╨╧рб▒с>■  ')■   &                                                                                                                                                                                                                                                                                                                                                                                                                                                ье┴M R┐lbjbj'2'22EXEXp       ]╪╪╪╪╪╪╪ььььь ° ьщpЦШШШШШШ$YЇM|╝-╪╝Д╪╪ДДДj╪╪Цьь╪╪╪╪ЦДДЦ╪╪Ц Ё╗¤в*q┼ььz ЦMimicking Nanometer-Scale Heterogeneity Using Gel-Liquid Coexisting Supported Lipid Bilayers 1Wan-Chen Lin, 1Craig D. Blanchette, 2Timothy Ratto, and 1,3Marjorie L. Longo 1Biophysics Graduate Group, UC Davis, Davis, CA 2Chemistry and Materials Science, Lawrence Livermore National Laboratory, Livermore, CA 3Chemical Engineering and Materials Science, UC Davis, Davis, CA Supported lipid bilayers are currently receiving increasing attention. They not only serve as model membranes in the study of cellular processes but also as promising biosensor components. We made our supported bilayers by quenched vesicle fusion (on a mica substrate) that consist of phase-separated dilauroylphosphotidylcholine (DLPC) and distearoylphosphotidylcholine (DSPC) in order to mimic nanometer-scale heterogeneous structures in biological membranes, or so called  raft structures. The size of DSPC domains (range form 30 nm to 40 ╝m) was controlled by the cooling rate during the supported bilayer formation. We were also able to manage the inter-monolayer coupling of phase-separated supported lipid bilayers by controlling the method of vesicle preparation. Using atomic force microscopy (AFM), fluorescence recovery after photobleaching (FRAP), and ligand-receptor binding assays we found that bilayers with partially asymmetric coupling are metastable and convert, through lipid flip-flop, to a state where all gel phase lipid domains partition to the top monolayer. During this conversion, we observed a fast, one-way DSPC flipping from the interface between coupled DSPC domains and uncoupled DSPC domains and also toward trapped DLPC pools within DSPC domains. Overall, the converting process seemed to be an Ostwald Ripening, which leads to less DSPC-DLPC interface. On the other hand, the interface between coupled DSPC domains and coupled DLPC region was stable. We believe this stability is due to highly ordered molecular packing in the coupled DSPC domains. We related these stable and metastable states to hydrophobic mismatch and molecular packing in gel-phase domains. In addition, we observed a depletion of fluorescent probe in the leaflet directly opposed to the gel phase domains, indicating the gel phase domains in one monolayer have an ordering effect on the opposing monolayer. Our results indicate that the hydrophobic mismatch at gel-fluid interface can be one of the important factors for maintaining lipid asymmetry in biology membranes. In addition, the ability to control lipid domain size and lipid superposition is necessary for further bio-mimetic applications of supported lipid bilayers such as platforms for protein-bilayer interaction studies. ^_mnГДЧЪмно▌▐56l№·№·№·№·°°°H*5Б5БH*]^мн▌5vwxkl¤·ўї··я··чт$ДД$ДДdh$dh$$ ]^мн▌5vwxkl¤· 0&P 1Рh░В. ░╞A!░е"░е#РS$РS%░░┼░┼ Р─ [4@ё 4 gQЗeCJ_HaJmH nHsH tH0@0 jLШ 1$@&5БPJ\БtH A@Є б Ш-К╡k=ДW[ЛW$B@Є$ ,gЗe$a$5Б\Бp     l l l wБе┴═ъЧЩ6@й░┼╧r r   wanlinhC:\Documents and Settings\wanlin.CHMS\Application Data\Microsoft\Word\AutoRecovery save of Document1.asdwanlin/D:\EXP\Presentation\2005 MRS spring meeting.docwanlin D:\EXP\Presentation\2005 ACS.doc Abby Vilchez)C:\My Documents\My Webs\SFMOE\ЧgЫ[┴Д╓КЗeXdБЙ.doc @А╚Ш(.(p а@аа@GРЗ: Times New Roman5РАSymbol3&Р З: Arial1РИ.░e0}f╘Ъ/5РИ .0}f╘ЪWРCenturyTimes New Roman"qИЁ╨hпsЦFпsЦFВЫ!ЁеSx┤ВВr0С   2005 MRS Spring Meetingwanlin Abby Vilchez■ рЕЯЄ∙OhлС+'│┘0ДРШ╕─╘рь $ @ L Xdlt|╢2005 MRS Spring Meeting005wanlinSanlanl Normal.dotr Abby Vilchezng 2byMicrosoft Word 8.0t@ П@т╫Ч*q┼@т╫Ч*q┼ВЫ■ ╒═╒Ь.УЧ+,∙оD╒═╒Ь.УЧ+,∙оH hpАИРШ аи░╕ └ ф╢CHMSSС ё 2005 MRS Spring Meeting TitleШ 6> _PID_GUID╢AN{E90903B7-37D3-44C3-A134-A983AE071985} ■   ■   ■    !"#$%■   ¤   (■   ■   ■                                                                                                                                                                                                                                                                                                                                                       Root Entry         └Fр}ьв*q┼╨в г*q┼*А1Table        WordDocument        2SummaryInformation(    DocumentSummaryInformation8            CompObj            f                        ■                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           ■       └FMicrosoft Word дхеє MSWordDocWord.Document.8Ї9▓q