Melanin: A Two Edged Sword?

Hill, Helene Z.; Li, Weixjiong; Xin, Patrick; Mitchell, David L.

doi:10.1111/j.1600-0749.1997.tb00478.x

Cited by 105 publications

(72 citation statements)

References 24 publications

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“…3,4 Eumelanins, macromolecules mainly composed of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and their redox forms, are the most ubiquitous melanins in humans and the most studied by material scientists (Scheme 1). 5 Back in the 1960-70s, eumelanin in form of pressed pellets was discovered to be conductive, photoconductive, and to show threshold switching.…”

Section: 2mentioning

confidence: 99%

Eumelanin thin films: solution-processing, growth, and charge transport properties

et al. 2013

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Eumelanin pigments show hydration-dependent conductivity, broad-band UV-vis absorption, and chelation of metal ions. Solution-processing of synthetic eumelanins opens new possibilities for the characterization of eumelanin in thin film form and its integration into bioelectronic devices. We investigate the effect of different synthesis routes and processing solvents on the growth, the morphology, and the chemical composition of eumelanin thin films using atomic force microscopy and X-ray photoelectron spectroscopy. We further characterize the films by transient electrical current measurements obtained at 50% to 90% relative humidity, relevant for bioelectronic applications. We show that the use of dimethyl sulfoxide is preferable over ammonia solution as processing solvent, yielding homogeneous films with surface roughnesses below 0.5 nm and a chemical composition in agreement with the eumelanin molecular structure. These eumelanin films grow in a quasi layer-bylayer mode, each layer being composed of nanoaggregates, 1-2 nm high, 10-30 nm large. The transient electrical measurements using a planar two-electrode device suggest that there are two contributions to the current, electronic and ionic, the latter being increasingly dominant at higher hydration, and point to the importance of time-dependent electrical characterization of eumelanin films.

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Section: 2mentioning

confidence: 99%

Eumelanin thin films: solution-processing, growth, and charge transport properties

et al. 2013

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“…Melanin is a photoreactive compound and can paradoxically act as a photosensitiser, as well as a photoprotector. 9 Increased intracellular melanin can increase the susceptibility of melanocytes to UV-induced DNA damage by the production of reactive oxygen species.…”

Section: Discussionmentioning

confidence: 99%

Association between choroidal pigmentation and posterior uveal melanoma in a white population

Harbour

Brantley

Hollingsworth

et al. 2004

British Journal of Ophthalmology

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“…This proper compartmentalization of melanin is likely important in avoiding the possible toxic effects of ectopic pigment formation. Melanin production involves the polymerization of DOPAquinone intermediates that can produce toxic oxygen free radicals and cellular damage (54); it has been proposed that melanosomes have evolved as a means to sequester this otherwise toxic molecule. In fact, substantial cell death was observed when WT tyrosinase was expressed…”

Section: Discussionmentioning

confidence: 99%

Nitisinone improves eye and skin pigmentation defects in a mouse model of oculocutaneous albinism

Onojafe¹,

Adams²,

Simeonov³

et al. 2011

J. Clin. Invest.

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Mutation of the tyrosinase gene (TYR) causes oculocutaneous albinism, type 1 (OCA1), a condition characterized by reduced skin and eye melanin pigmentation and by vision loss. The retinal pigment epithelium influences postnatal visual development. Therefore, increasing ocular pigmentation in patients with OCA1 might enhance visual function. There are 2 forms of OCA1, OCA-1A and OCA-1B. Individuals with the former lack functional tyrosinase and therefore lack melanin, while individuals with the latter produce some melanin. We hypothesized that increasing plasma tyrosine concentrations using nitisinone, an FDA-approved inhibitor of tyrosine degradation, could stabilize tyrosinase and improve pigmentation in individuals with OCA1. Here, we tested this hypothesis in mice homozygous for either the Tyr c-2J null allele or the Tyr c-h allele, which model OCA-1A and OCA-1B, respectively. Only nitisinone-treated Tyr c-h/c-h mice manifested increased pigmentation in their fur and irides and had more pigmented melanosomes. High levels of tyrosine improved the stability and enzymatic function of the Tyr c-h protein and also increased overall melanin levels in melanocytes from a human with OCA-1B. These results suggest that the use of nitisinone in OCA-1B patients could improve their pigmentation and potentially ameliorate vision loss.

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Melanin: A Two Edged Sword?

Cited by 105 publications

References 24 publications

Eumelanin thin films: solution-processing, growth, and charge transport properties

Eumelanin thin films: solution-processing, growth, and charge transport properties

Association between choroidal pigmentation and posterior uveal melanoma in a white population

Nitisinone improves eye and skin pigmentation defects in a mouse model of oculocutaneous albinism

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