We present a description of fluorescence decay kinetics in complex environments based on gamma functions rather than the conventional approach using exponentials. The gamma function description is tested in measurements on the temperature dependence of the protein human serum albumin (HSA), N-acetyl tryptophanamide (NATA), and 2, 5-dipenyl oxazole (PPO). The monitoring of macromolecular structure and dynamics is demonstrated by means of distinct tryptophan (Trp) rotamer populations and their interconversion in HSA.
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