13 results on '"Gilman E"'
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2. Multiple mechanisms contribute to fluorometry signals from the voltage-gated proton channel
- Author
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Papp, Ferenc, primary, Toombes, Gilman E., additional, Denes Petho, Zoltan, additional, Bagosi, Adrienn, additional, Feher, Adam, additional, Almassy, Janos, additional, Kuki, Akos, additional, Keki, Sandor, additional, Panyi, Gyorgy, additional, and Varga, Zoltan, additional
- Published
- 2022
- Full Text
- View/download PDF
3. A Real-Space Method to Measure the Persistence Length of Dynamic Microtubules
- Author
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Gilman E. S. Toombes, Antonina Roll-Mecak, Jeff Spector, and Kenton J. Swartz
- Subjects
Persistence length ,Physics ,Mathematical analysis ,Biophysics ,Space (mathematics) ,Measure (mathematics) - Published
- 2020
4. Detecting and Modelling Conformational States of the Proton Channel with Voltage-Clamp Fluorometry
- Author
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Adrienn Bagosi, Zoltan Petho, Gilman E. S. Toombes, Ferenc Papp, Gyorgy Panyi, and Zoltan Varga
- Subjects
Proton channel ,Materials science ,Voltage clamp ,Biophysics ,Fluorescence spectroscopy - Published
- 2020
5. Protein Spatial Distribution Depends on Membrane Curvature
- Author
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Mijo Simunovic, Andrew Callan-Jones, Sophie Aimon, Gilman E. S. Toombes, Coline Prévost, and Patricia Bassereau
- Subjects
Membrane bending ,Membrane ,Chemistry ,Membrane curvature ,Vesicle ,Biophysics ,Curvature ,Integral membrane protein ,Elasticity of cell membranes ,Transport protein ,Cell biology - Abstract
In cells, membranes are highly bent in many places in order to fulfill different functions. This is the case of membrane trafficking, which is accompanied by the formation of tubes or vesicles with diameter below 100 nm that transport proteins and lipids throughout the cell. Moreover, during vesicle budding, curvature at the neck becomes even higher before final scission. Structures at the cell periphery, such as lamellipodia’ edge or filopodia used for migration and environment sensing, also exhibit high membrane curvatures. Many peripheral or integral proteins have an intrinsic shape that produces membrane bending or can deform membrane upon binding. In membrane physics, this property is described by a phenomenological parameter, the protein spontaneous curvature Cp, which represents the capability of the protein to produce membrane spontaneous bending. It is expected that proteins that deform membranes can reciprocally be enriched in curved areas. We have addressed the question of the role of membrane curvature in protein sorting both experimentally and theoretically. We have tested the sorting hypothesis using in vitro membrane system (GUV) and different proteins with positive Cp (BAR-domain), negative Cp (I-BAR-domain) and with integral proteins reconstituted in the GUVs (a potassium channel KvAP). Membrane nanotubes with a controlled diameter (15-500 nm) are pulled out of the GUV with optical tweezers; the relative protein sorting is measured as a function of curvature (inverse of tube radius) from fluorescence measurements with a confocal microscope. We show that our mechanical model based on spontaneous curvature induction is in good agreement with these experiments. All together, this demonstrates that membrane shape is an important parameter that might drive the lateral distribution proteins in membranes, independently of more specific sorting mechanisms.
