Self-assembly of melanin studied by laser light scattering

Bridelli, Maria Grazia

doi:10.1016/s0301-4622(98)00148-3

Cited by 48 publications

(54 citation statements)

References 21 publications

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“…The work presented here is the first demonstration that another member of the Vibrionaceae, S. algae BrY, also produces the pigment melanin, as determined through conventional chemical characterization for melanin and FTIR evaluation. In MW comparisons S. algae BrY melanin was similar to HGA melanin but not to DOPA melanin (3). In addition previous work demonstrated that HGA, but not DOPA, is excreted by S. algae BrY and melanin production by S. algae BrY is inhibited by sulcotrione, a specific inhibitor of the enzyme p-hydroxyphenylpyruvate dioxygenase, which produces HGA (39).…”

Section: Discussionmentioning

confidence: 78%

Melanin Production and Use as a Soluble Electron Shuttle for Fe(III) Oxide Reduction and as a Terminal Electron Acceptor byShewanella algaeBrY

Turick

Tisa

Caccavo

2002

Appl Environ Microbiol

205

199

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Dissimilatory metal-reducing bacteria (DMRB) utilize numerous compounds as terminal electron acceptors, including insoluble iron oxides. The mechanism(s) of insoluble-mineral reduction by DMRB is not well understood. Here we report that extracellular melanin is produced by Shewanella algae BrY. The extracted melanin served as the sole terminal electron acceptor. Upon reduction the reduced, soluble melanin reduced insoluble hydrous ferric oxide in the absence of bacteria, thus demonstrating that melanin produced by S. algae BrY is a soluble Fe(III)-reducing compound. In the presence of bacteria, melanin acted as an electron conduit to Fe(III) minerals and increased Fe(III) mineral reduction rates. Growth of S. algae BrY occurred in anaerobic minimal medium supplemented with melanin extracted from previously grown aerobic cultures of S. algae BrY. Melanin produced by S. algae BrY imparts increased versatility to this organism as a soluble Fe(III) reductant, an electron conduit for iron mineral reduction, and a sole terminal electron acceptor that supports growth.

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Section: Discussionmentioning

confidence: 78%

Melanin Production and Use as a Soluble Electron Shuttle for Fe(III) Oxide Reduction and as a Terminal Electron Acceptor byShewanella algaeBrY

Turick

Tisa

Caccavo

2002

Appl Environ Microbiol

205

199

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“…Consistent with the latest development in understanding the properties of such complex surfaces in topological quantum chemistry it would be interesting to see whether melanin nanogranules could also be subjected to topochemical studies (Bradlyn et al 2017; Fiete 2017) which might explain some interesting properties. Melanins fractal dimensions results clearly implying that assembly of melanin nanogranules may occur in fractal pattern (Bridelli 1998; Eom et al 2017). It has been known that melanin purification steps lead to dehydration thus making the polymer more aggregated and it results in loss of capacity for physiological interactions (Nicolaus 1968; Prota 1992).…”

Section: Discussionmentioning

confidence: 99%

Purification and characterisation of a sulphur rich melanin from edible mushroom Termitomyces albuminosus Heim

2018

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Production, purification and characterisation of a black pigment from Termitomyces albuminosus as melanin is reported, for the first time, from shaken submerged culture condition using scanning electron microscopy (SEM), elemental analysis, ultraviolet–visible (UV-VIS), and Fourier transformed infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR) and 13C (CP/MAS) NMR spectra. SEM results on T. albuminosus revealed nanogranular nature of melanin nanoparticles within size range of 400–100 nm with fractal dimension D = 1.195–1.73. Elemental analysis of melanin indicated 54.6% C, 3.5% H, 2.4% N, 26.9% O, and 12% S. UV-VIS and FTIR spectra confirmed to the characteristic of melanin and were identical to the reference commercial sepia melanin. Further validation of the identity of pigment as melanin was achieved by EPR analysis. Termitomyces albuminosus melanin is postulated to be DOPA-type melanin confirmed by 13C (CP/MAS) NMR spectral analysis showing chemical shift at 200–170 ppm carbonyl, 160–110 ppm aromatic region, and with high 40–30 ppm open chain aliphatic region. Chemical modification through oxidation and cysteinylation (Pheomelanin) is implied as indicated by relatively high sulphur content (12%).

