Stability of 7-Rh and 7-P23H-Rh. A, stability of membrane-bound and detergent-solubilized 11-cis-7-ring Rh to hydroxylamine. B, sensitivity of 7-P23H-Rh to hydroxylamine. The pigment is stable in the presence of cell membranes (up to 500 mm hydroxylamine) but loses the chromophore when exposed to 20 mm hydroxylamine in detergent. C, stability of 7-Rh to thermal bleaching. 7-Rh remains unchanged up to 2 h at 37 °C. D, thermal stability of 7-P23H-Rh. 7-P23H-Rh loses its chromophore after 10 min at 37 °C. Insets, changes in absorption at 494 nm as a function of time.