Valence Anions of DNA-Related Systems in the Gas Phase: Computational and Anion Photoelectron Spectroscopy Studies

Abstract

Formation of stable radical anion is one of the most apparent event resulting from the interaction of a biomolecule with an electron. Although, the dipole-bound (DB) anions of nucleobases (NBs) prevail in the gas phase as indicated by negative ion photoelectron spectroscopy (PES), even relatively weak interactions such as those present in the uracil-water complexes are sufficient to render the valence bound (VB) anions adiabatically stable. Moreover, since the electron clouds of dipole bound anionic states are much more diffuse than those of valence bound anions, they are strongly destabilized with respect to the latter in condensed phase. This is why VB anions rather than DB anions of nucleobases are more relevant for biological systems, i.e., in particular for DNA. In this review article, we discuss molecular factors governing the stability of valence anions of nucleobases. On the basis of PES measurements and quantum chemical

Excess Electron Attachment to the Nucleoside Pair 2′-Deoxyadenosine (dA)–2′-Deoxythymidine (dT)

“…A proton transfer, often barrierless, was suggested in the past to be involved in a number of anionic nucleobase related complexes in the gas phase. 7 As regards a complex of isolated nucleobases adenine and thymine, the previous PES/computational studies revealed that in the most stable complex of AT, electron induced proton transfer takes place from N9H of adenine to O8 of thymine. 19 It was shown that PT increases the VDE of given anion radical by 0.7 eV compared with the non-PT structure with identical H-bond pattern.…”

“…The experimental investigations that followed this finding were accompanied by computational studies related to the molecular details of the electron-induced damage. In particular, theoretical works comprised electron interactions with a variety of systems starting from single nucleobases and ending up with the single-stranded and double-stranded nucleotide oligomers. − …”

Electrophilic Properties of 2′-Deoxyadenosine···Thymine Dimer: Photoelectron Spectroscopy and DFT Studies

“…Those studies revealed that both anionic nucleic bases, adenine and thymine, may be protonated as a result of the interaction with species of appropriate acidity, and adenine may also become a proton donor utilizing its N9H site or N6H site. 36 …”

“…Formation of the electronically stable anionic states of nucleobases has became the main assumption in numerous theoretical studies on the role of LEEs in such destructive to DNA phenomena such as the sugar–phosphate bond cleavage ,− and N -glycosidic bond cleavage. ,,,,− Extensive reviews devoted to the interactions of electrons with DNA components are available. ,− Barrierless electron-induced PT was shown in the past to contribute to the stabilization of gaseous anion radical complexes involving nucleobases. Those studies revealed that both anionic nucleic bases, adenine and thymine, may be protonated as a result of the interaction with species of appropriate acidity, and adenine may also become a proton donor utilizing its N9H site or N6H site …”

“…Those studies revealed that both anionic nucleic bases, adenine and thymine, may be protonated as a result of the interaction with species of appropriate acidity, and adenine may also become a proton donor utilizing its N9H site or N6H site. 36 The present report is devoted to studies on the attachment of excess electrons to DNA building blocks. Namely, by means of pulsed laser infrared desorption, we introduced a nucleoside, 2′-deoxyadenosine (dA), and a nucleobase, thymine (T), into the gas phase (for the chemical structure of monomers and atom numbering, see Scheme 1).…”