Figure 2.
a) Proposed reaction mechanism between NO (via N2O3) and SCR-NO. SCR-NO and the free carboxylate shown in blue are PA-active; however, after hydrolysis to the corresponding carboxylic acid product, spontaneous spiro-lactonization yields the closed PA-inactive product shown in grey. b) Chemical structural of SCR-NO (blue), PA-inactive turnover product form of SCR-NO (grey), and IR-1061 (green). c) Cartoon schematic showing the production of two SWIR signals before reaction with NO and one SWIR signal (from the reference) after reaction with NO.