporphyrins, but they are absent in the case of ammonium glycoporphyrins. The cationic beta-pyridiniumvinyl porphyrins show an atypical fragmentation due to the cleavage of the C(5)-C(6) bond of the sugar unit. Overall, the different patterns of fragmentation observed in the ESI-MS/MS spectra of the sugar pyridinium porphyrins and of the sugar ammonium phenyl porphyrins can give important information about the type of spacer between the porphyrin and the sugar unit.
authors.affiliation: Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Eduarda M P
authors.initials: EM
authors.lastname: Silva
authors.forename: Vanda Vaz
authors.initials: VV
authors.lastname: Serra
authors.forename: Anderson O
authors.initials: AO
authors.lastname: Ribeiro
authors.forename: João P C
authors.initials: JP
authors.lastname: Tomé
authors.forename: Pedro
authors.initials: P
authors.lastname: Domingues
authors.forename: M Amparo F
authors.initials: MA
authors.lastname: Faustino
authors.forename: M Graça P M S
authors.initials: MG
authors.lastname: Neves
authors.forename: Augusto C
authors.initials: AC
authors.lastname: Tomé
authors.forename: José A S
authors.initials: JA
authors.lastname: Cavaleiro
authors.forename: António J
authors.initials: AJ
authors.lastname: Ferrer-Correia
authors.forename: Yassuko
authors.initials: Y
authors.lastname: Iamamoto
authors.forename: M Rosário M
authors.initials: MR
authors.lastname: Domingues
mesh_terms: D002412:Cations; D005690:Galactose / Q000032:analysis* / Q000737:chemistry*; D011166:Porphyrins / Q000032:analysis* / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D002412:Cations; D011166:Porphyrins; D005690:Galactose