Dynamics of oxygen penetration and diffusion into horse skeletal myoglobin revealed by quenching of zinc protoporphyrin IX fluorescence
Carrero, Jenny
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Permalink
https://hdl.handle.net/2142/23776
Description
Title
Dynamics of oxygen penetration and diffusion into horse skeletal myoglobin revealed by quenching of zinc protoporphyrin IX fluorescence
Author(s)
Carrero, Jenny
Issue Date
1995
Doctoral Committee Chair(s)
Gratton, E.
Department of Study
Biology, Animal Physiology
Biophysics, General
Discipline
Biology, Animal Physiology
Biophysics, General
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Biophysics, General
Language
eng
Abstract
Oxygen quenching of tryptophan fluorescence in a number of globular proteins provided some of the early experimental evidence for conformational fluctuations in proteins. Gratton et al. (Biophysical J. 1984. 45:789-794) proposed a sequential two step model called the dynamic model for oxygen quenching of internally buried fluorophores in proteins. For this study, that model is utilized to analyze the dynamics associated with conformational fluctuations of oxygen entry into the protein and to obtain thermodynamic parameters associated with these fluctuations. We used zinc protoporphyrin IX reconstituted myoglobin and performed oxygen quenching experiments at different temperatures. The data was fit to the above model and k$\sp+$ (oxygen entry rate), k$\sp-$ (oxygen exit rate), and $\chi$ (oxygen migration rate) in horse skeletal myoglobin were obtained at each temperature. The activation energies were calculated using the value of k$\sp+$ and k$\sp-$ at each temperature. The protein-to-solvent partition coefficient for oxygen, $\alpha$, was also obtained at each temperature along with the thermodynamic variable, $\Delta$G, associated with this partition. The parameters k$\sp+$, k$\sp-$, $\chi$, and $\alpha$ have also been determined for the quenching of zinc protoporphyrin IX in 40% sucrose to assess the effect of viscosity on these parameters. The agreement of the steady state Stern-Volmer plot, calculated using the kinetic constants derived from the time resolved measurements with the experimental data, indicates that the dynamic model accurately represents the oxygen quenching process in horse skeletal myoglobin in all the temperature and viscosity range investigated.
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