Ohyashiki T, Ushiro H, Mohri T
Biochim Biophys Acta. 1986 Jun 26;858(2):294-300. doi: 10.1016/0005-2736(86)90334-2.
The effect of alpha-tocopherol on the lipid fluidity of porcine intestinal brush-border membranes was studied using pyrene as a fluorescent probe. Addition of alpha-tocopherol to the medium decreased fluorescence intensity and lifetime, but increased the fluorescence polarization of pyrene-labeled membranes. beta-, gamma-, and delta-Tocopherols gave no appreciable effect on the fluorescence intensity and polarization of the complex. The apparent dissociation constant (3.1 +/- 0.12 microM) of the interaction of alpha-tocopherol with the membranes, estimated from the change in the fluorescence intensity with varying concentrations of alpha-tocopherol, was in good agreement with the concentration required to cause the half-maximal inhibition of lipid peroxidation of the membranes performed by incubation with 100 microM ascorbic acid and 10 microM Fe2+. Decrease of the slope in the thermal Perrin plot of the polarization of pyrene-labeled membranes by alpha-tocopherol suggests that the movement of pyrene molecules in the membranes is restricted by binding of the tocopherol. This interpretation was confirmed by an increased harmonic mean of the rotational relaxation time of the dye molecules in the membranes from 10.9 +/- 0.16 to 18.5 +/- 0.51 microseconds after addition of 25 microM alpha-tocopherol to the medium. The perturbation of lipid phase in the membranes induced by alpha-tocopherol was also suggested from a decreased quenching rate constant of pyrene fluorescence in the membranes for Tl+. Based on these results, the effect of alpha-tocopherol on the lipid fluidity of the membranes is discussed.
以芘作为荧光探针，研究了α-生育酚对猪小肠刷状缘膜脂质流动性的影响。向培养基中添加α-生育酚会降低荧光强度和寿命，但会增加芘标记膜的荧光偏振。β-、γ-和δ-生育酚对复合物的荧光强度和偏振没有明显影响。根据不同浓度α-生育酚下荧光强度的变化估算，α-生育酚与膜相互作用的表观解离常数为（3.1±0.12微摩尔），这与通过与100微摩尔抗坏血酸和10微摩尔Fe2+孵育使膜脂质过氧化受到半数最大抑制所需的浓度高度一致。α-生育酚使芘标记膜的热佩林偏振图斜率降低，这表明膜中芘分子的运动因生育酚的结合而受到限制。向培养基中添加25微摩尔α-生育酚后，膜中染料分子的旋转弛豫时间的调和平均值从10.9±0.16微秒增加到18.5±0.51微秒，这证实了上述解释。对于Tl+，膜中芘荧光猝灭速率常数降低也表明α-生育酚诱导了膜中脂质相的扰动。基于这些结果，讨论了α-生育酚对膜脂质流动性的影响。
