Nonideal size-exclusion chromatography with zwitterions causes a pI-dependent elution of proteins from glycerol propylsilane-modified silica.

A potato homogenate containing proteins of similar molecular weights but varying pI values was separated by nonideal size-exclusion chromatography after attempts to resolve the proteins with common size-exclusion chromatography methods failed. The method used a zwitterion buffer to amplify electrostatic interactions between the proteins and the silica matrix. The proteins were sorted on the basis of pI in preference to molecular weight. Subsequent tests with marker proteins of known weight and pI verified the validity of the original findings. The method can be used for separation of isozymes and similarly sized proteins as an alternative to chromatofocusing or isoelectrofocusing.