title: Photopolymerization of Dienoyl Lipids Creates Planar Supported Poly(lipid) Membranes with Retained Fluidity.
abstract: 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 Lα and Lβ 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 Lα phase and a Lβ phase. This D range is comparable to ratios of D values reported for liquid-disordered (Ld) and liquid-ordered (Lo) lipid phases and indicates that the effect of UV polymerization on lateral diffusion in a dienoyl PSLB is similar to the transition from a Ld phase to a Lo phase. The partial retention of fluidity in UV-polymerized PSLBs, their enhanced stability, and the activity of incorporated transmembrane proteins and peptides is discussed.
authors.affiliation: Department of Chemistry and Biochemistry and ‡BIO5 Institute, University of Arizona , 1306 East University Boulevard, Tucson, Arizona 85721, United States.
authors.forename: Kristina S
authors.initials: KS
authors.lastname: Orosz
authors.affiliation: Department of Chemistry and Biochemistry and ‡BIO5 Institute, University of Arizona , 1306 East University Boulevard, Tucson, Arizona 85721, United States.
authors.forename: Ian W
authors.initials: IW
authors.lastname: Jones
authors.affiliation: Department of Chemistry and Biochemistry and ‡BIO5 Institute, University of Arizona , 1306 East University Boulevard, Tucson, Arizona 85721, United States.
authors.forename: John P
authors.initials: JP
authors.lastname: Keogh
authors.affiliation: Department of Chemistry and Biochemistry and ‡BIO5 Institute, University of Arizona , 1306 East University Boulevard, Tucson, Arizona 85721, United States.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Smith
authors.affiliation: Department of Chemistry and Biochemistry and ‡BIO5 Institute, University of Arizona , 1306 East University Boulevard, Tucson, Arizona 85721, United States.
authors.forename: Kaitlyn R
authors.initials: KR
authors.lastname: Griffin
authors.affiliation: Department of Chemistry and Biochemistry and ‡BIO5 Institute, University of Arizona , 1306 East University Boulevard, Tucson, Arizona 85721, United States.
authors.forename: Juhua
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Chemistry and Biochemistry and ‡BIO5 Institute, University of Arizona , 1306 East University Boulevard, Tucson, Arizona 85721, United States.
authors.forename: Troy J
authors.initials: TJ
authors.lastname: Comi
authors.affiliation: Department of Chemistry and Biochemistry and ‡BIO5 Institute, University of Arizona , 1306 East University Boulevard, Tucson, Arizona 85721, United States.
authors.forename: H K
authors.initials: HK
authors.lastname: Hall
authors.affiliation: Department of Chemistry and Biochemistry and ‡BIO5 Institute, University of Arizona , 1306 East University Boulevard, Tucson, Arizona 85721, United States.
authors.forename: S Scott
authors.initials: SS
authors.lastname: Saavedra
mesh_terms: D004058:Diffusion; D036681:Fluorescence Recovery After Photobleaching; D008051:Lipid Bilayers / Q000737:chemistry* / Q000528:radiation effects; D008560:Membrane Fluidity / Q000528:radiation effects*; D010713:Phosphatidylcholines / Q000737:chemistry* / Q000528:radiation effects; D010714:Phosphatidylethanolamines / Q000737:chemistry* / Q000528:radiation effects; D058105:Polymerization; D012235:Rhodamines / Q000737:chemistry* / Q000528:radiation effects; D044366:Transition Temperature; D014466:Ultraviolet Rays
chemical_list: D008051:Lipid Bilayers; C053685:N-(lissamine rhodamine B sulfonyl)-1,2-dioleoylphosphatidylethanolamine; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D012235:Rhodamines; C017251:1,2-oleoylphosphatidylcholine