An approximate approach to DNA denaturation.

A quantum-statistical-mechanical theory of equilibrium states was developed to present a simple realistic model of DNA denaturation. Applying the Feynman free energy minimum principle approach to the free energy of an anharmonic 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-cytosine and adenine-thymine base pairs were assigned using the Prohofsky self-consistent phonon approach; moreover, the Morse potential parameters 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 individual 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.