An Approximate Approach to DNA Denaturation

A quantum-statis tical-mechanical theory of equilibrium states was de­ veloped to present a simple realistic model of DNA denaturation. Applying the Feynman free energy minimum principle approach to the free energy of an anhar- monic oscillator representing an interchain H-bond between DNA strands a simple formula for its melting temperature was derived. Experimental Raman and IR vibrational data were used, and if not available the vibrational data for individual H-bonds in guanine-cytos ine and adenine-thymine base pairs were assigned using the Prohofsky self-consistent phonon approach; moreover, the Morse potential pa­ rameters were taken over from the same source. On the basis of them the H-bond force constants and then H-bond melting temperatures were calculated for individ­ ual H-bonds in the base pairs. The calculated average melting temperatures were compared with the experimental ones for various samples of DNA. Very reasonable results were obtained.