Abstract
Recently, many measurement methods have been used to study the structure change of protein after heating, such as differential scanning method, circularly polarized dichroism spectroscopy, X-ray diffraction crystallography method, etc. However, it is difficult for these methods to monitor the denaturation process of collagen solution in real time. In this study, a self-assembled optical heterodyne polarimeter that was capable of amplifying the optical rotation signal to 40-fold, and a precision thermoelectric cooler (TEC) were used to study the thermal denaturation phenomenon of collagen solution after heating.Our results indicated that when collagen solution was heated from 25oC to 55°C, the thermal denaturation was at 40.2±0.2°C. When the collagen solution was cooled from 55°C to 25oC, about 66% of its structure was refolded back to triple helix again. However, both the concentration of the aqueous protein solution and the rate of heating with TEC system have some effects on the processes of denaturation, but they are not the main factors.When collagen solution was mixed with Trifluoroethanol(TFE), we observed that the initial optical rotation value and the denaturation temperature were both decreased. This suggests that TFE will destroy the structure of collagen. Moreover, the destruction was saturated after the concentration of TFE exceeds 20% (v/v). At last, we added glycerol in the mixed solution of TFE and collagen. We observed that the denaturation temperature was increased when more glycerol was added. At high concentration of TFE, the protective effect is more significant than in low concentration. Not only these results can be applied to the processing of many proteins, but also are consistent with other studies using different methods.?