Hole Migration in Telomere‐Based Oligonucleotide Anions and G‐Quadruplexes. Issue 70 (15th November 2019) - Li, Wen
Abstract: Vacuum ultraviolet photoionization of a gas‐phase oligonucleotide anion leads to the formation of a valence hole. This hole migrates towards an energetically favorable site where it can weaken bonds and ultimately lead to bond cleavage. We have studied Vacuum UV photoionization of deprotonated oligonucleotides containing the human telomere sequence dTTAGGG and G‐quadruplex structures consisting of four dTGGGGT single strands, stabilized by NH4 + counter ions. The oligonucleotide and G‐quadruplex anions were confined in a radiofrequency ion trap, interfaced with a synchrotron beamline and the photofragmentation was studied using time‐of‐flight mass spectrometry. Oligonucleotide 12‐mers containing the 5'‐TTAGGG sequence were found to predominantly break in the GGG region, whereas no selective bond cleavage region was observed for the reversed 5'‐GGGATT sequence. For G‐quadruplex structures, fragmentation was quenched and mostly non‐dissociative single and double electron removal was observed. Abstract : Hole migration in DNA : The combination of tandem mass spectrometry with synchrotron radiation allows to track the migration of valence shell vacancies through gas‐phase oligonucleotides. The telomeric dTTAGGG sequence acts as an efficient hole trap.