Effect of oxygen on spin-spin and spin-lattice relaxation in DOPA-melanin. Complexes with chloroquine and metal ions

Abstract

Electron paramagnetic resonance (EPR) studies of complexes of chloroquine with melanin synthesized from 3,4-dihydroxyphenylalanine (DOPA) confirmed an important role of o-semiquinone free radicals during the drug binding by melanin. Chloroquine increases free radical concentration in DOPAmelanin. It has been also demonstrated that chloroquine binding to melanin is modified by metal ions. Co 2 § ions reduce and Zn 2 § ions increase the concentration of free radicals in both DOPA-melanin and melanin-chloroquine complexes. Free radical properties of melanin strongly depend on the presence of oxygen (02) in the environment of the sample. Interactions of melanin and oxygen molecules cause a decrease of the free radical concentration in the samples anda narrowing of the EPR lines. Higher values of both spin-spin and spin-lattice relaxation times were determined for melanin samples in air than for evacuated samples. Application of the observed effeets in oximetry is suggested.

Paramagnetic Centers in DOPA-Melanin-Dihydrostreptomycin Complexes

“…Eumelanins with characteristic single lines mainly exist in living organisms. Free radicals play an important role in biochemical reac-tions with drugs [2][3][4]. Application of aminoglycoside antibiotics therapy may be accompanied by toxic effects resulting from free radicals generation in melanin.…”

Triplet States in DOPA-Melanin and in Its Complexes with Kanamycin and Copper Cu(II) Ions

“…This drop is the greater the higher the concentration of paramagnetic ions added [5,11,19,21,24,27].…”

“…The EPR signal of melanin radicals undergoes microwave saturation [19][20][21], therefore the linewidth ∆B pp of EPR signal is determined by spin-lattice relaxation time T 1 and by spin-spin relaxation time T 2 [22,23]. The relaxation time T 1 is dependent on temperature of measurement, however, the relaxation time T 2 changes only slightly with temperature.…”

“…On this ground, we can say that kanamycin added to DOPA-melanin polymer increases the number of paramagnetic centres with spin S = 1. Because the mechanism describing how drugs are bound to melanin is not well recognised yet [19,20,25], it is difficult to explain fully this effect. It is known that intensity of EPR line of melanin increases after the addition of drugs [19,20,26].…”

Lasers in Ophthalmology

“…We described widely the two laser applications in ophthalmology which are connected with paramagnetic species and singlet oxygen. We chose these subjects, because of our experimental experience in spectroscopic studies of paramagnetic centers (Beberok et al, 2010;Buszman et al, 2003Buszman et al, , 2005aBuszman et al, , 2005bBuszman et al, , 2006Chodurek et al, 2003;Domagała et al, 2008;Latocha et al, 2004Latocha et al, , 2005Latocha et al, , 2006Matuszczyk et al, 2004;Najder-Kozdrowska et al, 2009, 2010Pilawa et al, 2002Pilawa et al, , 2003aPilawa et al, , 2003bPilawa et al, , 2005aPilawa et al, , 2008cZdybel et al, 2009Zdybel et al, , 2010 and singlet oxygen O 2 with zero spin (Bartłomiejczyk et al, 2008;Latocha et al, 2008;Pilawa et al, 2005bPilawa et al, , 2006Pilawa et al, , 2008aPilawa et al, , 2008b. In this work the view of the information in scientific papers is done.…”