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Intensity and anisotropy decays of [Leu5] enkephalin tyrosyl fluorescence by 10 GHz frequency-domain fluorometry
J R Lakowicz1, I Gryczynski, G Laczko
1University of Maryland School of Medicine, Department of Biological Chemistry, Baltimore 21201.
Abstract:
The technique of 10 GHz frequency-domain fluorometry was used to resolve the complex picosecond intensity and anisotropy decays of the tyrosyl emission of [Leu5] enkephalin. Enhanced resolution of anisotropy decay was obtained by using acrylamide quenching of the tyrosyl fluorescence and global analysis of the frequency-domain anisotropy data obtained with different amounts of acrylamide. The data indicates a 44 ps correlation time for local tyrosine motions, and a 219 ps correlation time for overall rotational diffusion of the pentapeptide. Our data are consistent with an initial loss of fluorescence anisotropy from r0 = 0.4 to a value of r0 = 0.326 occurring during the first two picoseconds after excitation.