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Most organisms use photoreceptors to sense and respond to light. Examples of photoreceptors include bacteriorhodopsins and bacteriophytochromes in some bacteria, phytochromes in plants, and rhodopsins in the photoreceptor cells of the vertebral retina. The light-sensitive property of these receptors is because of the bound chromophores, such as bilin in the phytochromes and retinal in the rhodopsins.
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Terahertz radiation from bacteriorhodopsin reveals correlated primary electron and proton transfer processes.

Proceedings of the National Academy of Sciences of the United States of America·2008

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Photocycle of dried acid purple form of bacteriorhodopsin.

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Characterization of the proton-transporting photocycle of pharaonis halorhodopsin.

Biophysical journal·2000

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Blue light regeneration of bacteriorhodopsin bleached by continuous light.

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Bleaching of bacteriorhodopsin by continuous light.

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Related Experiment Video

Updated: Jun 23, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Published on: June 27, 2014

How Many M Forms are there in the Bacteriorhodopsin Photocycle?

G I Groma, Z Dancshazy

Biophysical Journal

|May 12, 2009

Summary

Bacteriorhodopsin

Area of Science:

Biophysics
Photochemistry
Molecular Biology

Background:

Bacteriorhodopsin's photocycle is crucial for Halobacterium halobium's energy transduction.
The precise number of M intermediates in the photocycle remains debated.
Accurate photocycle models are needed for quantitative analysis of related effects.

Purpose of the Study:

To investigate the M intermediate decay kinetics in bacteriorhodopsin.
To determine the number of distinct decay components under various conditions.
To elucidate the photocycle scheme through kinetic analysis.

Main Methods:

Sophisticated kinetic measurements of M form decay.
Analysis using discrete exponential fitting (one, two, and three components).

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Atomic Force Microscopy of Red-Light Photoreceptors Using PeakForce Quantitative Nanomechanical Property Mapping

Published on: October 24, 2014

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Last Updated: Jun 23, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Published on: June 27, 2014

Atomic Force Microscopy of Red-Light Photoreceptors Using PeakForce Quantitative Nanomechanical Property Mapping

Atomic Force Microscopy of Red-Light Photoreceptors Using PeakForce Quantitative Nanomechanical Property Mapping

Published on: October 24, 2014

Fitting a continuous distribution of exponentials for independent verification.

Main Results:

Three distinct real decay components were identified in cell envelope vesicles (4 M NaCl).
These components followed Arrhenius law temperature dependence.
Two components were observed in NaCl-free purple membrane (suspension and gel), with a third appearing in 4 M NaCl-soaked gel.

Conclusions:

The study reveals multiple kinetic phases in M intermediate decay.
Salt concentration significantly influences the number of observable decay components.
Findings contribute to a more precise understanding of the bacteriorhodopsin photocycle.