The effects of 7β-hydroxycholesterol (7βOH) and 25-hydroxycholesterol (25OH) on the phase behavior and the structural properties of the multilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC) bilayers were investigated with comparing to the effects of cholesterol (Chol). Differential scanning calorimetry (DSC) measurements showed these three sterols have slightly but distinctly different effects on the thermal behavior of DPPC bilayers. X-ray diffraction data analysis on DPPC bilayers containing 30 mol% sterols with the aid of molecular volume data estimated by the neutral buoyancy method indicated that the order of apparent occupied surface area per molecule is DPPC/7βOH > DPPC/25OH > DPPC/Chol at both 25 ℃ and 50 ℃, suggesting that the strength of the condensation effect of these sterols follows inversely this order. Based on the findings in this study, we inferred the molecular orientations of Chol, 7βOH, and 25OH in DPPC bilayers.

中文翻译：

---

比较7β-羟基胆固醇，25-羟基胆固醇和胆固醇对多层二棕榈酰磷脂酰胆碱双层囊泡的结构和热相行为的影响。

对比胆固醇（Chol）的影响，研究了7β-羟基胆固醇（7βOH）和25-羟基胆固醇（25OH）对二棕榈酰磷脂酰胆碱（DPPC）双层多层囊泡的相行为和结构性质的影响。差示扫描量热法（DSC）测量表明，这三种固醇对DPPC双层的热行为具有轻微但明显不同的影响。借助中性浮力法估算的分子体积数据，对包含30 mol％甾醇的DPPC双层进行X射线衍射数据分析，结果表明，每个分子的表观占据表面积的顺序为DPPC /7βOH> DPPC / 25OH> DPPC / Chol在25℃和50℃时，表明这些固醇的缩合作用强度反比于此顺序。