Dynamic Properties of Bicellar Lipid Mixtures Observed by Rheometry and Quadrupole Echo Decay

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• 作者：Alanna Flynn ; Michael Ducey ; Anand Yethiraj ; Michael R. Morrow
• 刊名：Langmuir
• 出版年：2012
• 出版时间：February 7, 2012
• 年：2012
• 卷：28
• 期：5
• 页码：2782-2790
• 全文大小：500K
• 年卷期：v.28,no.5(February 7, 2012)
• ISSN：1520-5827

文摘

In bicellar dispersions of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), the transition from isotropic reorientation to partial orientational order, on warming, is known to coincide with a sharp increase in viscosity. In this work, cone-and-plate rheometry, ²H NMR spectroscopy, and quadrupole echo decay observations have been used to obtain new insights into the dynamics of phases observed in bicellar DMPC/DHPC mixtures. Samples with 25% of the DMPC component deuterated were used to correlate rheological measurements with phase behavior observed by ²H NMR spectroscopy. Mixtures containing only normal DMPC (DMPC/DHPC) or only chain perdeuterated DMPC (DMPC-d₅₄/DHPC) were used to refine rheology and quadrupole echo decay measurements respectively. The viscosity peaked at 4鈥? Pa路s, just above the isotropic-to-nematic transition, and then dropped as samples were warmed through the nematic-to-lamellar transition. Quadrupole echo decay times above the nematic-to-lamellar transition were significantly longer than typically observed in the liquid crystalline phase of saturated lipid multilamellar vesicles. This may indicate a damping of slow bilayer undulations resulting from the coupling of opposite bilayer surfaces by DHPC-lined pores.