Kagan V E, Quinn P J
Department of Biochemistry, King's College London, England.
Eur J Biochem. 1988 Feb 1;171(3):661-7. doi: 10.1111/j.1432-1033.1988.tb13837.x.
The intrinsic fluorescence of tocopherol homologues with hydrocarbon chains ranging from 1 carbon (C1) to 16 carbons (alpha-tocopherol, C16) and their ability to quench the fluorescence of 9-anthroyloxy derivatives of fatty acids with the fluorophore located at different positions in the hydrophobic domain of phospholipid bilayers has been used to model the interaction of tocopherol with lipid bilayer membranes. All the tocopherol homologues used, C1, C6, C11 and alpha-tocopherol, showed a similar fluorescence emission intensity at 325 nm in cyclohexane but were almost completely self-quenched by aggregation in water. Fluorescence was restored when dispersions of dimyristoylglycerophosphocholine were added but the maximum intensity was lower with the longer-chain homologues. Full intensity was observed in all homologues on addition of the detergent Triton X-100. Studies using 9-anthracenecarboxylic acid and 9-anthracenecarboxymethyl ester, 6-(9-anthroyloxy)stearic acid and 16-(9-anthroyloxy)palmitelaidic acid showed that the tocopherol homologues partitioned into the hydrophobic domain of phospholipid dispersions composed of dimyristoylglycerophosphocholine at 40 degrees C and dioleoylglycerophosphocholine at 40 degrees C. The 9-anthroyloxy fatty acids and 1,6-diphenyl-1,3,5-hexatriene were quenched by all the homologues and Stern-Volmer plots of the concentration dependence of the quenching indicated that this was predominantly via dynamic processes. No fluorescence energy transfer was observed between diphenylhexatriene and tocopherols but efficient transfer was recorded to the 9-anthroyloxy fatty acid probes. The results are consistent with a model in which the chromanol nucleus of tocopherol is oriented towards the lipid-water interface of the phospholipid bilayer. As the phytol chain length increases there is an increasing tendency for the chromanol nucleus to reside in the hydrophobic interior of the structure. alpha-Tocopherol appears to form clusters within the phospholipid dispersion which are not fluorescent and do not quench the fluorescence of the different fluorescent probes nor transfer fluorescence energy to them. It is suggested that the monomeric form is responsible for the vitamin effects of tocopherol and the aggregated form acts as a reservoir that does not markedly perturb bilayer stability.
生育酚同系物的固有荧光，其碳氢链长度从1个碳原子（C1）到16个碳原子（α-生育酚，C16），以及它们淬灭脂肪酸9-蒽氧基衍生物荧光的能力（荧光团位于磷脂双层疏水结构域的不同位置），已被用于模拟生育酚与脂质双层膜的相互作用。所有使用的生育酚同系物，C1、C6、C11和α-生育酚，在环己烷中于325nm处显示出相似的荧光发射强度，但在水中几乎完全通过聚集而自淬灭。当加入二肉豆蔻酰甘油磷酸胆碱分散体时，荧光恢复，但对于链更长的同系物，最大强度较低。加入去污剂Triton X-100后，在所有同系物中均观察到了全强度。使用9-蒽甲酸和9-蒽甲酸甲酯、6-(9-蒽氧基)硬脂酸和16-(9-蒽氧基)棕榈油酸的研究表明，生育酚同系物在40℃下分配到由二肉豆蔻酰甘油磷酸胆碱组成的磷脂分散体的疏水结构域中，以及在40℃下分配到二油酰甘油磷酸胆碱的疏水结构域中。所有同系物均淬灭9-蒽氧基脂肪酸和1,6-二苯基-1,3,5-己三烯，淬灭浓度依赖性的Stern-Volmer图表明，这主要是通过动态过程。在二苯基己三烯和生育酚之间未观察到荧光能量转移，但记录到向9-蒽氧基脂肪酸探针的有效转移。结果与一个模型一致，在该模型中生育酚的色满核朝向磷脂双层的脂质-水界面。随着叶绿醇链长度的增加，色满核越来越倾向于位于结构的疏水内部。α-生育酚似乎在磷脂分散体内形成不发荧光的聚集体，这些聚集体不会淬灭不同荧光探针的荧光，也不会将荧光能量转移给它们。有人认为，单体形式负责生育酚的维生素效应，而聚集形式充当一个储库，不会显著扰乱双层稳定性。
