Huang C H
Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville 22908, USA.
Lipids. 2001 Oct;36(10):1077-97. doi: 10.1007/s11745-001-0818-1.
It has long been established that diacyl phospholipids isolated from animal cell membranes are predominantly of a mixed-chain variety, meaning that the sn-1 and sn-2 acyl chains are saturated and unsaturated acyl chains, respectively. In general, monoenoic and dienoic acids are found in the sn-2 acyl chain of phosphatidylcholine (PtdCho), whereas polyenoic acids are in phosphatidylethanolamine (PtdEth). These unsaturated chains contain only cis-double bonds, which are always methylene-interrupted. In recent years, the structures and the chain-melting behavior of mixed-chain PtdCho and PtdEth have been systematically studied in this laboratory. Specifically, we have examined the effects of chain unsaturation of the sn-2 acyl chain on the phase transition temperature (Tm) of many PtdCho and PtdEth by high-resolution differential scanning calorimetry (DSC). The Tm values, for instance, obtained from all-unsaturated mixed-chain PtdEth derived from a common precursor can be grouped together according to their chemical formula to form a Tm-diagram. Hence, all the Tm values can be compared simply, systematically, and simultaneously using the Tm-diagram. In addition, the energy-minimized structures of mixed-chain phospholipids containing different numbers/positions of methylene-interrupted cis-double bonds have been simulated by molecular mechanics calculations (MM). In this review, the results of our MM and DSC studies carried out with various mixed-chain phospholipids are summarized. In addition, we emphasize that the combined approach of MM and DSC yields unique information that can correlate the various Tm-profiles seen in the Tm-diagram with the structural variation of mixed-chain lipids as caused by the introduction of different numbers/positions of methylene-interrupted cis-double bonds.
长期以来人们已经确定，从动物细胞膜分离出的二酰基磷脂主要是混合链类型，这意味着sn-1和sn-2酰基链分别是饱和酰基链和不饱和酰基链。一般来说，单烯酸和二烯酸存在于磷脂酰胆碱（PtdCho）的sn-2酰基链中，而多烯酸则存在于磷脂酰乙醇胺（PtdEth）中。这些不饱和链只含有顺式双键，且总是被亚甲基隔开。近年来，本实验室对混合链PtdCho和PtdEth的结构及链熔化行为进行了系统研究。具体而言，我们通过高分辨率差示扫描量热法（DSC）研究了sn-2酰基链的链不饱和度对许多PtdCho和PtdEth相变温度（Tm）的影响。例如，从源自共同前体的全不饱和混合链PtdEth获得的Tm值可以根据其化学式归为一组，形成一个Tm图。因此，使用该Tm图可以简单、系统且同时地比较所有的Tm值。此外，通过分子力学计算（MM）模拟了含有不同数量/位置的被亚甲基隔开的顺式双键的混合链磷脂的能量最小化结构。在这篇综述中，总结了我们用各种混合链磷脂进行的MM和DSC研究结果。此外，我们强调MM和DSC的联合方法产生了独特的信息，能够将在Tm图中看到的各种Tm曲线与由于引入不同数量/位置的被亚甲基隔开的顺式双键而导致的混合链脂质的结构变化联系起来。
