Fig. 1: The mean fluorescence lifetime of mCherry at different physico-chemical conditions.
a–f mean fluorescence lifetime (τ) of 100 nM mCherry as a measure of increasing NaCl concentrations a Glycerol, b Trehalose, c, and d–f polyethylene glycol (PEG). Crowding exclusively induces lifetime reduction, and only above 30% fractional volume occupancy (FVO). The values and error estimates are based on calculations (Eq. S2) using best-fit values of the recorded fluorescence decays (Supplementary Fig. 1) to a sum of two exponents function (Eq. S1). The values of the intrinsic mean fluorescence lifetimes are reported in Table S1. The error estimates were calculated directly from the fitting uncertainty, and are reported as the minimal and maximal intrinsic mean fluorescence lifetime values calculated from all lifetime component values and their amplitudes, using Supplementary Eq. 2, which have a reduced χ2-values within 95% confidence relative to the best-fit minimal reduced χ2 value. Red line that is set at 1.44 ns highlights the limit below which fluorescence lifetimes drop in the presence of elevated concentrations of PEG or trehalose. Titration of NaCl or glycerol, leads to non-monotonic changes in τ which fluctuate around the typical fluorescence lifetime of mCherry.
