Multiple valence electron detachment following Auger decay of inner-shell vacancies in gas-phase DNA.

We have studied soft X-ray photoabsorption in the doubly deprotonated gas-phase oligonucleotide [dTGGGGT-2H]. The dominating decay mechanism of the X-ray induced inner shell vacancy was found to be Auger decay with detachment of at least three electrons, leading to charge reversal of the anionic precursor and the formation of positively charged photofragment ions. The same process is observed in heavy ion (12 MeV C) collisions with [dTGGGGT-2H] where inner shell vacancies are generated as well, but with smaller probability.

Hole Migration in Telomere-Based Oligonucleotide Anions and G-Quadruplexes.

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 NH counter ions.

Light flashes in cancer patients treated with heavy ions.

Light flashes (phosphenes) are reported by most of the astronauts during spaceflight and patients treated with radiotherapy for brain tumors. They are induced by cosmic ray traversals, but the target area is unknown. With a correlation analysis of the visual sensation and the position of the beam in patients treated with energetic carbon ions for skull base tumors, we demonstrate here that light flashes are elicited only when the energetic particles hit the retina.