Size exclusion chromatography does not require pores

Abstract

Separation of macromolecules on the basis of their molecular weight by size exclusion chromatography has long been considered to be caused by the geometry-dependent partition of macromolecules between a continuous phase and the porous interior of a gel or cross-linked bead. The volume of a pore accessible to a solute is limited by its relative dimensions, so larger molecules will have access to a smaller volume and will remain in a bead for a shorter time than smaller solutes. Our recent alternate picture proposes that the partition coefficient can be calculated from a thermodynamic model for the free energy of mixing of the solute with the gel phase. Size-dependent exclusion caused by the unfavorable entropy of mixing associated with the partition is predicted; the magnitude of the effect is modified by enthalpic interactions between the solute and the gel phase. This concept is extended here to describe the partition of macromolecules into a layer of terminally attached polymer chains grafted onto a solid bead. Both simple mean field and self-consistent field theory calculations predict size-dependent entropic exclusion. Experimental results obtained with neutral polymer chains grafted onto solid polystyrene latex beads confirm the predictions.

Fabrication of high-capacity protein ion-exchangers with polymeric ion-exchange groups grafted onto micron-sized beads by atom transfer radical polymerization

“…Therefore, pGMA-H-DMCH had a much lower adsorption capacity for γ-globulin than pGMA-M-DMCH. The same finding was reported by several groups in polymer-grafted size exclusion chromatographic beads [32][33][34]. Therefore, the BIBB density should be optimized to achieve the maximal adsorption capacity for proteins.…”

On Schroeder's paradox

“…a statement is a cornerstone in the field of phase equilibrium thermodynamics with polymers, be it for material preparation, polymer devolatilization, or membrane and chromatographic processes for instance [3][4][5][6][7].…”

Immunocamouflage of latex surfaces by grafted methoxypoly(ethylene glycol) (mPEG): Proteomic analysis of plasma protein adsorption

“…When macromolecules interact with mPEG-modified surfaces, they contact and compress the polymer chains resulting in a further decrease in entropy. This highly thermodynamically unfavorable state is then reduced by the rejection of molecules from the polymer contact points thereby preventing protein adsorption and increasing entropy and conformational freedom of the polymer chains [23][24][25]. At higher surface polymer densities, (Figures 2 and 3) chains are even more restricted in conformational freedom thereby increasing plasma protein rejection from the biomaterial (bead) surface.…”