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Vibrational Dynamics of Biological Molecules: Multi-quantum Contributions
Bogdan M Leu1, J Timothy Sage, Marek Z Zgierski
1Steacie Institute for Molecular Science, National Research Council of Canada, Ottawa, Ontario, Canada K1A OR6.
The Journal of Physics and Chemistry of Solids
|August 9, 2006
Summary
Nuclear resonance vibrational spectroscopy (NRVS) reveals iron (Fe) vibrations in proteins. This study observes two-quantum excitations, aiding in determining Fe motion direction without single crystals.
Area of Science:
- Physics
- Chemistry
- Biochemistry
Background:
- Nuclear Resonance Vibrational Spectroscopy (NRVS) quantifies vibrational dynamics of iron sites in biomolecules.
- Previous studies measured vibrational fundamentals (frequencies, amplitudes) of iron (Fe) vibrations.
- Direction of Fe motion was determined using oriented single crystals.
Purpose of the Study:
- To observe and analyze two-quantum vibrational excitations (overtones and combinations) in heme protein active site mimics.
- To assess the utility of two-quantum excitations for determining Fe motion direction.
- To compare experimental observations with theoretical predictions.
Main Methods:
- High-resolution X-ray measurements near nuclear resonance.
- Analysis of vibrational fundamentals and two-quantum excitations.
- Comparison with Density Functional Theory (DFT) predictions and single crystal data.
Main Results:
- Successfully observed weaker two-quantum vibrational excitations in heme protein models.
- Intensity of two-quantum excitations strongly depends on the direction of Fe motion.
- Observed features align with predictions based on fundamentals and known Fe motion directions.
Conclusions:
- Two-quantum excitations provide valuable information on Fe motion direction.
- This method can identify Fe oscillation directions when single crystals are unavailable.
- NRVS, including two-quantum excitations, is a powerful tool for studying metalloproteins.