DISCRETE PHASE-TRANSITION OF GIANT DNA DYNAMICS OF GLOBULE FORMATION FROM A SINGLE MOLECULAR CHAIN

We found that a single chain of double strand DNA molecule undergoes a first-order phase transition by the direct observation of the conformation in individual DNA with fluorescence microscopy. It has become clear that a single DNA chain changes its higher order structure between expanded coil and shrunken globule in a discrete manner. The effective volume occupied by a single DNA chain in the coil state is ca. 10(4) times greater than that in the globule state. The dynamic process of the globule formation, or nucleation and growth, is analyzed by measuring individual DNA molecules with fluorescence microscopy. We show chat the apparent contour length of the DNA coil decreases with a constant speed, accompanied by the growth of the globular structure.