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The Study on the Model of the Unfolding of Cytochrome C and its Thermodynamic Properties
Date Issued
2008
Date
2008
Author(s)
Liang, Chia-Tsen
Abstract
The function of protein is dependent of its folding process. For studying thermodynamic properties of folding-unfolding of protein, cytochrome c is chosen to be the model. Equilibrium unfolding behaviors of cytochrome c induced by presence of urea or changes in temperature are examined via spectroscopic techniques, including absorption、fluorescence and circular dichroism spectrometer. The local structure change can be detected by these spectrometers. The experimental data are fitted by the modified Ising model successfully, and some thermodynamic parameters of the unfolding of cytochrome c are derived, for example, the denature free energy of the local site. Results indicate that the thermodynamic stability of three local sites in cytochrome c ,from stable to unstable, are α-helix local site、Trp-59 local site and heme local site. By comparing with the data of small angle X-ray scattering, we find that native cytochrome c is close to a globular envelope. The envelope elongates gradually to an ellipsoidal shape at high urea concentration (9M) and high temperature (338K). We find the unfolding of heme local site just influences the global volume a little bit. But with the unfolding of α-helix local site and Trp-59 local site, the semi-major axis of cytochrome c elongates dramatically, whereas the semi-minor axis stays roughly the same.
Subjects
Cytochrome c
Two state model
Ising model
Absorption spectrum
Fluorescence spectrum
Circular dichroism spectrum
Small angle X-ray scattering
Type
thesis
File(s)
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Name
ntu-97-R95223047-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):61d9604c2e53491cf64bc5e0b309f9bc