Untreated or treated WWF (0.5 g) was placed in a 50 mL micro centrifuge tube with 7.5 mL of 10 mM L-DOPA in 50 mM MOPS buffer (pH¼6.5), which was incubated at room temperature (20 C) for 1 h with a rotating mixer (10 rpm) and then centrifuged at 8000 g for 3 min.