Theoretical analysis of the adsorption of metal ions to the surface of melanin particles

Bridelli, Maria Grazia; Crippa, P.R.

doi:10.1007/s10450-007-9059-8

Cited by 29 publications

(32 citation statements)

References 35 publications

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“…Fitting the data to several different models Bridelli and Crippa found the affinity order Zn 2+ < Cd 2+ < Cu 2+ [38], which is the same order as observed here. In their study with bovine eye melanin and synthetic eumelanin (produced by the L-dopa/tyrosinase method) Potts and Au found that Zn 2+ had lower binding efficiency than Pb 2+ and Cu 2+ , which had had similar binding efficiency (Cd 2+ was not tested) [36].…”

Section: Resultssupporting

confidence: 81%

“…The Langmuir affinity constants (Table 1) for the hair-extract- and synthetic-coated discs are within the range of values of affinity constants (10 3 to 10 7 M −1 ) obtained by a variety of methods for different metal ions with synthetic and natural melanin samples [7, 38]. Earlier reports have suggested that natural and synthetic eumelanin samples have a high affinity for Pb 2+ compared to other metal ions [35, 36], but affinity constants were not established in these studies, and until recently [18], current studies have generally not included lead.…”

Section: Resultsmentioning

confidence: 82%

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Melanin-Based Coatings as Lead-Binding Agents

Sono

Lye

Moore

et al. 2012

Bioinorganic Chemistry and Applications

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Interactions between metal ions and different forms of melanin play significant roles in melanin biochemistry. The binding properties of natural melanin and related synthetic materials can be exploited for nonbiological applications, potentially including water purification. A method for investigating metal ion-melanin interactions on solid support is described, with lead as the initial target. 2.5 cm discs of the hydrophobic polymer PVDF were coated with synthetic eumelanin from the tyrosinase-catalyzed polymerization of L-dopa, and with melanin extracted from human hair. Lead (Pb2+) binding was quantified by atomic absorption spectroscopy (flame mode), and the data was well fit by the Langmuir model. Langmuir affinities ranged from 3.4 · 103 to 2.2 · 104 M−1. At the maximum capacity observed, the synthetic eumelanin coating bound ~9% of its mass in lead. Binding of copper (Cu2+), zinc (Zn2+), and cadmium (Cd2+) to the synthetic-eumelanin-coated discs was also investigated. Under the conditions tested, the Langmuir affinities for Zn2+, Cd2+, and Cu2+ were 35%, 53%, and 77%, respectively, of the Langmuir affinity for Pb2+. The synthetic-eumelanin-coated discs have a slightly higher capacity for Cu2+ on a per mole basis than for Pb2+, and lower capacities for Cd2+ and Zn2+. The system described can be used to address biological questions and potentially be applied toward melanin-based water purification.

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Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 82%

Melanin-Based Coatings as Lead-Binding Agents

Sono

Lye

Moore

et al. 2012

Bioinorganic Chemistry and Applications

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“…darker individuals may suffer less in these habitats), both through direct and indirect effects of melanogenesis. First, melanin is composed of negatively charged free carboxyl, hydroxyl and amine functions known to bind metal ions in vitro (Larsson & Tj€ alve, 1978;Liu et al, 2004;Bridelli & Crippa, 2007). For this reason, metal chelation is suggested as one of the main biological functions of melanin (McGraw, 2003;Hong & Simon, 2007;Chatelain et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Do trace metals select for darker birds in urban areas? An experimental exposure to lead and zinc

Chatelain

Gasparini

Frantz

2016

Global Change Biology

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Trace metals from anthropogenic activities are involved in numerous health impairments and may therefore select for detoxification mechanisms or a higher tolerance. Melanin, responsible for the black and red colourations of teguments, plays a role in metal ion chelation and its synthesis is positively linked to immunity, antioxidant capacity and stress resistance due to pleiotropic effects. Therefore, we expected darker birds to (1) store higher amounts of metals in their feathers, (2) maintain lower metal concentrations in blood and (3) suffer less from metal exposure. We exposed feral pigeons (Columba livia) exhibiting various plumage darkness levels to low, but chronic, concentrations of zinc and/or lead, two of the most abundant metals in urban areas. First, we found negative and positive effects of lead and zinc, respectively, on birds' condition and reproductive parameters. Then, we observed positive relationships between plumage darkness and both zinc and lead concentrations in feathers. Interestingly, though darker adults did not maintain lower metal concentrations in blood and did not have higher fitness parameters, darker juveniles exhibited a higher survival rate than paler ones when exposed to lead. Our results show that melanin-based plumage colouration does modulate lead effects on birds' fitness parameters but that the relationship between metals, melanin, and fitness is more complex than expected and thus stress the need for more studies.

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“…Because the property of melanin to bind metal ions may allow some body detoxification, we hypothesized that more melanic plumage may be selected in urban environments. Indeed, melanin is composed of several polymers with negatively charged free carboxyl, hydroxyl and amine functions which bind metal ions in vitro [14][15][16] explaining the relation found between some metals and melanic pigmentation [17]. Therefore, highly melanic birds could transfer more metals to their growing feathers during moult, thereby detoxifying their blood at a higher rate in comparison with less melanic individuals.…”

Section: Introductionmentioning

confidence: 99%

The adaptive function of melanin-based plumage coloration to trace metals

et al. 2014

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Trace metals produced by anthropogenic activities are of major importance in urban areas and might constitute a new evolutionary force selecting for the ability to cope with their deleterious effects. Interestingly, melanin pigments are known to bind metal ions, thereby potentially sequestering them in inert body parts such as coat and feathers, and facilitating body detoxification. Thus, a more melanic plumage or coat coloration could bring a selective advantage for animals living in polluted areas. We tested this hypothesis by investigating the link between melanin-based coloration and zinc and lead concentrations in feathers of urban feral pigeons, both at capture time and after one year of captivity in standardized conditions. Results show that differently coloured pigeons had similar metal concentrations at capture time. Metal concentrations strongly decreased after one year in standardized conditions, and more melanic pigeons had higher concentrations of zinc (but not lead) in their feathers. This suggests that more melanic pigeons have a higher ability to store some metals in their feathers compared with their paler counterparts, which could explain their higher success in urbanized areas. Overall, this work suggests that trace metal pollution may exert new selective forces favouring more melanic phenotypes in polluted environments.

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Theoretical analysis of the adsorption of metal ions to the surface of melanin particles

Cited by 29 publications

References 35 publications

Melanin-Based Coatings as Lead-Binding Agents

Melanin-Based Coatings as Lead-Binding Agents

Do trace metals select for darker birds in urban areas? An experimental exposure to lead and zinc

The adaptive function of melanin-based plumage coloration to trace metals

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