Solute-excluded volumes near the Novikoff cell surface

Abstract

A differential centrifugation technique, in which all extracellular water except that intimately associated with the cell (pericellular domain) is removed, has been applied to isolated Novikoff hepatoma cells. The pericellular volumes accessible to albumin, inulin, raffinose, and sucrose were inversely related to the molecular weights of the test solutes. This phenomenon was not detectable in erythrocytes or in fat cells. Selective removal of cell surface components by enzymatic treatment produced proportional changes in the relative volumes of distribution accessible to the solutes. This discrimination in the volume accessible to each of the solutes is analogous to that obtained in gel chromatographic separation and represents, in effect, excluded volumes which are inversely related to solute size. This exclusion is associated with components of the Novikoff cell surface, including the surface coat and the microvilli that cover the Novikoff cell. These structures provide an additional level of discrimination for the Novikoff cell not seen in certain other cell types.

Analysis of steric partition behavior of molecules in membranes using statistical physics. Application to gel chromatography and electrophoresis

“…The general expressions for the partition function (Eqs. 13 and 18) provide a simple approach to defining the partition behavior of molecules in a porous membrane. These two equations only require two fundamental parameters to fully describe the partitioning of solutes in membranes: v°and v'.…”

“…Since v°is well defined for many membrane systems,6 v is the only unknown variable in Eqs. 13 and 18 so that a mean effective value can be evaluated (using rigorous statistical methods already developed [4]) from elution volume data, size selectivity curves, Ferguson plots, or partition data. Under ideal conditions, v' will increase in proportion to v°or g, however, in reality v, will be affected by membranemolecule interactions7 or even changes in the geometry of the volume-excluding element that may occur with gel 5In size-exclusion chromatography, the interaction of anionic polyelectrolyte with anionic chromatographic packing frequently results in peaks eluting earlier than expected (lower apparent Kay, see Eq.…”

“…Using the same general approach as above, the accessible states or availability of positions for point molecules and molecules of finite size can be compared. Any molecule of s= Qg/Qb = 0, for Vr4g 1, (13) assuming both v°b and VEb = 0 (see Eqs. 7 and 10).…”

“…The partition function is essential in interpreting elution volumes in size exclusion chromatography (2,3), Ferguson plots in gel electrophoresis (3, 4), and molecular transport across filtration membranes and through solutions of macromolecules (5). In addition, partitioning of molecules within restrictive volumes strongly influences transmembrane transport through lipid membranes and ion channels (6-8), intracellular diffusion and convection through cytoplasm (9), intracellular compartmentalization of macromolecules (10), transcapillary exchange (11,12), and receptorligand interactions at cell membrane surfaces (i.e., lipid polar region or the glycocalyx) (7,(12)(13)(14). The equilibrium distribution coefficient (partition function) of macromolecules between the bulk and membrane phase must be known in order to characterize these systems.…”

Passage of ions and dextran molecules across the rete mirabile of the eel. The effects of charge.

“…These surface polymers, as might have been expected, exert an excluded volume effect. Larger molecules are excluded from a larger part of the polymer layer associated with the cell surface (Bojesen, 1982;Polefka et al, 1984).…”