E. V. Anufrieva, M. G. Krakovyak, V. D. Pautov, and T. D. Anan’eva
Institute of High-Molecular Compounds, Russian Academy of Sciences, St. Petersburg, 199004 Russia
Received March 10, 1998
Abstract—Lysozyme samples with different content of covalently bound anthracene-containing photoactive
groups (PhAG) (from 0.27 to 2.0 PhAG per molecule) were obtained as products of reaction between isothio-
cyanatomethyl-anthryl and NH2 groups of protein. Spectral and polarization analysis of PhAG luminescence
revealed that as the PhAG concentration in aqueous solution (0.01 M phosphate buffer, pH 7.4) of lysozyme is
raised from 1 to 1.3 PhAG per protein molecule, there is a cooperative increase in the electronic interaction
between the photoactive groups. This gives rise to excimer formation and migration of energy of PhAG elec-
tronic excitation. Studies of polarized luminescence (PL) revealed that addition of up to 3 M guanidine hydro-
chloride (GHC) to aqueous solution of lysozyme induces an increase in the intramolecular mobility of the pro-
tein globule domains containing PhAG, although has virtually no effect on the compact globular structure of
the protein. The increase in the intramolecular mobility of the protein globule is accompanied by intensification
of electronic interaction between PhAG. Further elevation of the GHC content in the reaction medium causes
unfolding of the lysozyme globule, a further increase in the intramolecular mobility, an increase in the distance
between PhAG, and a decrease in the efficiency of photophysical processes in the system.
Key words: protein globule, lysozyme, guanidine hydrochloride, photoactive groups, electronic excitation, pho-
tophysical processes, excimer formation, intramolecular mobility, polarized luminescence
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