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Nitrosyl hemoglobins: EPR above 80 K
E Wajnberg1, G Bemski, L J el-Jaick
1Centro Brasileiro de Pesquisas Fisicas, RJ, Brazil.
International Journal of Biological Macromolecules
|April 1, 1996
Summary
Electron paramagnetic resonance (EPR) revealed two states in hemoglobin and myoglobin. Above 150 K, a reversible decrease in EPR signal suggests a conformational change, impacting oxygen transport studies.
Area of Science:
- Biophysics
- Biochemistry
- Spectroscopy
Background:
- Nitrosyl hemoglobin and myoglobin are crucial for oxygen transport.
- Understanding their conformational dynamics is key to studying their function.
- Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for probing molecular structures and dynamics.
Purpose of the Study:
- To investigate the conformational states of nitrosyl hemoglobin and myoglobin under various conditions using EPR.
- To determine the thermodynamic parameters governing these conformational changes.
- To elucidate the role of coordination state (hexa- and penta-coordinated) in these dynamics.
Main Methods:
- Electron paramagnetic resonance (EPR) spectroscopy was employed.
- Measurements were conducted on nitrosyl hemoglobin, myoglobin, and hematin-NO.
- Experiments covered a temperature range of 80-280 K and included native, denatured, and lyophilized samples.
Main Results:
- A significant and reversible decrease in EPR spectral area was observed for all hemoglobin samples above 150 K.
- This phenomenon indicates the presence of two distinct conformational states in thermal equilibrium.
- Only one of these conformational states is detectable by EPR spectroscopy.
Conclusions:
- The study demonstrates temperature-dependent conformational changes in nitrosyl hemoglobin and myoglobin.
- These findings suggest that EPR detectability is conformation-specific.
- Thermodynamic parameters for both hexa- and penta-coordinated states were successfully determined.