resultant precipitate was collected by centrifugation at 10,000g for15 min at 4 _C and then dissolved in 0.5 M acetic acid. The solution obtained was dialysed against 0.1 M acetic acid for 3 days with a change of solution once per day, followed by lyophilization in a freeze-dryer, and finally, the ASC was obtained.Undissolved residue, obtained after acid extraction, was suspendedin 2 volumes of 0.5 M acetic acid containing 1.5% (w/w)pepsin for 30 h at 4 _C with continuous stirring. The PSC was obtained by the same method as the ASC. The extraction of collagen was performed three times and the yield value was the average of the triplicate determinations