Electron Binding to Nucleic Acid Bases. Experimental and Theoretical Studies. A Review (original) (raw)

2004, Collection of Czechoslovak Chemical Communications

Published as: Svozil D., Jungwirth P., Havlas Z., Electron binding to nucleic acid bases. Experimental and theoretical studies. A review., Collection Of Czechoslovak Chemical Communications 69 (7): Abstract An in-depth knowledge of an excess electron binding mechanism to DNA and RNA nucleobases is important for our understanding of radiation damage influence on the biological functions of nucleic acids, as well as for the possible use of DNA molecules as wires in molecular electronic circuits. The nature of anions created by electron attachment to individual nucleic acid bases is discussed in detail. The principles of the experimental and theoretical approaches to the description of these anions are outlined, and the available results concerning valence-and dipole-bound anions of nucleic acid bases are reviewed. Keywords: DNA; RNA; nucleobase; anion; dipole-bound; valence-bound; ab initio; photoelectron spectroscopy; Rydberg electron transfer; vertical detachment energy; adiabatic electron affinity; vertical electron affinity 1 Biochemists perceive double-helical DNA primarily as a target for molecular recognition. To understand in detail the remarkable variety of reactions involving the double helix in the cell, such as repair of DNA damage or coordination of the transcription of different genes, it becomes important to explore and consider also the rich physical chemistry of DNA. One of the most intriguing and fascinating issues is the charge transfer process in DNA. DNA-mediated charge transfer processes can be categorised either as oxidative hole transfer or as reductive electron transfer. Major efforts have focused on the investigation of oxidative hole transfer, 1-4 resulting in detailed insights on the mechanism. 5,6 On the other hand, the details of the electron transfer are still unclear. The biological implications of charge transfer in DNA are considerable. This is because the most important harmful effect of UV radiation on the living cell is the damage to the DNA component of the chromosome. 7 Radiation triggers 8,9 a release of free electrons and, consequently, single-electron oxidation or reduction initiates a cascade of reactions, the outcomes of which are far-reaching. 10,11 Ionising radiation can be absorbed directly by DNA, leading to the ionization of bases 12,13 (the direct effect), or react indirectly with the surrounding water molecules, 14,15 creating highly reactive radicals (the indirect effect). Radiation damage to DNA can be classified as (a) structural damage leading to a breakage of phosphodiester bonds and subsequent single-strand or double-strand breaks and, (b) change in information caused by the chemical modification of individual DNA bases. 16-18 Both types of damage can be lethal, and both may lead to mutagenic changes causing aging and disease. 7