Addition Of Melanin Research Articles

The protective role and mechanism of melanin for Aspergillus niger and Aspergillus flavus against chlorine-based disinfectants

Melanin is a critical component of fungal cell wall which protect fungi from adverse environmental tress. However, the role of melanin for fungi during the disinfection with chlorine-based disinfectants has not been elucidated. The results showed that the inactivation rate constants of Aspergillus niger with chlorine and chlorine dioxide decreased from 0.08 to 2.10 min−1 to 0 after addition of 0.32 mg/L melanin. The results indicated addition of extracted fungal melanin inhibited the inactivation efficiency of chlorine and chlorine dioxide. In contrast, the k of Aspergillus niger after inactivation with monochloramine ranged from 1.50 to 1.78 min−1 after addition of melanin which indicated effect of melanin on the inactivation efficiency of monochloramine was negligible. In addition, the extracted fungal melanin exhibited high reactivity with chlorine and chlorine dioxide but very low reactivity with monochloramine. The different inactivation mechanisms of chlorine-based disinfectants and different reactivity of melanin with chlorine-based disinfectants led to the different protective mechanism of melanin for A. niger and A. flavus spores against disinfection with chlorine-based disinfectants. The chlorine and chlorine dioxide appeared to react with functional groups of melanin in cell wall of spores, so sacrificial reactions between melanin and disinfectants decreased the available disinfectants and limited the diffusion of disinfectants to the reactive site on cell membrane, which led to the decrease of the disinfection efficiency for chlorine and chlorine dioxide. The monochloramine could penetrate into cell and damage DNA without the effect of melanin due to its strong penetration and low reactivity with melanin. Our results systematically demonstrate the protective roles of melanin on the fungal spores against chlorine-based disinfectants and the underlying mechanisms in resisting the environmental stress caused by chlorine-based disinfectants, which provides important implications for the control of fungi, especially for fungi producing melanin.

New Poly(lactic acid) Active Packaging Composite Films Incorporated with Fungal Melanin.

In this work, fungal melanin was used for the first time to prepare poly(lactic acid)-based composites. The films of various melanin concentrations (0.025%, 0.05% and 0.2% w/w) were prepared using an extrusion method. The mechanical, antioxidant, antimicrobial, water vapor and UV-Vis barrier properties, as well as available polyphenolics on the surface, were studied. FT-IR and Raman spectroscopy studies were carried out to analyze the chemical composition of the resulting films. The hydrophobicity, color response, thermal, optical properties, and opacity values were also determined. The results of this study show that the addition of fungal melanin to poly(lactic acid) (PLA) as a modifier influenced mechanical and water vapor barrier properties depending on melanin concentration. In low concentration, melanin enhanced the mechanical and barrier properties of the modified films, but in larger amounts, the properties were decreased. The UV-Vis barrier properties of PLA/melanin composites were marginally improved. Differential Scanning Calorimetry (DSC) analysis indicated that crystallinity of PLA increased by the addition of melanin, but this did not affect the thermal stability of the films. Modified PLA/melanin films showed good antioxidant activity and were active against Enterococcus faecalis, Pseudomonas aeruginosa and Pseudomonas putida. The addition of melanin caused changes in color values, decreasing lightness and increasing the redness and yellowness of films. Based on the results of this study, fungal melanin has good potential to be exploited as a value-added modifier that can improve the overall properties of PLA.

Влияние традиции на право современного Китая

The article discusses some features of the modern legal system in China , formed under the direct influence of Chinese traditional concepts about the role of the Right and the Law in the society. The attention is focused on moral teachings of Confucius and the views of legalists, that had had a decisive influence on legal culture and legal consciousness of a Chinese citizen. Explores the attitude of Chinee to liability and punishment, the death penalty, specificity of the legal regulation of social relations in the Chinese state. Provides examples from the law enforcement practices and legislative activity, confirming the close relationship between the modern and the traditional law in China. The special place in researching is occupied by issues of crackdown legal liability against violators of legal regulations. Analyzes the most resonance criminal cases in relation of those people, who sentenced to death , have committed crimes in the field of illicit drug trafficking , driving while intoxicated, resulted the death of two or more persons, verdicts to the supreme penalty of persons involved in the addition of melanin in infant formulas. The influence of tradition, customs and moral principles on modern legislative activities of Chinese legislator is confirmed by other examples through the prism of the modern and the traditional law in China. The author calls for to pay more attention to tradition while analyzing the current legislation of China. The modern law of China is closely connected with traditional Chinese concepts about place and role of the Law in society.

