Selective photoinduced Ca2+ diffusion in rhodopsin–lipid bilayers: an internal transmitter hypothesis

Triton X-100 purified rhodopsin has been incorporated into lipid bilayer membranes prepared by the combined lifting-and-touching method. The illumination of the membranes with white light and monochromatic light of λ = 498 nm resulted in a high selective increase of Ca2+ diffusion through the lipid bilayers compared to Na+ and K+. The stoichiometric ratios of photoinduced ion diffusion were found to be more than 888 Ca2+ Rh*−1 s−1 and 166 Na+ Rh*−1 s−1 at 290 K using the white light, and 1 277 Ca2+ Rh*−1 s−1, 96 K+ Rh*−1 s−1, and 50 Na+ Rh*−1 s−1 at 276 K using the monochromatic light. It was inferred that Ca2+ is an excellent candidate as internal transmitter in the visual photo-transduction.

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The Amino Terminus of Pseudomonas aeruginosaOuter Membrane Protein OprF Forms Channels in Lipid Bilayer Membranes: Correlation with a Three-Dimensional Model

Journal of Bacteriology ◽

10.1128/jb.182.18.5251-5255.2000 ◽

2000 ◽

Vol 182 (18) ◽

pp. 5251-5255 ◽

Cited By ~ 43

Author(s):

Fiona S. L. Brinkman ◽

Manjeet Bains ◽

Robert E. W. Hancock

Keyword(s):

Lipid Bilayer ◽

Lipid Bilayers ◽

Three Dimensional ◽

Comparative Modeling ◽

Three Dimensions ◽

Amino Terminus ◽

Lipid Bilayer Membranes ◽

Three Dimensional Model ◽

Sequence Comparisons ◽

Bilayer Membranes

ABSTRACT Pseudomonas aeruginosa OprF forms 0.36-nS channels and, rarely, 2- to 5-nS channels in lipid bilayer membranes. We show that a protein comprising only the N-terminal 162-amino-acid domain of OprF formed the smaller, but not the larger, channels in lipid bilayers. Circular dichroism spectroscopy indicated that this protein folds into a β-sheet-rich structure, and three-dimensional comparative modeling revealed that it shares significant structural similarity with the amino terminus of the orthologous protein Escherichia coliOmpA, which has been shown to form a β-barrel. OprF and OmpA share only 15% identity in this domain, yet these results support the utility of modeling such widely divergent β-barrel domains in three dimensions in order to reveal similarities not readily apparent through primary sequence comparisons. The model is used to further hypothesize why porin activity differs for the N-terminal domains of OprF and OmpA.

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Polyelectrolyte-induced domains in lipid bilayer membranes: the deuterium NMR perspective

Biochemistry and Cell Biology ◽

10.1139/o98-044 ◽

1998 ◽

Vol 76 (2-3) ◽

pp. 452-464 ◽

Cited By ~ 14

Author(s):

Peter M Macdonald ◽

Kevin J Crowell ◽

Carla M Franzin ◽

Peter Mitrakos ◽

Darlene J Semchyschyn

Keyword(s):

Lipid Bilayer ◽

Lipid Bilayers ◽

Domain Size ◽

Complete Analysis ◽

Deuterium Nmr ◽

Domain Formation ◽

Lipid Bilayer Membranes ◽

Bilayer Membranes ◽

H Nmr ◽

Oppositely Charged

Domain formation in lipid bilayer membranes can occur through electrostatic interactions between charged lipids and oppositely charged polyelectrolytes, such as proteins or polynucleic acids. This review describes a novel method for examining such domains in lipid bilayers, based on 2H NMR spectroscopy. The 2H NMR spectrum of choline-deuterated phosphatidylcholine is sensitive to, and reports on, lipid bilayer surface charge. When a charged lipid bilayer is exposed to an oppositely charged polyelectrolyte, the latter binds electrostatically to the bilayer surface and attracts charged lipids into its vicinity. The resulting inhomogeneous charge distribution produces overlapping 2H NMR subspectra arising from phosphatidylcholine within charge-enriched versus charge-depleted regions. Such spectral details as the quadrupolar splittings and the relative intensities of the subspectra permit a complete analysis of the domain composition, size, and, within limits, lifetime. Using 2H NMR, domain formation in lipid bilayer membranes can be observed with both cationic and anionic polyelectrolytes, whether of natural or synthetic origin. Domain size and composition prove to be sensitive to the detailed chemical structure of both the polyelectrolyte and the charged lipids. Within the domains there is always a stoichiometric anion/cation binding ratio, indicating that the polyelectrolyte lies flat on the membrane surface. The amount of phosphatidylcholine within the domain varies as a function of its statistical availability, in accordance with the predictions of a recent thermodynamic model of domain formation. When the molecular weight of the polyelectrolyte is varied, the domain size alters in accordance with the predictions of classical polymer physics. As expected for a predominantly electrostatic phenomenon, the observed domains dissipate at high ionic strength.Key words: electrostatic domains, polyelectrolytes, lipid bilayers, deuterium NMR.

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Triton X-100 as a channel-forming substance in artificial lipid bilayer membranes

Archives of Biochemistry and Biophysics ◽

10.1016/0003-9861(77)90343-5 ◽

1977 ◽

Vol 184 (1) ◽

pp. 204-208 ◽

Cited By ~ 83

Author(s):

P. Schlieper ◽

E. De Robertis

Keyword(s):

Lipid Bilayer ◽

Lipid Bilayer Membranes ◽

Bilayer Membranes ◽

Triton X

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Miniaturized Silicon Apertures for Lipid Bilayer Reconstitution Experiments

MRS Proceedings ◽

10.1557/proc-1191-oo08-05 ◽

2009 ◽

Vol 1191 ◽

Cited By ~ 2

Author(s):

Michael Goryll ◽

Nipun Chaplot

Keyword(s):

Ion Channels ◽

Lipid Bilayer ◽

Lipid Bilayers ◽

High Throughput ◽

Drug Screening ◽

Lab On A Chip ◽

Lipid Bilayer Membranes ◽

Bilayer Membranes ◽

High Throughput Drug Screening ◽

Micron Size

AbstractIon channels reconstituted into lipid bilayer membranes can be used as a very sensitive and selective platform for high-throughput drug screening applications. In order to employ suspended lipid bilayer membranes for these experiments in form of a “lab-on-a-chip” configuration, a robust and affordable platform is required. In our study, we investigated the feasibility of hosting lipid bilayer membranes across micron-size apertures ranging from 5 μm – 50 μm in silicon. On these substrates, lipid bilayers were formed and characterized concerning their seal resistance, capacitance and breakdown voltage. Seal resistance values of up to 60 GΩ could be achieved repeatedly on these substrates.

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