Rief M, Oesterhelt F, Heymann B, Gaub HE
M. Rief, F. Oesterhelt, H. E. Gaub, Lehrstuhl fur Angewandte Physik, Ludwig-Maximilians-Universitat, 80799 Munchen, Germany. B. Heymann, Theoretische Biophysik, Institut fur Medizinische Optik, Ludwig-Maximilians-Universitat 80333 Munchen, Germany.
Science. 1997 Feb 28;275(5304):1295-7. doi: 10.1126/science.275.5304.1295.
Recent developments in piconewton instrumentation allow the manipulation of single molecules and measurements of intermolecular as well as intramolecular forces. Dextran filaments linked to a gold surface were probed with the atomic force microscope tip by vertical stretching. At low forces the deformation of dextran was found to be dominated by entropic forces and can be described by the Langevin function with a 6 angstrom Kuhn length. At elevated forces the strand elongation was governed by a twist of bond angles. At higher forces the dextran filaments underwent a distinct conformational change. The polymer stiffened and the segment elasticity was dominated by the bending of bond angles. The conformational change was found to be reversible and was corroborated by molecular dynamics calculations.
皮牛顿仪器的最新进展使得对单分子的操控以及分子间和分子内力的测量成为可能。通过垂直拉伸，用原子力显微镜尖端探测连接到金表面的葡聚糖细丝。在低力作用下，发现葡聚糖的变形主要由熵力主导，并且可以用具有6埃库恩长度的朗之万函数来描述。在较高力作用下，链的伸长由键角扭转控制。在更高的力作用下，葡聚糖细丝发生了明显的构象变化。聚合物变硬，链段弹性主要由键角弯曲主导。发现这种构象变化是可逆的，并得到了分子动力学计算的证实。
