Column chromatography on polyethylenimine-silica: Rapid resolution of nucleotides and proteins with short columns and low pressures

Silica gel (100–200 mesh) can be coated with a stable layer of crosslinked polyethylenimine (PEI). The resulting material is useful in column chromatography for quantitative separation of adenine nucleotides. For example, 3′:5′-cyclic AMP can be separated from a mixture containing AMP, ADP, and ATP. A mixture of adenosine, AMP, ADP, and ATP can be resolved with quantitative recovery of components. Convenient separation of cytochrome c from albumin illustrates the applicability of this system to protein purification. PEI-Xama silica gel and PEI-glutaraldehyde silica gel have ion-exchange capacities of 0.27 and 0.21 meq/g, respectively. The materials are dimensionally rigid and chemically stable except in alkaline solutions (>pH 10) for prolonged periods.