Fragmentation of dinucleotides d(ApAp) following K shell ionization of phosphorus atom by monochromatic soft X-rays

Abstract A dinucleotide: d(ApAp) with molecular formula C 70 H 61 N 11 O 15 P 2 Cl 2 has been irradiated with monochromatic soft X-rays tuned to the K shell resonance energy of the phosphorus atom. The photofragments have been analysed with an electrospray mass spectrometer. The results suggest that among all the possible electronic relaxation mechanisms, a significant one involves the scission of the two phosphodiester bonds as a result of the multiply charged phosphorus ion produced in the electronic rearrangement following the inner shell excitation or ionization of the phosphorus atom.