[Study of oxygen accumulation in pea chloroplasts with spin labels]

Oxygen evolution in chloroplasts was studied by nitroxide fatty probes, introduced into chloroplasts membranes. The values of K(e)[O²] were determined from the measuring kinetics of nitroxide reduction under permanent illumination at two values of the microwave field, where K(e) was the constant of spin exchange between nitroxide and oxygen, [O²] --oxygen concentration. It was shown that in chloroplasts membranes, in contrast to liposomes there was no oxygen in the dark. This observation can be explained by oxygen consumption in various biochemical reactions. The values of K(e)[O²] were measured under permanent illumination. The highest value of K(e)[O²]=1.2.10(-5) s(-2) was observed in the middle of the membrane. At temperatures above 40⁰C and below -20⁰C oxygen was not evolved.