Poly(ethylene glycol)-conjugated phospholipids in aqueous micellar solutions: hydration, static structure, and interparticle interactions.
Poly(ethylene glycol)-conjugated phospholipids in aqueous micellar solutions: hydration, static structure, and interparticle interactions.
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DOI：
10.1021/jp067011k
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发表时间：
2007-02
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影响因子：
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通讯作者：
Takaaki Sato;H. Sakai;K. Sou;R. Buchner;E. Tsuchida
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作者：
Takaaki Sato;H. Sakai;K. Sou;R. Buchner;E. Tsuchida
利用介电弛豫谱（DRS）和小角X射线散射（SAXS）研究了聚乙二醇共轭二硬脂酰磷脂酰乙醇胺（DSPE-PEG）（PEG：M（PEG）= 2000、5000和12,000 Da）水溶液的水合行为、溶剂动力学和静态结构。本体水弛豫幅度的定量分析揭示了每个环氧乙烷单体单元的DSPE-PEG分子的有效水合数约为5.0-5.5，实际上与M（PEG）无关。DSPE-PEG分子的总水合数为约100。比相应的正常PEG（不含DSPE）高20%。这归因于DSPE中磷酸的带电头基的水合作用和PEG链到胶束结构中的填充效应。从SAXS强度的GIFT分析中提取的对距离分布函数p（r）表明，对于M（PEG）= 2000、5000和12，000 Da，DSPE-PEG在水中形成球形胶束，其最大直径分别为约16、22和31 nm，并且几乎相同的聚集数为72（+/-10%）。DSPE-PEG胶束表现为带电胶体，其粒子间相互作用势可以近似为屏蔽库仑势模型。提取的对相关函数g（r）表明，由带电的头部基团引起的静电排斥和完全水合的PEG层的排除体积效应都有助于PEG-脂质胶束之间的排斥相互作用。这应该是PEG脂质作为脂质体稳定剂的功能的关键因素。
By means of dielectric relaxation spectroscopy (DRS) and small-angle X-ray scattering (SAXS), we have investigated hydration behavior, solvent dynamics, and static structures of aqueous solutions of poly(ethylene glycol)-conjugated distearoyl phosphatidylethanolamine (DSPE-PEG) (molecular weight of PEG: M(PEG)= 2000, 5000, and 12,000 Da). A quantitative analysis of the bulk-water relaxation amplitude revealed the effective hydration number of a DSPE-PEG molecule per ethylene oxide monomer unit to be approximately 5.0-5.5, virtually independent of M(PEG). The overall hydration number of a DSPE-PEG molecule is ca. 20% higher than that of the corresponding normal PEG (without DSPE). This is attributed to both hydration of a charged head group of phosphoric acid in DSPE and a packing effect of PEG chains into micellar structures. The pair-distance distribution functions, p(r), extracted from the GIFT analysis of SAXS intensities show that the DSPE-PEGs form spherical-like micelles in water having the maximum diameter of approximately 16, 22, and 31 nm, respectively, for M(PEG) = 2000, 5000, and 12,000 Da and nearly identical aggregation numbers of 72 (+/-10%). The DSPE-PEG micelles behave as charged colloids whose interparticle interaction potential can be approximated by the screened Coulomb potential model. The extracted pair correlation function g(r) demonstrates that both electrostatic repulsion induced by the charged head group and excluded volume effects of the fully hydrated PEG layer contribute to repulsive interactions among the PEG-lipid micelles. This should be a key factor for the function of PEG lipids as a stabilizer of liposomes.