Probing the Building Blocks of Eumelanins Using Scanning Electron Microscopy

Nofsinger, J. Brian; Forest, Susan E.; Eibest, Leslie M.; Gold, Kathryn A.; Simon, John D.

doi:10.1034/j.1600-0749.2000.130310.x

Cited by 76 publications

(92 citation statements)

References 17 publications

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“…This shows that the metals coordinating with melanin granules are lost, while the ability to coordinate metals of melanin granules still remains. The melanin granular parenchyma is composed of fine particulate structures 20) , and these fine particulates still remain after bleaching with hydrogen peroxide solution 21) . This suggests that the molecular frames of melanin granules are still able to appreciably coordinate metals after bleaching.…”

Section: B Metal Elements In the Melanin Granules And Their Relationmentioning

confidence: 99%

The influence of hair bleach on the ultrastructure of human hair with special reference to hair damage

Imai

2011

Okajimas Folia Anat. Jpn.

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Summary: The influence of human hair bleaching agents with different bleaching strength on the ultrastructure of human hair was studied using a transmission electron microscope (TEM) and an energy dispersive X-ray spectrometer equipped with TEM (EDS-TEM). Two kinds of bleaching agents were used: a lightener agent with a weak bleaching effect and a powder-bleach with a stronger bleaching effect.From the comparison of the bleaching properties obtained by the electronic staining of black and white hair samples, it was suggested that the permeability of hair was increased by bleaching, and there was an increase of the stainability of hair subjected to electronic staining. The bleaching action provoked the decomposition of melanin granules and the flow out of granular contents into the intermacrofibrillar matrix. Some metal elements were detected in the melanin granular matrix by EDS-TEM. As a result, the diffusion of metal elements into the intermacrofibrillar matrix promoted further damage to the hair by catalytic action with the hydrogen peroxide in the bleaching agents outside the melanin granules. Further study will lead us to the edge of the development of a new bleaching agent, which reacts only with melanin granules and causes the minimum of damage to outside the melanin granules.

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Section: B Metal Elements In the Melanin Granules And Their Relationmentioning

confidence: 99%

The influence of hair bleach on the ultrastructure of human hair with special reference to hair damage

Imai

2011

Okajimas Folia Anat. Jpn.

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“…Therefore they cannot offer much information about melanin in terms of morphology, shape and size. Furthermore, most synthetic melanins as well as isolated natural ones are not stably dispersed in water, 9 restricting the analysis and related experiments to homogeneously dispersed systems. The ability of melanins to bind metal ions has been considered to be one of their unique biological functions, allowing the reservation of some metal ions and the quenching of redox reactive metals, thereby releasing the oxidative stress on biological systems.…”

Section: Introductionmentioning

confidence: 99%

The Synthetic Melanin Nanoparticles Having An Excellent Binding Capacity of Heavy Metal Ions

Kim¹,

Ju²,

Lee³

2012

Bulletin of the Korean Chemical Society

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Spherical-shape melanin nanoparticles with good water-dispersibility were successfully synthesized by a simple oxidation polymerization of 3,4-dihydroxy-phenylalanin (DOPA) with KMnO 4 . Similar features to those known from natural and synthetic melanin polymers were observed from prepared melanin nanoparticles by FT-IR, UV-Vis., and ESR spectroscopic methods. Their binding ability with several heavy metal ions from aqueous solution was quantitatively investigated, and the maximum binding capacities with melanin nanoparticles to lead, copper, and cadmium ions were obtained as 2.45, 2.17 and 1.88 mmol/g, respectively, which are much larger values than those reported from natural and synthetic melanin polymers. The large binding capacity and fast binding rate of melanin nanoparticles to metal ions can make them an excellent candidate for the remediation of contaminated water.

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“…17 Although this model of MNmacroaggregates composed of MN-microparticles may not be applicable to all MN that are present in vivo or the MN synthesized in the lab. 18 A key physical property of the MN class of pigments is their capacity to absorb light over a broad range of the electromagnetic spectrum giving the MN materials their dark brown or black appearance. MN is considered to have poor fluorescence properties, although treatment of MN with H 2 O 2 resulted in a markedly enhanced fluorescence that was attributed to the degradation of the pigment.…”

Section: Introductionmentioning

confidence: 99%

Dark- or Light-Colored Melanins: Generating Pigments Using Fe2+ and H2O2

Vercruysse

Russell²,

Knight³

et al. 2017

Preprint

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We have studied the formation of melanin-like pigments from catechol or pyrogallol and a wide range of other phenolic compounds using Fe 2+ and H 2 O 2 . Combining UV_Vis spectroscopic measurements and size-exclusion chromatography analyses we evaluated the impact of the intensity of the oxidation reaction by varying the concentration of H 2 O 2 present in the reaction mixtures. All compounds tested, except tyrosine, reacted readily leading to mixtures that were black, brown or yellow-orange in color. For many compounds tested, the use of increasing concentrations of H 2 O 2 resulted in either precipitation of the pigment or the formation of a soluble, lighter-colored pigment. With catechol or pyrogallol as model compounds, and using different concentrations of H 2 O 2 , several materials were synthesized, purified and dried. The physic-chemical properties of these materials were compared to the properties of melanin-like pigments synthesized from the same precursors using air-oxidation in an alkaline environment. For both precursors, a distinct chemical change, as judged from FT-IR spectroscopy, was introduced in the melanin structures when using H 2 O 2 as the oxidizing agent and the relative intensity of this distinct signal strengthened with increasing concentration of H 2 O 2 used in the reaction. In general, our results suggest that depending on the precursor molecule and the intensity of the oxidizing reaction conditions involved, light-or dark-colored melanin-like pigments can be generated. This may be an important factor when evaluating the visible outlook of histological or archeological specimens: the presence of a lighter color or the absence of a dark color may not necessarily mean the absence of melanin-like biomolecules.

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Probing the Building Blocks of Eumelanins Using Scanning Electron Microscopy

Cited by 76 publications

References 17 publications

The influence of hair bleach on the ultrastructure of human hair with special reference to hair damage

The influence of hair bleach on the ultrastructure of human hair with special reference to hair damage

The Synthetic Melanin Nanoparticles Having An Excellent Binding Capacity of Heavy Metal Ions

Dark- or Light-Colored Melanins: Generating Pigments Using Fe2+ and H2O2

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