Triton X-100 partitioning into sphingomyelin Bilayers at subsolubilizing detergent concentrations:: Effect of lipid phase and a comparison with Dipalmitoylphosphatidylcholine
Triton X-100 partitioning into sphingomyelin Bilayers at subsolubilizing detergent concentrations:: Effect of lipid phase and a comparison with Dipalmitoylphosphatidylcholine
复制标题
DOI：
10.1529/biophysj.107.104463
复制
发表时间：
2007-11-01
影响因子：
3.4
通讯作者：
Goni, Felix M.
中科院分区：
文献类型：
--
作者：
Arnulphi, Cristina;Sot, Jesus;Goni, Felix M.
我们检查了非离子去污剂 Triton X-100 在低溶解浓度下分配到鸡蛋鞘磷脂 (SM)、棕榈酰 SM 或二棕榈酰磷脂酰胆碱双层中的情况。众所周知，SM 需要比磷脂酰胆碱更少的去污剂来达到相同程度的溶解，并且对于所有三种磷脂来说，溶解都依赖于温度。此外，这三种脂质在 38-41 摄氏度的温度范围内表现出凝胶-流体相变。实验是在远低于临界胶束浓度的 Triton X-100 浓度下进行的，因此只需考虑洗涤剂单体。脂质/洗涤剂摩尔比绝不会< 10:1，从而确保永远不会达到溶解阶段。在 5-55 摄氏度的温度范围内应用等温滴定量热法、DSC、红外光谱、荧光光谱和 P-31-NMR 光谱。结果表明，无论脂质的化学性质如何，分配的 Delta G 度在凝胶相中保持在 -27 kJ/mol 脂质的范围内，在流体相中保持在 -30 kJ/mol 脂质的范围内。这种微小的差异不能解释所观察到的溶解过程中相依赖性的差异。这种几乎恒定的 Delta G 度是由于焓和熵分量的补偿而发生的，这些分量随温度和脂质组成而变化。因此，观察到的不同溶解敏感性不能归因于差异结合，而是归因于溶解过程中的进一步事件，例如。例如，去污剂对双层的饱和度或形成脂质-去污剂混合胶束的倾向。这里的数据揭示了相对未探索的膜溶解的早期阶段，并为理解膜对洗涤剂溶解的抵抗现象开辟了新的方法。
We examined the partitioning of the nonionic detergent Triton X-100 at subsolubilizing concentrations into bilayers of either egg sphingomyelin (SM), palmitoyl SM, or dipalmitoylphosphatidylcholine. SM is known to require less detergent than phosphatidylcholine to achieve the same extent of solubilization, and for all three phospholipids solubilization is temperature dependent. In addition, the three lipids exhibit a gel-fluid phase transition in the 38-41 degrees C temperature range. Experiments have been performed at Triton X-100 concentrations well below the critical micellar concentration, so that only detergent monomers have to be considered. Lipid/detergent mol ratios were never < 10:1, thus ensuring that the solubilization stage was never reached. Isothermal titration calorimetry, DSC, and infrared, fluorescence, and P-31-NMR spectroscopies were applied in the 5-55 degrees C temperature range. The results show that, irrespective of the chemical nature of the lipid, Delta G degrees of partitioning remained in the range of -27 kJ/mol lipid in the gel phase and of -30 kJ/mol lipid in the fluid phase. This small difference cannot account for the observed phase-dependent differences in solubilization. Such virtually constant Delta G degrees occurred as a result of the compensation of enthalpic and entropic components, which varied with both temperature and lipid composition. Consequently, the observed different susceptibilities to solubilization cannot be attributed to differential binding but to further events in the solubilization process, e. g., bilayer saturability by detergent or propensity to form lipid-detergent mixed micelles. The data here shed light on the relatively unexplored early stages of membrane solubilization and open new ways to understand the phenomenon of membrane resistance toward detergent solubilization.