Characterization by matrix‐assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry of the major photoproducts of temoporfin (m‐THPC) and bacteriochlorin (m‐THPBC)

Abstract

The photobleaching of 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (temoporfin, m-THPC) and 5,10,15,20-tetrakis(m-hydroxyphenyl)bacteriochlorin (bacteriochlorin, m-THPBC) was studied in ethanol-water (1 : 99, v/v) and in physiological medium (phosphate-buffered saline, PBS) with or without fetal calf serum (FCS). m-THPC solution was irradiated with the laser radiation of 650 nm, whereas m-THPBC solution underwent two consecutive irradiations at 532 and 650 nm. The photoproducts were characterized by UV-visible absorption spectrophotometry and by matrix-assisted laser desorption/ionization (MALDI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). Independent of the solvent used, the phototransformation of either photosensitizer yielded the formation of 5,10,15,20-tetrakis (m-hydroxyphenyl)porphyrin (m-THPP) through a major dehydrogenation process.

MALDI‐TOF mass spectrometric analysis for the characterization of the 5,10,15,20‐tetrakis‐ (m‐hydroxyphenyl)bacteriochlorin (m‐THPBC) photoproducts in biological environment

“…Rapid phototransformation of m ‐THPBC in m ‐THPC has already been observed in aqueous solution and in vivo. 13, 24, 25…”

“…Porphyrin‐like compounds have been extensively studied in the past by mass spectrometry coupled with electron ionization (EI),6 chemical ionization (CI),7 fast atom bombardment (FAB),8 plasma desorption,9 laser desorption10, electrospray (ESI)11 and matrix assisted laser desorption (MALDI) 12, 13. Among these ionization techniques, MALDI appears to be one of the most attractive and allows the analysis of complex media with salts and proteins.…”

Metabolite Fingerprinting in Transgenic Nicotiana tabacum Altered by the Escherichia coli Glutamate Dehydrogenase Gene

“…This study used metabolite analysis with FT-ICR-MS [5, 8] to associate phenotype with biochemical changes resulting from endogenous effects of ectopic glutamate synthesis in transgenic plants. The GDH plants were a suitable test for FT-ICR-MS because they have cell composition alterations that result from a specific biochemical alteration in a well-characterized pathway targeting the cellular glutamate pools [12].…”

“…In comparison about 30% of ions identified in plants by GC-MS could not be identified [4, 7, 11]. The unidentified ions detected may represent novel constituents of tobacco leaves or roots [38] or ionization artifacts of MS [5, 6]. Different abundances could also be experimental artifacts.…”

“…Libraries of compound identities have been developed at a mass accuracy of 10 ppm (about 0.01 d), often by MS-MS fragmentation. In contrast, the mass accuracy of full-scan MS in a Fourier transformed ion cyclotron resonance mass spectrometer (FT-ICR-MS) format provides for mass accuracy to 1 ppm (about 0.001–0.0001 d) if the ion cyclotron is not filled [5, 6, 7]. The greater potential for mass accuracy is derived from the longer path length that allows for separation of a larger number of compounds, protein fragments, or DNA molecules per analysis.…”