Electron-spin resonance studies of the structure and formation of bacterial diazodiphenoquinone pigments

The formation of diazodiphenoquinone pigments during bacterial oxidations of pyridinediols can be accounted for in terms of a free-radical mechanism similar to that operating for oxidations in vitro involving azasemiquinone radicals. Electron-spin-resonance spectra are of great value in pigment structure determinations.