Abstract
Time-resolved fluorescence and time resolved fluorescence anisotropy studies have been performed on wild-type azurin from Pseudomonas aeruginosa and two variants to study the mobility of Trp 48. The two azurin variants in which the microenvironment of Trp 48 was changed comprised the single mutations Ile 7Ser and Phe 110Ser. The experiments were performed on the holo-Cu(I), holo-Cu(II), and apo- forms at various pH values, viscosities, and temperatures; two distinct parts of the emission spectrum were selected for detection. Two prominent subnanosecond lifetimes in the fluorescence decays of the Cu(II) proteins could be observed. The decay of apo-azurin also consists of more than one component. The occurrence of more than one component in the fluorescence decays is explained by conformational heterogeneity. The anisotropy decay results appeared to be different for wild-type and mutated azurins. Phe 110Ser and Ile 7Ser azurin show more mobility of the Trp 48 residue, as reflected in the order parameter.
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