The Experts below are selected from a list of 6171 Experts worldwide ranked by ideXlab platform
John D W Madden - One of the best experts on this subject based on the ideXlab platform.
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hair cell inspired mechanotransduction with a gel supported Artificial Lipid Membrane
Soft Matter, 2011Co-Authors: Stephen A Sarles, John D W MaddenAbstract:A gel-supported Lipid bilayer formed at the base of an Artificial hair is used as the transduction element in an Artificial, Membrane-based hair cell sensor inspired by the structure and function of mammalian hair cells. This paper describes the initial fabrication and characterization of a bioderived, soft-material alternative to previous Artificial hair cells that used the transduction properties of synthetic materials for flow and touch sensing. Under an applied air flow, the Artificial hair structure vibrates, triggering a picoamp-level electrical current across the Lipid bilayer. Experimental analysis of this mechanoelectrical transduction process supports the hypothesis that the current is produced by a time-varying change in the capacitance of the Membrane caused by the vibration of the hair. Specifically, frequency analysis of both the motion of the hair and the measured current show that both phenomena occur at similar frequencies (0.1–1.0 kHz), which suggests that changes in capacitance occur as a result of Membrane bending during excitation. In this paper, the bilayer-based hair cell sensor is experimentally characterized to understand the effects of transMembrane potential, the applied air flow, and the dimensions of the hair.
Stephen A Sarles - One of the best experts on this subject based on the ideXlab platform.
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hair cell inspired mechanotransduction with a gel supported Artificial Lipid Membrane
Soft Matter, 2011Co-Authors: Stephen A Sarles, John D W MaddenAbstract:A gel-supported Lipid bilayer formed at the base of an Artificial hair is used as the transduction element in an Artificial, Membrane-based hair cell sensor inspired by the structure and function of mammalian hair cells. This paper describes the initial fabrication and characterization of a bioderived, soft-material alternative to previous Artificial hair cells that used the transduction properties of synthetic materials for flow and touch sensing. Under an applied air flow, the Artificial hair structure vibrates, triggering a picoamp-level electrical current across the Lipid bilayer. Experimental analysis of this mechanoelectrical transduction process supports the hypothesis that the current is produced by a time-varying change in the capacitance of the Membrane caused by the vibration of the hair. Specifically, frequency analysis of both the motion of the hair and the measured current show that both phenomena occur at similar frequencies (0.1–1.0 kHz), which suggests that changes in capacitance occur as a result of Membrane bending during excitation. In this paper, the bilayer-based hair cell sensor is experimentally characterized to understand the effects of transMembrane potential, the applied air flow, and the dimensions of the hair.
Fologea Daniel - One of the best experts on this subject based on the ideXlab platform.
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Temporary Membrane Permeabilization via the Pore-Forming Toxin Lysenin
'IUScholarWorks', 2020Co-Authors: Shrestha Nisha, Thomas, Christopher A., Richtsmeier Devon, Bogard Andrew, Hermann Rebecca, Walker Malyk, Abatchev Gamid, Brown, Raquel J., Fologea DanielAbstract:Pore-forming toxins are alluring tools for delivering biologically-active, impermeable cargoes to intracellular environments by introducing large conductance pathways into cell Membranes. However, the lack of regulation often leads to the dissipation of electrical and chemical gradients, which might significantly affect the viability of cells under scrutiny. To mitigate these problems, we explored the use of lysenin channels to reversibly control the barrier function of natural and Artificial Lipid Membrane systems by controlling the lysenin’s transport properties. We employed Artificial Membranes and electrophysiology measurements in order to identify the influence of labels and media on the lysenin channel’s conductance. Two cell culture models: Jurkat cells in suspension and adherent ATDC5 cells were utilized to demonstrate that lysenin channels may provide temporary cytosol access to Membrane non-permeant propidium iodide and phalloidin. Permeability and cell viability were assessed by fluorescence spectroscopy and microscopy. Membrane resealing by chitosan or specific media addition proved to be an effective way of maintaining cellular viability. In addition, we loaded non-permeant dyes into liposomes via lysenin channels by controlling their conducting state with multivalent metal cations. The improved control over Membrane permeability might prove fruitful for a large variety of biological or biomedical applications that require only temporary, non-destructive access to the inner environment enclosed by natural and Artificial Membranes
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Planar Bilayer Lipid Membranes: Preparation and Biophysical Characterization
'IUScholarWorks', 2020Co-Authors: Davis, Kyrie E., Eusepi Patrick, Finn Pangaea, Mckinney Fulton, Fologea DanielAbstract:Investigating the properties of a bilayer Lipid Membrane and using those investigations for scientific and biomedical purposes is made possible by the ability to create an Artificial Lipid Membrane from individual elements. When Artificially created, planar bilayer Membranes replicate the Lipid partition of natural cell Membranes. Similar to the natural cell, they can also reconstruct their own replica of other cell components, like the transporter. For the project, we aimed to characterize planar bilayer Lipid Membranes. An electric spark created a small hole in a piece of thin Teflon film, the material used to separate two electrolyte reservoirs. Embedded in the reservoirs were two Ag/AgCl electrodes connected to an electrophysiology amplifier. A mixture composed of Lipids and organic solvent was painted over the opening in the piece of film. Theoretical models were referenced in this experiment to describe the Membrane as a capacitator, and found that capacitance measurements could be used to predict Membrane thickness along with the development of the bilayer Lipid structure. Conductance values were found to predict the quality of the Lipid Membrane, some more permeable than others. By inserting large conductance protein channels into the target Membrane, we were able to exhibit the suitability of the Membrane for recreation of transMembrane transporters
Smith, Christopher M. - One of the best experts on this subject based on the ideXlab platform.
