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  • Title: Water proton relaxation as a monitor of membrane-bound manganese in spinach chloroplasts.
    Author: Wydrzynski T, Zumbulyadis N, Schmidt PG, Govindjee.
    Journal: Biochim Biophys Acta; 1975 Dec 11; 408(3):349-54. PubMed ID: 172133.
    Abstract:
    First measurements of proton relaxation on chloroplast membranes are presented here. Experiments show that the water proton spin-lattice relaxation rate in chloroplast thylakoid membrane suspensions can be used to monitor membrane-bound manganese. The relaxation effect is reduced to 0.4 of its original value upon manganese extraction by washing with either alkaline Tris buffer or NH2OH/EDTA solution. Large increases in the proton relaxation rate are measured in the presence of reductants such as tetraphenylboron and NH2OH; oxidants such as potassium ferricyanide or 2,6-dichlorophenolindophenol lead to an decrease in this rate. These results suggest that manganese exists as a mixture of oxidation states in dark-adapted chloroplasts.
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