The thermodynamic parameters of the alkaline transition of beef heart ferricytochrome c have been measured through direct electrochemistry experiments carried out at variable pH and temperature in the presence of different sulfate concentrations. Sulfate is known to bind specifically to cytochrome c in a sequential manner at two surface sites. The effects of such a specific binding reflect on the thermodynamics of the transition and can be satisfactorily interpreted within the frame of the Debye-Huckel theory with simple electrostatic considerations. In particular, the increase in the thermodynamic pK(a) values (extrapolated to I = 0) upon sulfate binding turns out to be a fully enthalpic effect which can be accounted for by considering the coulombic effects of the formation of ionic couple(s) on the protein surface. This study also shows that the apparent pK(a) values at finite ionic strength are only moderately affected by the nature of the anion in solution, and differences tend to vanish at high ionic strength.

Effects of specific anion-protein binding on the alkaline transition of cytochrome c / Battistuzzi, Gianantonio; Borsari, Marco; Ranieri, Antonio; Sola, Marco. - In: ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS. - ISSN 0003-9861. - STAMPA. - 386:(2001), pp. 117-122.

Effects of specific anion-protein binding on the alkaline transition of cytochrome c

BATTISTUZZI, Gianantonio;BORSARI, Marco;RANIERI, Antonio;SOLA, Marco
2001

Abstract

The thermodynamic parameters of the alkaline transition of beef heart ferricytochrome c have been measured through direct electrochemistry experiments carried out at variable pH and temperature in the presence of different sulfate concentrations. Sulfate is known to bind specifically to cytochrome c in a sequential manner at two surface sites. The effects of such a specific binding reflect on the thermodynamics of the transition and can be satisfactorily interpreted within the frame of the Debye-Huckel theory with simple electrostatic considerations. In particular, the increase in the thermodynamic pK(a) values (extrapolated to I = 0) upon sulfate binding turns out to be a fully enthalpic effect which can be accounted for by considering the coulombic effects of the formation of ionic couple(s) on the protein surface. This study also shows that the apparent pK(a) values at finite ionic strength are only moderately affected by the nature of the anion in solution, and differences tend to vanish at high ionic strength.
386
117
122
Effects of specific anion-protein binding on the alkaline transition of cytochrome c / Battistuzzi, Gianantonio; Borsari, Marco; Ranieri, Antonio; Sola, Marco. - In: ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS. - ISSN 0003-9861. - STAMPA. - 386:(2001), pp. 117-122.
Battistuzzi, Gianantonio; Borsari, Marco; Ranieri, Antonio; Sola, Marco
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/307491
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