Macroporous silica in chromatography and immobilization of biopolymers

Macroporous silicas--silica gel (xerogels) and silochroms--are used for the chromatography of proteins and viruses and for the immobilization of several enzymes. The stabilization of silica by aluminum and zirconium salts was investigated. The hydrolytic stability of silica in alkaline media can be significantly increased by the substitution of aluminum ions for hydrogen atoms of the surface silanol groups. The aluminum modification also enhances the stability of glucose isomerase immobilized on silica. The maximum capacity for the immobilization of enzymes is found with silicas having average pore sizes of 5 to 10 times those of the protein globules. A thin layer of pyrolytic carbon deposited on silica enhances the retention of the adsorbed enzyme by the carrier. The original, aluminated and modified by γ-aminopropyltriethoxysilane and carbohydrates silica gels and silochroms are applicable in the liquid chromatography of acid and neutral proteins and in the purification of viruses. Adsorption and steric and ionic exclusion were observed in the chromatography of biopolymers.