Krasnowska E K, Gratton E, Parasassi T
Istituto di Medicina Sperimentale, Consiglio Nazionale delle Ricerche, Rome, Italy.
Biophys J. 1998 Apr;74(4):1984-93. doi: 10.1016/S0006-3495(98)77905-6.
Fluorescence spectral features of 6-propionyl-2-dimethylaminonaphthalene (Prodan) in phospholipid vesicles of different phase states are investigated. Like the spectra of 6-lauroyl-2-dimethylaminonaphthalene (Laurdan), the steady-state excitation and emission spectra of Prodan are sensitive to the polarity of the environment, showing a relevant shift due to the dipolar relaxation phenomenon. Because of the different lengths of their acyl residues, the partitioning of the two probes between water and the membrane bilayer differs profoundly. To account for the contribution of Prodan fluorescence arising from water, we introduce a three-wavelength generalized polarization method that makes it possible to separate the spectral properties of Prodan in the lipid phase and in water, and to determine the probe partitioning between phospholipid and water and between the gel and the liquid-crystalline phases of phospholipids. In contrast to Laurdan, Prodan preferentially partitions in the liquid-crystalline phase with respect to the gel and is sensitive to the polar head pretransition, and its partition coefficient between the membrane and water depends on the phase state, i.e., on the packing of the bilayer. Prodan is sensitive to polarity variations occurring closer to the bilayer surface than those detected by Laurdan.
研究了6-丙酰基-2-二甲基氨基萘（Prodan）在不同相态磷脂囊泡中的荧光光谱特征。与6-月桂酰基-2-二甲基氨基萘（Laurdan）的光谱一样，Prodan的稳态激发光谱和发射光谱对环境极性敏感，由于偶极弛豫现象会出现相关位移。由于它们酰基残基长度不同，两种探针在水和膜双层之间的分配有很大差异。为了说明水中Prodan荧光的贡献，我们引入了一种三波长广义极化方法，该方法能够分离Prodan在脂质相和水中的光谱特性，并确定探针在磷脂与水之间以及磷脂凝胶相和液晶相之间的分配。与Laurdan不同，Prodan相对于凝胶更倾向于分配在液晶相中，并且对极性头部预转变敏感，其在膜与水之间的分配系数取决于相态，即取决于双层的堆积情况。Prodan对发生在比Laurdan检测到的更靠近双层表面处的极性变化敏感。
