Rhythmic Conformational Change in a SinglePolymer Chain Induced by Laser Irradiation.

We have investigated a rhythmic conformational change in a single polymer chain (T4DNA, 166 kbp, the contour length = 56 μm) between a folded state and a elongated state under thermodynamically open conditions using a focused continuons wave (cw) Nd:YAG laser beam (wavelength λ = 1064 nm), where the focused laser beam plays dual roles both of trapping of a polymer chain at the focus and making temperature gradient there. The oscillatory phenomenon is discuseed in terms of a limit-cycle oscillation with dissipation of photon energy.