Photopolymerization of Dienoyl Lipids Creates Planar Supported Poly(lipid) Membranes with Retained Fluidity

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• 作者：Kristina S. Orosz ; Ian W. Jones ; John P. Keogh ; Christopher M. Smith ; Kaitlyn R. Griffin ; Juhua Xu ; Troy J. Comi ; H. K. Hall Jr. ; S. Scott Saavedra
• 刊名：Langmuir
• 出版年：2016
• 出版时间：February 16, 2016
• 年：2016
• 卷：32
• 期：6
• 页码：1577-1584
• 全文大小：343K
• ISSN：1520-5827

文摘

Polymerization of substrate-supported bilayers composed of dienoylphosphatidylcholine (PC) lipids is known to greatly enhance their chemical and mechanical stability; however, the effects of polymerization on membrane fluidity have not been investigated. Here planar supported lipid bilayers (PSLBs) composed of dienoyl PCs on glass substrates were examined to assess the degree to which UV-initiated polymerization affects lateral lipid mobility. Fluorescence recovery after photobleaching (FRAP) was used to measure the diffusion coefficients (D) and mobile fractions of rhodamine-DOPE in unpolymerized and polymerized PSLBs composed of bis-sorbyl phosphatidylcholine (bis-SorbPC), mono-sorbyl-phosphatidylcholine (mono-SorbPC), bis-dienoyl-phosphatidylcholine (bis-DenPC), and mono-dienoyl phosphatidylcholine (mono-DenPC). Polymerization was performed in both the L_α and L_β phase for each lipid. In all cases, polymerization reduced membrane fluidity; however, measurable lateral diffusion was retained which is attributed to a low degree of polymerization. The D values for sorbyl lipids were less than those of the denoyl lipids; this may be a consequence of the distal location of polymerizable group in the sorbyl lipids which may facilitate interleaflet bonding. The D values measured after polymerization were 0.1–0.8 of those measured before polymerization, a range that corresponds to fluidity intermediate between that of a L_α phase and a L_β phase. This D range is comparable to ratios of D values reported for liquid-disordered (L_d) and liquid-ordered (L_o) lipid phases and indicates that the effect of UV polymerization on lateral diffusion in a dienoyl PSLB is similar to the transition from a L_d phase to a L_o phase. The partial retention of fluidity in UV-polymerized PSLBs, their enhanced stability, and the activity of incorporated transmembrane proteins and peptides is discussed.