Morphological Effects of G-Quadruplex Stabilization Using a Small Molecule in Zebrafish

Zebrafish (Danio rerio) embryos are transparent and advantageous for studying early developmental changes due to ex utero development, making them an appropriate model for studying gene expression changes as a result of molecular targeting. Zebrafish embryos were injected with a previously reported G-quadruplex selective ligand, and the phenotypic changes were recorded. We report marked discrepancies in the development of intersegmental vessels. In silico analysis determined that the putative G-quadruplex motif occur in the upstream promoter region of the Cdh5 (N-cadherin) gene. A real-time polymerase chain reaction-based investigation indicated that in zebrafish, CDH-2 (ZN-cad) was significantly downregulated in the ligand-treated embryos. Biophysical characterization of the interaction of the ligand with the G-quadruplex motif found in this promoter yielded strong binding and stabilization of the G-quadruplex with this ligand. Hence, we report for the first time the phenotypic impact of G-quadruplex targeting with a ligand in a vertebrate organism. This study has unveiled not only G-quadruplex targeting in non-human animal species but also the potential that G-quadruplexes can provide a ready tool for understanding the phenotypic effects of targeting certain important genes involved in differentiation and developmental processes in a living eukaryotic organism.

Effect of melanin on netilmicin-induced inhibition of collagen biosynthesis in human skin fibroblasts

It is known that various drugs form complexes with melanins and that melanins are abundant constituents of the inner ear. In this study, we determined whether the aminoglycoside antibiotic, netilmicin, interacts with melanin and how this process affects collagen biosynthesis in cultured human skin fibroblasts. The obtained results indicate that netilmicin forms stable complexes with melanin characterized by the association constants K 1 ∼ 10 6 M −1 and K 2 ∼ 10 3 M −1. We have suggested that prolidase, an enzyme involved in collagen metabolism, may be one of the targets for aminoglycoside-induced inhibition of collagen biosynthesis. We found that netilmicin strongly induced inhibition of prolidase activity (IC 50 < 5 μM) and collagen biosynthesis (IC 50 ∼ 10 μM). At 10 μM concentration of netilmicin, prolidase activity in human skin fibroblasts was inhibited by about 80% and DNA biosynthesis—only by about 25%. Melanin at 100 μg/mL produced about 30% inhibition of collagen biosynthesis and about 30% inhibition of prolidase activity in cultured fibroblasts. However, the addition of melanin (100 μg/mL) to netilmicin-treated cells (10 μM) restored the prolidase activity in fibroblasts to almost 100% of control values and partially reversed the inhibitory action of the drug on collagen and DNA biosynthesis. The data suggest that the ability of netilmicin to form stable complexes with melanin may prevent its toxicity on prolidase activity and collagen biosynthesis.

Melanin counter act puromycin-induced inhibition of collagen and DNA biosynthesis in human skin fibroblasts

