Thermodynamics and Kinetics on the Folding Transition of Single Molecular Chain

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A great progress has been attained with our studies on the folding phase transition at the level of a single molecule both in theoretical and experimental approaches. In the theoretical approach, we have employed simulations of molecular dynamics incorporating Brownian motion and kinetic analyses on folding processes of a single molecule. As a result, it has become clear that ordered structures in nanometer scale are generated through the process of nucleation ＆ growth. It has also been indicated that the probability of the nuclear formation is a Poisson-like process and the growth is a time-linear process. It has also become clear that disordered spherical condensed structure is generated by spinodal decomposition in high degree of non-equilibrium. In the experimental approach, studies on transportation and structure regulation of a single polymer chain by use of infrared laser have been developed. Dielectric traps by YAG laser light beam at 1000 nm in wave length were performed with setting the focus within about 1 μm. Under such experimental conditions, chemicai degradation on DNA molecules is avoided. We showed that a long DNA molecule in compact structure formed through folding transition can be easily transported in solution without any chemical modification. We further found that the structure of a long DNA molecule is regulated without any mechanical treatment, by transporting the specimen to the solution with different chemical compositions. Our study provides the principle technology that leads to a LABORATORY for the μm-scaled microscopic chemistry and molecular biology.