Studies on photosystem I. Characteristics of "310 material" isolated from spinach chloroplasts

Immunological quantitation of chloroplast ferredoxin

An immunosassy for the quantitative determinations of ferredoxins in cell free extracts from plant tissues is described. The method is accurate for the assay of 0.3-1.5 nmol ferredoxin directly from the extracts. The following average values (nmol ferredoxin/mg extractable protein) were obtained: 3.9, 1.8. 5.90, 14.8 and 10.9 for Euglena gracilis, spinach, parsley, lettuce, and broccoli, respectively. Specific factors affecting the method are discussed in detail.

Hydroxylation of p-Coumaric acid by illuminated chloroplasts. The role of superoxide

1. Chloroplasts isolated from leaves of spinach-beet (Beta vulgaris L. ssp. vulgaris) do not catalyse the hydroxylation of p-coumaric acid in the dark unless a reductant (such as ascorbate, NADH or NADPH) is added. Superoxide dismutase has no effect on this reaction. 2. Illuminated chloroplasts catalyse the hydroxylation in the absence of added reductant. This reaction is completely inhibited by superoxide dismutase, but catalase has little effect. 3. Both hydroxylation in the light and hydroxylation in the dark in the presence of reductants are inhibited by diethyldithiocarbamate, EDTA, cyanide and 2-mercaptoethanol. 4. It is proposed that O-2- generated by illuminated chloroplasts is involved in the provision of a reductant to the enzyme phenolase.