Perkins T T, Smith D E, Chu S
Department of Physics, Stanford University, CA 94305.
Science. 1994 May 6;264(5160):819-22. doi: 10.1126/science.8171335.
Tube-like motion of a single, fluorescently labeled molecule of DNA in an entangled solution of unlabeled lambda-phage DNA molecules was observed by fluorescence microscopy. One end of a 16- to 100-micrometer-long DNA was attached to a 1-micrometer bead and moved with optical tweezers. The molecule was stretched into various conformations having bends, kinks, and loops. As the polymer relaxed, it closely followed a path defined by its initial contour. The relaxation time of the disturbance caused by the bead was roughly 1 second, whereas tube-like motion in small loops persisted for longer than 2 minutes. Tube deformation, constraint release, and excess chain segment diffusion were also observed. These observations provide direct evidence for several key assumptions in the reptation model developed by de Gennes, Edwards, and Doi.
通过荧光显微镜观察到，在未标记的λ噬菌体DNA分子的缠结溶液中，单个荧光标记的DNA分子呈管状运动。一条16至100微米长的DNA一端附着在一个1微米的珠子上，并用光镊移动。该分子被拉伸成具有弯曲、扭结和环的各种构象。当聚合物松弛时，它紧密遵循由其初始轮廓定义的路径。珠子引起的扰动的松弛时间约为1秒，而小环中的管状运动持续超过2分钟。还观察到管变形、约束释放和过量链段扩散。这些观察结果为德热纳、爱德华兹和多伊提出的爬行模型中的几个关键假设提供了直接证据。
