Thermodynamics of thermal denaturation of ribonuclease A and cytochrome c in the presence of 1,1,1,3,3,3-hexafluoro-2-propanol |
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| Institution: | 1. Institute of Organic Chemistry, National Academy of Sciences of the Ukraine, Murmanskaya St., 5, UA-02094, Kyiv, Ukraine;2. Department of Chemistry, Taras Shevchenko National University of Kyiv, 64/13, Volodymyrska Str. Kyiv, 01601, Ukraine;3. The Chemours Company, 200 Powder Mill Rd., Experimental Station Wilmington, DE, 19803, USA;1. Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 501 Haike Road, Shanghai 201203, PR China;2. Jiangsu Hansoh Pharmaceutical Co., Ltd., 9 Dongjin Road, Lianyungang 222069, PR China;1. Laboratorio de Biofisicoquímica, Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México, México D. F. 04510, Mexico;2. Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Mexico;3. Departamento de Ingeniería Química, Conjunto E, Edificio de Ingeniería Química, Facultad de Química, Universidad Nacional Autónoma de México, Mexico |
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| Abstract: | The thermal denaturation of ribonuclease A and cytochrome c has been studied by differential scanning calorimetry (d.s.c.) and u.v.-visible spectrophotometry in the presence of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) at pH = 5.5 and pH = 4.0, respectively. The quantitative thermodynamic parameters accompanying the thermal transitions from native to denatured state have been evaluated. The results of the reversible thermal denaturations have been fitted with a two-state native-to-denatured mechanism. A comparison has been made of the relative effect of HFIP on the thermal stability of ribonuclease A and cytochrome c. It has been observed that the denaturation capacity of HFIP tends more towards cytochrome c compared with ribonuclease A. The results have been explained on the basis of a fine balance between the preferential exclusion and binding that take place during the course of the denaturation reaction and the structuring of water around the groups of the protein exposed upon denaturation. Using the thermodynamic data obtained from calorimetric and spectroscopic measurements, we have calculated the changes in preferential solvation of ribonuclease A and cytochrome c upon heat denaturation. It is observed that the preferential solvation of these two proteins is specific, indicating that the solvation mechanism is not the same for them. |
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