transformed into E. coli BL21 (DE3). Protein expression was
induced by administering 0.5 mmol/L of isopropyl-b-D-thiogalactopyranoside.
His-recombinant proteins were then
purified using Ni2þ-charged sepharose according to the
manufacturer’s instructions (Amersham plc, Amersham,
UK). The His-recombinant proteins were eluted using an
elution buffer (20 mmol/L of sodium phosphate, 500 mmol/
L of NaCl, and 500 mmol/L of imidazole). The samples were
massively dialyzed against the elution buffer without
imidazole and then into phosphate-buffered saline (PBS; pH
7.4) to reduce the salt concentrations.