3 30 20 mM Tris-HCl, pH 8.0 Column chromatography 4 0.23 M NaCl buffer (60 ml) to buffer + 0.4 M NaCl (60 ml) 7 crib220u270rib220u62607i anion exchange column chromatography (TOSOH CORPORATION, Super Q TOYOPEARL 650M) _