Decarboxylation of carnitine and

a-cyano-4-hydroxycinnamic acid under particle bombardment

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Eur. J. Mass Spectrom. 6, 175 - 185 (2000)

Decarboxylation of carnitine and a-cyano-4-hydroxycinnamic acid under particle bombardment

Sophie Bourcier and Yannik Hoppilliard^*
DCMR, UMR CNRS 7651, Ecole Polytechnique, 91128 Palaiseau Cedex, France. E-mail:
Jean Marie Pechiné and Felix Perez
ESA CNRS 8074, Université Paris-Sud, Batiment 410, 91405 Orsay Cedex, France

ABSTRACT:

Protonated carnitine and a-cyano-4-hydroxycinnamic acid were formed by laser photon irradiation, by MeV-ion bombardment and by electrospray. The spontaneous fragmentations of protonated molecules formed upon particle bombardment are compared with the decompositions induced by low- and high-energy collisions of molecules protonated by electrospray. The determination of fragmentation mechanisms was achieved using labelled compounds and by means of ab initio calculations. The most prominent fragmentation of protonated molecules formed under particle bombardment is an unexpected loss of carbon dioxide. More classical processes dominate the decomposition induced by collisions of electrosprayed species: loss of trimethylamine and 4-hydroxybutyrolactone from protonated carnitine, loss of water from protonated cinnamic acid but no loss of CO₂. Decarboxylation occurring before or concomitant with protonation is proposed to interpret these results.

Keywords: decarboxylation, laser desorption, plasma desorption, electrospray, ionization mechanisms, carnitine, a-cyano-4-hydroxycinnamic acid

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