washing, dehairing, and mincing. After that, the rabbit-skin was
soaked in glacial acetic acid at 4 ◦ C for 4 d and homogenized. Then it was processed with
pepsin in 0.5 mol/L acetic acid solu- tion (10 U/mL) at 4 ◦ C for 3 d. Subsequently, the
mixture was centrifuged at 20,000 × g for 30 min and the supernatant was
obtained.