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I. Causes of Multiple Diffusing Populations of Fluorescently Labeled Probes in Lipid Membranes II. Evaluation of PhosphoLipid Membranes Incorporating the Polymerizable Lipid Bis-Denpc (16, 16) and Suitability as Ultra-Stable Platforms for Ion Channel Based Sensors
The University of Arizona., 2019Co-Authors: Smith, Christopher M.Abstract:This dissertation is composed of two major projects, though some capabilities and findings from the first project were applied to the second. Project I focuses on advancements made in the understanding of the chemical interactions of a number of commonly used fluorescently labeled phosphoLipid probes. These probes are used for a variety of studies, including labeling of cellular or Artificial Membranes, examining transport and communication between different Membranes, and determining Membrane fluidity. Understanding the chemical behavior and interactions of these probes in Membranes can be key for the proper interpretation of experimental data. Utilizing fluorescent recovery after photobleaching (FRAP), in combination with other spectroscopic techniques, multiple diffusing populations of commonly used probes in various Artificial Lipid Membrane formats were identified, as were the causes for these populations. This allows for a fuller description of the fluidity of Lipid Membranes. These findings are the focus of Chapters 3 and 4 while the hardware developed that enabled critical measurements is the focus of Chapter 2. Project II focuses on addressing key limitations in developing ion channel (IC) based biosensors utilizing Artificial Lipid Membranes. Among these limitations are the weak mechanical, chemical, and electrical stabilities of Artificial Lipid bilayers due to the weak noncovalent interactions involved in the Membrane. To address these limitations, the polymerizable Lipid bis-dienoyl phosphatidylcholine (bis-DenPC(16, 16)) was characterized for its ability to form ultra-stable Membranes suitable for IC based sensors using the model IC gramicidin A (gA). Special attention was given to determining the Membrane fluidity given the requirement of gA that two subunits must laterally diffuse to converge and dimerize to form a conductive pore. These studies are the focus of Chapters 5 and 6.Release after 07/29/201
Yehuda G Assaraf - One of the best experts on this subject based on the ideXlab platform.
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the role of passive transbilayer drug movement in multidrug resistance and its modulation
Journal of Biological Chemistry, 1996Co-Authors: Gera D Eytan, Ronit Regev, Galit Oren, Yehuda G AssarafAbstract:The successful lowering of the intracellular concentration of multidrug resistance (MDR)-type drugs by P-glycoprotein (Pgp) relies on its ability to overcome the passive influx rate of each MDR-type drug. Thus, the aim of the present work was to study the effect of passive transbilayer drug movement on the multidrug resistance and its modulation. Fluorescence quenching studies indicated that whereas the Pgp substrate rhodamine 123 traverses an Artificial Lipid Membrane with a lifetime of 3 min, the transbilayer movement rate of the MDR modulators, quinidine and quinine, was too fast to be detected with present methods. Transbilayer movement rates of drugs and modulators were estimated from their equilibration rate throughout Artificial multilamellar vesicles. The equilibration rate of five selected modulators was faster than the equilibration rate of five representative MDR-type drugs tested, which was comparable with the rate of rhodamine 123 equilibration. Moreover, the carrier-type peptide ionophore, valinomycin, which is freely mobile in the Membrane, inhibited Pgp-mediated efflux of rhodamine 123 from MDR cells. In contrast, the channel-forming ionophore gramicidin D, a Pgp substrate that flip-flops slowly across the Membrane, did not modulate cellular Pgp activity. Pgp, with a turnover number of about 900 min−1 can keep pace with the influx of an MDR-drug like rhodamine 123 exhibiting a transbilayer movement with a lifetime of minutes. On the other hand, Pgp would fail to protect MDR cells against cytotoxic drugs that are freely mobile through biological Membranes and that re-enter cells faster than their Pgp-mediated active efflux rate. The relatively fast transbilayer movement exhibited by MDR modulators suggest that in contrast to MDR-type drugs, MDR modulators traverse the plasma Membrane faster than the maximal expulsion rate of Pgp.
