Current challenges in understanding melanogenesis: bridging chemistry, biological control, morphology, and function

Simon, John D.; Peles, Dana N.; Wakamatsu, Kazumasa; Ito, Shosuke

doi:10.1111/j.1755-148x.2009.00610.x

Cited by 341 publications

(345 citation statements)

References 142 publications

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“…Eumelanin is generated from these chemical building blocks, which are derived from the amino acid tyrosine (22). The biologically controlled copolymerization of DHI and DHICA produce eumelanin pigment with an unknown absolute structure (14,23).…”

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.

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172

168

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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.

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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.

Self Cite

172

168

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“…Besides the role in photoprotection, 1,3,4 melanogenesis itself has been investigated as a targeting strategy against melanoma growth. 5 Biosynthetically, eumelanins arise within organelles termed melanosomes by tyrosinase-catalyzed oxidation of tyrosine via oxidative polymerization of 5,6-dihydroxyindole (DHI), 5,6-dihydroxyindole-2-carboxylic acid (DHICA), and other biosynthetic intermediates (Scheme 1).…”

Section: ■ Introductionmentioning

confidence: 99%

Bottom-Up Approach to Eumelanin Photoprotection: Emission Dynamics in Parallel Sets of Water-Soluble 5,6-Dihydroxyindole-Based Model Systems

et al. 2012

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The molecular mechanisms by which the black eumelanin biopolymers exert their photoprotective action on human skin and eyes are still poorly understood, owing to critical insolubility and structural heterogeneity issues hindering direct investigation of excitation and emission behavior. Recently, we set up strategies to obtain watersoluble 5,6-dihydroxyindole (DHI)-based polymers as useful models for disentangling intrinsic photophysical properties of eumelanin components from aggregation and scattering effects. Herein, we report the absorption properties and ultrafast emission dynamics of two separate sets of DHI-based monomer−dimer−polymer systems which were made water-soluble by means of poly(vinyl alcohol) or by galactosyl-thio substitution. Data showed that dimerization and polymerization of DHI result in long-lived excited states with profoundly altered properties relative to the monomer and that glycosylation of DHI imparts monomer-like behavior to oligomers and polymers, due to steric effects hindering planar conformations and efficient interunit electron communication. The potential of S-glycation as an effective tool to probe and control emission characteristics of eumelanin-like polymers is disclosed.

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“…[1][2][3][4] Typically, melanins are categorized into two groups: eumelanin (black-brown, derived from 5,6-dihydroxy-indole, DHI; and 5,6-dihydroxy-indole-2-carboxylic acid, DHICA) and pheomelanin (red-yellow, derived from isomers of cysteinyl dopa). [5][6][7] Mixtures of these pigments are widely produced within melanosomes through in vivo melanogenesis, although some noted exceptions are the pure eumelanic melanosomes produced in black hair and the retinal pigment epithelium of the eye.…”

Section: Introductionmentioning

confidence: 99%

The Ultraviolet Absorption Coefficient of Melanosomes Decreases with Increasing Pheomelanin Content

Peles

Simon

2010

J. Phys. Chem. B

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Uveal melanosomes from the iridal stroma contain both eumelanin and pheomelanin, the ratio of which varies with iris color. Herein, we report the absorption coefficient at λ ) 244 nm for individual human iridal stroma melanosomes from dark brown and blue-green irides. The melanosomes are nearly identical in size, but differ in the relative concentration composition, ranging from a eumelanin/pheomelanin ratio of 14.8:1 (dark brown) to 1.3:1 (blue-green or hazel). The absorption coefficient of the melanosome decreases as its pheomelanin content increases. The origin of this decrease is attributed to a corresponding decrease in the number of UV-absorbing chromophores, reflecting the different molecular volumes of the monomeric building blocks of the two pigments. In agreement with reported data on synthetic pigments, the absorption coefficient of pheomelanin is found to be slightly larger than that for eumelanin at λ ) 244 nm (by a factor of 1.2). On the basis of the reported optical properties of synthetic models, this result suggests that the absorption of pheomelanin is less than eumelanin at wavelengths of biological relevance (∼315-400 nm).

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Current challenges in understanding melanogenesis: bridging chemistry, biological control, morphology, and function

Cited by 341 publications

References 142 publications

Direct chemical evidence for eumelanin pigment from the Jurassic period

Direct chemical evidence for eumelanin pigment from the Jurassic period

Bottom-Up Approach to Eumelanin Photoprotection: Emission Dynamics in Parallel Sets of Water-Soluble 5,6-Dihydroxyindole-Based Model Systems

The Ultraviolet Absorption Coefficient of Melanosomes Decreases with Increasing Pheomelanin Content

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