Time-resolved fluorescence study during denaturation and renaturation of curcumin–myoglobin complex

Curcumin influences the transition point, the concentration of denaturant required to effect 50% of the total change, of myoglobin denaturation. Curcumin enhances absorbance of myoglobin at 280 nm with a binding constant K = 3.0 × 104 M−1 whereas fluorescence of curcumin is quenched by myoglobin with a Stern–Volmer association constant of 2.5 × 105 M−1. Unfolding process of myoglobin–curcumin induces a recovery in fluorescence lifetime loss. The gain in time-resolved fluorescence lifetime during unfolding has been again lost during refolding of curcumin–myoglobin complex by dilution process suggesting partial reversibility of unfolding process for both myoglobin and curcumin–myoglobin complex.