Soft and semi-rigid gels

Sepharose 4B similarly displays a rather weak ionic strength dependence of SEC (81) Reduction of the ionic strength from 0.15 M to 0.008 M diminished SEC foi 8SA from 0.74 to 0.52 (Tris/NaCl pH 8.4 buffer). For the weakly basic protein, chymotrypsin (lEP = 8.4), the mean partition coefficient was essentially unaffected by ionic strength, but strongly basic cytochrome c (IPE = 10.5) was totally retained in 0.008 M buffer. 

Modern cross-linked agarose matrixes (82) may be yet less charged than other polysaccharide-based packings. A recent report (83) implies that KsEC protein-SDS complexes is insensitive to buffer concentration over the range 0.03 M - 0.1 M on such agarose-based gels. 

Evidence for electrostatic repulsion has been adduced from the small retention volumes for proteins in pure water on recently developed crosslinked poly(vinylalcohol) gels (84). Lysozyme and chymotrypsinogen elute late from these GS columns (Asahi Chemical Ind. Co.). On the other hand, the elution volumes of BSA and myoglobin are essentially unchanged over the ionic strength range ca. 0,3 M - 0.8 M. 

Prediction of the partition coefficient of a charged macroion on an SEC column of similar surface charge is a formidable task. The theoretical treatment for K ec of uncharged macromolecules is by no means simple (85, 86) and is furthermore impeded by the difficulty of providing a simple description for the pore geometry (87). A rigorous treatment including the electrostatic 

Sibility that some of the increase in Ve observed as the ionic strength increases from 0.01 to 0.1 M may be due to adsorption. 

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Natural and Synthetic Soft and Semi-Rigid Gels. 874... 

Natural soft and semi-rigid gels for the separation (A/D agarose-dextran copolymer, D/bA dextran... 

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