Magdalena Zdybel

EPR spectroscopy of chlorpromazine-induced free radical formation in normal human melanocytes

The purpose of this study was to estimate the effect of chlorpromazine on free radical concentration in HEMn-DP melanocytes using electron paramagnetic resonance (EPR) spectroscopy. It was found that chlorpromazine at concentrations of 1xa0×xa010−7 and 1xa0×xa010−6 M contributed to the formation of free radicals (g values ~2) in a dose-dependent manner. The increase in free radical formation was accompanied by an increase in cytotoxicity, as shown by a tetrazolium assay. Homogeneous broadening of EPR lines, slow spin–lattice relaxation processes, and strong dipolar interactions characterized all the tested cellular samples. The performed examination of free radical formation in cells exposed to different chlorpromazine concentrations confirmed the usefulness of electron paramagnetic resonance spectroscopy to determine the effect of a drug on free radical production in a cellular model system in vitro.

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

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 melanins 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.

Effect of simvastatin in different concentrations on free radicals in A-2058 human melanoma malignum cells-EPR studies: ZDYBEL et al.

The influence of concentration of simvastatin (SIM) on free radicals in A‐2058 human melanoma malignum cells was studied. The proliferation assay for melanoma A‐2058 cells with SIM in concentration range from 0.1 to 20u2009µM was performed. SIM in the concentrations of 0.1, 0.3, and 1u2009μM only slightly changed the growth of A‐2058 cells, but the growth of the cells considerably decreased for higher concentrations of SIM. Free radicals in the cells were examined by an X‐band (9.3u2009GHz) electron paramagnetic resonance (EPR) spectroscopy. o‐Semiquinone free radicals with g‐factors in the range of 2.0060 to 2.0065 were found in A‐2058 cells. The asymmetric broad EPR spectra with linewidths (ΔBpp) from 0.87 to 1.25u2009mT were measured. The fast spin‐lattice relaxation processes characterized all the tested cells. The free radical concentrations in the all A‐2058 cells cultured with SIM were lower than in the control cells. The quenching of free radicals in A‐2058 cells depended on concentration of SIM. This effect was the weakest for concentration of SIM of 3u2009μM. The strongest decrease of free radical concentration caused SIM in concentration of 1u2009μM.