Figure 9.

Structures and absorbance spectra of genetically encoded PA probes. (A) Diversity of genetically encoded PA probes with distinct chromophores/pigments. The upper and lower parts of the spectrum color bar show the crystal structures of PA probes and the chemical structures of corresponding chromophores or pigments. The chromophores of the probes in the upper part are shown as spheres. In the BphP-based probes (NIR-FPs and BphP1), the PAS domain is shown in blue, the GAF domain in dark red, the PHY domain in green and the output transducing module (OTM) in cyan. Eumelanin is a polymer comprising numerous cross-linked 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). The arrow in eumelanin denotes where the polymer continues. (B) Absorbance spectra of deoxygenated hemoglobin (Hb), oxygenated hemoglobin (HbO₂), GFP, cjBlue (GFP-like CP), mNeptune (GFP-like FP), iRFP713 (NIR FP), BphP1 Pfr (BphP1 in Pfr state), eumelanin and 5,5'-dibromo-4,4'-dichloro-indigo. Eumelanin and 5,5'-dibromo-4,4'-dichloro-indigo were artificially augmented 10-fold and 2-fold, respectively, to render them visible in the figure. The spectra data for Hb, HbO₂ and eumelanin are from http://omlc.ogi.edu, GFP from http://www.tsienlab.ucsd.edu/Documents.htm, cjBlue and iRFP713 and 5,5'-dibromo-4,4'-dichloro-indigo from ⁶², ⁶³ and ⁵³, respectively.