Sorption Effects in Gel Filtration: I. A Survey of Amino Acid Behavior on Sephadex G-10

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Abstract
Sephadex G-10, as supplied by the manufacturer, behaves as a weak cation exchanger. The cation-exchange capacity can be nearly eliminated by washing the gel with 1 M aqueous pyridine. The behavior of amino acids and other small solutes on pyridine-washed columns under defined conditions is very reproducible. The behavior of a solute on Sephadex G-10 fundamentally depends on its effective molecular size. Charged solutes tend to be excluded in media of low ionic strength, but the effective size and hence the degree of exclusion of such molecules can be decreased substantially by including high concentrations of small electrolytes in the medium. Salt can increase the adsorption of potentially adsorbable charged molecules in a passive way by increasing the amount of gel available to them. Salt might actively promote the adsorption of hydrophobic molecules by causing them to seek out regions within the gel where there is no salt, e.g., in the immediate vicinity of the gel matrix. Any pair of small water-soluble molecules that differ with respect to size, charge, content of delocalized π electrons, or hydrophobic character (e.g., the length of a linear hydrocarbon chain) should be separable on Sephadex G-10. The gel should therefore be very useful for purifying small water-soluble synthetic products.