MODEL MEMBRANES DISPLAYING COEXISTING LIQUID ORDERED AND DISORDERED PHASES

显示共存液态有序相和无序相的模型膜

• 批准号: 7420505
• 负责人: ANDREW SMITH
• 金额: $ 2.38万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-15 至 2007-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7420505
• 关键词: cell membrane; cholesterol; fluid; lipids; membrane model; model

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. To assess the validity of the raft hypothesis for the cellular plasma membrane we examined both the dynamics and equilibria of liquid-ordered (Lo) and liquid-disordered (Ld) phases in the brain-sphingomyelin (SPM) /dioleoylphosphatidylcholine (DOPC)/cholesterol model membrane system. Using the known phase diagram for this lipid system containing the phase boundary between the one-phase regions and the two-phase coexistence region of the Lo and Ld phases and an ESR spectral fitting method (New Method for Determining Tie-lines in Coexisting Membrane Phases using Spin-label ESR, Y.-W. Chiang, J. Zhao, J. Wu, Y. Shimoyama, G.W. Feigenson, J.H. Freed, Biophysica-Biochimica Acta 1668, 99-105,2005) from the linear superposition of boundary spectra, we determined one tieline thru the Lo+Ld coexistence region. Many pairs of Lo and Ld phase compositions can coexist at equilibrium for this ternary lipid system, so tielines are necessary to model rafts because they tell us which phase compositions coexist and therefore which pair of compositions best model the plasma membrane. If the Lo and Ld phases observed in the SPM/DOPC/cholesterol model system are physically similar to raft domains, then the dynamic parameters of spin probes in the model membranes determined from ESR spectral fitting should be similar to those of the same probe in plasma membranes. This was found to be true in that dynamic parameters from chain-labeled spin probes at the boundary compositions of the one tieline so far determined compared very well with dynamic parameters from the same spin probes in live cells (Coexisting Domains in the Plasma Membranes of Live Cells Characterized by ESR Spectroscopy, M.J. Swamy, L. Ciani, M. Ge, A.K. Smith, D. Holowka, B. Baird, and J.H. Freed, Biophys. J. 90, 4452-4465, 2006). A more extensive analysis of Lo and Ld phase equilibria and dynamic comparison between model and real plasma membranes will require the determination of the entire set of tielines for the Lo+Ld phase coexistence region.

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。为了评估筏假说的细胞质膜的有效性，我们研究了在脑鞘磷脂（SPM）/二油酰磷脂酰胆碱（DOPC）/胆固醇模型膜系统中的液体有序（Lo）和液体无序（Ld）相的动力学和平衡。使用包含Lo和Ld相的单相区域和两相共存区域之间的相边界的该脂质体系的已知相图和ESR光谱拟合方法（New Method for Determining Tie-lines in Coexisting Membrane Phases using Spin-label ESR，Y. W.蒋，J.赵，J.吴，Y. Shimoyama，G.W. Feigenson，J.H. Freed，Bioprophica-Biochimica Acta 1668，99- 105，2005），我们从边界光谱的线性叠加确定了一条穿过Lo+Ld共存区域的连接线。许多对的Lo和Ld相组合物可以共存于平衡的这个三元脂质系统，所以联络线是必要的模型筏，因为他们告诉我们哪些相组合物共存，因此哪对组合物最好的模型质膜。如果在SPM/DOPC/胆固醇模型系统中观察到的Lo和Ld相在物理上类似于筏结构域，则从ESR光谱拟合确定的模型膜中的自旋探针的动力学参数应该与质膜中相同探针的动力学参数相似。这被发现是真实的，因为来自链标记的自旋探针的动态参数在迄今为止确定的一个连接线的边界组成处与来自活细胞中的相同自旋探针的动态参数非常好地比较（Coexisting Domains in the Plasma Membranes of Live Cells Characterized by ESR Spectroscopy，M. J. Swamy，L. Ciani，M. Ge，A.K.史密斯，D.霍洛卡，B。Baird和J.H.自由，生物物理。J. 90，4452-4465，2006）。Lo和Ld相平衡的更广泛的分析以及模型和真实的质膜之间的动态比较将需要确定Lo+Ld相共存区域的整组联络线。