SOLID-STATE C-13 NMR OF UNLABELED PHOSPHATIDYLCHOLINE BILAYERS - SPECTRAL ASSIGNMENTS AND MEASUREMENT OF CARBON PHOSPHORUS DIPOLAR COUPLINGS AND C-13 CHEMICAL-SHIFT ANISOTROPIES
SOLID-STATE C-13 NMR OF UNLABELED PHOSPHATIDYLCHOLINE BILAYERS - SPECTRAL ASSIGNMENTS AND MEASUREMENT OF CARBON PHOSPHORUS DIPOLAR COUPLINGS AND C-13 CHEMICAL-SHIFT ANISOTROPIES
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DOI：
10.1016/s0006-3495(93)81352-3
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发表时间：
1993-01-01
影响因子：
3.4
通讯作者：
SANDERS, CR
中科院分区：
文献类型：
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作者：
SANDERS, CR
由于各向异性引起的光谱展宽，直接测量未标记L（α）相磷脂酰胆碱（PC）的C-13化学位移各向异性（CSA）和P-31-C-13偶极分裂在传统上是困难的。在这项研究中，二肉豆蔻酰磷脂酰胆碱（DMPC）与三种不同的洗涤剂的混合物，已知促进DMPC的磁取向被用来消除粉末图案性质的信号，而不完全平均的光谱各向异性。使用的去污剂是CHAPSO、Triton X-100和二己酰磷脂酰胆碱（DHPC）。使用这样的混合物，许多来自DMPC的单个C-13共振被解析，并且许多C-13-P-31偶极偶联是明显的。此外，观察到不同的线宽的组件的偶极双峰，偶极/化学位移各向异性（CSA）弛豫干涉效应的暗示。通过改变CHAPSO或DHPC与DMPC的比率以系统地缩放朝向各向同性极限的整体双层顺序来进行定向样品共振分配。以这种方式，可以基于外推到它们的各向同性位置来识别峰，先前已经对其进行了分配（Lee，C. W. B.，和R. G.格里芬1989. Biophys. J. 55：355-358;福布斯，J.，J. Bowers，X.尚湖，澳-地Moran，E. Oldfield和M. A.莫斯卡雷洛1988.美国化学会杂志，法拉第，Trans.184：3821-3849）。观察到CSA或偶极偶联与从DHPC和CHAPSO滴定获得的总体双层顺序的图是线性的。估计纯DMPC双层的固有偶极耦合和化学位移各向异性外推位移和耦合从洗涤剂滴定到零洗涤剂。两种去污剂滴定导致类似的“内在"CSA和偶极偶联。从定向Triton-DMPC混合物中提取的结果也导致了类似的估计无洗涤剂DMPC的位移和耦合。发现这些实验的结果与纯L（α）PC的有限测量结果相比是有利的。这种基于洗涤剂的分配光谱和确定偶极耦合和CSA在洗涤剂自由系统的方法应可扩展到其他脂质系统。从这项研究中得到的数据集可能被证明是有用的DMPC双层的结构和动力学的未来建模。此外，使用三种洗涤剂中的每一种的实验导致对纯DMPC的光谱参数的类似估计的手法，以及光谱参数与双层顺序图呈线性的事实，表明在三种洗涤剂的存在下DMPC的平均构象和动力学与纯L（α）-DMPC的那些非常相似。
The direct measurement of C-13 chemical shift anisotropies (CSA) and P-31-C-13 dipolar splitting in random dispersions of unlabeled L(alpha)-phase phosphatidylcholine (PC) has traditionally been difficult because of extreme spectral broadening due to anisotropy. In this study, mixtures of dimyristoyl phosphatidylcholine (DMPC) with three different detergents known to promote the magnetic orientation of DMPC were employed to eliminate the powder-pattern nature of signals without totally averaging out spectral anisotropy. The detergents utilized were CHAPSO, Triton X-100, and dihexanoylphosphatidylcholine (DHPC). Using such mixtures, many of the individual C-13 resonances from DMPC were resolved and a number of C-13-P-31 dipolar couplings were evident. In addition, differing line widths were observed for the components ot some dipolar doublets, suggestive of dipolar/chemical shift anisotropy (CSA) relaxation interference effects. Oriented sample resonance assignments were made by-varying the CHAPSO or DHPC to DMPC ratio to systematically scale overall bilayer order towards the isotropic limit. In this manner, peaks could be identified based upon extrapolation to their isotropic positions, for which assignments have previously been made (Lee, C. W. B., and R. G. Griffin. 1989. Biophys. J. 55:355-358; Forbes, J., J. Bowers, X. Shan, L. Moran, E. Oldfield, and M. A. Moscarello. 1988. J. Chem. Soc., Faraday, Trans. 1 84:3821-3849). It was observed that the plots of CSA or dipolar coupling versus overall bilayer order obtained from DHPC and CHAPSO titrations were linear. Estimates of the intrinsic dipolar couplings and chemical shift anisotropies for pure DMPC bilayers were made by extrapolating shifts and couplings from the detergent titrations to zero detergent. Both detergent titrations led to similar ''intrinsic'' CSAs and dipolar couplings. Results extracted from an oriented Triton-DMPC mixture also led to similar estimates for the detergent-free DMPC shifts and couplings. The results from these experiments were found to compare favorably with limited measurements made from pure L(alpha) PC. This detergent-based method for assigning spectra and for determining dipolar couplings and CSA in detergent-free systems should be extendable to other lipid systems. The resulting data set from this study may prove useful in future modeling of the structure and dynamics of DMPC bilayers. In addition, the tact that experiments utilizing each of the three detergents led to similar estimates for the spectral parameters of pure DMPC, and the fact that spectral parameter versus bilayer order plots were linear, indicate that the averaged conformation and dynamics of DMPC in the presence of the three detergents are very similar to those of pure L(alpha)-DMPC.