Song L, Maestre M F
Cell and Molecular Biology Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720.
J Biomol Struct Dyn. 1991 Aug;9(1):87-99. doi: 10.1080/07391102.1991.10507895.
It has been found that DNA molecules are often hooked around obstacles in a U-shaped configuration in gel electrophoresis. To understand the dynamics of the unhooking of U-shaped DNA molecules undergoing gel electrophoresis, we have examined the length changes of the longer and shorter arms of the U-shape as a function of time. Two types of unhooking have been found. In one type, the length changes of both arms are expontential in time but with different time constants. In another type, the length changes of the shorter arm is exponential and that of the longer one is linear with time. The interpretation is that the extent of stretch of the spring-like DNA chain decreases as the length difference between the two arms increases during the unhooking processes, and that the frictions at the pivot point can be relatively large depending upon the local structure of the gel. The friction coefficient at the pivot point is estimated to be nu 0 = (2.98 +/- 1.42)x10(-5) g/sec.
已发现，在凝胶电泳中，DNA分子常以U形结构钩绕在障碍物周围。为了解经历凝胶电泳的U形DNA分子解钩的动力学过程，我们研究了U形较长和较短臂的长度随时间的变化。发现了两种类型的解钩。在一种类型中，两臂的长度变化随时间呈指数关系，但时间常数不同。在另一种类型中，较短臂的长度变化呈指数关系，而较长臂的长度变化与时间呈线性关系。其解释是，在解钩过程中，随着两臂之间长度差的增加，弹簧状DNA链的拉伸程度减小，并且取决于凝胶的局部结构，枢轴点处的摩擦力可能相对较大。枢轴点处的摩擦系数估计为ν0 =(2.98±1.42)×10^(-5) g/秒。
