Eumelanins and Pheomelanins: Characterization by Electron Spin Resonance Spectroscopy

Sealy, Roger C.; Hyde, James S.; Felix, Christopher C.; Menon, I. A.; Prota, Giuseppe

doi:10.1126/science.6283638

Cited by 173 publications

(154 citation statements)

References 8 publications

Supporting

Mentioning

146

Contrasting

Order By: Relevance

“…For all the studied samples, complex EPR spectra with a poorly resolved hyperfine structure were recorded. According to Sealy et al [7], the EPR signals were characterized additionally by "R"-factor, defined as the height ratio of central high-field to low-field maximum. Such a parameter seems to be helpful for determination of the relative content of eu-and pheo-type components in the melanin pigments of mixed character.…”

Section: Resultsmentioning

confidence: 99%

EPR Investigations of Model Neuromelanins

2000

View full text Add to dashboard Cite

The aim of this work was to compare free radical properties of some model neuromelanins obtained from dopamine and its mixture with 5-S-cysteinyldopamine in various molar ratios. The EPR method was used in these investigations; the samples were detected at X and K bands. The parameters of EPR spectra, free radicals concentrations in air and in vacuum, the influence of microwave power and temperature on intensity of resonance signals were measured.

show abstract

Section: Resultsmentioning

confidence: 99%

EPR Investigations of Model Neuromelanins

2000

View full text Add to dashboard Cite

show abstract

“…A second fundamental method and the most used signature for melanin in physical chemistry, electron paramagnetic resonance spectroscopy (EPR), can verify the results of alkaline hydrogen peroxide oxidation. EPR probes the electronic properties of a material nondestructively (18,19).…”

Section: Resultsmentioning

confidence: 99%

Direct chemical evidence for eumelanin pigment from the Jurassic period

Glass

Ito

Wilby

et al. 2012

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

172

168

View full text Add to dashboard Cite

Melanin is a ubiquitous biological pigment found in bacteria, fungi, plants, and animals. It has a diverse range of ecological and biochemical functions, including display, evasion, photoprotection, detoxification, and metal scavenging. To date, evidence of melanin in fossil organisms has relied entirely on indirect morphological and chemical analyses. Here, we apply direct chemical techniques to categorically demonstrate the preservation of eumelanin in two >160 Ma Jurassic cephalopod ink sacs and to confirm its chemical similarity to the ink of the modern cephalopod, Sepia officinalis. Identification and characterization of degradation-resistant melanin may provide insights into its diverse roles in ancient organisms.

show abstract

“…EPR spectroscopy enables a sensitive and nondestructive analysis of natural melanin (18,23,31). Nanosecond timeresolved EPR (TREPR) studies have only recently been reported despite the relevance of TREPR to the study of melanin photochemistry being recognized years ago (18).…”

mentioning

confidence: 99%

“…Electron spin polarization arises from the chemistry associated with radical production and depletion and is routinely detected by TREPR, a major tool for exploring free radical chemistry (32)(33)(34)(35)(36)(37). Although different melanins are distinguishable by conventional EPR spectroscopy (31,38), the free radical chemistry of melanin is complex and not well characterized, especially the chemistry of melanin that protects the RPE from light and ROS (18,20). Substantial evidence supports a phototoxic role of RPE melanin, especially in aged cells, including production of superoxide anions and hydroxyl radicals that are implicated in RPE cell death (39)(40)(41)(42)(43)(44)(45).…”

mentioning

confidence: 99%

Photoprotection of human retinal pigment epithelium cells against blue light-induced apoptosis by melanin free radicals from Sepia officinalis

Seagle

Gasyna

Mieler

et al. 2006

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

View full text Add to dashboard Cite

Cultured retinal pigment epithelium (RPE) cells can phagocytize large foreign particles. Heterogeneous melanin aggregates fromSepia officinalis, a species of cuttlefish, were fed to cultured human RPE cells to produce cells laden with Sepia melanin. Blue lightinduced apoptosis (BLIA) assays were performed by flow cytometry on parallel cultures consisting of RPE cells isolated from independent eyes and evenly divided into two cultures, one fed Sepia melanin and one containing only native melanin. After culturing and growth of the cells under blue light illumination for 7 days, the apoptosis percentage of all cultures indicated that Sepia feeding significantly reduced BLIA. To account for Sepia photoprotection, continuous-wave EPR and time-resolved EPR experiments were performed with parallel RPE cultures by using UV (355 nm) and green (532 nm) laser irradiation. Continuous-wave EPR spectra prove that the concentrations of intrinsic and extrinsic melanin free radicals in the Sepia-RPE culture are large compared with those concentrations in the RPE culture. Time-resolved EPR spectra indicate that both UV and green light produced extrinsic melanin radicals as radical pairs from the triplet manifold with a linear dependence on the number of photons per second. These experiments conclusively demonstrate that decreased RPE susceptibility to BLIA correlates with increased intracellular melanin free radical concentrations and that nonnative melanin can supplement native melanin photoprotection of RPE cells.age-related macular degeneration ͉ continuous-wave EPR ͉ time-resolved EPR

show abstract

Eumelanins and Pheomelanins: Characterization by Electron Spin Resonance Spectroscopy

Cited by 173 publications

References 8 publications

EPR Investigations of Model Neuromelanins

EPR Investigations of Model Neuromelanins

Direct chemical evidence for eumelanin pigment from the Jurassic period

Photoprotection of human retinal pigment epithelium cells against blue light-induced apoptosis by melanin free radicals from Sepia officinalis

Contact Info

Product

Resources

About