Related Experiment Video
Updated: Jul 29, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Cooperativity-induced optical anisotropy changes during the photocycle of bacteriorhodopsin
1Institute of Biophysics, Biological Research Center, Szeged, Hungary.
Abstract:
Previous photoselection measurements showed that if the excitation is weak no optical anisotropy changes appear in immobilized purple membranes during the photocycle. The present study demonstrates that surprisingly at stronger excitations the anisotropy changes versus time. At 412 nm the dichroic ratio decreases after a few milliseconds, while at 570 nm the similar decrease is followed by an increase. The phenomenon cannot be described by tiltings of the retinal chromophore. It is the consequence of the cooperative interaction among the photocycling bacteriorhodopsin molecules that regulates the yields of more than one (expectedly two main) parallel pathways existing in the millisecond time domain of the photocycle.
More Related Videos
Related Concept Videos
Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Cooperative Allosteric Transitions
Properties of Enantiomers and Optical Activity
Cooperative Allosteric Transitions
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Cooperative Allosteric Transitions

