Exciton Band Structures in Homopolynucleotides

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Abstract
Singlet exciton band structures in single stranded homogeneous polynucleotides have been determined within the framework of Frenkel exciton model without or with interband configuration mixing. Intermonomer interactions are taken into account to a distance of the order of 20Å using the best available π-electron molecular orbitals obtained by us in the previous study. Configuration mixing between lowest nine exciton bands is taken into account explicitly. Mixing process seems to be very important to determine reliable band widths, especially in poly A. Obtained band widths are 0.64 eV in poly A, 0.34 eV in poly U, 0.55 eV in poly G and 0.26 eV in poly C respectively without configuration mixing and 0.25 eV in poly A, 0.34 eV in poly U, 0.49 eV in poly G and 0.23 eV in poly C respectively with configuration mixing. In poly A and poly U the absorption maximum corresponding to the lowest excitation slightly shifts to the short wave length side from that of monomer. On the contrary, appreciable red shifts can be found in poly G and poly C.