Studies related to the chemistry of melanins. Part VIII. The pyrrolecarboxylic acids formed by oxidation or hydrolysis of melanins derived from 3,4-dihydroxyphenethylamine or (±)-3,4-dihydroxyphenylalanine

Binns, Falmai; Chapman, Robert F.; Robson, N. C.; Swan, G. A.; Waggott, A.

doi:10.1039/j39700001128

Cited by 31 publications

(17 citation statements)

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“…Synthetic melanins from L-tyrosine, L-dopa (fl -(3.4-dihydroxyphenyl)-La-alanine), tyramine and eateehol were prepared by autoxidation of a 5 mM solution of the respective precursor in phosphate buffer (0.067 M, pH 8.0) or enzymatically (pH 6.8) by the use of crude potato tyrosinase or mushroom tyrosinase (Sigma Chemical Co.) according to Binns et al [11]. Adrenaline-melanin was obtained by oxidation of the substrate solution (2 raM) in TRIS-HC1 buffer (0.05 M, pH 8.0) in the presence of copper sulfate (0.1 raM) [12].…”

Section: Preparation Of Rnelaninsmentioning

confidence: 99%

Thermogravimetry and differential scanning calorimetry of natural and synthetic melanins

Simonović

Vučelić

Hadzi-Pavlovic

et al. 1990

Journal of Thermal Analysis

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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

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Section: Preparation Of Rnelaninsmentioning

confidence: 99%

Thermogravimetry and differential scanning calorimetry of natural and synthetic melanins

Simonović

Vučelić

Hadzi-Pavlovic

et al. 1990

Journal of Thermal Analysis

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“…DOPAmelanin was obtained according to the procedure of Bins et al [10]. 3,4-dihydroxyphenylalanine * corresponding author; e-mail: lkozdrowska@wp.pl (L-DOPA) was used as a precursor.…”

Section: Samplesmentioning

confidence: 99%

Influence of Microwave Power on EPR Signal of Melanin Radical and Copper(II) Ions in DOPA-Melanin Complexes

et al. 2013

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Electron paramagnetic resonance spectroscopy EPR was used for examination of microwave saturation in DOPAmelanin complexes with kanamycin and Cu(II) ions. The fast spinlattice relaxation processes take place in system of paramagnetic metal ions. EPR signal of melanin radical saturated with growing of microwave power used during measurements. After adding Cu(II) ions a shortening of relaxation time is observed for EPR signal of melanin radical.

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“…Synthetic DOPA-melanin was formed by oxidative polymerization of 3,4-dihydroxyphenylalanine (L-DOPA) in 0.07 M phosphate buffer at pH 8.0 according to the Binns method [8].…”

Section: Samplesmentioning

confidence: 99%

Effect of oxygen on spin-spin and spin-lattice relaxation in DOPA-melanin. Complexes with chloroquine and metal ions

et al. 2003

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Electron paramagnetic resonance (EPR) studies of complexes of chloroquine with melanin synthesized from 3,4-dihydroxyphenylalanine (DOPA) confirmed an important role of o-semiquinone free radicals during the drug binding by melanin. Chloroquine increases free radical concentration in DOPAmelanin. It has been also demonstrated that chloroquine binding to melanin is modified by metal ions. Co 2 § ions reduce and Zn 2 § ions increase the concentration of free radicals in both DOPA-melanin and melanin-chloroquine complexes. Free radical properties of melanin strongly depend on the presence of oxygen (02) in the environment of the sample. Interactions of melanin and oxygen molecules cause a decrease of the free radical concentration in the samples anda narrowing of the EPR lines. Higher values of both spin-spin and spin-lattice relaxation times were determined for melanin samples in air than for evacuated samples. Application of the observed effeets in oximetry is suggested.

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Studies related to the chemistry of melanins. Part VIII. The pyrrolecarboxylic acids formed by oxidation or hydrolysis of melanins derived from 3,4-dihydroxyphenethylamine or (±)-3,4-dihydroxyphenylalanine

Cited by 31 publications

References 0 publications

Thermogravimetry and differential scanning calorimetry of natural and synthetic melanins

Thermogravimetry and differential scanning calorimetry of natural and synthetic melanins

Influence of Microwave Power on EPR Signal of Melanin Radical and Copper(II) Ions in DOPA-Melanin Complexes

Effect of oxygen on spin-spin and spin-lattice relaxation in DOPA-melanin. Complexes with chloroquine and metal ions

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