Calorimetric study of thermal denaturation of vertebrate visual pigments
Shnyrov, V.L.; Berman, A.L.
Biomedica Biochimica Acta 47(4-5): 355-362
1988
ISSN/ISBN: 0232-766X PMID: 3266468 Document Number: 313926
The thermostability of visual pigments in bovine, rat and frog rod outer segments (ROS) has been studied by means of differential scanning calorimetry and thermal gel analysis methods. Use of the two different methods has allowed to assign calorimetric peaks to rhodopsin and opsin denaturation. The denaturation enthalpy changes for rhodopsin in bovine, rat and frog ROS are 630 kJ/mole (Td = 347.degree. C), 416 kJ/mole (Td = 340.degree. K) and 410 kJ/mole (Td = 340.degree. K), respectively. Corresponding values for opsins are 490 kJ/mole (Td = 332.degree. K), 269 kJ/mole (Td = 320.degree. K) and 158 kJ/mole (Td = 319.degree. K). The free energy of stabilization of the rhodopsin native structure is not very large and practically similar to that for native water soluble globular proteins.