Gater Deborah L, Seddon John M, Law Robert V
Department of Chemistry, Imperial College, South Kensington Campus, London, UKSW7 2AZ.
Soft Matter. 2008 Jan 22;4(2):263-267. doi: 10.1039/b710726a.
The role of cholesterol (Chol) in promoting lamellar phase formation in mixtures with 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (Lyso-PPC) in excess water was investigated using multinuclear solid-state NMR and X-ray scattering. It was found that mixtures containing Chol and Lyso-PPC form a liquid-ordered (Lo) lamellar phase over a range of temperatures and concentrations, as previously observed in mixtures of Chol with various diacylphospholipids. The maximum quadrupolar splitting of the 2H-NMR powder patterns for samples containing per-deuterated Lyso-PPC were 40-50 kHz which is strongly indicative of an Lo phase. This evidence was supported by wide angle X-ray scattering data which showed a characteristic diffuse peak centred at 4.2 Å. The Lo phase coexists with an isotropic Lyso-PPC phase at Chol concentrations up to 70 mol% Chol, and with Chol crystals at Chol concentrations above this value. Below 70 mol% Chol, an increase in the concentration of Chol in the system caused a corresponding increase in the proportion of the Lo phase present compared with the amount of isotropic Lyso-PPC. The chemical-shift anisotropy (CSA) of the static 31P-NMR spectra of the Lo phase showed the symmetry of a lamellar phase, but the linewidth, Δσ, was much narrower than CSA powder patterns obtained for diacylphospholipids in similar conditions, being ∼20 ppm as opposed to ∼40 ppm, respectively.
利用多核磁共振固态核磁共振和X射线散射技术，研究了胆固醇（Chol）在与过量水中的1-棕榈酰-2-羟基-sn-甘油-3-磷酸胆碱（Lyso-PPC）混合时促进层状相形成中的作用。研究发现，含Chol和Lyso-PPC的混合物在一定温度和浓度范围内形成液序（Lo）层状相，这与之前在Chol与各种二酰基磷脂混合物中观察到的情况一致。含全氘代Lyso-PPC的样品的2H-NMR粉末图谱的最大四极分裂为40-50 kHz，这强烈表明存在Lo相。广角X射线散射数据支持了这一证据，该数据显示在4.2 Å处有一个特征性的漫散射峰。在Chol浓度高达70 mol%时，Lo相与各向同性的Lyso-PPC相共存，而在Chol浓度高于此值时，则与Chol晶体共存。在Chol浓度低于70 mol%时，系统中Chol浓度的增加导致与各向同性Lyso-PPC相比，Lo相所占比例相应增加。Lo相的静态31P-NMR光谱的化学位移各向异性（CSA）显示出层状相的对称性，但线宽Δσ比在类似条件下二酰基磷脂获得的CSA粉末图谱窄得多，分别约为20 ppm和40 ppm。
