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 theoretical considerations and experimental evidences discussed in this paper indicate that quantitative study of photochromic processes in labeled objects open up new possibilities for investigating microviscosity and conformation transitions in biological systems. The proposed method of photochrome labeling features higher sensitivity and simplicity, and uses labels which are more stable under physiological conditions compared with traditional spin labels.
