2.1. Materials
GdnHCl, p -nitrophenyl acetate, acetone, ethanol, and hydrochloric acid were purchased from Wako Pure Chemical Industries (Osaka, Japan). Coomassie Plus (Bradford) AssayTM kits for measuring the protein concentration were purchased from Thermo Fisher Scientific K.K. (Rockford, USA). Carbonic Anhydrase from bovine erythrocytes was purchased from Sigma-Aldrich Co. LLC (St. Louis, USA). Sylgard184 was obtained from Dow Corning Corp. (Midland, USA), and cellulose tubes (MWCO 12–14 kDa, pore size 5 nm, thickness 39.2 μm, diameter 28.6 mm) were purchased from Nihon Medical Science, Inc. (Tokyo, Japan).