Search results for "melanin."
showing 10 items of 68 documents
Etude des mécanismes physiologiques et moléculaires permettant la prise en charge des substrats hydrophobes par la levure Yarrowia lipolytica au nive…
2012
Yarrowia lipolytica can grow on many hydrophobic substrates and metabolize them via the β-oxidation pathway or store them into lipid bodies. The first contact between the cell and the hydrophobic substrates is by the cell wall. In this step, cell-wall proteins (CWP), β-glucane and chitin of the cell wall could play an important role for the adhesion and uptake of hydrophobic substrates. The aim of this work was to study the effect of a hydrophobic carbon source (compared with glucose) and the culture medium composition on the cell wall composition and the melanin production by Y. lipolytica. The results of our biochemical and molecular analysis showed that the presence of methyl oleate and …
Melanin-based colour polymorphism signals aggressive personality in nest and territory defence in the tawny owl (Strix aluco)
2013
Nest and territory defence are risky and potentially dangerous behaviours. If the resolution of life history trade-offs differs between individuals, the level of defence may also vary among individuals. Because melanin-based colour traits can be associated with life history strategies, differently coloured individuals may display different nest and territory defence strategies. We investigated this issue in the colour polymorphic tawny owl (Strix aluco) for which plumage varies from dark to light reddish melanic. Accordingly, we found that (1) our presence induced a greater response (flying around) from dark-coloured than light-coloured females and (2) dark reddish males suffered lower nest…
The nature of black stains in Lascaux Cave, France, as revealed by surface-enhanced Raman spectroscopy
2012
We used surface-enhanced Raman spectroscopy to investigate the chemical composition of the black stains threatening the rock-art paintings of Lascaux Cave, Montignac, France. The stains are mainly composed of melanin from the fungus Ochroconis sp. and the faecal pellets of the collembolan Folsomia candida. Surface-enhanced Raman spectroscopy is a useful technique for revealing the structure of unknown macromolecules in cultural heritage research. Copyright © 2011 John Wiley & Sons, Ltd. The chemical composition of the black stains threatening the rock-art paintings of Lascaux Cave, Montignac, France was studied using surface-enhanced Raman spectroscopy (SERS). The stains are mainly composed…
Multispectral autoflourescence detection of skin neoplasia using steady-state techniques
2019
In the current study were used excitation-emission matrices (EEMs) and synchronous fluorescence spectroscopy (SFS) steady-state techniques in a broad spectral regions (excitation at 220-500 nm and emission at 280-850 nm) to achieve the whole set of endogenous fluorophores, existed in normal and neoplastic cutaneous tissues. Several types of benign, dysplastic and malignant types of skin lesions were investigated ex vivo using both EEM and SFS modalities, namely the basal cell papilloma and carcinoma, pigmented nevi, dysplastic nevi, squamous cell carcinoma and malignant melanoma. Histological analysis was used as a “gold standard” for evaluation of clinical diagnosis of the lesions investig…
Copper Proteins with Dinuclear Active SitesBased in part on the article Copper Proteins with Dinuclear Active Sites by Konrad Lerch which appeared in…
2006
Copper proteins with dinuclear active sites comprise proteins with different structures and functions. The phenoloxidase, tyrosinase, and catecholoxidase are responsible for browning by starting the synthesis of melanin. These enzymes are involved in the primary immune response in invertebrates, plants, fungi as well as in the sclerotization of arthropods. The respiratory proteins hemocyanins are responsible for oxygen transport in some arthropods and molluscs. However, they can be converted to enzymes exhibiting phenoloxidase activity. Based on X-ray structures of hemocyanins and a catecholoxidase, large parts of folding motifs are very similar although the sequence identities are far belo…
A three-dimensional model of mammalian tyrosinase active site accounting for loss of function mutations
2007
Tyrosinases are the first and rate-limiting enzymes in the synthesis of melanin pigments responsible for colouring hair, skin and eyes. Mutation of tyrosinases often decreases melanin production resulting in albinism, but the effects are not always understood at the molecular level. Homology modelling of mouse tyrosinase based on recently published crystal structures of non-mammalian tyrosinases provides an active site model accounting for loss-of-function mutations. According to the model, the copper-binding histidines are located in a helix bundle comprising four densely packed helices. A loop containing residues M374, S375 and V377 connects the CuA and CuB centres, with the peptide oxyge…
Multispectral fluorescence detection of pigmented cutaneous tumours
2020
We investigated pigmented skin tumour lesions in vivo and ex vivo, including benign and dysplastic nevi, as well as malignant lesions, such as pigmented basal cell carcinoma (BCC) and malignant melanoma (MM) lesions, to obtain a complex view about the feasibility of different excitation sources solely and/or in combination to induce fluorescence signal useful for diagnosis of various low-fluorescent cutaneous neoplasia. A specialized multispectral analysis of the data obtained was applied by using excitation in broad spectral range, covering ultraviolet, visible and near-infrared spectral range, that contribute considerably to: (1) fundamental determination of tumour tissues’ spectral prope…
Eumelanin Coating of Silica Aerogel by Supercritical Carbon Dioxide Deposition of a 5,6-Dihydroxyindole Thin Film
2018
Eumelanin integration in silica aerogel (SA) was achieved via supercritical adsorption of 5,6-dyhydroxyindole (DHI) from CO2. Notably, after the supercritical treatment, DHI evolved towards spontaneous polymerization, which resulted in uniform pigment development over the SA. The new material was characterized for its morphological and physicochemical properties, disclosing the formation of a eumelanin-like coating, as confirmed by UV&ndash
Spotlight on fundus autofluorescence
2018
Ana M Calvo-Maroto,1 Alejandro Cerviño2 1Department of Ophthalmology, Clínica Universidad de Navarra, University of Navarra, Madrid, Spain; 2Optometry Research Group, Department of Optics and Optometry and Vision Sciences, University of Valencia, Valencia, Spain Abstract: Fundus autofluorescence (FAF) imaging is based on the fluorescence from ocular endogenous fluorophores located in the retinal pigment epithelium and choroid, mainly lipofuscin and melanin. It is a noninvasive technique that provides information about the spatial distribution of lipofuscin/melanin and retinal pigment epithelium health status. An overview about the fluorophores responsible for FAF imaging and t…
Melanin type and concentration determination using inverse model
2011
Abnormality of melanin production causes skin pigmentation disorders. Currently, assessment of treatment efficacy (under Physician's Global Assessment framework) only refers to visual conditions of skin surface and not the condition of the underlying skin layers and pigments. Albeit researches on models and simulations of light interaction with human skin have been reported, none has been specifically developed for pigmentation analysis of melanin types - eumelanin and pheomelanin. Therefore, our research objectives are to develop image analysis of skin pigmentation for classification and quantification of eumelanin and pheomelanin pigment types in human skin. In this research, the model is…