8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P10.30Tue 611:23-14:00Three-dimensional analysis of lipid vesicletransformationsAi Sakashita, 1 Naohito Urakami, 2 Primoz Ziherl, 3 and Masayuki Imai 11 Ochanomizu University, Department of Physics, Otsuka 2-1-1, Bunkyo 112-8610, Tokyo,Japan2 Yamaguchi University, Yamaguchi, Japan3 University of Ljubljana, Ljubjana, SloveniaSome structural features of biological cells and cell organelles can be understood in terms ofsimple model. One of the most useful being the lipid bilayer vesicle [1] often described in termsof the area-difference-elasticity (ADE) model [2]. The predictions of this model agree well withexperimental observations but most experiments reported so far rely on phase-contrast microscopeimages, which need not show the representative 2D cross-section of the vesicle. In addition,some equilibrium vesicle shapes are nonaxisymmetric, which means that no single representativecross section is sufficient. In this study, we analyzed the full three-dimensional shape of lipidvesicles using a fast confocal microscope, thereby overcoming the limitations of standard opticalmicroscopy. We prepared giant vesicles using DOPC and a fluorescent dye, and we varied theosmotic pressure to control vesicle shape. Using the confocal microscope, we monitored thespontaneous shape transformations seen in vesicles suspended in water, which typically includedthe sequence cigar → nonaxisymmetric shapes → discocyte → stomatocyte. We computed thegeometrical parameters characterizing the shapes of vesicles and we compared our results withthe predictions of the ADE model to quantitatively interpret the observed staggered process ofvesicle shape transformation. The experimental results obtained provide further support for theADE model.[1] U. Seifert, Adv. Phys. 46, 13 (1997)[2] S. Svetina and B. Zeks, Eur. Biophys. J. 17, 101 (1989)30