Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
Department of Clinical Pharmacology and Therapeutics, Faculty of Medicine, Oita University, 1-1 Idaigaoka, Hasama-machi, Yufu, Oita 879-5593, Japan.
Biochemistry. 2020 Oct 13;59(40):3929-3938. doi: 10.1021/acs.biochem.0c00589. Epub 2020 Sep 30.
Diphytanoylphosphatidylcholine (DPhPC) is a synthetic phospholipid in which two methyl-branched acyl chains are introduced into the glycerol moiety, mimicking phospholipids of eukaryotic and eubacterial origins. The lipid bilayers of DPhPC reproduce the outstanding physical properties of methyl-branched lipids that occur in archaeal membranes. DPhPC is commonly used as the base lipid in biophysical experiments, particularly for recording ion-channel currents. However, the dynamics of lipid molecules that induces their useful physical properties is still unclear. In this study, we examined the conformation and orientation of the methyl-branched acyl chain of DPhPC in a membrane using H nuclear magnetic resonance (NMR) measurements of the synthetic lipid with a high stereochemical purity and molecular dynamics (MD) simulations. Deuterium-labeled 3',3'-CD,D-DPhPC () and 7',7'-CD,D-DPhPC () showed the characteristic quadrupole splitting width in the H NMR spectra, which corresponded to the bent orientation reported for the archaeal lipid PGP-Me [Yamagami, M., et al. (2019) , 3869-3879]. However, MD simulations, which reproduced the H NMR results well, unveiled the unknown features of DPhPC in the membrane; DPhPC has a chain-specific average orientation, where two bent orientations with upward and downward methyl groups occur at positions C3 and C7 of the -1 and -2 chains of DPhPC, respectively. These MD and NMR results reveal that these two bent orientations define the average orientation of DPhPC for the shallow part of the acyl chains, which is considered to be an important factor in the stability of DPhPC membranes.
二植酰基磷脂酰胆碱（DPhPC）是一种合成磷脂，其中两条甲基支链酰基被引入甘油部分，模拟真核生物和原核生物的磷脂。DPhPC 的脂质双层再现了在古菌膜中出现的甲基支链脂质的出色物理性质。DPhPC 通常用作生物物理实验的基础脂质，特别是用于记录离子通道电流。然而，诱导其有用物理性质的脂质分子的动力学仍然不清楚。在这项研究中，我们使用具有高立体化学纯度的合成脂质的 H 核磁共振（NMR）测量和分子动力学（MD）模拟研究了膜中 DPhPC 的甲基支链酰基的构象和取向。氘标记的 3',3'-CD,D-DPhPC（）和 7',7'-CD,D-DPhPC（）在 H NMR 光谱中表现出特征的四极分裂宽度，这与古菌脂质 PGP-Me 的弯曲取向相对应[Yamagami，M.等。（2019），3869-3879]。然而，很好地再现了 H NMR 结果的 MD 模拟揭示了 DPhPC 在膜中的未知特征；DPhPC 具有链特异性的平均取向，其中两条弯曲取向，带有向上和向下的甲基基团，分别出现在 DPhPC 的-1 和-2 链的 C3 和 C7 位置。这些 MD 和 NMR 结果表明，这两种弯曲取向定义了 DPhPC 酰链浅部的平均取向，这被认为是 DPhPC 膜稳定性的重要因素。
