Southern E M, Anand R, Brown W R, Fletcher D S
Nucleic Acids Res. 1987 Aug 11;15(15):5925-43. doi: 10.1093/nar/15.15.5925.
The idea that large DNA molecules adopt a stretched conformation as they pass through gels suggests a simple mechanism for the separation of DNA by crossed field electrophoresis: at each change in field direction a DNA molecule takes off in the new direction of the field by a movement which is led by what was formerly its back end. The effect of this ratcheting motion is to subtract from the DNA molecule's forward movement, at each step, an amount which is proportional to its length. We find that this model explains most of the features of the separation, and we describe experiments, using a novel electrophoresis apparatus, which support the model. The apparatus turns the gel between two preset orientations in a uniform electric field at preset time intervals. This separation method has the practical advantage over some others that the DNA molecules follow straight tracks. A further advantage is that the parameters which determine the separation are readily predicted from the simple theory describing their motion.
大的DNA分子在通过凝胶时会呈现拉伸构象，这一观点为通过交变电场电泳分离DNA提供了一种简单机制：在电场方向每次改变时，DNA分子会从前端开始移动，朝着电场的新方向前进。这种棘轮运动的效果是，在每一步中，从DNA分子的向前移动中减去与其长度成正比的量。我们发现该模型解释了分离的大部分特征，并描述了使用新型电泳装置进行的实验，这些实验支持该模型。该装置在预设的时间间隔内，在均匀电场中将凝胶在两个预设方向之间转动。这种分离方法相对于其他一些方法具有实际优势，即DNA分子沿着直线轨迹移动。另一个优点是，从描述其运动的简单理论中可以很容易地预测决定分离的参数。
