Effect of oxygen on free radicals in DOPA–melanin complexes with netilmicin, diamagnetic Zn(II), and paramagnetic Cu(II)

Electron paramagnetic resonance (EPR) spectroscopy was used to examine interactions between molecules of oxygen O2 and free radicals of DOPA–melanin and its complexes with netilmicin, Zn(II) and Cu(II). EPR spectra were measured for evacuated samples and then compared to earlier data for the samples in air. The concentrations of free radicals in the evacuated samples were higher than for samples in air. The strongest effect was observed for DOPA–melanin and melanin samples containing Cu(II). Evacuation of DOPA–melanin and DOPA–melanin–Cu(II) samples causes high EPR line broadening. Faster spin–lattice relaxation processes exist in evacuated melanin samples than in samples in air.