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“…Melanocytes in the human epidermis (in vivo) or in cell cultures (in vitro) have been shown to be much more sensitive to the cytotoxicity of ROS than keratinocytes (17,27). This concept is especially well-documented by the cytotoxicity of hydrogen peroxide (H 2 O 2 ) to melanocytes both (in vivo) and (in vitro) (6,14,15,17). Consequently, melanocytes have evolved an effective strategy to deal with the removal of superoxide anion radicals (O 2 ª ) before these radical anions disproportionate to H 2 O 2 .…”

Section: Viewpointmentioning

confidence: 99%

“…It is known that melanins can form supermolecular aggregates that vary in size as a function of pH and ionic strength (16,17). Changes in aggregation state are often monitored through light scattering.…”

Section: Kowichi Jimbow Dept Of Dermatologymentioning

confidence: 99%

What's the use of generating melanin?

Wood¹,

Jimbow²,

Boissy³

et al. 1999

Experimental Dermatology

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The CONTROVERSIES featured in the August 1998 issue of Exp Dermatol have discussed the controls of melanogenesis (Schallreuter et al., Exp Dermatol 7: 143-150, 1998). Now, we explore the biological functions of the endproduct of melanogenesis, the various melanin biopolymers. As delineated in the subsequent contributions, melanins are func- Viewpoint 1Melanins are found in highly oxidizing situations where significant concentrations of oxygen radicals are generated. Such reactive oxygen species (ROS) are produced by UV-light in the skin and eye, by sound and ultrasound in the inner ear, and in the highly oxidizing conditions of catecholaminergic neurons in the brain. The role of the melanins as oxygen radical trapping polymers, UV-light filters, polymeric buffers for transition metals, calcium and catecholamines will be considered in this viewpoint. For the Dermatologist it is of special interest to understand those factors that control melanogenesis in the skin and hair (3). In this context the pterins, alpha melanocyte stimulating hormone (a-MSH) and calcium appear to be central in the regulation of both melanin content and composition in melanocytes. There is accumulating evidence that the evolution of melanogenesis in human melanocytes is primarily antioxidant in character and is designed to protect these pigment cells from the cytotoxicity of ROS. However, the subtle link between calcium homeostasis and melanogenesis suggests that natural skin colours in the human population may have evolved secondarily as a consequence of salt balance/dehydration fac-153 tionally much more complex and fascinating than their evident colour-awarding and UV-light-filtering properties suggest, and dermatologists and pigment biologists alike have yet to discover and define the full range of biologically relevant melanin functions in health and disease.tors as primates adapted to extreme differences in local climates. It is tempting to speculate that skin colour emerged as a side effect through Darwinian natural selection principles in tropical versus temperate climates.There is increasing evidence that melanogenesis represents a major antioxidant defence mechanism in melanocytes. Melanocytes in the human epidermis (in vivo) or in cell cultures (in vitro) have been shown to be much more sensitive to the cytotoxicity of ROS than keratinocytes (17, 27). This concept is especially well-documented by the cytotoxicity of hydrogen peroxide (H 2 O 2 ) to melanocytes both (in vivo) and (in vitro) (6,14,15,17). Consequently, melanocytes have evolved an effective strategy to deal with the removal of superoxide anion radicals (O 2 ª ) before these radical anions disproportionate to H 2 O 2 .The preferential utilization of O 2 ª compared to dioxygen (O 2 ) is quite a common event in the skin. The enzymes tyrosinase, proline hydroxylase and indoleamine 2,3 dioxygenase selectively utilize O 2 ª as the preferred substrate over O 2 for the formation of dopaquinone, hydroxyproline residues in collagen, and kynurenic acid respectively (2, 20, 21,...

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Self-assembly of melanin studied by laser light scattering

Cited by 48 publications

References 21 publications

Melanin Production and Use as a Soluble Electron Shuttle for Fe(III) Oxide Reduction and as a Terminal Electron Acceptor byShewanella algaeBrY

Melanin Production and Use as a Soluble Electron Shuttle for Fe(III) Oxide Reduction and as a Terminal Electron Acceptor byShewanella algaeBrY

Purification and characterisation of a sulphur rich melanin from edible mushroom Termitomyces albuminosus Heim

What's the use of generating melanin?

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