- Published
- 2015
- Full Text
- View/download PDF
6. Got Ion Accumulation or Depletion (In Your Recording)?
- Author
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Gilman E. S. Toombes, Mufeng Li, Shai D. Silberberg, and Kenton J. Swartz
- Subjects
Chemistry ,Inorganic chemistry ,Biophysics ,Ion - Published
- 2017
7. Studying Voltage Dependent Proteins with Giant Unilamellar Vesicles in a 'Whole Cell' Configuration
- Author
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Gilman E. S. Toombes, Matthias Garten, Sophie Aimon, and Patricia Bassereau
- Subjects
Membrane potential ,0303 health sciences ,Chemistry ,Vesicle ,Pipette ,Biophysics ,Adhesion ,Potassium channel ,Cell biology ,03 medical and health sciences ,Electrophysiology ,0302 clinical medicine ,Membrane ,Cytoskeleton ,030217 neurology & neurosurgery ,030304 developmental biology - Abstract
Biophysical characterization of voltage dependent proteins in-vivo is challenging because of the complex feedback and active regulation in living systems. One approach to overcome these difficulties is to reconstitute the proteins in bio-mimetic model systems such as Giant Unilamellar Vesicles (GUVs), solvent-free, cell-sized proteo-liposomes in which membrane composition, tension and curvature can be readily controlled. The membrane potential of a small patch of the GUV membrane can be controlled by aspirating it into a micropipette (“GUV-attached” patch-clamp), thereby allowing measurements of protein function [1].However, electrophysiological and fluorescence studies of the structural rearrangements mediating protein function would clearly benefit from the ability to control the membrane potential of entire, intact GUVs. For cells, electrical access to the cell interior can be obtained either by inserting a micro-electrode or breaking a “cell-attached” membrane patch to go “whole-cell”. Unfortunately the lack of a cytoskeleton makes GUVs far more sensitive to mechanical stresses than cells, which makes the “whole-cell” configuration quite challenging.Examination of failed “whole-cell” GUV experiments suggested key roles for micropipette pressure and adhesion between the GUV membrane and micropipette, and by controlling these we were able to maintain the “whole-GUV” configuration for experimentally useful periods (tens of minutes). We will describe efforts to further optimize the “whole-GUV” technique, and to use it to study the effects of protein-lipid interactions and protein curvature preferences on the function of KvAP, a voltage-gated potassium channel.[1] S. Aimon et al. Functional Reconstitution of a Voltage-Gated Potassium Channel in Giant Unilamellar Vesicles (2011), PLOSone 6:e25529
- Published
- 2013
- Full Text
- View/download PDF
8. Rapid Activation of Distinct Conducting States in P2X Receptor Channels
- Author
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Kenton J. Swartz, Mufeng Li, Gilman E. S. Toombes, and Shai D. Silberberg
- Subjects
Alkali ions ,Immune system ,Apoptosis ,Chemistry ,Purinergic receptor ,Biophysics ,Extracellular ,Receptor ,Intracellular ,Channel density - Abstract
P2X receptors are trimeric cation channels that are activated by extracellular ATP. These purinergic receptors have been reported to undergo pore dilation following activation by high concentrations of ATP, a phenomenon thought to mediate apoptosis in the immune system. Here we demonstrate that the widely reported slow time-dependent increase in the relative permeability of NMDG to Na, thought to reflect pore dilation, results from a gradual inhibition of small-cation-selective channels following depletion of intracellular alkali ions. Moreover, we find that P2X receptors enter both small-cation-selective open states and large-cation-permeable open states within milliseconds of ATP application. Taken together, our results demonstrate that P2X receptors can rapidly enter a large-cation-permeable open state without requiring either high ATP concentrations or high channel density, indicating that the ability of ATP to permeabilize cells can occur under physiologically realistic conditions.
- Published
- 2015
9. Ion Accumulation and Depletion in Patch Clamp Experiments
- Author
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Shai D. Silberberg, Mufeng Li, Kenton J. Swartz, and Gilman E. S. Toombes
- Subjects
Membrane potential ,Membrane ,Voltage-gated ion channel ,Chemistry ,Electrode ,Biophysics ,Pipette ,Analytical chemistry ,Ionic bonding ,Patch clamp ,Ion - Abstract
The flow of ions through channels and transporters depends sensitively on the concentration of the ionic species and voltage at the membrane. In the widely used patch-clamp technique, voltage and current are measured using electrodes in the pipette and bath that are distant from the membrane. Although the importance of voltage differences between the membrane and electrodes is widely appreciated, concentration gradients arising from the flow of ions are often neglected. In this study, we modeled changes in voltage and ion concentrations during patch-clamp experiments using the Nernst-Plank equation and we derived simple formulas for estimating the timescale and extent of ion accumulation and depletion. For excised patch experiments, ions crossing the membrane can directly diffuse into or out of the patch pipette and ion concentrations stabilize on the millisecond timescale after a change in membrane current. In contrast, in whole-cell experiments the cytosol acts as a reservoir and ion concentrations change on the timescale of seconds. In either configuration, ion accumulation or depletion at steady-state depends primarily on the electrode access resistances and currents carried by each ionic species. As a practical illustration, simulations were performed for bi-ionic protocols previously used to characterize the dynamic ionic selectivity of P2X and TRPV channels. Importantly, even when the net current was small and the membrane voltage effectively clamped, ion accumulation and depletion could cause significant, time-dependent changes in current resembling reported examples of “pore dilation”. Thus, limitations for clamping ion concentrations should be considered when performing and interpreting patch-clamp experiments.
