释义：

Because of the long lifetimes of excited fluorescent molecules (nanoseconds), fluorescence can be used to monitor the rotational motion of molecules, which occurs on this timescale. This is accomplished experimentally by excitation with plane-polarized light, followed by measurement of the emission at parallel and perpendicular planes. Since rotational correlation times depend on the size of the molecule, this method can be used to measure the binding of two proteins because the observed polarization increase when a larger complex is formed. A fluorescence anisotropy experiment is normally carried out with a protein bearing a covalently added fluorescent group, which increases both the observed fluorescence lifetime of the excited state and the intensity of the fluorescent signal. Residue modification can be assessed by addition of an antibody which binds to the modified residue and alters the molecular weight of the complex. A variation of this technique has been used to show interaction of a DNA binding protein with another protein. In this case the DNA rather than protein is fluorescently labelled.

由于激发荧光分子的寿命较长 (纳秒级)， 荧光可以用来监测分子旋转运动，旋转运动发生在此时间尺度内。实验中通过平面极化光激发，随后测量平行和平面垂直的发射。由于旋转相关时间依赖于分子大小，因此该方法可以用来测量两个蛋白质的结合，因为当较大复合物形成时，观察到的极化度会增加。荧光各向异性实验通常使用带有共价荧光标签的蛋白质，这样既增加了激发态的荧光寿命，也增加了荧光信号的强度。