Representative concentration profiles of 3-pHis at pH 6.5 with increasing concentrations of pyridine. The smaller the squares, the shorter the observed half-life. E. Sankey-diagram to visualize the phosphate flow in the system (5 mM pyridine, pH 6.5). F and G. The percentage of fuel converted to phosphate directly and through pyridine (black) or phosphorylated histidine species (magenta) depends on the pH and the amount of pyridine added. All experiments were performed in triplicate, and all data is shown.