Anabaena Sensory Rhodopsin: Effect of point mutations on PSBR photo-isomerization speed

Abstract

We report new experimental results on the ultrafast photo-isomerization of ASR - PSBR where, unlike other retinal proteins, point mutations lead to a 2-fold increase of the photo-isomerization speed for the all-trans isomer. Prominent low-frequency vibrational coherences are reported for both the excited and photo-product ground states.

Sub-picosecond C=C bond photo-isomerization: evidence for the role of excited state mixing

“…First vibrational spectra obtained by femtosecond non-resonant (pump-)DFWM were also reported in this paper [105] for the isomer ground states in DA and LA, as well as their photoisomerized K states (pump delay 100 ps). The procedure for extracting AT-and 13C-pure vibrational spectra was explained in detail, and exploited more thoroughly in a subsequent publication [91], summarised and discussed in the following.…”

“…Our first joint paper on mutation-induced effect in ASR, published in 2018, reported a combined experimental and computational study of the spectral shifts, the ground state vibrational spectra and isomerization reaction times of the AT and 13C isomers in the mutants L83Q, V112N and W76F [105].…”

“…In L83Q and V112N, the nonpolar residues Valine and Leucine are replaced by the polar but neutral Glutamine (Q) and Asparagine (N), respectively, while the W76F mutation reduces the electron density and removes a small dipole close to the rPSB backbone (Figure 4). All mutations lead to blue-shifts of the DA and LA ground state absorption spectra with respect to wt-ASR [105]. Light-adaptation was carried out either with an orange (OA, 590 nm) or a blue (BA, 460nm) LED, and the light-adaptation with the highest 13C isomer ratio was retained.…”