A membrane interferometer

Freestanding phospholipid bilayers have been assembled spanning shallow, micrometer-sized wells etched into a Si wafer substrate so that the bilayers are near (within hundreds of nanometers) but not in contact with the wafer surface. The proximity of the bilayers to the highly reflective Si/SiO2 interface allows them to be probed by using fluorescence-interference techniques. These interferometry measurements show that the bilayers are curved and that the curvature can be varied by changes in osmotic pressure. Furthermore, the ionophore gramicidin can be incorporated into the bilayers, making them selectively permeable to monovalent cations. This freestanding architecture may overcome surface-interaction problems that occur when cell membrane proteins are introduced into solid supported bilayers, while also allowing for high-precision measurements of changes in fluorophore position by interferometry.

[1]  E. Evans,et al.  Water permeability and mechanical strength of polyunsaturated lipid bilayers. , 2000, Biophysical journal.

[2]  S. Boxer,et al.  Probing the structure of supported membranes and tethered oligonucleotides by fluorescence interference contrast microscopy. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[3]  H. Ti Tien,et al.  METHODS FOR THE FORMATION OF SINGLE BIMOLECULAR LIPID MEMBRANES IN AQUEOUS SOLUTION , 1963 .

[4]  Michael A Nash,et al.  Automated formation of lipid-bilayer membranes in a microfluidic device. , 2006, Nano letters.

[5]  J. Heath,et al.  Black Lipid Membranes: Visualizing the Structure, Dynamics, and Substrate Dependence of Membranes , 2004 .

[6]  H. Bayley,et al.  A storable encapsulated bilayer chip containing a single protein nanopore. , 2007, Journal of the American Chemical Society.

[7]  C. Maldarelli,et al.  Arraying of intact liposomes into chemically functionalized microwells. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[8]  S. White,et al.  Formation of planar bilayer membranes from lipid monolayers. A critique. , 1976, Biophysical journal.

[9]  Shoji Takeuchi,et al.  Lipid bilayer formation by contacting monolayers in a microfluidic device for membrane protein analysis. , 2006, Analytical chemistry.

[10]  S. Bezrukov,et al.  Partitioning of differently sized poly(ethylene glycol)s into OmpF porin. , 2002, Biophysical journal.

[11]  G. Schütz,et al.  Simultaneous optical and electrical recording of single gramicidin channels. , 2003, Biophysical journal.

[12]  F. Jähnig,et al.  What is the surface tension of a lipid bilayer membrane? , 1996, Biophysical journal.

[13]  S H White,et al.  Formation of "solvent-free" black lipid bilayer membranes from glyceryl monooleate dispersed in squalene. , 1978, Biophysical journal.

[14]  S. Boxer,et al.  Lipid-anchored DNA mediates vesicle fusion as observed by lipid and content mixing , 2008, Biointerphases.

[15]  J. Mervis.  Science in Japan: Competition on Campus , 1996 .

[16]  L. Tamm,et al.  Measuring distances in supported bilayers by fluorescence interference-contrast microscopy: polymer supports and SNARE proteins. , 2003, Biophysical journal.

[17]  Y. Santoso,et al.  Enhanced stability and fluidity in droplet on hydrogel bilayers for measuring membrane protein diffusion. , 2007, Nano letters.

[18]  S. Boxer,et al.  Variable incidence angle fluorescence interference contrast microscopy for z-imaging single objects. , 2005, Biophysical journal.

[19]  J. Groves,et al.  Hydrodynamic damping of membrane thermal fluctuations near surfaces imaged by fluorescence interference microscopy. , 2006, Physical review letters.

[20]  D. Urry.  The gramicidin A transmembrane channel: a proposed pi(L,D) helix. , 1971, Proceedings of the National Academy of Sciences of the United States of America.

[21]  Tae-Joon Jeon,et al.  Hydrogel-encapsulated lipid membranes. , 2006, Journal of the American Chemical Society.

[22]  Armin Lambacher,et al.  Fluorescence interference-contrast microscopy on oxidized silicon using a monomolecular dye layer , 1996 .

[23]  J. Groves,et al.  Protein patterns at lipid bilayer junctions. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[24]  George M Whitesides,et al.  Microfabricated teflon membranes for low-noise recordings of ion channels in planar lipid bilayers. , 2003, Biophysical journal.

[25]  J. Israelachvili.  Intermolecular and surface forces , 1985 .

[26]  E. Sackmann,et al.  Supported Membranes: Scientific and Practical Applications , 1996, Science.

[27]  Armin Lambacher,et al.  Luminescence of dye molecules on oxidized silicon and fluorescence interference contrast microscopy of biomembranes , 2002 .

[28]  M Montal,et al.  Formation of bimolecular membranes from lipid monolayers and a study of their electrical properties. , 1972, Proceedings of the National Academy of Sciences of the United States of America.

[29]  Hywel Morgan,et al.  Air-exposure technique for the formation of artificial lipid bilayers in microsystems. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[30]  C. Steinem,et al.  Membrane-suspended nanocompartments based on ordered pores in alumina. , 2002, Chemphyschem : a European journal of chemical physics and physical chemistry.

[31]  S. Hladky,et al.  Ion transfer across lipid membranes in the presence of gramicidin A. I. Studies of the unit conductance channel. , 1972, Biochimica et biophysica acta.

[32]  T. Yanagida,et al.  Simultaneous optical and electrical recording of a single ion-channel. , 2002, The Japanese journal of physiology.

[33]  S. Boxer,et al.  Model membrane systems and their applications. , 2007, Current opinion in chemical biology.

[34]  Daniela Weiskopf,et al.  Micro-BLMs on highly ordered porous silicon substrates: rupture process and lateral mobility. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[35]  R. Pastor,et al.  On simulating lipid bilayers with an applied surface tension: periodic boundary conditions and undulations. , 1996, Biophysical journal.

[36]  Erich Sackmann,et al.  Polymer-supported membranes as models of the cell surface , 2005, Nature.

[37]  H. Tien,et al.  Planar lipid bilayers (BLMs) and their appilcations , 2003 .

[38]  Peter Fromherz,et al.  Membrane-transistor cable , 1998 .

[39]  Ingo Köper,et al.  Tethered bimolecular lipid membranes - A novel model membrane platform , 2006 .

[40]  Shoji Takeuchi,et al.  Highly reproducible method of planar lipid bilayer reconstitution in polymethyl methacrylate microfluidic chip. , 2006, Langmuir : the ACS journal of surfaces and colloids.