[EPR study of redox titration of Chromatium minutissimum chromatophores].

Redox titration of chromatophores through the region +300 +570 mV at room temperature results in generation of two dark ESR signals, a well-known reaction center signal and a new narrow line. This line is characterized by deltaH pp = 4.2 Oe, g-factor about that of RC and a Lorentzian shape. It is insensitive to illumination. The determination of an RC signal midpoint potential is affected by the presence of the narrow line. Taking into account the superposition of the two ESR signals it was measured to be +(486+/-+/-18)mV.