带电纳米通道中的热透:表面电荷和离子强度的影响

A number of natural and synthetic materials exhibit selective permeation, meaning that only molecules or ions of a certain size, shape, polarity, charge, and so forth, are capable of passing through (permeating) the material. Biological cell membranes provide elegant examples of selective permeation in nature, while dialysis tubing used to remove metabolic wastes from blood is a more simplistic technological example. Regardless of how they may be fabricated, these materials are generally...

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...

Osmosis is the movement of free water molecules through a semipermeable membrane.  The water's concentration gradient across the membrane is inversely proportional to the solutes' concentration. Whereas diffusion transports material across membranes and within cells, osmosis transports only water across a membrane, and the membrane limits the diffusion of solutes in the water. Osmosis is a special case of diffusion.
Water, like other substances, moves from a high concentration of...

The movement of ions like sodium, potassium, and calcium into and out of the cell is essential to maintain the electrochemical gradient in living cells. The ion channels—a class of membrane transport proteins—help maintain this ionic gradient for the smooth functioning of physiological activities such as maintaining cell size and volume, conducting nerve impulses, and gas and nutrient exchange.
Ion channels are specialized integral membrane proteins on the plasma membrane that allow...

The ionic strength of a solution is a quantitative way of expressing the total electrolyte concentration of a solution. This concept was first introduced in 1921 by two American physical chemists, Gilbert N. Lewis and Merle Randall, while describing the activity coefficient of strong electrolytes. During the calculation of ionic strength (I or μ), all the cations and anions are considered. However, the concentration (c) of an ion with a greater charge number (z) has a greater contribution...

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:
The electrical gradient: The electrical gradient across cell membranes refers to the difference in electric charge between the inside and outside of a cell.  This difference drives the movement of ions towards or away from the cells. For instance, if the inside of the cell is more negatively charged relative to...