Dynamical structure of water around biopolymers investigated by microwave dielectric measurements using time domain reflectometry method

Abstract

The dynamical structure of free water around biopolymers, such as gelatin, collagen, and globular proteins, has been characterized based on relaxation time, τ, and Cole–Cole parameter, β, obtained from microwave dielectric measurements using a time domain reflectometry method. As reported previously, the plots of β against τ for free water in seven types of synthetic polymers in aqueous solutions against τ are classified into two groups based on polymer hydrophilicity. It is indicated that the dynamical structure of water around low-hydrophilic polymers is more uniform than those around high-hydrophilic polymers. In the present work, the plots for the aqueous gels of gelatin and globular protein in aqueous solutions indicate the same feature as those for high-hydrophilic polymers. It can be expected that the dynamical structure of free water around biopolymers is uneven. However, the water structure around collagen appears to be uniform, although collagen consists almost of the same peptide chains as those of gelatin. These results suggested that the water structure around highly ordered polymers, e.g., collagen, is also uniform.