[Free radical centers in the chromatophores and preparations of Rhodospirillum rubrum reaction centers].

The light-induced free radical ESR signals in chromatophores and reaction center preparation of R. rubrum were studied. It has been shown that the properties of the signals in both systems were strictly identical. At the microwave powers higher than 10 mW the ESR signal at g approximatley 2.00 is saturated and its asymmetry arises. Changes of the ESR signal shape may be explained by the superposition of P870+ signal with that from the ubisemiquinone. Addition of ferricyanide to chromatophores induces in the dark a new ESR signal characterized by a linewidth of 4.5 Oe which presumably arises from the antenna bacteriochlorophyll aggregates, because this signal is absent in the reaction center preparations.