The refractive indices of wet-spun films of CsDNA have been measured for light polarized parallel and perpendicular to the helical axis as a function of relative humidity (RH). These data have been combined with previously published data (Biopolymers 30 (1990) 877-887) for the volume per base pair and water content as a function of RH in order to extract the optical polarizabilities. This work was motivated by the study of Weidlich et al. (Biopolymers 26 (1987) 439-453) who reported a approximately 35% increase at the A-to-B transition in the parallel and perpendicular polarizabilities of NaDNA. In contrast, a much smaller increase in the polarizabilities of CsDNA is found near the A-to-B transition: approximately 12% for the perpendicular direction and < or = 4% for the parallel direction.

SYNOPSISThe uv absorption of Na-hyaluronate ( NaHA) films and the refractive indices, water content, and swelling of LiHA films have been measured as a function of relative humidity. Three peaks are observed in the uv absorption of NaHA (at about 250, 310, and 330 nm) for water content above 10 water molecules per disaccharide. The absorptivity of the 250, 310, and 330 nm peaks increase as the water content increases, indicating a change in the electronic properties of the HA molecule. The refractive indices, water content, and swelling of LiHA films are used to determine the optical polarizability via the Lorentz-Lorenz relation. The polarizability of LiHA is found to have a similar dependence on water content as NaHA, though the changes observed are larger in magnitude.

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