Mechano-capacitive properties of polarized membranes and the application to conductance measurements of lipid membrane patches

Zecchi, Karis A.; Mosgaard, Lars D.; Heimburg, Thomas

doi:10.1088/1742-6596/780/1/012001

Cited by 10 publications

(14 citation statements)

References 18 publications

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“…• since thickness and area of membranes change, transitions can also affect the capacitance of the membrane (19,65). We have previously shown that the capacitance in an artificial membrane can double when going from the gel to the fluid phase (66).…”

Section: Discussionmentioning

confidence: 99%

Melting transitions in biomembranes

Mužić¹,

Tounsi²,

Madsen³

et al. 2019

Biochimica et Biophysica Acta (BBA) - Biomembranes

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We investigated melting transitions in biological membranes in their native state that include their membrane proteins. These membranes originated from E. coli, B. subtilis, lung surfactant and nerve tissue from the spinal cord of several mammals. For some preparations, we studied the pressure, pH and ionic strength dependence of the transition. For porcine spine, we compared the transition of the native membrane to that of the extracted lipids. All preparations displayed melting transitions of 10-20 degrees below physiological or growth temperature, independent of the organism of origin and the respective cell type. The position of transitions in E. coli membranes depends on the growth temperature. We discuss these findings in the context of the thermodynamic theory of membrane fluctuations that leads to largely altered elastic constants, an increase in fluctuation lifetime and in membrane permeability associated with the transitions. We also discuss how to distinguish lipid transitions from protein unfolding transitions. Since the feature of a transition slightly below physiological temperature is conserved even when growth conditions change, we conclude that the transitions are likely to be of major biological importance for the survival and the function of the cell.

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Section: Discussionmentioning

confidence: 99%

Melting transitions in biomembranes

Mužić¹,

Tounsi²,

Madsen³

et al. 2019

Biochimica et Biophysica Acta (BBA) - Biomembranes

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“…The original Hodgkin and Huxley model ( 1952) of the propagation of nerve impulses in a neuron modelled the membrane as a fixed capacitance. Subsequent studies have shown that changes in the membrane properties, such as thickness (Heimburg 2012), curvature (Petrov 2002) and the conformational state of the lipids in the membrane (Antonov et al 1985;Taylor et al 2017), result in changes in capacitance, which can result in excitation of nerve impulses (Heimburg 2012;Luan et al 2014;Plaksin et al 2014Plaksin et al , 2017Shapiro et al 2012;Zecchi et al 2017). US has been previously shown to induce capacitive currents in pure lipid membranes (Prieto et al 2013), which can be explained on the basis of flexoelectric effects or conformational changes.…”

Section: Membrane Capacitance: Flexoelectricity and Conformational Changesmentioning

confidence: 99%

Ultrasound Neuromodulation: A Review of Results, Mechanisms and Safety

Blackmore

Shrivastava

Sallet

et al. 2019

Ultrasound in Medicine & Biology

368

285

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Ultrasonic neuromodulation is a rapidly growing field, in which low-intensity ultrasound (US) is delivered to nervous system tissue, resulting in transient modulation of neural activity. This review summarizes the findings in the central and peripheral nervous systems from mechanistic studies in cell culture to cognitive behavioral studies in humans. The mechanisms by which US mechanically interacts with neurons and could affect firing are presented. An in-depth safety assessment of current studies shows that parameters for the human studies fall within the safety envelope for US imaging. Challenges associated with accurately targeting US and monitoring the response are described. In conclusion, the literature supports the use of US as a safe, non-invasive brain stimulation modality with improved spatial localization and depth targeting compared with alternative methods. US neurostimulation has the potential to be used both as a scientific instrument to investigate brain function and as a therapeutic modality to modulate brain activity.

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“…For a pipette with 1 μm diameter, the maximum curvature is c = 1/500 nm . However, if one uses black lipid membranes spanning a hole with a diameter of about 100 μm, the maximum possible curvature is 100 times smaller (see Zecchi et al, 2017 for details about this argument). If the voltage offset were in fact caused by flexoelectricity, the voltage offset would be practically absent in black lipid membrane measurements.…”

Section: Resultsmentioning

confidence: 99%

“…In a previous publication (Zecchi et al, 2017) we suggested that the offset voltage responsible for the asymmetry and the apparent outward rectification of the I-V profiles is caused by flexoelectricity. Bending of the membrane creates an electrical polarization that is roughly proportional to the curvature (Petrov, 2001;Petrov and Sachs, 2002;Mosgaard et al, 2015b).…”

Section: Symmetric I-v Profiles In Black Lipid Membranesmentioning

confidence: 89%

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Non-linear Conductance, Rectification, and Mechanosensitive Channel Formation of Lipid Membranes

Zecchi

Heimburg

2021

Front. Cell Dev. Biol.

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There is mounting evidence that lipid bilayers display conductive properties. However, when interpreting the electrical response of biological membranes to voltage changes, they are commonly considered as inert insulators. Lipid bilayers under voltage-clamp conditions display current traces with discrete conduction-steps, which are indistinguishable from those attributed to the presence of protein channels. In current-voltage (I-V) plots they may also display outward rectification, i.e., voltage-gating. Surprisingly, this has even been observed in chemically symmetric lipid bilayers. Here, we investigate this phenomenon using a theoretical framework that models the electrostrictive effect of voltage on lipid membranes in the presence of a spontaneous polarization, which can be recognized by a voltage offset in electrical measurements. It can arise from an asymmetry of the membrane, for example from a non-zero spontaneous curvature of the membrane. This curvature can be caused by voltage via the flexoelectric effect, or by hydrostatic pressure differences across the membrane. Here, we describe I-V relations for lipid membranes formed at the tip of patch pipettes situated close to an aqueous surface. We measured at different depths relative to air/water surface, resulting in different pressure gradients across the membrane. Both linear and non-linear I-V profiles were observed. Non-linear conduction consistently takes the form of outward rectified currents. We explain the conductance properties by two mechanisms: One leak current with constant conductance without pores, and a second process that is due to voltage-gated pore opening correlating with the appearance of channel-like conduction steps. In some instances, these non-linear I-V relations display a voltage regime in which dI/dV is negative. This has also been previously observed in the presence of sodium channels. Experiments at different depths reveal channel formation that depends on pressure gradients. Therefore, we find that the channels in the lipid membrane are both voltage-gated and mechanosensitive. We also report measurements on black lipid membranes that also display rectification. In contrast to the patch experiments they are always symmetric and do not display a voltage offset.

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Mechano-capacitive properties of polarized membranes and the application to conductance measurements of lipid membrane patches

Cited by 10 publications

References 18 publications

Melting transitions in biomembranes

Melting transitions in biomembranes

Ultrasound Neuromodulation: A Review of Results, Mechanisms and Safety

Non-linear Conductance, Rectification, and Mechanosensitive Channel Formation of Lipid Membranes

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