Figure 1.

Rho thermal bleaching at 50°C. Rho samples, in 100 mM HEPES, pH 7.4, containing 0.05% DM, were spectroscopically analyzed in the presence of 3.5 M NaCl, KCl, and NH₄Cl. (A) Spectra obtained from the thermal stability of the retinal chromophore environment tested in the presence of these salts. Ctrl refers to the control sample in the absence of high salt concentration. Spectra were recorded at 5-min intervals for a total time of 35 min. (B) Absorbance decay at λ_{500 nm} was plotted versus time in the absence and presence of the different salts for the control sample (●), Na⁺ (○), K⁺ (▾), and NH₄⁺(▵).