Vincent M, de Foresta B, Gallay J, Alfsen A
Biochemistry. 1982 Feb 16;21(4):708-16. doi: 10.1021/bi00533a019.
A set of n-(9-anthroyloxy) fatty acids [2-, 7-, 9-, and 12-(9-anthroyloxy)stearic acid (AS) and 16-(9-anthroyloxy)palmitic acid (16-AP)] has been studied by time-resolved and steady-state fluorescence anisotropy measurements in isotropic media (i.e., propylene glycol and a liquid paraffinic oil, Primol 342) and in vesicles of dipalmitoylphosphatidylcholine. The two modes of rotation, "in-plane" and "out-of-plane", of the anthroyl ring can be detected by varying the excitation wavelength. In both isotropic solvents, the value of the in-plane rotational rate is of the same order of magnitude as the out-of-plane rate for each one of the n-(9-anthroyloxy) fatty acids. In propylene glycol, the anthroyl ring motions are similar for all derivatives except for the 16-AP for which the fluorophore rotates at a higher rate. In the liquid paraffinic oil, identical motions of the fluorophore are observed for the 7-, 9-, and 12-AS; the motion for the 16-AP is again faster, while that for the 2-AS is slower. Moreover, the fluorophore motion for each probe is faster in this solvent that in propylene glycol in conditions of identical viscosity. When embedded in phospholipid bilayers, these probes report the microenvironment at a graded series of depths from the surface to the center of the bilayer [Haigh, E. A., Thulborn, K. R., & Sawyer, W. H. (1979) Biochemistry 18, 3525--3532]. Studies in dipalmitoylphosphatidylcholine vesicles have been performed at three temperatures (21, 37, and 47 degrees C) corresponding to different lipid phases. The out-of-plane mode of rotation is unhindered as demonstrated by an anisotropy decay profile asymptotic to zero. Thus, evaluation of a membrane "fluidity" parameter at different depths of the bilayer is possible, even in the steady-state mode of observation. When the in-plane mode of rotation contributes to the anisotropy decay, a hindrance to the motion is observed below the gel to liquid-crystalline transition. Then information about lipid order can be obtained from the plateau value (r infinity) of the fluorescence anisotropy decay. In the pretransition temperature range (37 degrees C), the results evidence the existence of structural lipid changes mainly localized in the hydrophobic core of the bilayer. The main transition leads to a complete disappearance of the hindrances on the in-plane rotation.
通过在各向同性介质（即丙二醇和液态链烷烃油Primol 342）以及二棕榈酰磷脂酰胆碱囊泡中进行时间分辨和稳态荧光各向异性测量，研究了一组n -（9 - 蒽氧基）脂肪酸[2 -、7 -、9 - 和12 -（9 - 蒽氧基）硬脂酸（AS）以及16 -（9 - 蒽氧基）棕榈酸（16 - AP）]。通过改变激发波长，可以检测到蒽环的两种旋转模式，即“面内”和“面外”旋转。在两种各向同性溶剂中，对于每种n -（9 - 蒽氧基）脂肪酸，面内旋转速率的值与面外旋转速率处于相同的数量级。在丙二醇中，除了16 - AP的荧光团旋转速率较高外，所有衍生物的蒽环运动相似。在液态链烷烃油中，观察到7 -、9 - 和12 - AS的荧光团运动相同；16 - AP的运动再次更快，而2 - AS的运动较慢。此外，在相同粘度条件下，每种探针在这种溶剂中的荧光团运动比在丙二醇中更快。当嵌入磷脂双层时，这些探针报告了从双层表面到中心一系列不同深度处的微环境[Haigh, E. A., Thulborn, K. R., & Sawyer, W. H. (1979) Biochemistry 18, 3525 - 3532]。在二棕榈酰磷脂酰胆碱囊泡中进行的研究是在对应于不同脂质相的三个温度（21、37和47摄氏度）下进行的。面外旋转模式不受阻碍，这通过渐近于零的各向异性衰减曲线得到证明。因此，即使在稳态观察模式下，也可以评估双层不同深度处的膜“流动性”参数。当面内旋转模式对各向异性衰减有贡献时，在凝胶态到液晶态转变以下观察到运动受到阻碍。然后可以从荧光各向异性衰减的平台值（r∞）获得有关脂质有序性的信息。在转变前温度范围（37摄氏度）内，结果表明主要存在于双层疏水核心中的结构脂质变化。主要转变导致面内旋转的阻碍完全消失。
