AN ELECTRON-SPIN-RESONANCE STUDY OF INTERACTIONS BETWEEN PHOSPHATIDYLCHOLINE AND PHOSPHATIDYLSERINE IN ORIENTED MEMBRANES
AN ELECTRON-SPIN-RESONANCE STUDY OF INTERACTIONS BETWEEN PHOSPHATIDYLCHOLINE AND PHOSPHATIDYLSERINE IN ORIENTED MEMBRANES
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DOI：
10.1016/s0006-3495(94)80942-7
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发表时间：
1994-05-01
影响因子：
3.4
通讯作者：
FREED, JH
中科院分区：
文献类型：
--
作者：
GE, MT;BUDIL, DE;FREED, JH
报道了1-棕榈酰基-2-油酰基磷脂酰胆碱(POPC)和磷脂酰丝氨酸(POPS)在液晶相取向多层膜中混合物的电子自旋共振(ESR)研究，目的是表征头基混合对酰基链结构和动力学性质的影响。这些研究是在POPC和POPS的一系列混合物和温度下进行的，利用自旋标记的脂类16-磷脂酰胆碱和5-磷脂酰胆碱以及胆碱酯(CSL)。用非线性最小二乘拟合法对ESR谱进行了详细的谱模拟分析。虽然CSL在有序性和转动动力学方面对摩尔分数POP几乎没有变化(即x(PS))，而5-PC表现出较小的影响，而标记为16-PC的弱有序端链显示出较大的相对影响，使得取向有序参数S在x(PS)=0.5时最小，约为x(PS)=0和1时观测到的值的三分之一。这直接反映在ESR谱中，这是随着x(PS)的超精细分裂的实质性变化。最小二乘分析还表明，当x(PS)=0.5时，旋转扩散系数R减小了2倍，并允许估计S-2，有序参数表示与柱对称排列的偏差。这些结果与氢核磁共振研究形成对比，后者对混合头基对酰基链的影响不敏感。ESR结果与POPC和POPS混合时末端链区无序度增加以及少量链倾斜是一致的。它们展示了ESR对链有序和动力学中的微妙影响的高度敏感性。
detailed electron spin resonance (ESR) study of mixtures of 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and phosphatidylserine (POPS) in oriented multilayers in the liquid crystalline phase is reported with the purpose of characterizing the effects of headgroup mixing on the structural and dynamical properties of the acyl chains. These studies were performed over a range of blends of POPC and POPS and temperatures, utilizing the spin-labeled lipids 16-phosphatidylcholine and 5-phosphatidylcholine as well as cholestane (CSL). The ESR spectra were analyzed by nonlinear least-squares fitting using detailed spectral simulations. Whereas CSL shows almost no variation in ordering and rotational dynamics versus mole fraction POPS, (i.e. x(ps)), and 5-PC shows small effects, the weakly ordered end-chain labeled 16-PC shows large relative effects, such that the orientational order parameter, S is at a minimum for x(ps) = 0.5 where it is about one-third the value observed for x(ps) = 0 and 1. This is directly reflected in the ESR spectrum as a substantial variation in the hyperfine splitting with x(ps). The least-squares analysis also shows a reduction in rotational diffusion coefficient, R perpendicular to by a factor of 2 for x(ps) = 0.5 and permits the estimation of S-2, the ordering parameter representing deviations from cylindrically symmetric alignment. These results are contrasted with H-2 NMR studies which were insensitive to effects of mixing headgroups on the acyl chains. The ESR results are consistent with a somewhat increased disorder in the end-chain region as well as a small amount of chain tilting upon mixing POPC and POPS. They demonstrate the high sensitivity of ESR to subtle effects in chain ordering and dynamics.