Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 36: Biopolymers and Biological Systems
CPP 36.9: Vortrag
Freitag, 29. Februar 2008, 12:30–12:45, C 264
Thermodynamics of proteins: pressure and temperature denaturation curves — •Johannes Wiedersich1,2, Simone Köhler1, Josef Friedrich1, and Arne Skerra3 — 1Lehrstuhl für Physik Weihenstephan, TU München — 2Physikdepartment E13, TU München — 3Lehrstuhl für Biologische Chemie, TU München
The folding and unfolding of proteins shows a complex scenario, the details of which are not yet fully understood. One important aspect concerns the stability of proteins. By means of fluorescence spectroscopy we obtain the equillibrium constant for the denaturation of the engineered fluorescein-binding protein FluA as a function of both pressure and temperature. From the full thermodynamic analysis of the transition curves all of the involved global thermodynamic parameters of protein folding are determined, in particular the changes in entropy and volume, compressibility, thermal expansion and specific heat.
We demonstrate that the phase diagram of protein folding is closed and assumes an elliptic shape. The thermodynamic condition for such an elliptic phase diagram is related to the degree of correlation between fluctuations of the changes in volume and enthalpy at the phase boundary. This correlation is moderately low, on the order of 0.05 in our case. Our study suggests that the elliptic phase diagram is a consequence of the inherent conformational disorder of proteins and that it may be viewed as the thermodynamic manifestation of the high degeneracy of conformational energies that is characteristic for this class of macromolecules.