Mechanistic insights into the bleaching of melanin by alkaline hydrogen peroxide

Smith, Rachel K.; Garrett, B. S.; Naqvi, K.R.; Fülöp, A.; Godfrey, S.; Marsh, Jennifer; Chechik, Victor

doi:10.1016/j.freeradbiomed.2017.03.014

Cited by 38 publications

(24 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The only treatment known to degrade melanosomes in a laboratory context is oxidation in a highly alkaline solution, which ruptures the melanosomal membrane and solubilizes melanin (Smith et al . ). Feather samples were oxidized using a modified version of the AHPO protocol described in Ito et al .…”

Section: Methodsmentioning

confidence: 97%

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

et al. 2019

View full text Add to dashboard Cite

Fossils are a key source of data on the evolution of feather structure and function through deep time, but their ability to resolve macroevolutionary questions is compromised by an incomplete understanding of their taphonomy. Critically, the relative preservation potential of two key feather components, melanosomes and keratinous tissue, is not fully resolved. Recent studies suggesting that melanosomes are preferentially preserved conflict with observations that melanosomes preserve in fossil feathers as external moulds in an organic matrix. To date, there is no model to explain the latter mode of melanosome preservation. We addressed these issues by degrading feathers in systematic taphonomic experiments incorporating decay, maturation and oxidation in isolation and combination. Our results reveal that the production of mouldic melanosomes requires interactions with an oxidant and is most likely to occur prior to substantial maturation. This constrains the taphonomic conditions under which melanosomes are likely to be fossilized. Critically, our experiments also confirm that keratinous feather structures have a higher preservation potential than melanosomes under a range of diagenetic conditions, supporting hitherto controversial hypotheses that fossil feathers can retain degraded keratinous structures.

show abstract

Section: Methodsmentioning

confidence: 97%

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

et al. 2019

View full text Add to dashboard Cite

show abstract

“…9 Eumelanin is composed of tyrosine derivatives, mostly dihydroxyindole (DHI) and dihydroxyindole carboxylic acid monomers (DHICA), in pheomelanin cysteine residues are included forming benzothiazine units. Studies on melanin degradation products [10][11][12][13][14] showed that 1H-pyrrole-2,3,5-tricarboxylic acid (PTCA, c.f. inserted structural formula in Figure 1) 15,16 is the main product of eumelanin oxidation, whereas aminohydroxphenylalanine isomers (AHP) are degradation products of pheomelanin.…”

Section: Introductionmentioning

confidence: 99%

PTCA (1H‐pyrrole‐2,3,5‐tricarboxylic acid) as a marker for oxidative hair treatment

Petzel‐Witt

Meier

Schubert‐Zsilavecz

et al. 2017

Drug Testing and Analysis

View full text Add to dashboard Cite

Hair analysis for the assessment of alcohol or drug abstinence has become a routine procedure in forensic toxicology. Hair coloration leading to loss of incorporated xenobiotics and to false negative results has turned out to be a major problem. Currently only colored extracts provide hints of manipulations but not bleaching. A liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method was developed and validated to determine 1H-pyrrole-2,3,5-tricarboxylic acid (PTCA), a major oxidation product of melanin. PTCA was determined in natural hair samples (n = 21) after treatment with 3% hydrogen peroxide (H O ) for 30 or 40 minutes with concentrations up to 12% for 40 minutes. In another series, 12 natural hair samples were submitted to different coloration procedures (henna, tinting, semi-permanent and permanent dyeing, bleaching) and the changes in PTCA content were determined. A significant increase in the PTCA content was found for both incubation times and increasing H O concentrations. Coloration with henna or tinting had no influence on PTCA levels detected, but a significant increase was observed after semi-permanent and permanent dyeing and bleaching. As PTCA concentrations in natural hair were found to be in a range of <2.1-16.4 ng/mg (8.4 ± 3.8 ng/mg, mean ± SD, n = 33), a cut-off of 20 ng/mg is recommended for the distinction between natural vs. excessively oxidized hair. In case of naturally low melanin content (light-blond or white hair), no marked increase in PTCA may occur. The present study demonstrated that PTCA is formed during oxidative treatment of melanin in hair, which can be used to detect previous hair coloration including oxidation.

show abstract

“…Both peaks may result from the overlap of the absorption of collections of oligomers . A further contribution to the peak at 320 nm could be ascribed to the polypyrroles resulting from the peroxidation of eumelanin during MFA treatment …”

Section: Resultsmentioning

confidence: 99%

Eumelanin for nature‐inspired UV‐absorption enhancement of plastics

Mauro

Camaggi

Vandooren

et al. 2019

Polymer International

View full text Add to dashboard Cite

In the human body, the black‐brown biopigment eumelanin blocks harmful ultraviolet (UV) radiation. In the plastics industry, additives are often added to polymers to increase their UV‐absorption properties. We herein report an assessment of the biopigment eumelanin as a nature‐inspired additive for plastics to enhance their UV absorption. Since eumelanin is produced by natural sources and is nontoxic, it is an interesting candidate in the field of sustainable plastic additives. In this work, the eumelanin‐containing films of commercial ethylene–vinyl acetate copolymer, a plastic used for packaging applications, were obtained by melt compounding and compression molding. The biopigment dispersion in the films was improved by means of the melanin free acid treatment. It was observed that eumelanin amounts as low as 0.8 wt% caused an increase of the UV absorption, up to one order of magnitude in the UVA range. We also evaluated the effect of eumelanin on the thermal stability and photostability of the films: the biopigment proved to be double‐edged, working both as UV‐absorption enhancer and photo‐prooxidant, as thermogravimetric analysis and infrared spectroscopy revealed. © 2019 Society of Chemical Industry

show abstract

Mechanistic insights into the bleaching of melanin by alkaline hydrogen peroxide

Cited by 38 publications

References 26 publications

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

PTCA (1H‐pyrrole‐2,3,5‐tricarboxylic acid) as a marker for oxidative hair treatment

Eumelanin for nature‐inspired UV‐absorption enhancement of plastics

Contact Info

Product

Resources

About