Description_x000D_ Application_x000D_ β-Galactosidase was used as a control antigen in the selection of human antibody fragments by phage display._x000D_ Biochem/physiol Actions_x000D_ β-galactosidase cleaves lactose into its monosaccharide components, glucose and galactose. It also catalyses the transglycosylation of glucose into allolactose, the inducer of β-galactosidase, in a feedback loop._x000D_ Packaging_x000D_ Package size based on protein content_x000D_ Unit Definition_x000D_ One unit will hydrolyze 1.0 μmole of o-nitrophenyl β-D-galactoside per min at pH 7.3 at 37 °C._x000D_ Physical form_x000D_ Lyophilized powder containing Tris-acetate, DTT, MgCl2, and isopropyl β-D-thiogalactopyranoside_x000D_ Preparation Note_x000D_ Biotinylated using biotin–maleimide (B 1267) which incorporates an extended spacer.