Puromycin is an experimental anti-tumor antibiotic acting through inhibition of protein synthesis. Because of its untoward side effects (as inner ear and renal lesions) the antibiotic was not approved for clinical trials. The mechanism underlying the organ specificity of the side effect is not understood. In view of the fact that a number of drugs form with melanin complexes that affect their pharmacological activity, we determined whether puromycin interacts with melanin and how this process affects biosynthesis of collagen in cultured human skin fibroblasts. Our results indicate that puromycin forms complexes with melanin. The amount of puromycin bound to melanin increases with increase of initial drug concentration. The Scatchard plot analysis of the drug binding to melanin has shown that at least two classes of independent binding sites are implicated in the puromycin-melanin complex formation: one class of strong binding sites with the association constant K 1 = 1.84 × 10 6 M −1, and the second class of weak binding sites with the association constant K 2 = 5.26 × 10 3 M −1. The number of total binding sites were n 1 = 0.1260 and n 2 = 0.2861 μmol puromycin per 1 mg melanin. We found that puromycin induced inhibition of collagen and DNA biosynthesis (IC 50 ∼ 2 μM). Melanin at 100 μg/ml produced about 20% inhibition of DNA synthesis, but it had no effect on collagen biosynthesis in cultured fibroblasts. However, the addition of melanin (100 μg/ml) to puromycin - treated cells (2 μM) abolished the inhibitory action of puromycin on collagen and DNA biosynthesis. We have suggested that IGF-I receptor expression, involved in collagen metabolism, may be one of the targets for puromycin - induced inhibition of collagen biosynthesis. It was found that melanin abolished puromycin induced decrease in the expression of IGF-I receptor as well MAP kinases expression: ERK1 and ERK2 as shown by Western immunoblot analysis. These data suggest that tissue specific pharmacological activity of puromycin may depend on the melanin abundance in tissues.

Electron transfer from Shewanella algae BrY to hydrous ferric oxide is mediated by cell-associated melanin

Shewanella algae BrY uses insoluble mineral oxides as terminal electron acceptors, but the mechanism of electron transfer from cell surface to mineral surface is not well understood. We tested the hypothesis that cell-associated melanin produced by S. algae BrY serves as an electron conduit for bacterial–mineral reduction. Results from Fourier transform infrared spectroscopy and cell surface hydrophobicity assays indicated that extracellular melanin was associated with the cell surface. With H 2 as electron donor, washed cell suspensions of melanin-coated S. algae BrY reduced hydrous ferric oxide (HFO) 10 times faster than cells without melanin. The addition of melanin (20 μg ml −1) to these melanin-free cells increased their HFO reduction rate two-fold. These results suggest that cell-associated melanin acts as an electron conduit for iron mineral reduction by S. algae BrY.

Melanin potentiates gentamicin-induced inhibition of collagen biosynthesis in human skin fibroblasts

One of the recognized side effects of gentamicin is ototoxicity. The mechanism underlying the organ specificity of this side effect of gentamicin has not been fully established. In view of the fact that a number of pharmacologic agents are known to form complexes with melanin and melanin is an abundant constituent of the inner ear tissues, we determined whether gentamicin interacts with melanin and how this process affects the biosynthesis of collagen in cultured human skin fibroblasts. Our results indicate that gentamicin forms complexes with melanin. The amount of gentamicin bound to melanin increases with increasing of initial drug concentration. The Scatchard plot analysis of drug binding to melanin showed that at least two classes of independent binding sites are implicated in gentamicin–melanin complex formation: one class with an association constant K 1∼4×10 3 M −1, and the second class with an association constant K 2∼3×10 2 M −1. The number of total binding sites ( n 1+ n 2) was calculated as about 1.36 μmol gentamicin per 1 mg melanin. We have suggested that prolidase, an enzyme involved in collagen metabolism, may be one of the targets for gentamicin-induced inhibition of collagen biosynthesis. We found that gentamicin-induced inhibition of prolidase activity (IC 50∼100 μM) and collagen biosynthesis (IC 50∼100 μM). At this concentration of gentamicin, DNA biosynthesis in human skin fibroblasts was inhibited only by about 30%. Melanin at 100 μg/ml produced about 25% inhibition of DNA synthesis and about 30% inhibition of prolidase activity, but it had no effect on collagen biosynthesis in cultured fibroblasts. However, the addition of melanin (100 μg/ml) to gentamicin-treated cells (100 μM) augmented the inhibitory action of gentamicin on collagen and DNA biosynthesis and partially reversed its inhibitory effect on prolidase activity. A melanin-induced augmentation of the inhibitory effects of gentamicin on collagen and DNA biosynthesis may explain the mechanism for the organ specificity of gentamicin-induced hearing loss in patients administered this drug.

