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首页> 外文期刊>Biochemistry >Effect of sphingomyelin composition on the phase structure of phosphatidylcholine-sphingomyelin bilayers.
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Effect of sphingomyelin composition on the phase structure of phosphatidylcholine-sphingomyelin bilayers.

机译：鞘磷脂成分对磷脂酰胆碱-鞘磷脂双层结构的影响。

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In this study, we examine the phase behavior as well as lateral diffusion and percolation in the region of coexisting gel and fluid phases in binary mixtures composed of dimyristoylphosphatidylcholine and one of two totally synthetic D-erythro-sphingomyelins (having either C16 or C24 acyl chains, both having similar gel to liquid-crystalline phase transition temperatures). This study stems from the uniqueness of sphingomyelins having gel to liquid-crystalline transition temperatures in the range of physiological interest, and the fact that more than 50% of the naturally occurring sphingomyelin species have a chain mismatch. The presence of sphingomyelin in biological membranes can thus be expected to give rise to a complex phase structure. Fluorescence recovery after photobleaching, differential scanning calorimetry, and electron microscopy are used to show that, despite similarity in the temperature range of the gel to liquid-cystalline phase transition of the two sphingomyelins, the two differ in their phase structure. Also they differ to a large extent in their mixing with dimyristoylphosphatidylcholine. Dimyristoylphosphatidylcholine and C16 sphingomyelin mix nearly ideally, with the percolation threshold locus lying close to the liquidus on the phase diagram. In contrast, the C24 sphingomyelin and dimyristoylphosphatidylcholine mix nonideally, with the percolation threshold locus lying close to the solidus. In addition, mixtures containing C24 sphingomyelin have a complex thermotropic behavior which may be related to the observation that these dispersions contain several types of particles, some of which are not multilamellar vesicles. These studies suggest that the degree of sphingomyelin chain mismatch is an important factor in determining lateral organization in the membrane.
机译：在这项研究中，我们研究了由二肉豆蔻酰磷脂酰胆碱和两种完全合成的D-赤型-鞘磷脂（具有C16或C24酰基链）之一组成的二元混合物中共存的凝胶相和流体相区域中的相行为以及横向扩散和渗滤。 ，两者的凝胶与液晶相变温度相似。这项研究源于具有在生理学关注范围内的凝胶至液晶转变温度的鞘磷脂的独特性，以及超过50％的天然鞘磷脂物种具有链错配的事实。因此可以预期鞘磷脂在生物膜中的存在会引起复杂的相结构。光漂白，差示扫描量热法和电子显微镜后的荧光恢复用于显示，尽管两种鞘磷脂的凝胶至液体-胱氨酸相变的温度范围相似，但两者的相结构却不同。它们在与二肉豆蔻酰基磷脂酰胆碱的混合中也有很大不同。 Dimyristoylphosphatidylcholine和C16鞘磷脂几乎理想地混合，其渗流阈值位点在相图上接近液相线。相比之下，C24鞘磷脂和二肉豆蔻酰基磷脂酰胆碱不理想地混合，其渗透阈值位点靠近固相线。另外，含有C24鞘磷脂的混合物具有复杂的热致行为，这可能与以下观察有关：这些分散体包含几种类型的颗粒，其中一些不是多层囊泡。这些研究表明鞘磷脂链错配的程度是决定膜的侧向组织的重要因素。

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