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Updated: Jun 30, 2026
10:03
Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Switch from conventional to distributed kinetics in the bacteriorhodopsin photocycle
Andrei K Dioumaev1, Janos K Lanyi
1Department of Physiology and Biophysics, University of California, Irvine, California 92697-4560, USA. dioumaev@uci.edu
Biochemistry
|September 30, 2008
Summary
Bacteriorhodopsin photocycle kinetics shift from distributed to exponential above 245 K. This change is attributed to a protein-specific thermodynamic phase transition, not lipid interactions.
Area of Science:
- Biophysics
- Protein Dynamics
- Spectroscopy
Background:
- Bacteriorhodopsin photocycle kinetics differ at low temperatures, requiring distributed kinetics.
- This contrasts with conventional exponential kinetics observed at ambient temperatures.
Purpose of the Study:
- Investigate factors causing the kinetic regime switch in bacteriorhodopsin.
- Determine the critical temperature for this transition.
Main Methods:
- Time-resolved Fourier-transform infrared (FTIR) spectroscopy.
- Monitoring the D96N mutant bacteriorhodopsin photocycle between 180 K and 280 K.
Main Results:
- A critical temperature around 245 K was identified for a kinetic switch.
- Above this temperature, photocycle intermediate decay accelerated significantly.
- Below 240 K, distributed kinetics dominated, deviating from conventional models.
Conclusions:
- The kinetic transition is linked to a thermodynamic phase transition within the protein.
- This is likely related to the freezing/thawing of internal protein fluctuations (dynamic phase transition).
- The observed transition temperature is not correlated with lipid phase transitions.
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