Protein separation with surfactant-coated octadecylsilyl silica involving Cibacron blue 3GA-conjugated nonionic...

A novel medium for protein separation, namely affinity admicelle, was prepared by mixing of octadecylsilyl (ODS) silica gels, a polyoxyethylene-type nonionic surfactant (Triton X-100), and a surfactant-conjugated substrate (affinity ligand) in an aqueous solution. The ligand was synthesized by mixing a triazine dye (Cibacron Blue 3GA, CB) and a polyethylene glycol monooleyl ether (C18EO7, C18EO10, or C18EO20) having different length of polyoxyethylene moiety in weakly alkaline solutions. The amount of Triton X-100 sorbed on 1 g of ODS silica was 0.2 mmol. Affinity ligands having highly hydrophobic oleyl group were predominantly sorbed on ODS silica. The losses of Triton X-100 and affinity ligand were within 0.3% and negligible by washing the admicelles were with a 25-fold volume of 1 mM Tris-HCl solution (pH 7.4). The coating ODS silica with Triton X-100 was effective to prevent the irreversible sorption of albumin (bovine, serum). An NADH-dependent enzyme, alcohol dehydrogenase (ADH, yeast), was successfully collected on the admicelles involving CB-conjugated ligands (CB-C18EO20). The maximum collection of ADH to 90 mg/ml of affinity admicelles was 68+/-4%. However, CB-C18EO7 and CB-C18EO10 having shorter polyoxyethylene unit were not available, suggesting the requirement of the spacer moiety in the affinity ligand. The recovery and purification factor based on the ratio of activity (unit)/protein (mg) from Whatman DE52-treated yeast extract was 27% and 12, respectively.