Optical properties of deoxyribonucleic acid (DNA) polymer host

Abstract

DNA is emerging as a novel exciting photonic polymer material due to its unique double-helix structure and the ability to act as a host capable to be aligned itself and capable of inducing orientation of nonlinear optical (NLO) chromophores. Physical and optical properties of DNA are remarkably modified with the alteration of the nucleic acid counter-ions. We determined optical properties of salmon-derived DNA and DNA complexed with cetyltrimethyl-ammonium (CTMA) surfactant in solutions and films. Absorption coefficients derived for an average nucleotide formula weight indicated DNA of high purity. Prism coupling measurements showed a large birefringence in refractive indices in the direction parallel and perpendicular to the surface plane of the films indicating anisotropic alignment of DNA molecules. Almost isotropic refractive indices were measured in DNA-CTMA films indicating disorder in orientation of DNA-CTMA molecules in the films. Doping with about 5 wt% Disperse Red 1 (DR1) essentially did not change this very weak birefringence in the DNA-CTMA films. Optical properties of DNA films were sensitive to environmental humidity while the DNA-CTMA films were less susceptible to it. The Z-scan technique using femtosecond pulsed laser system was employed to determine the NLO properties of DNA in solutions in the 530-1300 nm wavelength range.