Rotational diffusion of markers of the fluorescein family in solutions of bovine serum albumin, according to the data from polarized fluorescence

The polarized fluorescence and rotational diffusion of markers of the fluorescein family (initial fluorescein and its halogenated derivatives erythrosine, eosin, and Rose Bengal) in solutions of bovine serum albumin (BSA) are studied. Elevated degrees of the polarization of fluorescence markers, increased times of rotational relaxation, and reduced coefficients of the rotational diffusion of markers are observed in solutions of BSA. It is shown that all four markers of the fluorescein family can be used to register binding with BSA, but fluorescein is better for studies of BSA with varied pH values and weakly electronegative hydrogen atoms in the structural formula. It is found that increasing the electronegativity of atoms in the structural formulas of markers raises the polarization of their fluorescence, reducing the coefficient of their rotational diffusion and lengthening their periods of rotational relaxation.