THE CONFORMATIONAL BEHAVIOR OF PHOSPHATIDYLINOSITOL IN MODEL MEMBRANES - H-2-NMR STUDIES
THE CONFORMATIONAL BEHAVIOR OF PHOSPHATIDYLINOSITOL IN MODEL MEMBRANES - H-2-NMR STUDIES
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DOI：
10.1016/0005-2736(92)90391-x
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发表时间：
1992-12-09
期刊：
影响因子：
--
通讯作者：
REID, DG
中科院分区：
文献类型：
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作者：
HANSBRO, PM;BYARD, SJ;REID, DG
二myristoylphosphatidylinositol （DMPI）已通过适当的天然立体化学合成，并在d -myo-肌醇头基的特定位点上用氘标记。在70°c和水脂摩尔比为129时，DMPI片层相的H-2-NMR谱显示，d -肌醇头基的5个轴向C-D键和1个平向C-D键的四极分裂DELTAnu分别为3.83和2.17 kHz。在R（W/L）比率为129和210之间，以及在30°c和80°c之间，这些分裂的DELTAnu(ax)/DELTAnu（eq）的值变化显著（在1.17和4.38之间）。如果假设在特定温度下，肌醇头基团有一个单一的首选取向，并且DPMI分子的运动建立了相对于双层法线的轴对称，那么这些四极分裂的比例可以用来对该取向施加约束。例如，数据与肌醇环平行于膜表面的情况不一致，很难与肌醇环垂直于膜表面的情况相协调。计算模型确定了四种可能的“倾斜”方向，所有这些方向都与数据一致，其中两种可以形成良好的分子内氢键。一种是在肌醇C2-OH和磷酸前r氧之间形成氢键。这接近于先前确定的在DMSO溶液中占主导地位的构象(Bushby, r.j., Byard, s.j., Hansbro， P.M.和Reid， D.G. (1990) biochem。Biophys。学报1044,231-236)。
Dimyristoylphosphatidylinositol (DMPI) has been synthesised with the appropriate natural stereochemistry and labelled with deuterium at specific sites in the D-myo-inositol headgroup. H-2-NMR spectroscopy of DMPI in its lamellar phase at a molar ratio of water-to-lipid R(W/L) of 129 and at 70-degrees-C reveals quadrupolar splittings DELTAnu of 3.83 and 2.17 kHz, respectively, for the five axially oriented C-D bonds and the single equatorially oriented C-D bond of the D-myo-inositol headgroup. Between R(W/L) ratios of 129 and 210 and between 30-degrees-C and 80-degrees-C the value of the ratio of these splittings DELTAnu(ax)/DELTAnu(eq) varies significantly (between 1.17 and 4.38). If it is assumed that, at a particular temperature, there is a single preferred orientation of the inositol headgroup, and that motion of the DPMI molecule establishes axial symmetry with respect to the bilayer normal then the ratio of these quadrupolar splittings can be used to impose constraints on that orientation. For example, the data are inconsistent with a situation in which the inositol ring lies parallel to the membrane surface and are difficult to reconcile with an arrangement where the inositol ring lies perpendicular to the surface. Computational modelling identifies four possible 'tilted' orientations, ail of which are consistent with the data, and two of these allow good intramolecular hydrogen bonds to be formed. In one there is hydrogen bonding between the inositol C2-OH and the phosphate pro-R oxygen. This is close to the conformation previously identified as being dominant in DMSO solution (Bushby, R.J., Byard, S.J., Hansbro, P.M. and Reid, D.G. (1990) Biochim. Biophys. Acta 1044, 231-236).