RNA Fragmentation in MALDI Mass Spectrometry Studied by H/D-Exchange: Mechanisms of General Applicability to Nucleic Acids

To reveal the gas-phase chemistry of RNA and DNA fragmentation during MALDI mass spectrometry in positive ion mode, we performed hydrogen/deuterium exchange on a series of RNA and DNA tetranucleotides and studied their fragmentation patterns on a high-resolution MALDI TOF-TOF instrument. We were specifically interested in elucidating the remarkably different fragmentation behavior of RNA and DNA, i.e., the characteristic and abundant production of c- and y-ions from RNA versus a dominating generation of (a-B)- and w-ions from DNA analytes. The analysis yielded important information on all significant backbone cleavages as well as nucleobase losses. Based on this, we suggest common fragmentation mechanisms for RNA and DNA as well as an important RNA-specific reaction requiring a 2′-hydroxyl group, leading to c- and y-ions. The data is viewed and discussed in the context of previously published data to obtain a coherent picture of the fragmentation of singly protonated nucleic acids.