Membrane surface, interaction forces

Figure 2. Atomic force microscopy images showing the surface of a rhesus monkey erythrocyte membrane. Damage, such as formation of humps on the peripheral surface and pits in other parts, results from the interaction with virions of the canine parvovirus, (a) edge of erythrocyte (b) pits on membrane surface. (Source http //www.ntmdt.ru/ publications/download/211.pdf, Reproduced with permission from Dr Boris N. Zaitser)...

Nonpolar Parameters. In a reverse osmosis system involving cellulose acetate membranes and aqueous solutions of hydrocarbon solutes, the adsorption of water and that of solute on the polar and nonpolar sites of the membrane surface respectively may be expected to take place essentially independently. Further, since the polymer-solute interaction forces are attractive in nature for the above case, the mobility of the solute molecules through the membrane pore is retarded, and they also tend to agglomerate... 

Calculation of Solute Separation and Product Rate. Once the pore size distribution parameters R, ou R >,2, 02, and h2 are known for a membrane and the interfacial interaction force parameters B and D are known for a given system of membrane material-solute, solute separation f can be calculated by eq 6 for any combination of these parameters. Furthermore, because the PR-to-PWP ratio (PR/PWP) can also be calculated by the surface force-pore flow model (9), PR is obtained by multiplying experimental PWP data by this ratio. 

Possible Role of Long-Range VDW Forces Between Cell Membrane Surfaces. The above discussion has been based on the model of macro-molecular bridging, and the Eb is caused by the interaction between the bridging macromolecule and the cell surface. Recent theoretical and experimental studies (41,42) have shown that VDW attractive forces can be exerted between cell surfaces over distances in the range found in RBC rouleaux. 

We thus see that the interaction force P(h) is positive (repulsive) for the interaction between likely charged membranes and negative (attractive) for oppositely charged membranes. It must be stressed that the sign of the interaction force P(h) remains unchanged even when the potential minimum disappears (for the case Zj, Z2 > 0) or even when the surface potential of one of the membranes reverses its sign (for the case Zj > 0 and Z2 < 0). 

It is interesting to note that i/ oi and 1//02, are, respectively, the unperturbed surface potentials of membranes 1 and 2 (i.e., the surface potentials at /i = 00) and that Eq. (16.9) states that the interaction force is proportional to the product of the unperturbed surface potentials of the interacting membranes. This is generally true for the Donnan potential-regulated interaction between two ion-penetrable membranes in which the distribution of the membrane-fixed charges far inside the membranes is uniform but may be arbitrary in the region near the membrane surfaces (see Eq. (8.28)). 

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