Fig. 6. Organic solvent effects on PSI structural stability. Organic solvent effects on PSI stability were assessed using 77 K low temperature chlorophyll fluorescence emission spectra. Baseline correction was performed, peak intensities of the PSI peak were normalized, and percent free chlorophyll (660 nm) along with PSI-bound chlorophyll (720 nm) shift were calculated at 1 and 24 hour timepoints from Gaussian curve fitting. All spectra shown are the average of triplicate results. (A) 77 K chlorophyll fluorescence emission spectra of 1 and 24 hour timepoint of PSI in 0–50% acetonitrile. Left panel 1 h timepoint, center 24 h timepoint, right panel PSI peak shift and chlorophyll loss quantification. (B) 77 K chlorophyll fluorescence emission spectra of 1 hour and 24 hour timepoint of PSI in 0–60% ethylene carbonate. Left panel 1 h timepoint, center 24 h timepoint, right panel PSI peak shift and chlorophyll loss quantification. (C) 77 K chlorophyll fluorescence emission spectra of 1 hour and 24 hour timepoint of PSI in 30% acetonitrile + 50% ethylene carbonate, 20% aqueous buffer. Right panel is chlorophyll loss quantitation.