Nonexponential kinetics of a single tRNA(Phe) molecule under physiological conditions

The fluorescence decay functions of individual, specifically labeled tRNA(Phe) molecules exhibit nonexponential character as a result of conformational dynamics occurring during the measurement on a single molecule. tRNA(Phe) conformational states that interchange much more slowly are evidenced by the distribution of lifetimes observed for many individual molecules. A structural model for the nonexponential decay indicates that the tRNA(Phe)–probe adduct fluctuates between two states, one of which provides conditions that quench the probe fluorescence.