Melanins analysis

Harki, E., Talou, T., and Dargent, R., Purification, characterisation and analysis of melanin extracted from Tuber melanosporum Vitt., Food Chem., 58, 69, 1997. 

Phenylephrine (27) is a low-potency sympathomimetic amine used as a decongestant. Solutions become coloured due to an auto-oxidation accelerated by light. In a series of experiments, aqueous solutions of the hydrochloride were left under a UV lamp until a tan colour developed. HPLC analysis showed four main products of which one was identified as adrenaline (19). Even after prolonged irradiation, there was never more than 2% adrenaline in the solution. It was assumed that the catecholamine was removed as it formed by further reaction to adrenochrome and melanine, which accounted for the colour [34],... 

Potentials problems with the use of hair include a strong influence of hair pigmentation on nicotine and cotinine binding and uptake (Dehn et al. 2001). Nicotine and cotinine are bound to melanin. As a result, dark hair binds much more nicotine than does blond or white hair. This makes comparison across individuals difficult. Also, hair is exposed to nicotine and cotinine from sweat and from sebaceous gland secretions, and to nicotine from environmental tobacco smoke exposure. Washing the hair before analysis may reduce this problem of environmental contamination, but it is not likely to remove all environmental nicotine and cotiiune. 

Tricyclazole is reported to inhibit the melanin biosynthesis pathway between 1,3,8 trihydoxynaphthalene and vermelone whereas chromatographic analysis of P. oryzae culture media indicates that KTU 3616 treatment stimulates the accumulation of the intermediate, scytalone. 

The hair matrix possesses a large monitoring window (months/years) that allows a retrospective analysis and the study of past history. Hair is also characterized by a high stability and a minimum possibility of adulteration [41, 42], The structure of the hair can be considered as a repeated network of keratin fibers. There are also melanins, lipids, and all the compounds of cells that led to the formation of the stem. The growth of hair is in the range of 0.6-1.4 cm/month [43,44],... 

Further analysis of the UV spectrum revealed that this compound is a gallic acid derivative. A search of the Dictionary of Natural Products for molecular ion and plant genus name leads to the identification of a known compound - Pterocaryanin B. The compounds with poly-hydroxyl groups in their structures are very well known as tyrosinase inhibitors and are responsible for the inhibition of melanin synthesis. Therefore, no further isolation was necessary. 

QSRR analysis of HPLC data determined on an immobilized human serum albumin (HSA) column helped to propose the topography of two binding sites of different affinity to benzodiazepine enantiomers 1143.163). Also, the mechanism of interaction of phenothiazine neuroleptics with melanin was rationalized by means of QSRR analysis of HPLC retention data [132,164]. Another QSRR study concerned the interactions of drugs with immobilized keratin and collagen [ 165). 

Recently, Ha et al. (2005) reported the inhibitory potentials of JV,Ar-unsubsti-tuted selenourea derivatives 5-8 on tyrosinase. Three types of Ar,AT-unsubsti-tuted selenourea derivatives exhibited an inhibitory effect on the DOPAoxi-dase activity of mushroom tyrosinase. For the structures of these selenourea derivatives (5-8), see Fig. 4. Compound 8 exhibited 55.5% inhibition at a concentration of 200 xM (ICso = 170 xM). This inhibitory effect was higher than that of reference compound kojic acid (39.4%, for structure see Fig. 1) [44]. Interestingly, this compound (8) was identified as a noncompetitive inhibitor by Lineweaver-Burk plot analysis. In addition, 8 also inhibited melanin production in melan-a cells [44]. 

Takano, Y., Kubo, Y., Shimizu, K., Mise, K., Okuno, T., and Furusawa, I. (1995). Structural analysis of PKSl, a polyketide synthase gene involved in melanin biosynthesis in Colletotri-chum lagenarium. Mol. Gen. Genet. 249, 162-167. 

Scytalone dehydratase catalyzes two analogous steps in DHN melanin biosynthesis (Fig. 20.1). Various biochemical aspects of the catalysis have been investigated by Douglas Jordan and coworkers from DuPont [Basarab et al., 2002 Zheng et al, 2002 Jordan et al, 2000 a Jordan et al., 2000 b Basarab et al., 1999 Jordan et al, 1999]. Based on crystal structure analysis, which is discussed below in much more detail with respect to inhibitor design, a biochemical reaction mechanism can be proposed (Fig. 20.3). 

Thomas M (1955) Melanins. In Peach K, Trecey MV (eds.) Modem Methods of Plant Analysis. Vol. IV, p. 661. Springer, Berlin Gottingen Heidelberg... 

Zeise L, Chedekel MR (1992) Melanin Standard Method Titrimetric Analysis. Pigment Cell Res 5 230... 

Absorption-mode spectral peaks located less than about 10 line widths from the peak from which a DISPA plot is constructed can produce significant distortion of that DISPA plot (see Figure 7 and ref. 11). Therefore, DISPA analysis in ESR spectroscopy should be restricted either to systems with just a single signal (as for melanin or coal), or to systems with well-separated peaks (as for nitrox-ide "spin-labels" in relatively rapid motion). For a s etrical ESR triplet, such as the nitroxide, the central line will give the least distortion from the other peaks ). 

Considerable inference has been made from melanin binding to ocular toxicity. Analysis of the data by Leblanc et al. (1998) indicates that in aU cases, there are no direct consequences of drug-melanin binding. Any drug-related toxicity of the retina in humans and animals was described... 

Takano U, Kubo Y. Shimizu K, Mise K. Okuno T, Furusawa 1. Stmctinal analysis of PKSt, a polyketide synthase gene involved in melanin biosynthesis in CoUetotrichiim tagenonum. Mol Gen Genet 1995 249 162-167. 

This approach can also be used to assist modeling faces in the visible and infrared bands (Figure 22.3) [12]. The texture maps represent the hemoglobin and melanin contents (in the visible spectrum) and the temperature distribution of the facial skin. These maps are the output of the face analysis and modeling module. This information is used for evaluating the physical and psychoemotional state of a person. 

N. Tsumura, N. Ojima, K. Sato, M. Shiraishi, H. Shimizu, H. Nabeshima, S. Akazaki, K. Hori, and Y. Miyake, "Image-Based Skin Color and Texture Analysis/Synthesis by Extracting Hemoglobin and Melanin Information in the Skin," ACM Transactions on Graphics (TOG), Vol. 22, No. 3, pp. 770-779,2003. 

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