Specific ions modulate diffusion dynamics of hydration water on lipid membrane surfaces
Jinsuk Song1, John Franck, Philip Pincus
1Department of Chemistry and Biochemistry and ‡Materials and Physics Department, University of California, Santa Barbara , Santa Barbara, California 93106, United States.
Journal of the American Chemical Society
|January 25, 2014
Summary
Specific ions influence water diffusion near lipid vesicles, with Hofmeister ions altering water binding strength. This study reveals how ions impact surface water dynamics and hydrogen bonding.
Area of Science:
- Physical Chemistry
- Biophysics
- Surface Science
Background:
- Understanding water dynamics at interfaces is crucial for biological and chemical processes.
- Lipid vesicles are common model systems for cell membranes.
- The Hofmeister series describes ion-specific effects on protein solubility and other phenomena.
Purpose of the Study:
- To investigate the effect of specific ions on the translational diffusion of water near hydrophilic lipid vesicle surfaces.
- To quantify the retardation of water diffusion at hydrophilic interfaces.
- To determine if ion-induced changes in water diffusion correlate with the Hofmeister series.
Main Methods:
- Overhauser dynamic nuclear polarization (ODNP) was employed to measure local water diffusion.
- ODNP utilizes electron spin probes on vesicle surfaces to probe water dynamics within ~10 Å.
- High-frequency (10 GHz) nuclear magnetic resonance relaxometry enabled measurement of picosecond to subnanosecond water dynamics.
Main Results:
- Water diffusion within ~10 Å of hydrophilic vesicle surfaces is approximately 5 times slower than bulk water.
- The presence of specific ions modulates this surface water diffusion retardation.
- The order of ion influence on water diffusion follows the Hofmeister series.
Conclusions:
- Hofmeister ions directly modulate the diffusivity of water at hydrophilic surfaces.
- This modulation implies a direct impact on the hydrogen bond network strength of surface hydration water.
- While the precise molecular mechanism requires further investigation, ion-specific effects on surface water dynamics are experimentally confirmed.
More Related Videos
Related Concept Videos
02:42Aqueous Solutions and Heats of Hydration
14.3K
Water and other polar molecules are attracted to ions. The electrostatic attraction between an ion and a molecule with a dipole is called an ion-dipole attraction. These attractions play an important role in the dissolution of ionic compounds in water.
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process...
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process...
14.3K
03:13Intermolecular Forces
62.9K
Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen...
62.9K
01:12Diffusion
176.6K
Diffusion is the passive movement of substances down their concentration gradients—requiring no expenditure of cellular energy. Substances, such as molecules or ions, diffuse from an area of high concentration to an area of low concentration in the cytosol or across membranes. Eventually, the concentration will even out, with the substance moving randomly but causing no net change in concentration. Such a state is called dynamic equilibrium, which is essential for maintaining overall...
176.6K
01:26Membrane Fluidity
14.0K
Membrane fluidity is explained by the fluid mosaic model of the cell membrane, which describes the plasma membrane structure as a mosaic of components—including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character.
Mosaic nature of the membrane
The mosaic characteristic of the membrane helps the plasma membrane remain fluid. The integral proteins and lipids exist as separate but loosely-attached molecules in the membrane. The membrane is...
Mosaic nature of the membrane
The mosaic characteristic of the membrane helps the plasma membrane remain fluid. The integral proteins and lipids exist as separate but loosely-attached molecules in the membrane. The membrane is...
14.0K
01:23Membrane Fluidity
150.1K
Cell membranes are composed of phospholipids, proteins, and carbohydrates loosely attached to one another through chemical interactions. Molecules are generally able to move about in the plane of the membrane, giving the membrane its flexible nature called fluidity. Two other features of the membrane contribute to membrane fluidity: the chemical structure of the phospholipids and the presence of cholesterol in the membrane.
150.1K
01:17Factors Affecting Activity Coefficient
1.6K
The extended Debye-Hückel equation indicates that the activity coefficient of an ion in an aqueous solution at 25°C depends on three partially interdependent properties: the ionic strength of the solution, the charge of the ion, and the ion size.
The activity coefficient value for an ion is close to one when the solution has almost zero ionic strength, i.e., when the solution shows close to ideal behavior. As the ionic strength of the solution increases from 0 to 0.1 mol/L, a...
The activity coefficient value for an ion is close to one when the solution has almost zero ionic strength, i.e., when the solution shows close to ideal behavior. As the ionic strength of the solution increases from 0 to 0.1 mol/L, a...
1.6K