Change in the excited state dynamics of Archae-Rhodopsin-3 via site specific mutations

Archaerhodopsin-3 (AR-3) is a light-driven proton pump found in Halorubrum sodomense. AR-3 was put forward as a possible candidate for optogenetic investigations. Also, multiple mutants then emerged, with fluorescence quantum yields reaching up to 1.2% which is a 100-fold increase with respect to the wild-type protein. To understand this exceptionally strong effect of the mutations in detail, we studied changes in the electrostatic interactions of the protein cavity containing retinal chromophore induced in the double mutant DETC and the quintuple mutant Arch-5. Multiple ultrafast optical techniques, such as Impulsive Vibrational, Transient Absorption and Fluorescence Up-conversion spectroscopies together with temperature-dependent measurements were used to study excited state dynamics.