ABSTRACT
A photochromic compound, stilbazolium betaine M, when associated with metmyoglobin undergoes an accelerated thermal cis-trans isomerization. A study of the pH and ionic strength dependence of the isomerization reaction rate of the photochrome associated with metmyoglobin was performed. A comparative investigation of the reaction carried out in the presence of three proteins, metmyoglobin, apomyoglobin, and human albumin, indicates a specific influence of the heme pocket environment on the reaction. Possible mechanisms of the reaction acceleration are considered.
Subject(s)
Benzylidene Compounds/metabolism , Dihydropyridines/metabolism , Metmyoglobin/metabolism , Albumins/metabolism , Apoproteins/metabolism , Benzylidene Compounds/chemistry , Catalysis , Dihydropyridines/chemistry , Heme/chemistry , Humans , Hydrogen-Ion Concentration , Kinetics , Models, Structural , Myoglobin/metabolism , Osmolar Concentration , Stereoisomerism , TemperatureABSTRACT
The back thermal cis-trans isomerization reaction of stilbazole betaine in the presence of metmyoglobin was studied. The catalytic effect of metmyoglobin heme on the back thermal cis-trans isomerization reaction of stilbazole betaine was observed.
Subject(s)
Betaine/radiation effects , Metmyoglobin , Pyridines/radiation effects , Styrenes/radiation effects , Betaine/analogs & derivatives , Betaine/chemistry , Catalysis , Darkness , Pyridines/chemistry , Stereoisomerism , Styrenes/chemistry , Temperature , Ultraviolet RaysABSTRACT
The temperature dependence of the rate constant of photoinduced electron transfer in the modified eosin-myoglobin complex by monitoring of the phosphorescence quenching of eosin is measured. The values of electron transfer rate constants are equal 10(2) + 10(3) s-1 in the temperature region 150-200 K. The kinetics of relaxation of the maximum of the time-resolved phosphorescence spectra of eosin on apomyoglobin is measured in the same temperature range. The solvation relaxation of the time-resolved phosphorescence spectra is nonexponential. The characteristic times of the solvation relaxation are given 10(-2) + 10(-4) s-1, that correlate with the time of electron transfer in this system. It was observed the "acceleration" of the relaxation rate of the time-resolved phosphorescence spectra of eosin in metmyoglobin due to nonequilibrium photoinduced electron transfer. The role of the matrix dynamics in photoinduced electron transfer in proteins is discussed.
