title: Nanometric thermal fluctuations of weakly confined biomembranes measured with microsecond time-resolution.
abstract: We probe the bending fluctuations of bio-membranes using highly deflated giant unilamellar vesicles (GUVs) bound to a substrate by a weak potential arising from generic interactions. The substrate is either homogeneous, with GUVs bound only by the weak potential, or is chemically functionalized with a micro-pattern of very strong specific binders. In both cases, the weakly adhered membrane is seen to be confined at a well-defined distance above the surface while it continues to fluctuate strongly. We quantify the fluctuations of the weakly confined membrane at the substrate proximal surface as well as of the free membrane at the distal surface of the same GUV. This strategy enables us to probe in detail the damping of fluctuations in the presence of the substrate, and to independently measure the membrane tension and the strength of the generic interaction potential. Measurements were done using two complementary techniques - dynamic optical displacement spectroscopy (DODS, resolution: 20 nm, 10 μs), and dual wavelength reflection interference contrast microscopy (DW-RICM, resolution: 4 nm, 50 ms). After accounting for the spatio-temporal resolution of the techniques, an excellent agreement between the two measurements was obtained. For both weakly confined systems we explore in detail the link between fluctuations on the one hand and membrane tension and the interaction potential on the other hand.
authors.affiliation: Aix-Marseille Université, CNRS UMR 7325 (Centre Interdisciplinaire de Nanosciences de Marseille - CINaM), Marseille Cedex 9, France. sengupta@cinam.univ-mrs.fr cornelia.monzel@curie.fr and Institute of Complex Systems 7 (ICS-7), Forschungszentrum Jülich, Jülich, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Monzel
authors.affiliation: II. Institut für Theoretische Physik, Universität Stuttgart, Germany and Institut für Theoretische Physik, Friedrich Alexander Universität Erlangen-Nürnberg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schmidt
authors.affiliation: II. Institut für Theoretische Physik, Universität Stuttgart, Germany.
authors.forename: Udo
authors.initials: U
authors.lastname: Seifert
authors.affiliation: Institut für Theoretische Physik, Friedrich Alexander Universität Erlangen-Nürnberg, Germany and Division of Physical Chemistry, Ruđer Bošković Institute, 10000 Zagreb, Croatia.
authors.forename: Ana-Sunčana
authors.initials: AS
authors.lastname: Smith
authors.affiliation: Institute of Complex Systems 7 (ICS-7), Forschungszentrum Jülich, Jülich, Germany.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Merkel
authors.affiliation: Aix-Marseille Université, CNRS UMR 7325 (Centre Interdisciplinaire de Nanosciences de Marseille - CINaM), Marseille Cedex 9, France. sengupta@cinam.univ-mrs.fr cornelia.monzel@curie.fr.
authors.forename: Kheya
authors.initials: K
authors.lastname: Sengupta
mesh_terms: D055592:Biophysical Phenomena; D008566:Membranes; D008857:Microscopy, Interference; D008962:Models, Theoretical; D013057:Spectrum Analysis; D053835:Unilamellar Liposomes
chemical_list: D053835:Unilamellar Liposomes