Melanin functions

Chemical Descriptions A nanoparticulate suspension that imparts a natural color to formulae, hair, and skin. Melanin is compo.sed of four major monomeric units uncyclized units indoles indolines and pyrroles, It has an empirical formula of C74.7S H45.62N Oi ..,. Both the fractional nature and range of the empirical fonnula reflect the fact that melanin is a polymer composed of various percentages of more than one type of monomeric unit Trade Names Melanlnk, SepiaMelanInk, All Natural Melanin Function in Formula Free-radical neutralization, adjuvant for boosting SPF Use Concentration 0.1-10% in skin care formulations 0.1-10% in hair care formulations... 

Hill, H. Z. (1992). The function of melanin or six blind people examine an elephant. BioEssays 14 49-56. 

Figure 1.6 (A) Changes in c-Fos IR in hypocretin/orexin(HCRT+)- containing neurons in response to BIC treatment as a function of distance from the microdialysis probe. The percentage of double-labeled cells was greatest closer to the probe (grids 1 and 2, compared with 3 and 4) and was greater with higher concentrations or exposure times. Contralateral cells were not affected. (B) Much lower percentages of melanin-concentrating hormone (MCH+) exhibited c-Fos IR activation in response to BIC. From Alam et al. (2005).

The presence of catechols and more complex, oxidizable polyphenols in nature is widespread, and their functions are not limited to chemical defense. However, biological control of their oxidation is usually a feature of their function, as it is (1) in melanin synthesis,3 (2) in immunologically mediated delayed-type hypersensitivity responses,4 (3) in the hardening or curing of arthropod secretions (for example, as in the surface attachment adhesives of the barnacle and in tanning of the cuticle in insects),5 as well as (4) in defensive mechanisms in higher plants, particularly in the unleashing of immediate necrotrophic responses.6... 

Copper is an essential component of numerous key metalloenzymes which are critical in melanin formation, myelin formation and crosslinking of collagen and elastin. Copper plays a vital role in hemopoiesis, maintenance of vascular and skeletal integrity, and structure and function of the nervous system. Thus a deficiency of copper can lead to a variety of adverse effects such as increased fragility in bones, aneurysm formation in arteries and a loss of lysyl oxidase activity in cartilage.54 57 Articles on copper also appear in Siget1, volumes 3 and 5, all of volumes 12 and 13, and volume 14,... 

The ciliary body, situated posterior to the iris, performs several functions. It connects the anterior part of the choroid to the circumference of the iris, and contains the ciliary muscles necessary for accommodation. The ciliary body secretes aqueous humor into the posterior together with nutrients to nourish the lens. In the ciliary body, melanin is located only in the outer pigmented epithelium [24]. Aqueous humor is actively secreted and passively filtered by the ciliary body. Although the rate of secretion is about 2 pL/min the same volume is drawn-off via Schlemm s canal from where it is conducted into veins [25]. 

To study the function of the chimeric cefE enzymes generated by recombination in S. lividans, the cell-free ring expansion abilities of several recombinants were determined. Three white strains, W21 (6.3-kb plasmid), W25 (8-kb) and W76 (8-kb) as well as the controls Bll and B18 (melanin-positive pJA680) showed activity, producing inhibition zones in the agar diffusion bioassay. Although S. 

Cells have substantial chemical defenses against the UV photoproducts produced in seawater and intracellular fluids. Many organisms have antioxidants (e.g., carotenoids, ascorbate, tocopherols, anthocyanins, and tridentatols) that quench photo-oxidative reactions.64-67 Cells also have enzymes (e.g., catalase and superoxide dismutase) that can counteract the oxidative nature of peroxides and other radicals.26 Some compounds, such as the UV-absorbing pigment melanin, can act as both optical filter and antioxidant.68 The MAA mycosporine-glycine (Figure 15.3) functions in a similar dual capacity.69 The role of UV-mediated reactions in seawater relative to biological effects is an important current area of study. 

---