title: Spin symmetry transitions make DNA strands separate. New insight into the mechanism of transcription.
abstract: The DFT:B3LYP (6-31G** basis set) method, including the hyperfine and spin-orbit couplings (HFC and SOC, respectively), is used to study the separation of two complementary trinucleotide sequences, (dC-dG-dA)-(dG-dC-dT), upon the action of two Mg(2+) cofactors (a simplified model). The computations reveal a crossing of the singlet (S) potential energy surface by the triplet (T) surface at two distinct points. Within the crossing region the T curve lies below the S curve. Adhering to the concept of the minimal energy path, one can assume that the T path is more favorable compared to that of the S path. The T path is not simple; it consists of two, T+ and T-, curves initially separated by the HFC and SOC. On reaching the second crossing point, both curves merge into the T0 state, which facilitates the T → S transfer. Totally, the process of the two trinucleotide separation (the first step of transcription) appears as the S → T → S symmetry conversion.
authors.affiliation: Centre for Interdisciplinary Computational and Dynamical Analysis, University of Manchester, Oxford Road, Manchester M13 9PL, UK. Saint-Petersberg State University, University Embankment, 7/9 Saint-Petersberg, 199034, RF.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Tulub
authors.forename: Vassily E
authors.initials: VE
authors.lastname: Stefanov
mesh_terms: D002412:Cations / Q000378:metabolism; D003198:Computer Simulation; D004247:DNA / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D008958:Models, Molecular; D009711:Nucleotides / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D002412:Cations; D009711:Nucleotides; D004247:DNA; D008274:Magnesium