Studies related to the chemistry of melanins. Part X. Quantitative assessment of different types of units present in dopa-melanin

Swan, G. A.; Waggott, A.

doi:10.1039/j39700001409

Cited by 37 publications

(22 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Degradation of uncycled moieties cannot be excluded considering the fact that the decomposition of tyrosine has been reported between 250–400 °C . The last phenomenon, starting at 731 ± 46 °C and not completed at 1000 °C, may be tentatively associated with the rupture of covalent bonds, the decomposition of indole and pyrrole rings, possibly accompanied by the evolution of CO 2 and NH 3 …”

Section: Resultsmentioning

confidence: 99%

Novel insights on the physicochemical properties of eumelanins and their DMSO derivatives

Albano

Mauro

Kumar

et al. 2016

Polymer International

View full text Add to dashboard Cite

The biopigment eumelanin, ubiquitous in flora and fauna, is made up of chemically heterogeneous macromolecules based on the 5,6‐dihydroxyindole and 5,6‐dihydroxyindole‐2‐carboxylic acid building blocks. The exciting possibility of designing eumelanin‐based technologies for bioelectronics and sustainable electronics has to be properly assessed by gaining insights on the charge transfer and charge carrier transport in the pigment, preferably in film form, easily amenable to devices. In this work, we report a study on the electrochemical behaviour of films of eumelanin and its derivatives synthesized in dimethyl sulfoxide (DMSO eumelanins) in different aqueous electrolytes, with different chemical compositions and pH. DMSO eumelanins feature an improved solubility in the solvent DMSO, of relevance for processing purposes. The voltammetric currents are higher at relatively low pH (5.5), as expected considering the well‐established proton transport properties of the biopigment. Raman spectroscopy and atomic force microscopy performed on eumelanin films were combined with thermogravimetry with the aim of advancing knowledge on the molecular and supramolecular features of synthetic commercially available eumelanin, DMSO eumelanins as well as natural eumelanin (Sepia melanin). The results collected permit unprecedented insights on the physicochemical properties of eumelanin. © 2016 Society of Chemical Industry

show abstract

Section: Resultsmentioning

confidence: 99%

Novel insights on the physicochemical properties of eumelanins and their DMSO derivatives

Albano

Mauro

Kumar

et al. 2016

Polymer International

View full text Add to dashboard Cite

show abstract

“…Thus, it is considered that the dopaminergic neurotoxicity of HPP + is responsible for events that occur after HPP + passes into the cells. In the mammalian brain, it has been reported that neuromelanin derived from the auto-oxidation of dopa is abundant in dopaminergic neurons, and that some aromatic organic cations form a complex with melanin (Swan and Waggott, 1970;Prota, 1980 investigated. Scatchard analysis indicated that HPP + could interact with synthetic melanin at two binding sites: a high affinity site (K d1~2 0 nM) and a low affinity site (K d2~4 .0 µM) (FIG.…”

Section: Discussionmentioning

confidence: 99%

Binding of 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]pyridinium ion (HPP+), a metabolite of haloperidol, to synthetic melanin: Implications for the dopaminergic neurotoxicity of HPP+

et al. 2004

View full text Add to dashboard Cite

The toxicity of 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]pyridinium ion (HPP+), a metabolite of haloperidol, toward dopaminergic neurons was investigated. When HPP+ (approximately 100 microM) was added to primary cultures prepared from rat embryonic mesencephalon for 1 h, the survivability of dopaminergic neurons decreased significantly, and this effect was not inhibited by the dopamine transporter (DAT) inhibitor GBR 12909. In addition, HPP+ bound to neuromelanin, which is abundant in dopaminergic neurons. A binding analysis using the Scatchard method showed that there are two classes of binding sites: high affinity sites with a dissociation constant K(d1) of 20.2 nM, and low affinity sites with a K(d2) of 4.0 microM. HPP+ was released easily from synthetic melanin using phosphate buffer (pH 7.0), suggesting that this binding is reversible. The results suggest that the toxicity of HPP+ in dopaminergic neurons is due not to DAT-mediated uptake, but to the binding to neuromelanin.

show abstract

“…Chemically modified melanins were prepared by treatment of melanin samples with methanol saturated with gaseous HC1 or with an excess of diazomethane [13]. Methylation of melanin with methanol-HCl resulted in the esterification of carboxy acid groups, whereas the treatment with diazomethane involved the methylation of carboxy and hydroxy groups as well as the indole and pyrrole NH groups of melanin.…”

Section: Y Thamd Anal $~ 1990mentioning

confidence: 99%

Thermogravimetry and differential scanning calorimetry of natural and synthetic melanins

Simonović

Vučelić

Hadzi-Pavlovic

et al. 1990

Journal of Thermal Analysis

View full text Add to dashboard Cite

The thermal stability of natural melanins from bovine eyes, black human hair and the hard core of banana peel, synthetic melanins obtained enzymatically or by autoxidation of various precursors, and chemically modified synthetic mclanins was studied by DSC and TG analysis. It was shown that the resistance of melanins to thermal degradation depends on their origin. Synthetic melanins were found to be more stable to thermal decomposition than natural melanins. Methylation of melanins caused a significant increase in thermal stability. The DSC curves of melanins reveal typical relaxation phenomena in the temperature range 293-413 K. It is generally believed that melanins

show abstract

Studies related to the chemistry of melanins. Part X. Quantitative assessment of different types of units present in dopa-melanin

Cited by 37 publications

References 0 publications

Novel insights on the physicochemical properties of eumelanins and their DMSO derivatives

Novel insights on the physicochemical properties of eumelanins and their DMSO derivatives

Binding of 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]pyridinium ion (HPP+), a metabolite of haloperidol, to synthetic melanin: Implications for the dopaminergic neurotoxicity of HPP+

Thermogravimetry and differential scanning calorimetry of natural and synthetic melanins

Contact Info

Product

Resources

About