Microcalorimetric studies of conformational transitions of ferricytochrome c in acidic solution.

The conformational transitions of ferricytochrome c in acidic solutions with different NaCl concentrations have been studied by scanning and isothermal microcalorimetry. It is shown that ferricytochrome c adopts three different forms which are realized under the considered conditions: native, denatured (unfolded) and a compact native-like form with unique tertiary structure. The thermodynamic parameters of the corresponding transitions have been measured and the changes in the number of bound ligands (H+ and Cl-), accompanying these transitions, have been determined by analyzing the temperature, pH and ionic strength dependence of these parameters.