Transition dynamics of biological systems on mesoscopic scales: Effects of flexibility and fluctuations

The biological systems described as soft matter on mesoscopic scales manifest, in contrast to hard (condensed) matter, a number of characteristics: complexity, flexibility, and fluctuations. Due to these, there arise a variety of conformational and nonequilibrium phase transitions at physiological temperatures, which seems to be relevant to biological functions. Also, the novel noise-induced phenomena such as stochastic resonance and resonant activation give rise to new possibilities for biological cooperativity and sensitivity to environment. This paper reviews our recent theoretical studies of transition dynamics in membrane/polymer systems based on the methodology of soft matter and stochastic process physics, with emphasis on the effects of flexibility and fluctuations, and their implication to biological self-organization. As examples, polymer translocation and the related problem of pore growth in membrane will be discussed.