Abstract: The interaction of Cu²⁺ with Myoglobin(Mb) was investigated by UV-Vis absorption spectra, fluorescence spectra, synchronous fluorescence spectra and circular dichroism(CD) spectra. It is shown that Cu²⁺ enhanced the intensity of UV absorption peak of Mb, accompanied with blue shift. The fluorescence spectrum shows that Mb fluorescence at 323 nm was quenched regularly with the addition of Cu²⁺. The quenching belongs to the static fluorescence quenching. The binding constants and the numbers of the binding sites at different temperatures were calculated. The thermodynamic parameters were calculated(ΔH＝-11.60 kJ/mol, ΔS＝33.77 J·mol^-1·K^-1) according to van′t Hoff equation, which indicate that the static interaction played major roles in the binding process. The binding distance r between Cu²⁺ and Mb was obtained(2.56 nm) on the basis of Förster theory of non-radiation energy transfer. The effect of Cu²⁺ on the conformation of Mb was further analyzed by synchronous fluorescence spectra and circular dichroism. The results indicate that Cu²⁺ had a strong impact on Mb conformation with the change of the microcircumstance of aromatic amino residues and decreases of α-helical content of the protein.

Key words: Myoglobin(Mb), UV-Vis spectrum, Fluorescence spectrum, Synchronous fluorescence spectrum, Circular dichroism spectrum