Photoinduced transformations in bacteriorhodopsin membrane monitored with optical microcavities

Area of Science:

• Biophysics
• Spectroscopy
• Materials Science

Background:

• Bacteriorhodopsin (bR) is a light-activated protein containing a retinal chromophore.
• Understanding molecular transformations in bR is crucial for its applications.
• Self-assembled monolayers offer a platform for studying molecular behavior.

Purpose of the Study:

• To monitor photoinduced molecular transformations in a bacteriorhodopsin (bR) monolayer.
• To quantify changes in molecular polarizability and orientation.
• To establish optical microcavities as a tool for probing molecular self-assemblies.

Main Methods:

• Utilized a microsphere optical cavity to monitor bR monolayer.
• Observed shifts in near-infrared resonant wavelengths of polarized modes.
• Quantified molecular polarizability changes and orientation of the retinal chromophore.

Main Results:

• Successfully monitored photoinduced molecular transformations in bR.
• Quantified a molecular polarizability change of approximately -57 ų upon retinal isomerization and deprotonation.
• Determined the orientation of retinal relative to the bR membrane to be approximately 61 degrees.

Conclusions:

• Optical microcavities serve as a sensitive spectroscopic tool for molecular self-assemblies.
• The technique can probe molecular conformations, orientations, and polarizability changes.
• Potential applications in studying molecular dynamics and developing novel optical sensors.