ESR: STUDY OF DYNAMIC STRUCTURE OF HEADGROUPS IN DOPC MULTILAMELLAR MEMBRANES

ESR：DOPC多层膜头基动态结构的研究

• 批准号: 7602636
• 负责人: MAOCHEN GE
• 金额: $ 0.05万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2008-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7602636
• 关键词: Binding; Biological; Biophysics; Cell membrane; Cell surface; Cholesterol; Computer Retrieval of Information on Scientific Projects Database; Dehydration; Entropy; Freezing; Funding; Grant; Head; Hydration status; Institution; Lead; Lipid Bilayers; Measurement; Membrane; Membrane Fusion; Modeling; Molecular; Osmosis; Personal Satisfaction; Phase Transition; Publishing; Research; Research Personnel; Resources; Source; Spin Labels; Structure; Swelling; Temperature; United States National Institutes of Health; Variant; Vesicle; Water; Water Movements; Wit; Work; bulk phase water; physical property; pressure

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The molecular mechanism of the main phase transition of lipid bilayers is a fundamental problem of membrane biophysics. Since this mechanism is not well understood, anomalous physical properties of lipid bilayers around the main phase transition are still puzzling. We have completed an ESR study of the structure of head groups in DOPC multilamellar vesicles. By comparing our ESR spin labeling results with published x-ray diffraction and 2H NMR measurements we found (1) that the ordering of the head group is correlated with the ordering of the interbilayer water; (2) that the change of ordering of head groups is correlated with water movement between the interbilayer and the bulk water phases. It is suggested that increased ordering in the bilayer region, implying a lowering of entropy, will itself lead to further dehydration of the interbilayer region until its lowered pressure resists further flow, i.e. an osmotic phenomenon. The anomalous swelling of PC bilayers around the main phase transition can also be interpreted in terms of this osmosis model. Further studies have been conducted on the effect of cholesterol on these observations. Addition of 10 mol% of cholesterol slightly reduces both the freezing temperature of the vesicles, and the main phase transition of DOPC bilayers. However, the variation of the order parameter of DOPC head groups with temperature does not change after addition 10 mol% cholesterol nor is the transition broadened. Since the osmosis model relates the change in the structure on the surface of cell plasma membrane, i.e., the ordering and the hydration of head groups, wit h t he change in the molecular interactions between the head groups and other groups which may bind to the surface of the cell, its biological significance could be significant. This is especially the case for membrane fusion, which may well be facilitated by membrane dehydration. This work has been published.

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 脂双层主要相变的分子机制是膜生物物理学的一个基本问题。 由于这一机制尚未得到很好的理解，脂质双层在主要相变附近的异常物理性质仍然令人困惑。 我们已经完成了在DOPC多层囊泡的头部基团的结构的ESR研究。 通过比较我们的ESR自旋标记结果与已发表的X-射线衍射和~ 2 H NMR测量结果，我们发现：（1）头基的有序性与双分子层间水的有序性相关;（2）头基有序性的变化与水在双分子层间和体相之间的运动相关。 有人建议，在双层区域中的有序性增加，这意味着熵的降低，本身将导致进一步的双层间区域的脱水，直到其降低的压力抵抗进一步的流动，即渗透现象。 PC双分子膜的异常溶胀周围的主要相变也可以解释在这个渗透模型。 对胆固醇对这些观察结果的影响进行了进一步的研究。 添加10摩尔%的胆固醇稍微降低了囊泡的冷冻温度，和DOPC双层的主要相变。 然而，随着温度的DOPC头基的顺序参数的变化不改变后，加入10摩尔%的胆固醇，也不是过渡加宽。 由于渗透模型涉及细胞质膜表面结构的变化，即，头部基团的有序化和水合作用，以及头部基团与可能结合到细胞表面的其它基团之间的分子相互作用的改变，其生物学意义可能是显著的。 对于膜融合尤其如此，膜脱水可以很好地促进膜融合。 这项工作已经出版。