The final solution was dialysed against cold distilled water using a dialysis bag with a nominal manufacturer’s specified MW cut-off of 7 kDa (Shanghai Green Bird Science and Technology Development Co., Shanghai, China) and then lyophilized using the Labconco freeze dryer (Labconco Corp., Kansas, MO, USA). The yield was calculated on the basis of the wet weight of the fins and bones, respectively. The procedures for extraction of PSC from the scales (0.5 kg) were slightly different in that the times for decalcification was shorten to 3 days, and the step for removing fat was omitted.