COMPLEMENTARY MOLECULAR SHAPES AND ADDITIVITY OF THE PACKING PARAMETER OF LIPIDS
COMPLEMENTARY MOLECULAR SHAPES AND ADDITIVITY OF THE PACKING PARAMETER OF LIPIDS
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DOI：
10.1073/pnas.88.2.444
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发表时间：
1991-01-01
影响因子：
11.1
通讯作者：
KUMAR, VV
中科院分区：
文献类型：
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作者：
KUMAR, VV
膜组分的物理尺寸影响其对水合作用的相选择。无量纲填充参数S由S=V/al给出，其中V是烃体积，a是头基的面积，L是碳氢链的临界长度，对于双层来说，S的值通常在0.5到1之间。本文计算了磷脂酰胆碱(PC)和溶血磷脂酰胆碱(LysoPC)随链长变化的S指数，结果表明，S值为0.74的双磷脂酰胆碱不形成双分子层。例如，长达8个碳原子的双链IPC只形成胶束，而与S 0.74同系物形成双分子层。研究还表明，当具有互补形状的脂分子缔合时，S的值变得相加。利用S的可加性，可以解释脂类混合物的一些实验结果。例如，溶血磷脂酶和胆固醇在45和几乎等于80摩尔%的胆固醇之间形成片层结构，S对这一区域的加和值在0.74到1之间。同样，S的加和性表明，胆固醇可以被掺入到PC双层中的最大量是50摩尔%，这与实验研究一致。
Physical dimensions of a membrane component influence its phase preference upon hydration. A dimensionless packing parameter, S, given by S = V/al, where V is the hydrocarbon volume, a is the area of the head group, and l is the critical length of the hydrocarbon chain, is useful in determining the phase preference of a lipid, and the value of S usually lies between 0.5 and 1 for bilayers. Here, the value of S is calculated for phosphatidylcholine (PC) and lysophosphatidylcholine (lysoPC) as a function of chain length, and it is shown that diacyIPC having an S value of < 0.74 does not form bilayers. For example, diacyIPC, up to a chain length of eight carbon atoms, forms only micelles, whereas higher homologs with S > 0.74 form bilayers. It is also shown that when lipid molecules having complementary shapes associate, the value of S becomes additive. Using the additivity of S, a number of experimental results for lipid mixtures can be explained. For example, lysoPC and cholesterol form lamellar structures between 45 and almost-equal-to 80 mol% cholesterol, and the additive value of S for this region is between 0.74 and 1. Similarly, the additivity of S shows that the maximum amount of cholesterol that can be incorporated into PC bilayers is 50 mol%, in agreement with experimental studies.