FIGURE 1.

Fluorescence characteristic of free PPIX and EfeB-PPIX complex. The initial concentration of PPIX is 2 mm and was diluted to different concentrations from 10 to 60 μm using Tris-HCl buffer (10 mm Tris-HCl, pH 8.0, 100 mm NaCl). Apo-EfeB was diluted to different concentrations from 10 to 60 μm using the same buffer, and then PPIX was added to the apo-EfeB solution to a final concentration ranging from 10 to 60 μm and was mixed and measured. A, excitation and emission wavelength scan for free PPIX of 10 μm, showing that the distinctive excitation wavelength is 398 nm and emission wavelength is 620 nm. B, excitation and emission wavelength scan for EfeB-PPIX complex of 10 μm, showing that the excitation wavelength is 407.5 nm and emission wavelength is 622.5 nm. C, fluorescence intensity of free PPIX increased nonlinearly as concentration rises. However, the fluorescence intensity of EfeB-PPIX complex increased linearly with rising concentrations.