INVESTIGATION OF THE CONDITIONS OF PHOTO-REDUCTION OF METHYLVIOLOGEN BY CHLOROPLASTS

  • 1 January 1978
    • journal article
    • research article
    • Vol. 12  (6) , 984-992
Abstract
The condition of methylviologen photoreduction by chloroplasts was investigated. Argon bubbling through the suspension of chloroplasts or degasing in vacuum caused inhibition of methylviologen reduction probably due to the denaturation of chloroplast membranes at the water/air boundary. Adding glycerol or bovine serum albumin or removing O2 from chloroplast suspension with the aid of O2 absorbing-systems preserved the activity of chloroplasts. Methylviologen photoreduction was inhibited by DCMU [3-(3''4''-dichlorophenyl)-1,1, dimethylurea] (10-7 M) and Tris-buffer treatment and was activated by uncouples. The pH-dependence is similar to that of the Hill reaction. Triton X-100 (0.007%), ethyl ether (2%) and heating up to 42.degree. activated the Hill reaction but inhibited methylviologen reduction. The water molecule probably acts as an initial electron donor in the reaction. The steady level of methylviologen photoreduction was determined by a relationship between the rate of methylviologen electron acceptance and cyclic electron flow short-circuiting photosystem I.

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