title: Noncanonical Stacking Geometries of Nucleobases as a Preferred Target for Solar Radiation.
abstract: Direct DNA absorption of UVB photons in a spectral range of 290-320 nm of terrestrial solar radiation is responsible for formation of cyclobutane pyrimidine dimers causing skin cancer. Formation of UVB-induced lesions is not random, and conformational features of their hot spots remain poorly understood. We calculated the electronic excitation spectra of thymine, cytosine, and adenine stacked dimers with ab initio methods in a wide range of conformations derived from PDB database and molecular dynamics trajectory of thymine-containing oligomer. The stacked dimers with reduced interbase distances in curved, hairpin-like, and highly distorted DNA and RNA structures exhibit excitonic transitions red-shifted up to 0.6 eV compared to the B-form of stacked bases, which makes them the preferred target for terrestrial solar radiation. These results might have important implications for predicting the hot spots of UVB-induced lesions in nucleic acids.
authors: Department of Molecular Biophysics and Polymer Physics, St. Petersburg State University , 7/9 Universitetskaya nab., St. Petersburg 199034 Russia.
authors: Ruslan R
authors: RR
authors: Ramazanov
authors: Department of Molecular Biophysics and Polymer Physics, St. Petersburg State University , 7/9 Universitetskaya nab., St. Petersburg 199034 Russia.
authors: Dmitriy A
authors: DA
authors: Maksimov
authors: Department of Molecular Biophysics and Polymer Physics, St. Petersburg State University , 7/9 Universitetskaya nab., St. Petersburg 199034 Russia.
authors: Alexei I
authors: AI
authors: Kononov
mesh_terms: D019281:Dimerization; D056004:Molecular Dynamics Simulation; D009696:Nucleic Acids / Q000737:chemistry*; D013941:Thymine / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D009696:Nucleic Acids; D013941:Thymine