NICOTINAMIDE COFACTORS OF INTACT CHLOROPLASTS ISOLATED ON A SUCROSE DENSITY GRADIENT

1. 1. The potassium content of chloroplasts expressed as a potassium-chlorophyll ratio was adopted as a new criterion of chloroplast integrity. 2. 2. Chloroplast fractions from pea seedlings were prepared using a sucrose density gradient and found to contain not less than 80% intact chloroplasts and no recognisable cellular components as contaminants. 3. 3. NADP+, NADPH, NAD+ and NADH assays on these preparations are reported, and compared with published values. 4. 4. The light-induced reduction of endogenous NADP+ and NAD+ was followed and similarly the reduction of exogenous NADP+. A NADPH peak occurred during the initial 30-sec illumination, in agreement with data published for illumination of the whole leaf. 5. 5. The observations indicate that these chloroplasts are freely permeable to NADP+ and may accumulate it against a concentration gradient. There is also some evidence to indicate that conversion of exogenous NADP+ into NAD(H) occurs on illumination. © 1969.