[Effect of medium polarity and protein microenvironment on indo-1 fluorescence]

Fluorescent properties of indo-1 in protein containing solutions have been investigated. No changes have been defined in indo-1 fluorescent parameters in solutions of such proteins as trypsin, calmodulin, papain, lysozyme. Significant changes of indo-1 fluorescent parameters have been observed in solutions of histones, bovine and human serum albumins. Results obtained suggest that indo-1 binds well with protein sites containing hydrophobic "pockets" and positively charged amino-acid residues such as arginine and lysin. The destruction of the compact structure of serum albumin in 8 M urea leads to shift of indo-1 fluorescence spectrum and it approaches to the spectrum in water. Fluorescence spectra of indo-1 in dioxane prove that the binding of indo-1 by some proteins occurs in hydrophobic microenvironment of protein globule.