Johnson P, Thornton A C
Biochem J. 1969 Dec;115(4):725-32. doi: 10.1042/bj1150725.
The rotational relaxation time, rho, calculated from measurements of fluorescence depolarization, is clearly dependent on the assumed mean life-time, tau, of the excited state. However, variations in tau with experimental conditions (temperature and solvent composition) occur and the effect of such alterations in tau is demonstrated. In particular it should be noted that, unless life-time changes can be excluded, the occurrence of linear plots of reciprocal degree of polarization against the temperature/viscosity ratio does not necessarily indicate the absence of intramolecular freedoms. An attempt to correct for such life-time changes by measurement of the fluorescence intensity is made for the bovine serum albumin-1-dimethyl-aminonaphthalene-5-sulphonyl chloride system. The value of rho/3tau thus obtained for this system at 20 degrees is approx. 4.7, as against approx. 3.4 obtained by several workers in the absence of life-time corrections.
由荧光去极化测量计算得到的转动弛豫时间ρ显然取决于所假定的激发态平均寿命τ。然而，τ会随实验条件（温度和溶剂组成）发生变化，并且展示了τ的这种改变所产生的影响。特别需要注意的是，除非能够排除寿命变化的影响，否则极化度倒数与温度/粘度比的线性关系图的出现并不一定表明不存在分子内自由度。对于牛血清白蛋白 - 1 - 二甲基氨基萘 - 5 - 磺酰氯体系，尝试通过测量荧光强度来校正这种寿命变化。该体系在20摄氏度时由此得到的ρ/3τ值约为4.7，而在未进行寿命校正时，几位研究人员得到的值约为3.4。
