ASSIGNMENT OF LOG-NORMAL COMPONENTS OF PR OTEIN FLUORESCENCE-SPECTRA TO INDIVIDUAL TRYPTOPHAN RESIDUES USING THEIR MICROENVIRONMENT PROPERTIES IN TRIDIMENSIONAL STRUCTURE

Parameters of fluorescence of three single-tryptophan-containing prote ins and of two log-normal components of proteinase K (2 tryptophans) w ere analyzed in relation to the microenvironment characteristics of in dolic atoms in crystal structures of the proteins. For this purpose, i t was constructed a system of microenvironment description including a ccessibility of the atoms to the bulk and bound water; the density, po larity and mobility of environment within radii of 5,5 and 7,5 Angstro m from each indolic atom; and the existence of eventual partners in hy drogen bonding with excited fluorophore. The analysis showed that, in the cases of the most shorter-wavelength emission bands (those structu red at 308 nm for azurin and at 316 nm for L-asparaginase), as well as of the monomer melittin band at 350 nm, the microenvironment characte ristics well agreed to those predicted in the model of discrete states of tryptophan in proteins [1,3,7] and can be used for assignment of p rotein fluorescence spectral components to individual tryptophan resid ues. However, differences of the microenvironment parameters included in the system are little discernible for the component bands of protei nase K emission at ca. 330 and 340 nm. In order to reliably assign suc h components of tryptophan fluorescence, it seems to be sufficient to take into account some additional structural characteristics, which co uld be revealed in a comprehensive analysis of a great number of prote ins possessing such spectral components.