QuasAr1 undergoes thermal isomerization and deprotonation dynamics over long time periods with measurable spectral changes.
The long-time absorption spectroscopic development of the genetically encoded microbial rhodopsin fluorescent voltage indicator QuasAr1 at room temperature in the dark was reinvestigated, mainly theoretically. The data analysis indicates protein aggregation within one day to some ten-nanometer sized Mie scattering particles. The absorption coefficient spectra can be deduced from measured attenuation coefficient spectra by scattering contribution subtraction. The initially present protonated retinal Schiff base (PRSB) Ret₅80 isomerized and then deprotonated to neutral retinal Schiff base (RSB). One part of Ret₅80, Ret₅80I, (fraction 43%), isomerized moderately fast to Ret₅00 which then deprotonated to neutral retinal Schiff base Ret₄05 (time constant ≈ 1000 h). The other part of Ret₅80, Ret₅80II, (fraction 57%), isomerized slowly to Ret₄60 which deprotonated to Ret₃40 (time constant ≈ 400 h). The dynamics are described by a differential equation system which is solved numerically. Reaction parameters are determined by fitting the simulations to the experimental results.
Penzkofer et al. (Mon,) conducted a other in Absorption Spectroscopic Thermal Dynamics. QuasAr1 was evaluated on Isomerization and deprotonation kinetics of QuasAr1. QuasAr1 undergoes thermal isomerization and deprotonation dynamics over long time periods with measurable spectral changes.