Low-frequency spectroscopy of four-photon scattering of laser radiation in aqueous solutions of biopolymers

Abstract

Four-photon scattering (FPS) spectroscopy is used to record rotational resonances of H2O and H2O2 molecules in aqueous solutions of DNA and denatured DNA within a range of ±10 cm-1 with a spectral resolution of 3 GHz. The resonance contribution of rotational transitions of these molecules in solutions was found to be considerably larger than that in distilled water. This fact is interpreted as a manifestation of the specific properties of a hydrate layer at the interface between water and DNA or denatured DNA molecules. An analysis of the FPS spectra shows that the concentration of H2O2 molecules in the hydrate layer of the DNA molecule increases threefold after denaturation. In addition, the FPS spectra of aqueous solutions of α-chymotrypsin protein with concentrations of 0-20 mg cm-3 were measured in the spectral range of ±7 cm-1. It is found that the velocity of hypersound in the protein aqueous solution, which is measured by the shift of the Mandelstam—Brillouin scattering spectrum components, is a cubic function of the concentration and reaches 3000 m/s at 20 mg/cm3.