of 20% trichloroacetic acid was added, and the mixture was centrifuged at 10,000 rpm for 5 min. The pellet was washed three times with 1 mL of ethanol/ethyl acetate (1:1), dissolved in 3 mL of 6 M guanidine hydrochloride (pH 2.3) at 37 °C for 15 min, and then
centrifuged at 10,000 rpm for 3 min.