Interdigitation does not affect translational diffusion of lipids in liquid crystalline bilayers
Interdigitation does not affect translational diffusion of lipids in liquid crystalline bilayers
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DOI：
10.1016/s0006-3495(95)80122-0
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发表时间：
1995-12-01
影响因子：
3.4
通讯作者：
Thompson, TE
中科院分区：
文献类型：
--
作者：
Schram, V;Thompson, TE
不对称磷脂酰胆碱分子的一个酰基链是另一个酰基链的两倍长，在其相变温度下，形成一个混合的交错相，其中较长的酰基链跨越整个双层。文献中的实验证据表明，在它们的相变温度以上，这些分子可能仍然表现出部分交叉，较长的酰基链部分延伸到相反的小叶中，并且比同等对称的磷脂酰胆碱排列得更紧密。利用光漂白后的荧光恢复技术，我们研究了不对称磷脂酰胆碱，1-硬脂酰-2-癸基-磷脂酰胆碱（C18C10PC）的液晶相在多层中的平移扩散。我们使用相同酰基链组成的磷脂类似物ndd - c18c10pe作为荧光探针，或相同分子量的对称等效物N-（7-硝基苯甲酸-2,3-二氮唑-4-基）-二肉豆醇基-磷脂酰乙醇胺（ndd - dmpe）作为荧光探针，并通过使用这两种探针在多层二肉豆醇基-磷脂酰胆碱（DMPC）和共晶混合物DMPC/C18C10PC （40/60 mol）中测定平移扩散系数。我们发现，在给定的宿主脂质中，NBD-C18C10PE和NBD-DMPE以相同的速率扩散，这表明它们的双分子层自由面积几乎相同。这一结果可以通过考虑在液晶状态下，分子堆积的增加被酰基链动力学的增加所补偿来解释。这一观点得到了文献数据的支持，清楚地表明，在液晶相中发生的酰基链交错是高度动态的。
Asymmetric phosphatidylcholine molecules with one acyl chain twice as long as the other, below their phase transition temperature, form a mixed interdigitated phase in which the longer acyl chain spans the entire bilayer. Experimental evidence in the literature suggests that, above their phase transition temperature, these molecules may still exhibit partial interdigitation, with the longer acyl chain extending partially into the opposite leaflet, and are packed more tightly than equivalent symmetric phosphatidylcholines. Using the fluorescence recovery after photobleaching technique, we have investigated the translational diffusion in multilayers of a liquid crystalline phase, asymmetric phosphatidylcholine, 1-stearoyl-2-capryl-phosphatidylcholine (C18C10PC). We used as a fluorescent probe either a phospholipid analog of the same acyl chain composition, NBD-C18C10PE, or the symmetric equivalent of the same molecular weight, N-(7-nitrobenzoxa-2,3-diazol-4-yl)-dimyristoyl-phosphatidylethanolamine (NBD-DMPE), Translational diffusion coefficients were also determined by using both probes in multilayers of dimyristoyl-phosphatidylcholine (DMPC) and in the eutectic mixture DMPC/C18C10PC (40/60 mol). We found that in a given host lipid, NBD-C18C10PE and NBD-DMPE diffuse at the same rate, which suggests that their bilayer free area is almost identical. This result can be explained by considering that in the liquid crystalline state, the increase in molecular packing is compensated by an increase in acyl chain dynamics. This view, which is supported by literature data, clearly suggests that the acyl chain interdigitation occurring in the liquid crystalline phase is highly dynamic.