Charge reduction of oligonucleotide anions via gas-phase electron transfer to xenon cations.

Multiply-charged anions derived from electrospray (ES) ionization of the oligonucleotide 5'-d(GTCTTAGCGCTAAGAC)-3' have been subjected to electron transfer reactions with ionized xenon in a quadrupole ion trap and found to undergo minimal fragmentation. This observation stands in contrast with electron transfer to rare gases from anions of smaller oligonucleotides which have been shown to undergo extensive fragmentation. The present results are attributed to longer anion lifetimes for the larger oligonucleotide anions (following highly exothermic electron transfer) which then allow for collisional cooling by the helium bath gas. Reduction to singly charged anions with minimal fragmentation is noted, indicating that xenon cations can be considered as a reagent for simplifying ES mass spectra of moderately sized oligonucleotides. The relative merits of the use of xenon cations in the quadropole ion trap for this purpose is discussed.