Electrospray tandem mass spectrometry of new porphyrin amino acid conjugates

Abstract

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 phenyl-CO 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.

Long-Range Electronic Communication in Free-Basemeso-Poly(Ferrocenyl)-Containing Porphyrins

“…The protonated molecular ions dominated the APCI spectra of all investigated porphyrins (Supporting Information Figure 2), which is consistent with the earlier reported APCI data on transition-metal ferrocenyl-containing MTFcP and the other porphyrins. ,, Representative collision-induced dissociation data for H 2 FcPh 3 P, cis -H 2 Fc 2 Ph 2 P, trans -H 2 Fc 2 Ph 2 P, and H 2 Fc 3 PhP are shown in Supporting Information Figure 2 and compared to the known H 2 TFcP. In all cases, APCI-MS/MS reveals similar patterns to the H 2 TFcP and MTFcP compounds investigated earlier.…”

Urinary Metabolic Fingerprint of Acute Intermittent Porphyria Analyzed by 1H NMR Spectroscopy

“…2,3 Mass spectrometry has much lower detection limits, but it is destructive, and a more targeted approach is often needed, including prior separation of metabolites using either chromatography or capillary electrophoresis. 4,5 Mass spectrometry methods have been developed, validated and applied for the analysis of porphyrin precursors, with good accuracy, precision, and repeatability 6 Proton nuclear magnetic resonance ( 1 H NMR) spectroscopy is a noninvasive and highly reproducible method for the detection of a wide range of small molecules in body fluids, with good analytical precision and accuracy. All metabolites in a biofluid are detected simultaneously and nondestructively with little sample preparation.…”

“…1 H NMR spectroscopy is noninvasive, highly reproducible and has a detection limit in the submicromolar range. All hydrogen-containing metabolites in a biofluid are detected simultaneously and nondestructively with little sample preparation. , Mass spectrometry has much lower detection limits, but it is destructive, and a more targeted approach is often needed, including prior separation of metabolites using either chromatography or capillary electrophoresis. , Mass spectrometry methods have been developed, validated and applied for the analysis of porphyrin precursors, with good accuracy, precision, and repeatability…”