Fig. 2.

Absorbance spectra (a) of 40 µM FlamS in HEPES buffer (10 mM, pH = 7.4) containing 40% (v/v) DMSO titrated with CuSO₄ up to 1.25 eq. No further spectral changes are observed upon addition of excess Cu²⁺. Emission spectra (b) of 10 µM FlamS in the same solvent conditions with 1 equivalent of CuSO₄. λ_ex = 495 nm.