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Size exclusion chromatography does not require pores

TitleSize exclusion chromatography does not require pores
Publication TypeJournal Article
Year of Publication2000
AuthorsBrooks, DE, Haynes, CA, Hritcu, D, Steels, BM, Muller, W
JournalProceedings of the National Academy of Sciences of the United States of America
Date PublishedJun
Type of ArticleArticle
ISBN Number0027-8424

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.

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