Abstract: Differential scanning calorimetry (DSC) analysis was used to systematically study the effect of different concentrations of Na+, Ca2+ and H+ on the thermal denaturation temperatures of type I and type II collagens from whale sharp skin. The type I collagen had maximum absorption at 233.05 nm and the type II collagen at 232.90 nm and 277.88 nm. Aggregation dynamic analysis indicated that the turbidity of the type I and II collagens exhibited an S-shaped curve with 3 stages including initial stage, growth stage and stable stage. The thermal stability of the two types of collagens was examined by high-sensitivity differential scanning calorimetry. The thermal denaturation temperatures of the type I and II collagens were at 40 and 62 ℃, respectively. Their thermal denaturation temperatures were reduced at low concentrations of Na+ and Ca2+. These results indicated that metal ions could affect charged residues in native collagen molecules, thus leading to the reduction in thermal denaturation temperature. At intermediate concentrations of Na+ and Ca2+, the thermal denaturation temperature of type I and II collagens revealed a continuous reduction, which suggested that the loss of thermal stability might be due to the competition for water molecules between metal ions and collagen. High concentrations of Na+ and Ca2+ resulted in an increase in collagen denaturation temperature due to protein salting out. Extreme pH treatment caused partial denaturation of collagen and the denaturation peak became smaller or even disappeared.

Key words: Rhincodon typus, collagen, thermal denaturation, aggregation dynamic curve, differential scanning calorimetry(DSC)