Effect of Cu2+ and Zn2+ ions on DOPA-melanin structure as analyzed by pyrolysis–gas chromatography–mass spectrometry and EPR spectroscopy

Chodurek, Ewa; Pilawa, Barbara; Dzierżęga‐Lęcznar, Anna; Kurkiewicz, Sławomir; Świa̧tkowska, Longina; Wilczok, Tadeusz

doi:10.1016/s0165-2370(02)00094-3

Cited by 17 publications

(24 citation statements)

References 19 publications

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“…Cu(II) ions added into melanin prompt to shortening of spinlattice relaxation time T 1 . Kanamycin and another drug do not change the time T 1 [11,12,14]. EPR signal recorded for DOPAmelanin and next for melaninkanamycin complex saturate at the similar microwave power.…”

Section: Resultsmentioning

confidence: 86%

“…Lowering of amplitude of EPR signal with increase of microwave powers was promoted by spins from higher energy level which are not able to return on lower energy level in proper time. Microwave saturation did not exist for paramagnetic Cu(II) ions in melanin complexes [11,14]. Cu(II) ions are characterized by short spinlattice relaxation time [11,13] and in used range of microwave power microwave saturation is not noticed.…”

Section: Resultsmentioning

confidence: 91%

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Influence of Microwave Power on EPR Signal of Melanin Radical and Copper(II) Ions in DOPA-Melanin Complexes

et al. 2013

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Electron paramagnetic resonance spectroscopy EPR was used for examination of microwave saturation in DOPAmelanin complexes with kanamycin and Cu(II) ions. The fast spinlattice relaxation processes take place in system of paramagnetic metal ions. EPR signal of melanin radical saturated with growing of microwave power used during measurements. After adding Cu(II) ions a shortening of relaxation time is observed for EPR signal of melanin radical.

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Section: Resultsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 91%

Influence of Microwave Power on EPR Signal of Melanin Radical and Copper(II) Ions in DOPA-Melanin Complexes

et al. 2013

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“…The opposite was observed for D39-P8, D37-P9, and D43-P5, whose TREPR signals were mimicked by acidified synthetic melanin, where melanin is insoluble and aggregated. RPE cells under physiological conditions are not likely to be very acidic or very basic; nonetheless, several in vivo factors appear to influence or modulate melanin organization within cells, particularly metal ions (53)(54)(55)(56), RPE age (8,14,16), and proteins (9,34). In synthetic systems, pH is a main factor controlling the organization of melanin and determining the type of EPR-observable photochemistry that occurs (52).…”

Section: Discussionmentioning

confidence: 99%

Melanin photoprotection in the human retinal pigment epithelium and its correlation with light-induced cell apoptosis

Seagle

Rezai

Kobori

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

103

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Time-resolved electron paramagnetic resonance (TREPR) spectroscopy was used to study melanin free radicals in human retinal pigment epithelium (RPE) cells and tyrosine-derived synthetic melanin. TREPR signal traces from RPE cells reveal in vivo light-induced melanin free radical photochemistry in more detail than previously known. Electron spin polarization reflecting a non-Boltzmann population within the energy levels of the spin system is observed in RPE cells as the result of the triplet state photoproduction and subsequent disappearance of free radicals in the melanin polymer. In a set of RPE cells cultured from individual sources, differences in optical absorption, continuous wave EPR spectra, and TREPR signals were correlated with apoptosis assays performed by flow cytometry. Continuous wave EPR spectra of RPE cells and TREPR of acidified synthetic melanin suggest that increased melanin aggregation provides an increase in photoprotection in the RPE cells that are relatively less susceptible to blue light-induced apoptosis.continuous wave EPR ͉ electron spin polarization ͉ time-resolved EPR I n the eye, retinal pigment epithelium (RPE) is a monolayer of cuboidal cells between the photoreceptors and choriocapillaris of the eye and is specialized to uptake, phagocytize, and recycle the outer segment of photoreceptors and retinaldehyde, the chromophore of rhodopsin (1). RPE cell death plays a major role in the pathogenesis of age-related macular degeneration, the leading cause of blindness in the population Ͼ60 years of age in the developed world (2). Possible reasons given for the degeneration of RPE cells are their exposure to high oxidative stress and damaging irradiation (2-6).The pigment melanin, found in RPE cells, is a heterogeneous polymer consisting of various monomers believed to be oxidation products of dopa (dihydroxyphenylalinine) derived from tyrosine (7). Melanin contains intrinsic, indolesemiquinone-like doublet-state radicals (8, 9). Extrinsic indolesemiquinone-like radicals are reversibly photogenerated under visible or UV irradiation (9). RPE melanin serves a photoprotective role by absorbing radiation and scavenging free radicals and reactive oxygen species (ROS) (8-11). Evidence also exists for a phototoxic role for melanin in RPE cells, especially in aged cells, including measurable ROS photoproduction (8,(12)(13)(14)(15)(16)(17)(18). Electron paramagnetic resonance (EPR) spectroscopy enables a sensitive and nondestructive analysis and differentiation of natural melanin (9,19,20). The photophysical, redox, and aggregation properties of melanin as well as its ability to bind metals, proteins, and drugs have stimulated numerous studies in chemical, physical, and medical research (8, 9). The diversity and interrelations of its properties and the lack of chemical structures have hampered a clear understanding of the roles of melanin in RPE cells (8,9). Nanosecond time-resolved (TR) EPR studies have not been reported despite the relevance of TREPR to the study of melanin photochemistry (9). El...

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“…The usefulness of this method is well documented [16][17][18], especially in its ability to differentiate between eumelanins and pheomelanins [19]. Additionally, some reports suggest that melanin precipitation by HCl acidification does not have any influence on the melanin pyrolytic pattern [15,18].…”

Section: Introductionmentioning

confidence: 99%

Thermal and mass spectroscopic characterization of a sulphur-containing bacterial melanin from Bacillus subtilis

Gómez–Marín

Sanchez

2010

Journal of Non-Crystalline Solids

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Effect of Cu2+ and Zn2+ ions on DOPA-melanin structure as analyzed by pyrolysis–gas chromatography–mass spectrometry and EPR spectroscopy

Cited by 17 publications

References 19 publications

Influence of Microwave Power on EPR Signal of Melanin Radical and Copper(II) Ions in DOPA-Melanin Complexes

Influence of Microwave Power on EPR Signal of Melanin Radical and Copper(II) Ions in DOPA-Melanin Complexes

Melanin photoprotection in the human retinal pigment epithelium and its correlation with light-induced cell apoptosis

Thermal and mass spectroscopic characterization of a sulphur-containing bacterial melanin from Bacillus subtilis

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