Melanin Pigments

INTRODUCTION

Pigments are zilch but a naturally existing colored composite that absorbs light in the visible range of the electromagnetic spectrum. Most pigments are used in manufacturing and visual arts. These pigments could be employed to dye not only natural fibers like silk, cotton and wool, but also synthetic fibers like nylon and vinylon, and generally gave a good color tone. Synthetic inorganic chemical manufacturing rather than by grinding and washing clays or minerals taken directly from the earth. Several synthetic inorganic pigments are still used today, including iron blue, cobalt green dyed mainly with synthetic pigments. Pigments from natural sources have been obtained since long time ago, and

The origin of the name is from melanos (Greek dark) is usually attributed to the Swedish chemist Berzelius in 1840. The term “melanin” has been used fairly indiscriminately to mean any dark pigment. The synthesis of melanin is one of the most universal, but at the same time enigmatic adaptations of living organisms to the variable conditions of the Earth. Melanin is widely dispersed in the animal and plant kingdoms and also synthesized from microorganisms (Riley , 1997). The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms. All melanin are derivatives of polyacetylene. There are three major types of melanin; Eumelanin (black or brown), Pheomelanin (yellow-red) and all melanins. The most common melanin is a Eumelanin which is also known as DOPAmelanin, it is a mixed copolymer of polyacetylene, polyaniline, and polypyrrole. Another common form of melanin is pheomelanin, a red-brown polymer of benzothiazine units largely responsible for red hair and freckles. The presence of melanin in the archaea and bacteria kingdoms is an issue of ongoing debate among researchers in the field (Plonka and Grabacka, 2006). The photochemical properties of melanin make it an excellent,

The melanin synthesis using homogentisic acid as a precursor of was first reported in Vibrio cholerae, Hyphomonas species and Shewanella colwelliana (Kotob et al., 1995). The synthesis of melanin and its characterization such as solubility, free radical nature was initially studied in Proteus mirabilis (Agodi et al.,1996). A novel marine bacterium Alteromonas strain MMB-1, was isolated from the Mediterranean Sea and its melanin synthesis ability was studied using L-tyrosine as a precursor previously (Solano et al., 1997). The melanin pigment from Burkholderia cepacia was formerly reported for escaping monocyte respiratory burst activity by scavenging superoxide anion (Zughaier et al.,1999). The extra cellular melanin from Shewanella algae BrY was reported previously to serve as the sole terminal electron acceptor. Upon reduction the reduced, soluble melanin reduced insoluble hydrous ferric oxide in the absence of bacteria, and melanin was proved as a soluble Fe (III)-reducing compound (Turick et al.