The structure of water absorbed in collagen. I. The dielectric properties.

Abstract

AbstractThe dielectric constant and the loss factor of water in collagen are measured for various water, NaCl, and HCl contents at frequencies ranging from 102 to 105 Hz and at temperatures ranging from −70° to +23°C. For all measurements, both the dielectric constant and the loss decrease monotonically as the frequency increases, or the temperature decreases; the absence of a maximum in the loss curves as a function of temperature and frequency indicates an extremely broad spectrum of relaxation times. By shifting the curves obtained for the dielectric constant and the loss factor along the log–frequency axis, all data, obtained at different temperatures, can be represented on master curves valid for 23°C.In order to explain these results, water molecules are assumed to be hydrogen bonded to each other in long chains. All water molecules in a chain can, cooperatively, be oriented in two different directions along the channel, resulting in large, reversible, dipole moments. These chains are not rigid, but are flexible liquid‐like structures. Diffusion of chains as entities is assumed to be the rate‐limiting step for dipole reorientation. Although the rate of diffusion decreases inversely proportional to chain length, the activation energy is independent of chain length. At lower temperatures, diffusion becomes slower, until at the glass point, approximately −100°C, it ceases.