Lattice vibrational modes of poly(rU) and poly(rA)

Abstract

Abstract A normal coordinate analysis has been performed for the polyribonucleotides poly(rU) and poly(rA). The polymers are assumed to be 11‐fold infinite helical structures in the A conformation. The hydrogen atoms have been rigidly attached to the appropriate atoms in order to reduce the dimension of the problem. The potential energy is defined in terms of a valence force field initially and a model for the inclusion of nonbonded interactions has been presented. A method for factoring the secular equation for infinite helical polymers in Cartesian coordinates is presented. All of the general features of polyribonucleotide spectra have been reproduced and, in many cases, good quantitative agreement between observed and calculated frequencies is obtained. More specific assignments are offered for some of the observed lines.