We report measurements of the water content and swelling of wet-spun films of Na-, K-, Rb-, and Cs-DNA as a function of relative humidity (rh). The water contents (number of water molecules per base pair of DNA) of these films are found to be quite similar, indicating that the identity of the counterion species is unimportant for the water content. Since the A to B transition for these DNAs occurs at different rhs, the corresponding water contents of the A to B transition are found to be quite different. These films swell as a function of rh in a very similar manner, implying that the changes in the intermolecular bonds in the different DNAs are similar. Dramatic changes are observed in the dimensions of the films above 84% rh for all types of DNA. Combining the water content and swelling measurements yields the dependence of the volume per base pair on water content. The volume per base pair is observed to be a nonlinear function of water content, indicating nonideal mixing of the water with the DNA.

A lattice-dynamical model has been developed of DNA in a crystalline lattice. This model is used to evaluate the harmonic nearest-neighbor force constants of highly oriented films of Na-, K-, Rb-, and Cs-DNA as a function of relative humidity from Raman data. These DNA-counterion systems were chosen since they all undergo an A to B transition. The analysis suggests that the 3 to B transition takes place in these different DNA's when the effective force constant of the intermolecular bond falls below a "critical" value.

The refractive indices, water content, and volume of wet-spun films of Na-hyaluronate have been measured as a function of relative humidity (rh). These data are used with the Lorentz-Lorenz formula to determine the optical polarizabilities of Na-hyaluronate parallel and perpendicular to the helical axis. The analysis reveals a drop in the optical polarizabilities of approximately 20% between 80 and 88% rh, indicating a phase transition.

We report the successful growth of ZnTe and ZnSe epitaxial layers on GaAs by pulsed laser deposition. A frequency doubled Nd:YAG laser was used to ablate/evaporate II-VI bulk targets and pressed powder targets in an ultra high vacuum enclosure. For typical growth temperatures in the range 200°-400°C x-ray analysis of the layers revealed sharp <100> peaks with no evidence of growth in other orientations. Polarization dependent Raman spectroscopy was also used to further characterize the epitaxial layers, by verifying the selection rules for backscattering from <100> oriented films. The low temperature photoluminescence spectra show distinct near-band-edge features indicating high crystalline quality. The photoluminescence of the films grown from bulk targets was superior to that of films grown from pressed powder targets, indicating that the use of high purity bulk targets is critical. Our results indicate that pulsed laser deposition is a promising new growth technique for the fabrication of II-VI epitaxial layers with unique advantages.

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.