Statistical physics has been shown to be useful for understanding macroscopic properties of a physical system from the interactions of atoms or molecules of that system. After the development of molecular biology, it is of interest to know whether statistical physics can be useful for understanding some fundamental problems in biological systems, e.g. "Why a biological system can maintain in a non-equilibrium state?". This talk will try to provide some hints for answering this question. It has been widely known that a spin glass model can be used to understand the slow relaxation behavior of a glass at low temperatures [1]. We have used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that polymer chains with neighboring monomers connected by rigid bonds can relax very slowly and show glassy behavior [2]. We have also found that native collagen fibrils [3] and a hemoglobin crystal [4] show glassy behavior at room temperatures . The results of [2-4] about the glassy behavior of polymers or proteins are useful for understanding the mechanism for a biological system to maintain in non-equilibrium state, including the ancient seed [5], which can maintain in a non-equilibrium state for a very long time.

(1) C. Dasgupta, S.-K. Ma, and C.-K. Hu, Phys. Rev. B 20, 3837 (1979).
(2) W.-J. Ma and C.-K. Hu, J. Phys. Soc. Japan 79, 024005, 024006, 054001, and 104002 (2010).
(3) S. G. Gevorkian, A. E. Allahverdyan, D. S. Gevorgyan and C.-K. Hu, EPL 95, 23001 (2011).
(4) S. G. Gevorkian, A. E. Allahverdyan, D. S. Gevorgyan and C.-K. Hu, PRL, submitted.
(5) S. Sallon, et al. Germination, genetics, and growth of an ancient date seed, Science 320, 1464 (2008).