The Formation of DNA Photodamage: The Role of Exciton Localization

• Published in: Chemphyschem Vol. 11; no. 9; pp. 2011 - 2015
• Main Authors: Rössle, Shaila, Friedrichs, Jana, Frank, Irmgard
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 21.06.2010; WILEY‐VCH Verlag; Wiley
• Subjects: Biological and medical sciences; Chemistry; Cyclobutane pyrimidine dimers; density functional calculations; DNA; DNA Damage; Exact sciences and technology; frontier orbitals; Fundamental and applied biological sciences. Psychology; General and physical chemistry; Molecular biophysics; Oligonucleotides; Oligonucleotides - chemistry; Oligonucleotides - radiation effects; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); potential energy surfaces; Pyrimidine Dimers - chemistry; Quantum Theory; Radiation-biomolecule interaction; Thymine; Thymine - chemistry; Ultraviolet Rays; Potential energy; Frontier orbital; Thymine; Orientation; density functional calculations; Electronic structure; potential energy surfaces; DNA; Potential surface; Density functional method; Environment; Dimer; Models; Oligonucleotide; Aqueous solution; Chemical reactivity; frontier orbitals; Dimerization; Photochemistry
• ISSN: 1439-4235; 1439-7641; 1439-7641
• DOI: 10.1002/cphc.201000081

The electronic structure during the formation of a cyclobutane pyrimidine dimer (CPD) between two thymine bases is investigated using semi‐empirical and first‐principles approaches. The dimerization of two isolated thymine bases is found to have no barrier or a very small barrier in agreement with previous studies suggesting low photostability of DNA. The well‐known high photostability of DNA can only be explained taking other factors into account. We investigate the role of the exciton location in the particular environment. Different model systems, from isolated thymine bases to an oligonucleotide in aqueous solution, are discussed. Analysis of the frontier orbitals allows one to understand the connection between the location of the exciton, the relative orientation of the thymine bases, and the observed reactivity. The amazing photostability of DNA: The location of the exciton contributes strongly to the low quantum yield of the formation of the cyclobutane pyrimidine dimer (CPD damage). Density functional calculations of DNA oligomers (see picture) demonstrate how exciton localization on a pair of pyrimidine bases is connected to their relative orientation at the time of excitation.