An effective and optimal combination of three reagents commonly used for modifying the structure of proteins has been developed for causing quantitative dissolution of membrane structure. Alkaline solution, 1.5% Triton X-100, and 6 m urea at 0° for about 2 hr causes quantitative conversion of chromatophores from wild-type Rhodopseudomonas spheroides into Triton–protein complexes having particle weights of less than 200, 000. No trap activity is lost as evidenced by light-induced absorbance and electron paramagnetic resonance changes. Good rates for photoxidation of exogenous cytochrome c also are demonstrated. Especially significant is the maintenance of a near-normal absorbance spectrum in both the bacteriochlorophyll and carotenoid regions in spite of the marked conversion into smaller units. Also, of possible importance and utility is the ability to cause reaggregation of the small units into chromatophore-like structures by the removal of excess detergent. Evidence is given for nearly total lipid displacement by the alkaline–urea–Triton treatment and subsequent sucrose density gradient centrifugation.
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