Continuous microwave saturation of EPR spectra of melanin complexes at different temperatures

Paramagnetic centers in DOPA-melanin and complexes of DOPA-melanin with netilmicin and Cu(II) were studied by the use of an X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy. Measurements of continuous microwave saturation of EPR spectra at temperatures: 125 K, 175 K, 225 K, 275 K, were performed. Homogeneous broadening of all the examined EPR spectra was observed. EPR spectra of DOPA-melanin-Cu(II) complexes saturated at higher microwave powers than the others tested melanin samples. Fast spin-lattice relaxation exists in DOPA-melanin-Cu(II) complexes. Slow spin-lattice relaxation processes exist in melanin's paramagnetic centers of DOPA-melanin and its complexes with netilmicin, and its complexes with both netilimicin and Cu(II). EPR spectra of all the tested samples saturated at higher microwave powers with increasing of the measuring temperature. Faster spin-lattice relaxation processes occurs in DOPA-melanin and its complexes with netilmicin and Cu(II) at higher temperature.