MALDI-TOF and electrospray tandem mass spectrometric analysis of fatty acyl-CoA esters

Abstract

Coenzyme A (CoA) thioesters play a central role in many biochemical reactions, and methods for sensitive identification of these compounds are important for studies of cellular processes. The direct analysis of intact long-chain fatty acyl CoA esters was investigated using matrix assisted laser desorption time-of-flight and electrospray ionization mass spectrometry. Both techniques resulted in the formation of abundant positive and negative ions indicative of the molecular weight of the fatty acyl CoA molecular species. Several structurally significant fragment ions, in particular positive ions indicative of the fatty acyl portion of the molecule, were formed during ionization processes. Metastable (MALDI-TOF) and collision-induced decomposition (quadrupole tandem mass spectrometry) of these molecular ion species resulted in the formation of similar product ions independent of the mode of ionization. Abundant product ions, corresponding to the fatty acyl portion as well as the pantetheine-ADP portion of the molecule, were observed with both ionization techniques. Decomposition of the [M + H] + ion of hexadecyl coenzyme A (C16:0 CoA) at m / z 1006 yielded a prominent product ion at m / z 499 which was characteristic of the fatty acyl portion of the molecule. Similar fatty acyl product ion fragments corresponding to a neutral loss of 609 were found for the [M + H] + species of all the fatty acyl CoA esters investigated. This prominent and diagnostic fragment could be used to detect molecular species of CoA esters present in complex biological mixtures.