THE POLAR GROUP CONFORMATION OF 1,2-DIALKYL PHOSPHATIDYLCHOLINES - AN NMR-STUDY
THE POLAR GROUP CONFORMATION OF 1,2-DIALKYL PHOSPHATIDYLCHOLINES - AN NMR-STUDY
复制标题
DOI：
10.1016/0005-2736(81)90326-6
复制
发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
HAUSER, H
中科院分区：
文献类型：
--
作者：
HAUSER, H
研究了1，2-二-O-烷基甘油磷脂酰胆碱（二烷基磷脂酰胆碱（醚磷脂酰胆碱））的极性基团构象，并与相应的二酰基磷脂酰胆碱（酯磷脂酰胆碱）的极性基团构象进行了比较。甘油磷酸胆碱基团的运动平均构象在2类化合物中是相似的。基于1H自旋-自旋耦合常数分析，醚键取代酯键对极性基团的平均构象和链段运动没有显著影响，该分析给出了关于甘油构象的信息（扭转角θ 1至θ 4，）和极性基团的其余部分除了磷酸二酯基团的构象（扭转角α 2和α 3）之外，其它构象（扭转角α 1、α 4、α 5）都是相同的。二烷基和二酰基磷脂酰胆碱的31 P粉末光谱的比较表明，后者组的构象也是非常相似的2类化合物。用在H2O中作为单体或小胶束存在的短链化合物（二己基磷脂酰胆碱）和在CHCl 3/CH 3OH中形成小胶束的长链化合物（二油基磷脂酰胆碱）进行1H-NMR测量。31 P-NMR的工作进行了与二棕榈酰磷脂酰胆碱，在水中形成多层双层结构。使用这些不同的结构的NMR测量表明，醚和酯磷脂酰胆碱的平均构象和链段运动是独立的聚集状态。CHCl_3/CH_3OH置换水化水对构象和链段运动影响不大。极性基团的运动平均构象主要由分子内能量学决定。~ 1H-NMR表明，磷酸胆碱基团在C_2-C_3甘油键附近几乎可以自由旋转。因此，相对于分子的二酰基甘油部分，磷酸胆碱基团没有优选的构象。这种旋转可能是负责平均的化学屏蔽张量，导致轴对称的31 P粉末光谱观察到的水溶性磷脂酰胆碱分散体低于和高于转变温度。
The polar group conformation of 1,2-di-O-alkylglycerophosphocholine (dialkylphosphatidylcholine (ether phosphatidylcholine)) is investigated and compared to that of the corresponding diacylphosphatidylcholine (ester phosphatidylcholine). The motionally averaged conformation of the glycerophosphocholine group is similar in the 2 classes of compounds. The replacement of the ester linkages by ether bonds has no significant effect on the average conformation and segmental motion of the polar group, based on 1H spin-spin coupling constant analysis which gives information about the conformation of the glycerol (torsion angles .theta.1 to .theta.4,) and the remainder of the polar group (torsion angles .alpha.1, .alpha.4, .alpha.5) except for the conformation of the phosphodiester group (torsion angles .alpha.2 and .alpha.3). Comparison of 31P powder spectra of dialkyl- and diacylphosphatidylcholine shows that the conformation of the latter group is also very similar in the 2 classes of compounds. The 1H-NMR measurements were carried out with short chain compounds (dihexylphosphatidylcholine) which are present as monomers or small micelles in H2O and long chain compounds (dioleylphosphatidylcholine) forming small micelles in CHCl3/CH3OH. The 31P-NMR work was carried out with dipalmitylphosphatidylcholine which forms multilamellar bilayer structures in H2O. NMR measurements using these different structures show that for both ether and ester phosphatidylcholines the average conformation and segmental motion is independent of the state of aggregation. Displacement of water of hydration by CHCl3/CH3OH has little effect on conformation and segmental motion. The motionally averaged conformation of the polar group is mainly determined by intramolecular energetics. 1H-NMR shows that there is almost free rotation of the phosphocholine group about the C2-C3 glycerol bond. As a result there is no preferred conformation of the phosphocholine group with respect to the diacylglycerol part of the molecule. This rotation is probably responsible for the averaging of the chemical shielding tensor leading to axially symmetric 31P powder spectra as observed for aqueous phosphatidylcholine dispersions both below and above the transition temperature.