PURPOSE The goal of this study is the characterization of the strong yellow fluorescence of oxidized melanin in the retinal pigment epithelium (RPE) and the choroid. METHODS Naturally occurring melanin in the human retina and choroid was oxidized by exposing fixed and plastic-embedded sections of a human eye to light and hydrogen peroxide. Synthetic melanin was also oxidized in vitro by expos...

Melanin synthesis is associated with virulence for the pathogenic fungus Cryptococcus neoformans. Exposure of nonmelanized C. neoformans 4067 cells to 4 M guanidinium isothiocyanate followed by 6 M HCl at 100 degrees C resulted in complete solubilization of cellular structures. However, exposure of melanized C. neoformans 24067 to the same conditions produced a suspension of black particles. An...

The application of electron paramagnetic resonance (EPR) spectroscopy in pharmacy of melanin complexes with netilmicin and Cu(II) was presented. The continuous microwave saturation of EPR spectra of DOPA-melanin and the complexes was performed. EPR spectra were measured on an X-band (9.3 GHz) spectrometer at temperatures in the range of 105-300 K. Paramagnetic copper ions decrease the intensity...

Melanin is a virulence factor for many pathogenic fungal species, including Cryptococcus neoformans. Melanin is deposited in the cell wall, and melanin isolated from this fungus retains the shape of the cells, resulting in hollow spheres called "ghosts". In this study, atomic force, scanning electron, and transmission electron microscopy revealed that melanin ghosts are covered with roughly sph...

Bleaching of eumelanin has been studied in model systems consisting of synthetic dopa-melanin and various concentrations of hydrogen peroxide, molecular oxygen, and copper(II) ions at neutral and alkaline pH. The data show that at neutral pH, in the dark, metal-ion-free melanin is very resistant to oxidation by hydrogen peroxide. However, the rate of bleaching of melanin, induced by H2O2 is sig...

Melanin formation and assembly by fungi has largely been investigated mainly for its importance in pathogenesis, as well as to establish the functions and biosynthetic pathways of melanin formed during the process of successional wood decay. It is known that melanin formation varies based on fungal species, especially melanin produced by ascomycetes versus basidiomycetes, and that the mechanism...

objective: the incidence and prevalence of kidney stone is increasing worldwide. after the first recurrence the risk of subsequent relapses is higher and the time period between relapses is shortened. urinary stones can be severely painful and make a huge economic burden. the stone disease may increase the vulnerability of patients to other diseases such as renal failure. medicinal herbs are ri...

The role of melanin in nicotine uptake and metabolism has received little attention. Because nicotine has been shown to accumulate in tissues containing melanin, exploring links between melanin and nicotine may provide additional clues to understanding smoking behavior and disease effects. To examine the scientific literature on the relationship between melanin and nicotine, we conducted a PubM...

Electron paramagnetic resonance (EPR) spectroscopy may be applied to examine interactions of melanin with metal ions and drugs. In this work EPR method was used to examination of changes in free radical system of DOPA-melanin--the model eumelanin after complexing with diamagnetic cadmium(II) ions. Cadmium(II) may affect free radicals in melanin and drugs binding by this polymer, so the knowledg...