Evidence for glass transitions in biological systems from dielectric studies

Despite several reports in recent years on glass or glass-like transitions in different biological systems, their existence is still controversial. In the present work, the authors use the method of thermally stimulated depolarization currents (TSDC), which is very sensitive to transitions and has been widely used in the study of glass transitions in synthetic polymeric systems, to investigate this question. Thermograms obtained with different systems (plant tissue, proteins, saccharides) show, at high water contents, transitions in the temperature range of 170-200 K, which shift to higher temperatures with decreasing water content. The results are discussed in terms of glass transitions of the hydration water and the matrix structure