Hydration properties of DNA-lysine gels by microwave dielectric measurements as a function of temperature

Dielectric measurements by a cavity perturbation method at 10 GHz in the temperature range from -20 degrees C to +45 degrees C are reported for aqueous gels of herring sperm DNA in the presence of 1 or 3 lysine molecules per nucleotide. Measurements for lysine-water and DNA-water systems are also reported. The experimental results can be accounted for by the presence of interfacial water, with dielectric properties different from those of bulk water, and are analyzed in terms of a three component equation (solute molecules, interfacial water and bulk water) to calculate hydration parameters of the systems. The lysine molecule is found to coordinate a particular number of water molecules, in agreement with the literature. The specific hydration of DNA is reduced by the presence of lysine, indicating a direct interaction between the polyion and the aminoacid: a decrease to about 50% was observed at a ratio of one molecule of lysine per nucleotide. A suggestion is made that the interaction is mainly electrostatic in nature.