Optical Properties of Polymers: Model Calculations for Dinucleoside Phosphates

Publisher Website
Google Scholar
Abstract
The optical properties (absorption, polarizability, circular dichroism, and optical rotatory dispersion) are calculated for models of dinucleoside phosphates using the time‐dependent Hartree theory with a simple free‐electron monomer model. Detailed results over the entire frequency spectrum have been obtained for a variety of dimer and polymer structures. The relation between the following conformational effects and the resulting polymer optical properties were determined: base stacking and unstacking, helical winding and unwinding, and changes in distance between monomer planes. In addition, several other optical effects were calculated: the relative contributions of nearest and nonnearest neighbors along an infinite helical polymer; the effect of band half‐width on the observable splitting; and the relation between monomer and polymer line shape. The calculated results predict reasonable quantitative values as well as the main qualitative features of the experimental dinucleoside phosphate and polyribonucleotide spectra. The stacking–unstacking calculations are consistent with the experimental temperature dependencies of the hypochromism and optical rotation of ApA, and the right‐handed‐stacked conformation of this dimer is confirmed.