Hyper Rayleigh scattering from DNA nucleotides in aqueous solution.

Nucleotides are organic compounds consisting of a phosphate group, a nitrogenous base, namely adenine (A), thymine (T), cytosine (C), or guanine (G), and a sugar, here deoxyribose. The magnitude of the first hyperpolarizability β of these four DNA nucleotides was determined in aqueous solution with the nonlinear optical technique of hyper rayleigh scattering under non resonant conditions at a fundamental wavelength of 800 nm. The smallest value is found to be 1.67 ± 0.15 × 10-30 esu for thymidine-5'-monophosphate and the highest is 1.76 ± 0.16 × 10-30 esu for 2'-guanosine-5'-monophosphate. Polarization resolved studies were also performed to question the symmetry of the first hyperpolarizability tensor and access the ratio of some elements of the first hyperpolarizability tensor. These experimental results were then compared to the theoretical values of these first hyperpolarizabilities obtained with the density functional theory at the level of the PCM-B3LYP/6-31G+(d) basis and taking into account the solvent.