Osmotic behavior

Transport systems. Partitioning of various types of molecules such as allelochemlcals into the lipid bilayer of the mitochondrial inner membrane can perturb the membrane and alter the conformation, properties, and function of components of the membranes. Unfortunately, it is not always possible to demonstrate directly the existence of carrier systems, but indirect evidence can be obtained. Alterations induced to the membrane are sometimes reflected in the osmotic behavior of mitochondria. The inner membrane is relatively impermeable to many cations, including K and H, and many solutes (31). Hence, the organelles are osmotic-ally stable under certain conditions. Indications were obtained that the allelochemlcals inhibited the action of carrier-mediated transport processes associated with the mitochondrial inner membrane (as reflected in the osmotic behavior). Responses obtained with quercetin are shown in Figure 3. Mitochondria are osmotically... 

Figure 19.2. Diagram of osmotic behavior and the effect of solute concentration and molecular weight on osmotic pressure, (a) Osmotic-pressure behavior of solutions Ais the excess pressure on the solution required to stop flow of solvent through the semipermeable membrane, (b) Effects of solute concentration and molecular weight on osmotic pressure.

N 2 Newman, S., L. Loeb and C. M. Conrad Viscosity, sedimentation, diffusion, and osmotic behavior of long chain nitrocellulose molecules. J. Polymer Sci. 10, 463 (1953). 

Miscible Liquid Behavior. Further concerning osmotic behavior, there is the behavior of, say, two miscible liquids, or miscible liquid components, but with each separated from the other by a semipermeable membrane, more permeable to one liquid than the other. Movement of the more permeable liquid phase to the less permeable liquid phase will occur, building up a pressure difference. However, there will likely be membrane leakage from the latter phase to the former, in the reverse direction, eventually producing the same equilibrium composition on both sides of the membrane. This brings up the relative permeation of two miscible liquids from a zone of composition on the one side of a membrane... 

Not only was it possible to explain, by the new theory, the anomalous osmotic behavior of strong electrolytes, but intensive quantitative studies indicated clearly the existence of a simple relationship between the irrationality factor i and the degree of electrolytic dissociation a. In a solution of a uni-univalent electrolyte of concentration c, the sum of concentrations of all particles evidently exceeds c. This summation is equal to (1 — a)c -f 2ac = c(l -1- a). From the definition of irrationality factor. 

The ion selectivity data clearly indicate that veiy specific ion-solvent interactions take place in the vicinal water and that these bear little resemblance to expectations from bulk-phase observations. This, in turn, means that such quantities as the classical standard ion activity coefficients are not applicable, and hence osmotic coefficients must also differ from the expected values. In fact, the use of the generally accepted osmotic coefficients is simply inappropriate, and unusual osmotic behavior must be anticipated. Likewise, if the activity coefficients display anomalous behavior so must cell membrane potentials. In other words, ion distribution and the osmotic behavior of cells must be influenced by vicinal water, and models of cell volume regulation must anticipate and take into account this aspect (see also Wiggins, 1979). 

By this approach the inherent deficiency of the earlier attempts to evaluate this term by assuming a particular osmotic behavior in the dilute concentration range (6,7,10-12,19,21) was avoided. 

Dj is proportional to the fixed ion concentration of the membrane and inversely proportional to the specific flow resistance and specific conductivity. Also, Df is independent of membrane thickness. Figure 2.6 shows the change in electro-osmotic water transport with the fixed ion concentration of an anion exchange membrane measured with 0.5 N sodium chloride solution.25 Dj decreases with increasing fixed ion concentration. The specific conductance of the membrane increases and the water content of the membrane decreases (po increases) with increasing fixed ion concentration of the membrane. The electro-osmotic behavior through the membrane is not simply explained from this experimental data. 

Fig. 12.6 Osmotic behavior of red blood cells in aqueous NaCl solutions at concentration c.

Fiuthermore, the osmotic behavior of dilute binary solutions can be used to describe the partial pressure of its components. In the gas phase, which is in contact with a solution, each component of the solution shows a partial pressure, which is lower than the vapor pressure of this component Therefore, in the case of a binary solution where solute b has a negligible vapor pressure, an elevation of the boiling point occurs in relation to that of the pure solvent a. This reduction compared to the... 

The rise of the osmotic pressure with the amount of substance dissolved at higher concentration ranges has been the subject of many experiments. The osmotic behavior of moderately concentrated solutions has been examined experimentally, in proteins by Adair,Pauli and Pent and... 

Small unilamellar vesicles (SUV)(hydrodynamic diameter, Dft < 50 nm) are not adequate for the purpose of site dissection. With total internal volumes seldom exceeding 11/mole of amphiphile in the bilayer, SUV s do not permit the entrapment of analytically convenient amounts of substrate. Larger (DODA)C and DCP vesicles (Dh > 300 nm), LUV, were first obtained by chloroform vaporization at 70 °C [36]. (DODA)C LUV have a sharp gel-liquid crystalline phase transition temperature (Tc), an internal volume of 9 + 11/mole and exhibit ideal osmotic behavior towards KCl (0-0.050 M) and sucrose [36b]. LUV of comparable properties, obtained by dichloro-methane vaporization, at 40 °C and membrane extrusion. 

They note that the Debye-Hiickel theory relates osmotic behavior to the effective ionic diameter. It would be expected then that species containing the same anions and having cations of similar diameter would have nearly equal osmotic coefficients unless there was a "chemical" difference between the two. This difference could be interpreted as incomplete dissociation or complex formation. 

Soldano, B.A. C.S. Patterson, "Osmotic behavior of aqueous salt solutions at elevated temperatures. Part II", J. Chem. Soc., pp937-940 (1962)... 

Effect of size of AMP-PUF on Cs" sorption. To elucidate the above, AMP-PUF was milled and sieved to fragmentize by size. Effect of the size on sorption kinetics of Cs was studied for 10 mL solution containing 500 pg of Cs. Fig. 4 shows the results by decreasing the size of the composite, sorption kinetics was effectively improved. Comparison of the results between milled fragments and 5 mm cube suggests that sorption kinetics is considerably improved by increase in an effective surface area of the composite and will be strongly influenced by osmotic behavior of solution into PUF. 

Cytarabine loaded W/OAV multiple emulsions were prepared using nonionic surfactants (Tween and Span ) by the emulsification-sonication technique and characterized by studying the osmotic behavior. The system exhibited prolonged release pattern (Kim et al., 1995). 

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