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Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Correlation between absorption maxima and thermal isomerization rates in bacteriorhodopsin
1Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973 USA.
Biophysical Journal
|May 12, 2009
Summary
The thermal isomerization rate of protonated Schiff base of retinal (PSBR) correlates with its absorption maximum. Protein interactions in bacteriorhodopsin (BR) also influence this isomerization, suggesting a role in the BR photocycle.
Area of Science:
- Biochemistry
- Photochemistry
- Structural Biology
Background:
- Protonated Schiff base of retinal (PSBR) undergoes thermal isomerization.
- Bacteriorhodopsin (BR) is a light-driven proton pump utilizing retinal.
- The absorption maximum of chromophores is linked to electronic delocalization.
Purpose of the Study:
- To investigate the correlation between thermal isomerization rates and spectral shifts in PSBR.
- To determine the influence of the protein environment in BR on PSBR isomerization.
- To propose a model for later stages of the BR photocycle.
Main Methods:
- Comparative analysis of isomerization rates and absorption maxima.
- Modeling of PSBR in solution and within the BR protein.
- Kinetic analysis of the BR photocycle.
Main Results:
- Isomerization rates of PSBR correlate with red shifts in absorption maxima.
- The correlation differs between solution and the BR protein environment.
- Specific protein-chromophore interactions in BR modulate isomerization rates.
Conclusions:
- Chromophore delocalization significantly regulates thermal isomerization rates.
- Protein-specific interactions in BR are crucial for controlling isomerization.
- The 13-cis to all-trans isomerization likely occurs during the O intermediate in the BR photocycle.
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