Paramagnetic Centers in DOPA-Melanin-Dihydrostreptomycin Complexes

DOPA-melanin-dihydrostreptomycin complexes with drug concentrations 1×10$\text{}^{-4}$-1×10$\text{}^{-2}$ M were examined by the use of electron paramagnetic resonance spectroscopy at X-band (9.3 GHz). Dihydrostreptomycin was chosen for studies, because this aminoglycoside antibiotic causes strong toxic effects in organism. It was stated that dihydrostreptomycin generates o-semiquinone free radicals with g=2.0038 in melanin. Free radicals formation increases with increase in the antibiotic concentration. Changes of EPR lines with microwave powers pointed out that slow spin-lattice relaxation processes exist in DOPA-melanin and in its complexes with dihydrostreptomycin. The measured EPR lines were homogeneously broadened.