- Published
- 2015
10. Patient Attitudes and Psychological Considerations in Dialysis Discontinuation
- Author
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Cohen, Lewis M., primary, Germain, Michael, additional, Woods, Anne, additional, Deborah Gilman, E., additional, and McCue, Jack D., additional
- Published
- 1993
- Full Text
- View/download PDF
11. Reducing sea turtle interactions in the Hawaii-based longline swordfish fishery
- Author
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Gilman, E, Kobayashi, DR, Swenarton, T, Brothers, N, Dalzell, P, Kinan-Kelly, I, Gilman, E, Kobayashi, DR, Swenarton, T, Brothers, N, Dalzell, P, and Kinan-Kelly, I
- Abstract
The reduction of sea turtle mortality in fisheries may contribute to recovering populations. To reduce turtle interactions, regulations for the Hawaii-based longline swordfish fishery required vessels to switch from using a J-shaped hook with squid bait to a wider circleshaped hook with fish bait. Analyses of observer data showed that, following the introduction of the regulations, significant and large reductions in sea turtle and shark capture rates occurred without compromising target species catches. Capture rates of leatherback and loggerhead turtles significantly declined by 83% and 90%, respectively. The swordfish catch rate significantly increased by 16%. However, combined tuna species and combined mahimahi, opah, and wahoo catch rates significantly declined by 50% and 34%, respectively. The shark catch rate significantly declined by 36%, highlighting the potential for the use of fish instead of squid for bait to contribute to addressing concerns over the sustainability of current levels of shark exploitation. There was also a highly significant reduction in the proportion of turtles that swallowed hooks (versus being hooked in the mouth or body or entangled) and a highly significant increase in the proportion of caught turtles that were released after removal of all terminal tackle, which may increase the likelihood of turtles surviving the interaction. A quarter of turtle captures were in clusters (>1 turtle caught per set and consecutive sets with turtle captures), which is substantially higher than predicted by chance if the events were independent. This suggests that turtles aggregate at foraging grounds and that instituting methods to avoid real-time turtle bycatch hotspots may further reduce turtle interactions. There was no significant correlation between turtle and swordfish catch rates (vessels with high swordfish CPUE do not necessarily have high turtle CPUE), indicating that there may be a fishing practice or gear design causing some vessels to h
12. Reducing sea turtle interactions in the Hawaii-based longline swordfish fishery
- Author
-
Gilman, E, Kobayashi, DR, Swenarton, T, Brothers, N, Dalzell, P, Kinan-Kelly, I, Gilman, E, Kobayashi, DR, Swenarton, T, Brothers, N, Dalzell, P, and Kinan-Kelly, I
- Abstract
The reduction of sea turtle mortality in fisheries may contribute to recovering populations. To reduce turtle interactions, regulations for the Hawaii-based longline swordfish fishery required vessels to switch from using a J-shaped hook with squid bait to a wider circleshaped hook with fish bait. Analyses of observer data showed that, following the introduction of the regulations, significant and large reductions in sea turtle and shark capture rates occurred without compromising target species catches. Capture rates of leatherback and loggerhead turtles significantly declined by 83% and 90%, respectively. The swordfish catch rate significantly increased by 16%. However, combined tuna species and combined mahimahi, opah, and wahoo catch rates significantly declined by 50% and 34%, respectively. The shark catch rate significantly declined by 36%, highlighting the potential for the use of fish instead of squid for bait to contribute to addressing concerns over the sustainability of current levels of shark exploitation. There was also a highly significant reduction in the proportion of turtles that swallowed hooks (versus being hooked in the mouth or body or entangled) and a highly significant increase in the proportion of caught turtles that were released after removal of all terminal tackle, which may increase the likelihood of turtles surviving the interaction. A quarter of turtle captures were in clusters (>1 turtle caught per set and consecutive sets with turtle captures), which is substantially higher than predicted by chance if the events were independent. This suggests that turtles aggregate at foraging grounds and that instituting methods to avoid real-time turtle bycatch hotspots may further reduce turtle interactions. There was no significant correlation between turtle and swordfish catch rates (vessels with high swordfish CPUE do not necessarily have high turtle CPUE), indicating that there may be a fishing practice or gear design causing some vessels to h
13. Standardized procedures for planting vegetation on completed sanitary landfills
- Author
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GILMAN, E, primary, FLOWER, F, additional, and LEONE, I, additional
- Published
- 1985
- Full Text
- View/download PDF
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