Pressure and temperature dependence of fluorescence anisotropy of Green Fluorescent Protein

TL;DR

This study investigates how high pressure and temperature influence the fluorescence anisotropy of GFP, revealing that pressure decreases anisotropy likely due to environmental changes around the chromophore.

Contribution

It provides new insights into the pressure-temperature effects on GFP fluorescence anisotropy and suggests environmental hydrogen bonding changes as a key factor.

Findings

Anisotropy decreases with increasing pressure at constant temperature.

Anisotropy varies with temperature, showing a maximum at higher pressures.

Viscosity increase is not the main cause of anisotropy decrease.

Abstract

We have studied the effect of high hydrostatic pressure and temperature on the steady state fluorescence anisotropy of Green Fluorescent Protein (GFP). We find that the fluorescence anisotropy of GFP at a constant temperature decreases with increasing pressure. At atmospheric pressure, anisotropy decreases with increasing temperature but exhibits a maximum with temperature for pressure larger than 20 MPa. The temperature corresponding to the maximum of anisotropy increases with increasing pressure. By taking into account of the rotational correlation time changes of GFP with the pressure-temperature dependent viscosity of the solvent, we argue that viscosity increase with pressure is not a major contributing factor to the decrease in anisotropy with pressure. Our results suggest that the decrease of fluorescence anisotropy with pressure may result from changes in H-bonding environment around the chromophore.