Order parameters and areas in fluid-phase oriented lipid membranes using wide angle x-ray scattering
Order parameters and areas in fluid-phase oriented lipid membranes using wide angle x-ray scattering
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DOI：
10.1529/biophysj.107.127845
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发表时间：
2008-07-15
影响因子：
3.4
通讯作者：
Nagle, John F.
中科院分区：
文献类型：
--
作者：
Mills, Thalia T.;Toombes, Gilman E. S.;Nagle, John F.
我们利用广角x射线散射（WAXS）技术测量了由1,2-二油基-sn-甘油-3-磷脂胆碱(DOPC)/胆固醇和1,2-二棕榈酰-sn-甘油-3-磷脂胆碱(DPPC)/胆固醇组成的模型膜的链取向顺序参数和脂质面积。在DOPC或DPPC中加入40%的胆固醇，由于酰基链取向顺序的增加而改变了WAXS模式，这是区分富含胆固醇的液体有序相（Lo）和液体无序相（Ld）的主要性质之一。相比之下，来自多层囊泡的粉末x射线数据没有提供有关取向顺序的信息，并且来自Lo和Ld相的散射看起来相似。利用分析模型描述了链的取向分布与WAXS数据之间的关系，得到了平均取向序参数sx - x。当40%的胆固醇添加到DOPC或DPPC时，Sx-ray增加了一倍以上，与以前的NMR顺序参数测量一致。将平均链取向信息与链-链相关间距相结合，将一种常用的计算凝胶相脂类面积的方法推广到液相脂类，得到的结果与文献值的一致性在5%以内。
We used wide angle x-ray scattering (WAXS) from stacks of oriented lipid bilayers to measure chain orientational order parameters and lipid areas in model membranes consisting of mixtures of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/cholesterol and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)/cholesterol in fluid phases. The addition of 40% cholesterol to either DOPC or DPPC changes the WAXS pattern due to an increase in acyl chain orientational order, which is one of the main properties distinguishing the cholesterol-rich liquid-ordered (Lo) phase from the liquid-disordered (Ld) phase. In contrast, powder x-ray data from multilamellar vesicles does not yield information about orientational order, and the scattering from the Lo and Ld phases looks similar. An analytical model to describe the relationship between the chain orientational distribution and WAXS data was used to obtain an average orientational order parameter, Sx-ray. When 40% cholesterol is added to either DOPC or DPPC, Sx-ray more than doubles, consistent with previous NMR order parameter measurements. By combining information about the average chain orientation with the chain-chain correlation spacing, we extended a commonly used method for calculating areas for gel-phase lipids to fluid-phase lipids and obtained agreement to within 5% of literature values.