Unprecedented Matrix-Induced Reduction of Flavins Observed Under FAB and MALDI Conditions

Title: Unprecedented Matrix-Induced Reduction of Flavins Observed Under FAB and MALDI Conditions

Volume: 7 Issue: 15

Author(s): Yoko Ohashi and Yoshiyuki Itoh

Affiliation:

Keywords: Matrix-Induced Reduction, Flavins, thermospray, prosthetic groups, aerobic dehydrogenases

Abstract: Flavin-derived compounds such as riboflavin, riboflavin 5-phosphate (flavin mononucleotide, FMN) and flavin-adenine dinucleotide (FAD), under matrix-assisted laser desorption ionization (MALDI) and fast atom bombardment (FAB) conditions produce unprecedented reduced species that can be attributed to [M+2H]+. and [M+3H]+ in addition to the anticipated [M+H]+ ions. On the other hand, electrospray ionization (ESI) conditions generate only the expected [M+H]+ as the sole molecular-related ion. A protonation from the matrix accompanied by a concomitant electron transfer, rather than the transfer of hydrogen atom(s), [H. of CH groups], is proposed to explain the observed reduction process. The reduction site expands to N(1)=C(10a)-C(4a)=N(5), a 1,4-diaza-1,3-butadiene system, in the isoalloxazine ring, resembling the behavior of prosthetic groups of aerobic dehydrogenases. Interestingly, CID-MS / MS of most abundant molecular-related ions generated by the FAB and ESI modes, namely [M+2H]+. for FAB and [M+H]+ for ESI, produce the identical even-electron fragment ion of isoalloxazine moiety, indicating a radical loss vs. the evenelectron molecule loss from the individual precursor ions. The observed phenomena are compared with those previously reported for FABMS, thermospray mass spectrometry (TSPMS) and ESIMS.

Cite this article as:

Ohashi Yoko and Itoh Yoshiyuki, Unprecedented Matrix-Induced Reduction of Flavins Observed Under FAB and MALDI Conditions, Current Organic Chemistry 2003; 7 (15) . https://dx.doi.org/10.2174/1385272033486288