EFFECT OF LIBRATIONAL MOTION ON FLUORESCENCE DEPOLARIZATION AND NUCLEAR MAGNETIC-RESONANCE RELAXATION IN MACROMOLECULES AND MEMBRANES
EFFECT OF LIBRATIONAL MOTION ON FLUORESCENCE DEPOLARIZATION AND NUCLEAR MAGNETIC-RESONANCE RELAXATION IN MACROMOLECULES AND MEMBRANES
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DOI：
10.1016/s0006-3495(80)85109-5
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发表时间：
1980-01-01
影响因子：
3.4
通讯作者：
SZABO, A
中科院分区：
文献类型：
--
作者：
LIPARI, G;SZABO, A
本文发展了圆柱形探针在膜悬浮液中的荧光发射各向异性[r（t）]理论。它表明，独立于任何模型，极限各向异性[r（无穷大）]正比于探针序参量的平方。序参数决定了探针的平衡取向分布函数在一系列勒让德多项式中展开的第一个非平凡项。遵循Kinosita、Kawato和Ikegami，探针的运动被描述为在半角θ 0的圆锥内的扩散（摆动）。在该模型的框架内，考虑了r（t）的精确单指数近似。导出了将出现在上述近似中的有效弛豫时间与θ 0和用于摆动的扩散系数相关联的解析表达式。该模型被推广到的情况下，探针被附着到一个大分子的运动不能忽略的时间尺度上的荧光实验。通过利用荧光去极化和13 C-NMR偶极弛豫理论之间的形式相似性，对于非刚性地附着于大分子并经历描述为在半角θ 0的球冠上扩散的自由运动的质子化碳，导出T1、T2和核Overhauser增强的表达式。
The theory of fluorescent emission anisotropy [r(t)] of a cylindrical probe in a membrane suspension is developed. It is shown, independent of any model, that the limiting anisotropy [r (.infin.)] is proportional to the square of the order parameter of the probe. The order parameter determines the 1st nontrivial term in the expansion of the equilibrium orientational distribution function of the probe in a series of Legendre polynomials. Following Kinosita, Kawato and Ikegami, the motion of the probe is described as diffusion (wobbling) within a cone of semiangle .theta.0. Within the framework of this model, an accurate single-exponential approximation for r(t) is considered. An analytic expression relating the effective relaxation time, which appears in the above approximation, to .theta.0 and the diffusion coefficient for wobbling is derived. The model is generalized to the situation where the probe is attached to a macromolecule whose motion cannot be neglected on the time scale of the fluorescence experiment. By exploiting the formal similarity between the theory of fluorescence depolarization and 13C-NMR dipolar relaxation, expressions for T1, T2 and the nuclear Overhauser enhancement are derived for a protonated carbon which is nonrigidly attached to a macromolecule and undergoes librational motion described as diffusion on a spherical cap of semiangle .theta.0.