Melanin potentiates daunorubicin-induced inhibition of collagen biosynthesis in human skin fibroblasts

One of the recognized side effects of antineoplastic anthracyclines is poor wound healing, resulting from an impairment of collagen biosynthesis. The most affected tissue is skin. The mechanism underlying the tissue specificity of the side effects of anthracyclines has not been established. In view of the fact that a number of pharmacologic agents are known to form complexes with melanin and melanins are abundant constituents of the skin, we determined whether daunorubicin interacts with melanin and how this process affects collagen biosynthesis in cultured human skin fibroblasts. Results indicated that daunorubicin forms complexes with melanin. Scatchard analysis showed that the binding of daunorubicin to melanin was heterogeneous, suggesting the presence of two classes of independent binding sites with K 1=1.83×10 5 M −1 and K 2=5.52×10 3 M −1. The number of strong binding sites was calculated as n 1=0.158 μmol/mg of melanin and the number of weak binding sites as n 2=0.255 μmol/mg of melanin. We have suggested that prolidase, an enzyme involved in collagen metabolism, may be one of the targets for anthracycline-induced inhibition of collagen synthesis. We found that daunorubicin induced inhibition of prolidase activity (IC 50=10 μM), collagen biosynthesis (IC 50=70 μM) and DNA biosynthesis (IC 50=10 μM) in human skin fibroblasts. Melanin (100 μg/ml) by itself produced about 25% inhibition of DNA synthesis and prolidase activity but it had no effect on collagen biosynthesis in cultured fibroblasts. However, the addition of melanin (100 μg/ml) to daunorubicin-treated cells (at IC 50 concentration) augmented the inhibitory action of daunorubicin on collagen and DNA biosynthesis without having any effect on prolidase activity. The same effect was achieved when the cells were treated with daunorubicin at one-fourth of the IC 50 given at 0, 6, 12 and 18 h during a 24-h incubation. The data suggest that the melanin-induced augmentation of the inhibitory effects of daunorubicin on collagen and DNA biosynthesis may result from: (i) accumulation of the drug in the extracellular matrix, (ii) gradual dissociation of the complex, and (iii) constant action of the released drug on cell metabolism. The phenomenon may explain the potential mechanism for the organ specificity of daunorubicin-induced poor wound healing in patients administered this drug.

A melanin pigment purified from an epidemic strain of Burkholderia cepacia attenuates monocyte respiratory burst activity by scavenging superoxide anion.

The acquisition of Burkholderia cepacia in some cystic fibrosis patients is associated with symptoms of acute pulmonary inflammation that may be life threatening. The ability of lipopolysaccharide (LPS) from B. cepacia to prime a monocyte cell line for enhanced superoxide anion generation was investigated and compared with the priming activities of LPSs from Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Escherichia coli. The human monocyte cell line MonoMac-6 (MM6) was primed overnight with different LPSs (100 ng/ml), and the respiratory burst was triggered by exposure to opsonized zymosan (125 micrograms/ml). Superoxide generation was detected by enhanced chemiluminescence with Lucigenin. B. cepacia LPS was found to prime MM6 cells to produce more superoxide anion than P. aeruginosa or S. maltophilia LPS, and this priming response was CD14 dependent. In addition, the inhibition of respiratory burst responses in monocytes by a bacterial melanin-like pigment purified from an epidemic B. cepacia strain was investigated. The melanin-like pigment was isolated from tyrosine-enriched media on which B. cepacia had been grown and was purified by gel filtration, anion ion-exchange chromatography, and ethanol precipitation. The scavenging potential of the melanin-like pigment for superoxide anion radical (*O2-) generated during the respiratory burst was confirmed with superoxide produced from a cell-free system with xanthine-xanthine oxidase and detected by electron paramagnetic resonance spectroscopy with the spin trap 5-diethoxyphosphoryl-5-methyl-1-pyrroline-n-oxide. The addition of melanin during the LPS priming stage had no effect on the subsequent triggering of the respiratory burst, but melanin inhibited *O2- detection when added at the triggering stage of the respiratory burst. We conclude that melanin-producing B. cepacia may derive protection from the free-radical-scavenging properties of this pigment.