PREFERRED CONFORMATION AND DYNAMICS OF THE GLYCEROL BACKBONE IN PHOSPHOLIPIDS - AN NMR AND X-RAY SINGLE-CRYSTAL ANALYSIS
PREFERRED CONFORMATION AND DYNAMICS OF THE GLYCEROL BACKBONE IN PHOSPHOLIPIDS - AN NMR AND X-RAY SINGLE-CRYSTAL ANALYSIS
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DOI：
10.1021/bi00426a014
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发表时间：
1988-12-27
期刊：
影响因子：
2.9
通讯作者：
SUNDELL, S
中科院分区：
文献类型：
--
作者：
HAUSER, H;PASCHER, I;SUNDELL, S
通过1H高分辨率核磁共振和x射线晶体学研究了一些二酰基和单酰基（lyso）磷脂的甘油基团的构象，这些磷脂的头基团的化学性质不同。核磁共振测量是用氘化有机溶剂或2H2O中的脂质溶液或胶束分散体进行的。这两种溶液，其中脂质以单体形式存在，脂质胶束产生良好的高分辨率核磁共振光谱，显示自旋耦合超精细相互作用。由1H自旋偶联可知，磷脂的甘油C(2)-C(3)键有两种稳定的构象。其中之一（旋转体A）的特征是扭转角。3 =反周面面，。4 = +向斜，另一个（旋转体B）为。3 = +向斜，. θ。4 = -向斜。在两个旋体A和B中，甘油碳原子C(2)和C(3)上的酯氧是向斜的，因此两种类型的旋体都很容易使两条烃链平行排列。通过核磁共振和单晶x射线数据的比较，可以明显看出这两种构象都是最小自由能构象。旋转体A是磷脂单晶结构中普遍存在的构象。旋转体B的构象也在磷脂单晶结构中发现，但在较小程度上，例如在2,3-二脲酰- dl -甘油-1-磷酸- n， n -二甲基乙醇胺和2,3-二肉豆醇-d -甘油- dl -甘油中发现。核磁共振测量表明，在液晶中，磷脂的二酰基甘油部分在旋转体A和B的两个稳定的交错构象之间波动。在核磁共振时间尺度上，旋转体A和B之间的转变是快速的，必须伴随着扭转角的适当变化。1到。。4和。1到。两个脂肪酰基链中的4个。这些扭转角的变化使得脂肪酸酰基链的平行排列是合理的。通过对磷脂单晶结构的检查，扭转角的最小变化。1到。。4和。1到。4伴随转轮A和B之间的过渡可以导出。从所提供的数据可以清楚地看出，碳氢化合物链的平行排列或磷脂聚集体（如双层或胶束）中的链堆叠是控制C(2)-C(3)甘油键构象的基本原理。
The conformation of the glycerol group of a number of diacyl and monoacyl (lyso) phospholipids differing in the chemical nature of the head group was studied by 1H high-resolution NMR and X-ray crystallography. The NMR measurements were carried out with solutions or micellar dispersions of the lipids in deuteriated organic solvents or 2H2O. Both solutions, in which the lipid is present as monomers, and lipid micelles give rise to good high-resolution NMR spectra exhibiting spin coupling hyperfine interactions. From 1H spin coupling it is concluded that there are two stable conformations about the glycerol C(2)-C(3) bond of phospholipids. One of these (rotamer A) is characterized by torsion angles .theta.3 = antiperiplanar, .theta.4 = +synclinal, and the other (rotamer B) by .theta.3 = +synclinal, .theta.4 = -synclinal. In both rotamers A and B the ester oxygens on the glycerol carbon atoms C(2) and C(3) are synclinal, and hence both types of rotamers readily allow the parallel alignment of the two hydrocarbon chains. By comparison of NMR and single-crystal X-ray data it is obvious that both conformations are minimum free energy conformations. Rotamer A is the conformation prevailing in phospholipid single-crystal structures. The conformation of rotamer B is also found in phospholipid single-crystal structures though to a lesser extent, e.g., in 2,3-dilauroyl-DL-glycero-1-phospho-N,N-dimethylethanolamine and 2,3-dimyristoyl-D-glycerophospho-DL-glycerol. NMR measurements indicate that in liquid crystals the diacylglycerol part of phospholipids fluctuates between the two stable staggered conformations of rotamers A and B. The transition between rotamers A and B is fast on the NMR time scale and must be accompanied by appropriate changes in the torsion angles .beta.1 to .beta.4 and .gamma.1 to .gamma.4 of the two fatty acyl chains. The changes in these torsion angles are such that the parallel alignment of the fatty acyl chains is warranted. From examination of the single-crystal structures of phospholipids, the minimum changes in torsion angles .beta.1 to .beta.4 and .gamma.1 to .gamma.4 accompanying the transition between rotamers A and B can be derived. It is clear from the data presented that the parallel alignment of the hydrocarbon chains or chain stacking in phospholipids aggregates such as bilayers or micelles is the fundamental principle governing the conformation of the C(2)-C(3) glycerol bond.