Fig. 2: Spectroscopic characterization of viral channelrhodopsins.
From: Viral rhodopsins 1 are an unique family of light-gated cation channels
a Normalized absorption spectra of OLPVR1 and VirChR1 proteins at neutral pH (pH 7.5). b, c Absorption spectra of OLPVR1 and VirChR1 at acidic (pH 2.1–7.1) pH range, normalized for absorption at 280 nm. d Schiff base region of OLPVR1 protein, key residues and water molecules are shown as sticks and spheres; hydrogen bonds are shown as dashed lines. e Absorption spectra of OLPVR1 at acidic (pH 2.8–7.0) pH range, normalized for absorption at 280 nm. e Red shift of UV-visible absorption spectrum and protonation of counterion of OLPVR1 and VirChR1. Wavelength maximum values are shown as circles. Sigmoidal curve fits are presented as dashed lines. The pKa values were calculated using a sigmoidal fit. f Ion-transport activity assay of OLPVR1-containing proteoliposomes in 100 mM NaCl salt. The onset of illumination is indicated with white (light on) and gray (light off) background color, pH was adjusted to pH 6.0 prior to measurements. LR/Mac-containing liposomes and empty liposomes were used as positive and negative controls, respectively. g Schematic model of viral rhodopsins photocycle. h Transient absorption spectra and i time traces at specific wavelengths of wild type OLPVR1 protein at pH 7.5.
