Fig. 2. Binding pocket and spectroscopic properties of the Pfr crystal structure. (a and b) Zoom-in of the protein-binding pocket in the crystal chain A (a) and chain B (b) with the most important amino acids interacting with BV and pyrrole water. (c) Absorption (Abs., top) and circular dichroism (CD, bottom) electronic spectra calculated on chain A (left panel) and chain B (right panel). All spectra were calculated at the CAM-B3LYP/6-31+G(d) level and shifted by −0.16 eV, to be comparable with our previous calculations on the Pr crystal.²⁸.