Recent Advances in Characterization of Melanin Pigments in Biological Samples

Abstract

The melanin pigments eumelanin (EM) and pheomelanin (PM), which are dark brown to black and yellow to reddish-brown, respectively, are widely found among vertebrates. They are produced in melanocytes in the epidermis, hair follicles, the choroid, the iris, the inner ear, and other tissues. The diversity of colors in animals is mainly caused by the quantity and quality of their melanin, such as by the ratios of EM versus PM. We have developed micro-analytical methods to simultaneously measure EM and PM and used these to study the biochemical and genetic fundamentals of pigmentation. The photoreactivity of melanin has become a major focus of research because of the postulated relevance of EM and PM for the risk of UVA-induced melanoma. Our biochemical methods have found application in many clinical studies on genetic conditions associated with alterations in pigmentation. Recently, besides chemical degradative methods, other methods have been developed for the characterization of melanin, and these are also discussed here.

Forensic DNA Phenotyping: Genes and Genetic Variants for Eye Color Prediction

“…To enhance our knowledge on color eye formation and its DNA-based prediction, it is necessary to understand the molecular basis of eye color formation related to the main polymorphisms involved in the determination of iris pigmentation [ 95 , 96 ], especially for the SNPs in non-coding regions that seem to be the most predictive for this phenotype. Among the 14 SNPs currently used in the main forensic DNA prediction systems (see Table 3 ), only two are missense mutations (in the OCA2 and SLC45A2 genes), with the large majority (11 SNPs) being in the introns and one (in the HERC2 gene) corresponding to a synonymous substitution.…”

Melanin: Nature's 4th bioorganic polymer

“…Sci., 2023, 24(9), 8305. 11 Even here though, there are outstanding questions in regards to its morphology, which we will discuss below.…”

“…The detailed aspects of in vivo and in vitro synthetic pathways leading to the formation of corresponding structures are out of the scope of the current text, but can be read in detailed reviews elsewhere. 4,7,9,10,11,12 However, to set the context for the rest of the work, we will briefly describe the synthesis of EM and PM, since they are characteristic to animals and fungi and are the most available and studied types of material.…”

Taphonomic experiments reveal authentic molecular signals for fossil melanins and verify preservation of phaeomelanin in fossils

“…The most diagnostic chemical assay for eumelanin is AHPO-HPLC 34 . This assay is the accepted standard in the field of melanin biochemistry for the analysis of the molecular composition of melanin 35 and quantifies derivatives of discrete eumelanin monomers (Fig. 1 ) 36 , 37 .…”