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Related Concept Videos

Mechanisms of Membrane-bending01:15

Mechanisms of Membrane-bending

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The living membranes are flexible due to their fluid mosaic nature; however, their bending into different shapes is an active process regulated by specific lipids and proteins. The membrane bending can be transient as seen in vesicles or stable for a long time as in microvilli. Cells regulate the size, location, and duration of the membrane curvature.
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Electrochemical systems provide a fascinating insight into the dynamic interplay of charged species within various phases. One notable example is the interaction between a membrane permeable to K⁺ ions but not to Cl⁻ ions, separating an aqueous KCl solution from pure water. As K⁺ ions diffuse through the membrane, they generate net charges on each phase, leading to a potential difference between them.Similarly, when a piece of Zn is immersed in an aqueous ZnSO₄ solution,...
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Enzymes like flippase, floppase, and scramblase transfer phospholipids from one layer to another in the membrane, thereby affecting membrane asymmetry.
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An electrochemical gradient is a fundamental concept in biology and chemistry. It regulates the movement of ions across cell membranes. This movement is influenced by two factors:
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Membrane electrodes, also known as p-ion electrodes, use membranes that selectively interact with free analyte ions, generating a potential difference across the membrane. The resulting membrane potential, known as the asymmetry potential, is not zero even when analyte concentrations on both sides of the membrane are equal. The membrane's response is typically not selective to a single analyte but proportional to the concentration of all ions in the sample solution capable of interacting at...
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Related Experiment Video

Updated: Apr 5, 2026

Neutron Spin Echo Spectroscopy as a Unique Probe for Lipid Membrane Dynamics and Membrane-Protein Interactions
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Equilibrium fluctuation relations for voltage coupling in membrane proteins.

Ilsoo Kim1, Arieh Warshel1

  • 1Department of Chemistry, University of Southern California, SGM 418, 3620 McClintock Avenue, Los Angeles, CA 900089, USA.

Biochimica Et Biophysica Acta
|August 21, 2015
PubMed
Summary

A new theoretical framework explains how external potentials affect membrane protein energy. This model connects voltage coupling to ion channel gating charge and activation, offering insights into protein function and electrogenic phenomena.

Keywords:
(Gating) Charge-Voltage Relation ElectrogenicityCoarse-grained ModelEquilibrium Fluctuation-Response RelationGating ChargeLinear Response Approximation

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Area of Science:

  • Biophysics
  • Theoretical Chemistry
  • Computational Biology

Background:

  • Membrane proteins are crucial for cellular functions, and their activity is often modulated by external electrical potentials.
  • Understanding the energetics of membrane protein conformational changes, particularly in response to voltage, is key to deciphering their function.
  • Existing models often lack a unified theoretical framework to connect microscopic details with macroscopic voltage-dependent behavior.

Purpose of the Study:

  • To develop a general theoretical framework for the energetics of membrane proteins under external potentials.
  • To investigate the relationship between voltage coupling, free energy landscapes, and ion channel gating.
  • To derive a novel expression for gating charge and quantitatively link coarse-grained models to macroscopic behavior.

Main Methods:

  • Developed a theoretical framework based on free energy relations and probability densities, generalized for non-equilibrium processes.
  • Applied the framework to analyze conformational states along a voltage coupling reaction coordinate for ion channels.
  • Utilized a coarse-graining (CG) model of membrane proteins, including electrolytes and electrodes, to illustrate the theory.

Main Results:

  • Established an equivalence between the chemical component of free energy change and the free energy difference between resting and activated states.
  • Derived a closed-form expression for gating charge using linear response approximation, linking it to equilibrium fluctuation-response relations.
  • CG model simulations yielded Marcus-type voltage-dependent free energy parabolas, consistent with electron transfer theory and predicting channel activation (Q-V curves).

Conclusions:

  • The developed framework provides new thermodynamic perspectives on voltage activation in membrane proteins.
  • It offers a quantitative link between coarse-grained models and macroscopic treatments of voltage-gated ion channels.
  • The theory facilitates understanding structure-function correlations and electrogenic phenomena in various membrane transport proteins.