title: Beyond Saffman-Delbruck approximation: a new regime for 2D diffusion of α-hemolysin complexes in supported lipid bilayer.
abstract: Cell mechanisms are actively modulated by membrane dynamics. We studied the dynamics of a first-stage biomimetic system by Fluorescence Recovery After Patterned Photobleaching. Using this simple biomimetic system, constituted by α -hemolysin from Staphylococcus aureus inserted as single heptameric pore or complexes of pores in a glass-supported DMPC bilayer, we observed true diffusion behavior, with no immobile fraction. We find two situations: i) when incubation is shorter than 15 hours, the protein inserts as a heptameric pore and diffuses roughly three times more slowly than its host lipid bilayer; ii) incubation longer than 15 hours leads to the formation of larger complexes which diffuse more slowly. Our results indicate that, while the Saffman-Delbruck model adequately describes the diffusion coefficient D for small radii, D of the objects decreases as 1/R(2) for the size range explored in this study. Additionally, in the presence of inserted proteins, the gel-to-fluid transition of the supported bilayer as well as a temperature shift in the gel-to-fluid transition are observed.
authors.affiliation: CNRS, UMR, Aix-Marseille Université, CINaM, Marseille, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Harb
authors.forename: Joe
authors.initials: J
authors.lastname: Sarkis
authors.forename: Natalie
authors.initials: N
authors.lastname: Ferte
authors.forename: Bernard
authors.initials: B
authors.lastname: Tinland
mesh_terms: D001427:Bacterial Toxins / Q000737:chemistry* / Q000378:metabolism; D004058:Diffusion; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D013696:Temperature
chemical_list: D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D008051:Lipid Bilayers; C021091:staphylococcal alpha-toxin; D004134:Dimyristoylphosphatidylcholine