A new photosynthetic pigment, "P430": its possible role as the priary electron acceptor of photosystem I.

The technique of flash kinetic spectrophotometry was used to demonstrate a broad absorption band around 430 nm, which was kinetically different from P700, in several photosystem-I particles from spinach and blue-green algae. The component represented by this absorption band, designated as "P430", was bleached as fast as P700. Its recovery in the dark was accelerated by ferredoxin and by various artificial electron acceptors with redox potentials as low as -521 mV. The recovery kinetics have been demonstrated to be identical to those of a concomitant reduction of several of the artificial electron acceptors used. Tentatively, "P430" has been proposed as a possible primary electron acceptor of photosystem I.