日 時：2010年4月8日(金曜日) 15:30-16:30
場 所：工学部６号館１階 大会議室（１０３号室）
講 師：Prof.Chin-Kun Hu
(Institute of Physics, Academia Sinica,Taiwan)
題 目：”Simple models for relaxation and aggregation of biopolymers, and q-statistics”
Many important biological macromolecules, such as starch, DNA, RNA, protein, etc are biopolymers. Relaxation and aggregation of biopolymers are closely related to biological functions of biological systems, e.g. many neurodegenerative diseases in humans or animals, such as Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, frontotemporal lobar degeneration, etc. are related to the aggregation of proteins. Here we propose simple models for relaxation and aggregation of biopolymers. We have used molecular dynamics to simulate various systems of polymer chains and Lennard-Jones molecules; the neighboring monomers along a polymer chain are connected by rigid bonds  or spring of strength kspring . We find that the velocity distributions of monomers in a wide range of simulation time can be well described by Tsallis q-statistics  with q larger or equal 1 and a single scaling function; the value of q is related to the conformation constraining potential, the interactions with background fluid, the destruction of chain homogeneity or the value of kspring; when q → 1, the velocity distribution of monomers becomes Maxwell-Boltzmann distribution. We have calculated some correlation functions along the polymer chains to understand the geometrical origin of q-statistics with q larger or equal 1. We also find that the polymer chains tend to aggregate as neighboring monomers of a polymer chain have small or zero bending-angle and torsion-angle dependent potentials [4,5]. Our result is useful for understanding mechanism of protein aggregation.
1. W.-J. Ma, and C.-K. Hu, J. Phys. Soc. Jpn. 79, 204005 (2010).
2. W.-J. Ma, and C.-K. Hu, J. Phys. Soc. Jpn. 79, 204006 (2010).
3. C. Tsallis, J. Stat. Phys. 52, 479 (1988).
4. W.-J. Ma, and C.-K. Hu, J. Phys. Soc. Jpn. 79, in press (2010).
5. C.-K. Hu and W.-J. Ma, Prog. Theo. Phys. Supp., in press (2010).