Effects of molecular shape on osmotic reflection coefficients

Effects of charge on osmotic reflection coefficients of macromolecules in porous membranes

“…For like charges and constant surface charge densities, particle positions within a pore are energetically unfavorable, which decreases the equilibrium partition coefficient, Φ [11]. As recognized previously [3][4][5], decreases in Φ lead to increases in σ o . In terms of the ability to induce an osmotic flow, adding like charges to the macromolecules and pore walls is qualitatively similar to increasing the macromolecular radius.…”

“…which was derived originally for uncharged spheres in uncharged cylindrical pores [3] and shown to be nearly exact also for uncharged spheroids (oblate or prolate) in such pores [5]. It is seen that Eq.…”

“…(36) is somewhat less reliable for charged than for uncharged systems. It should be mentioned also that it is restricted to cylindrical pores; for example, results obtained for neutral spheroids in slit pores followed a somewhat different relationship [5].…”

“…For macromolecules, the concentration at a particular point is that of the sphere centers. Evaluating osmotic pressures using concentrations of particle centers is not precisely correct, although it greatly simplifies the calculations and for neutral particles was shown to result in only small errors in σ o [5]. Implicit in Eq.…”

“…Results for dilute solutions of spheres in slits or cylindrical pores were obtained by Anderson and Malone [3], and their analysis was extended to capsule-shaped solutes by Anderson [4]. More recently, the underlying assumptions were reexamined and calculations done for dilute solutions of prolate or oblate spheroids in slits or cylindrical pores [5]. The effects of solute concentration have been considered for spheres in slits or cylindrical pores [6].…”