scholarly journals Interaction of ions and water in gramicidin A channels: streaming potentials across lipid bilayer membranes.

1978 ◽  
Vol 72 (3) ◽  
pp. 327-340 ◽  
Author(s):  
P A Rosenberg ◽  
A Finkelstein
Keyword(s):  
Osmotic Pressure ◽  
Pressure Difference ◽  
Gramicidin A ◽  
Water Molecules ◽  
Lipid Bilayer Membranes ◽  
Bilayer Membranes ◽  
Narrow Channels ◽  
Streaming Potentials ◽  
Gramicidin Channel ◽  
Osmotic Pressure Difference

For very narrow channels in which ions and water cannot overtake one another (single-file transport), electrokinetic measurements provide information about the number of water molecules within a channel. Gramicidin A is believed to form such narrow channels in lipid bilayer membranes. In 0.01 and 0.1 M solutions of CsCl, KCL, and NaCl, streaming potentials of 3.0 mV per osmolal osmotic pressure difference (created by urea, glycerol, or glucose) appear across gramicidin A-treated membranes. This implies that there are six to seven water molecules within a gramicidin channel. Electroosmotic experiments, in which the water flux assoicated with current flow across gramicidin-treated membranes is measured, corroborate this result. In 1 M salt solutions, streaming potentials are 2.35 mV per osmolal osmotic pressure difference instead of 3.0 mV. The smaller value may indicate multiple ion occupancy of the gramicidin channel at high salt concentrations. Apparent deviations from ideal cationic selectivity observed while attempting to measure single-salt dilution potentials across gramicidin-treated membranes result from streaming potential effects.

scholarly journals Water permeability of gramicidin A-treated lipid bilayer membranes.

1978 ◽  
Vol 72 (3) ◽  
pp. 341-350 ◽  
Author(s):  
P A Rosenberg ◽  
A Finkelstein
Keyword(s):  
Water Permeability ◽  
Permeability Coefficient ◽  
Pore Radius ◽  
Gramicidin A ◽  
Water Molecules ◽  
Lipid Bilayer Membranes ◽  
Bilayer Membranes ◽  
Single File ◽  
Water Permeability Coefficient ◽  
Single File Transport

In membranes containing aqueous pores (channels), the osmotic water permeability coefficient, P f, is greater than the diffusive water permeability coefficient, P d. In fact, the magnitude of P f/P d is commonly used to determine pore radius. Although, for membranes studied to date, P f/P d monotonically declines with decreasing pore radius, there is controversy over the value it theoretically assumes when that radius is so small that water molecules cannot overtake one another within the channel (single-file transport). In one view it should equal 1, and in another view it should equal N, the number of water molecules in the pore. Gramicidin A forms, in lipid bilayer membranes, narrow aqueous channels through which single-file transport may occur. For these channels we find that P f/P d approximately 5. In contrast, for the wider nystatin and amphotericin B pores, P f/P d approximately 3. These findings offer experimental support for the view that P f/P d = N for single-file transport, and we therefore conclude that there are approximately five water molecules in a gramicidin A channel. A similar conclusion was reached independently from streaming potential data. Using single-channel conductance data, we calculate the water permeability of an individual gramicidin A channel. In the Appendix we report that there is a wide range of channel sizes and lifetimes in cholesterol-containing membranes.

Branchiostoma lanceolatum – A Freshwater Reject?

1979 ◽  
Vol 59 (1) ◽  
pp. 61-67 ◽  
Author(s):  
John Binyon
Keyword(s):  
Osmotic Pressure ◽  
Functional Ability ◽  
Pressure Difference ◽  
Great Difficulty ◽  
Body Fluids ◽  
Branchiostoma Lanceolatum ◽  
Osmotic Pressure Difference

The ultrastructure and dimensions of the solenocytes of Branchiostoma lanceolatum are reviewed briefly. The functional ability of these units is calculated upon theoretical grounds in a manner similar to that applied to flame cells. Their more delicate construction would suggest that Branchiostoma would have great difficulty in maintaining any significant osmotic pressure difference between the medium and its body fluids.

Determining Maximum Chemico-Osmotic Pressure Difference across Clay Membranes

2020 ◽  
Vol 146 (1) ◽  
pp. 06019018 ◽  
Author(s):  
Cameron J. Fritz ◽  
Joseph Scalia ◽  
Charles D. Shackelford ◽  
Michael A. Malusis
Keyword(s):  
Osmotic Pressure ◽  
Pressure Difference ◽  
Osmotic Pressure Difference

Evaluation of the Starling Fluid Flux Equation

Physiology ◽  
1987 ◽  
Vol 2 (2) ◽  
pp. 48-52 ◽  
Author(s):  
AE Taylor ◽  
MI Townsley
Keyword(s):  
Osmotic Pressure ◽  
Pressure Difference ◽  
Fluid Pressure ◽  
Colloid Osmotic Pressure ◽  
Lymph Flow ◽  
Tissue Fluid ◽  
Fluid Flux ◽  
Dynamic Factors ◽  
Osmotic Pressure Difference ◽  
Absorption Theory

It is commonly thought that fluid is filtered in the arterial and is absorbed in the venous end of the capillary, cuased by the considerable hydrostatic pressure difference between the arterial and the venous end, while the transcapillary colloid osmotic pressure difference remains nearly constant. We now know that extravascular forces, i.e., tissue fluid pressure, tissue colloid osmotic pressure, and lymph flow, are dynamic factors that change to oppose transcapillary fluid movement. Therefore, the filtration-absorption theory will apply only transiently until the tissue forces readjust.

Flows of Electrolytes Through Charged Hydrated Biological Tissue

1994 ◽  
Vol 47 (6S) ◽  
pp. S277-S281 ◽  
Author(s):  
W. M. Lai ◽  
W. Gu ◽  
V. C. Mow
Keyword(s):  
Osmotic Pressure ◽  
Pressure Difference ◽  
Finite Thickness ◽  
Concentration Field ◽  
Ion Concentration ◽  
Solid Matrix ◽  
Hydraulic Pressure ◽  
Neutral Salt ◽  
Apparent Permeability ◽  
Osmotic Pressure Difference

In this paper, analyses of the flows of water and electrolytes through charged hydrated biologic tissues (e.g., articular cartilage) are presented. These analyses are based on the triphasic mechano-electrochemical theory developed by Lai and coworkers (1991). The problems analyzed are 1-D steady permeation flows generated by a hydraulic pressure difference and/or by an osmotic pressure difference across a finite thickness layer of the tissue. The theory allows for the complete determination of the ion concentration field, the matrix strain field as well as the ion and water velocity field inside the tissue during the steady permeation. For flows generated by a hydraulic pressure difference, the frictional drag induces a compaction of the solid matrix causing the fixed charge density (FCD) to increase and the neutral salt concentration to decrease in the downstream direction. Further, while both ions move downstream, but relative to the solvent (water), the anions (Cl−) move with the flow while the cations (Na+) move against the flow. The theory also predicts a well-known experimental finding that the apparent permeability decreases nonlinearly with FCD. For flows generated by an osmotic pressure difference, first, fluid flow varies with the FCD in a nonlinear and non-monotonic manner. Second, there exists a critical FCD below which negative osmosis takes place.

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