Comparative Analysis of Hair Melanins by Chemical and Electron Spin Resonance Methods

Abstract

Eighteen hair samples from Karakul newborn lambs with various colors were estimated for eumelanin and pheomelanin contents (Ce and Cp, respectively) by electron spin resonance (ESR) spectrometry and by high-performance liquid chromatography (HPLC). Correlation coefficients between the values estimated by the ESR and HPLC methods were 0.96, 0.93, and 0.99 for Ce, Cp, and Ce/Cp, respectively. The high correlation coefficients show that both methods fit well for estimation of relative values of these parameters. The absolute values of Ce and Ce/Cp coincide rather well when Ce is high, but considerable discrepancies appear when Ce is low. The reasons for these discrepancies are discussed. The HPLC method appears to be more sensitive for detection of low concentrations of pheomelanin, while the ESR method fits well for mass selection purposes.

Pheomelanin in the skin of Hymenochirus boettgeri (Amphibia: Anura: Pipidae)

“…The a/b ratio calculated from its EPR spectrum quantities the proportion of pheo/eumelanin-like paramagnetic centres in the polymer. It was close to the value obtained for standard yellow mice fur and cysteinylodopa melanin, both revealing high contribution of pheomelanin-like paramagnetic centres (3)(4)(5)28). This was fully confirmed by TEM analysis of melanosomes which, as round and amorphic, resembled pheomelanosomes.…”

Electron paramagnetic resonance (EPR) spectroscopy for investigating murine telogen skin after spontaneous or depilation-induced hair growth

“…2B) which prompted us to analyze biophysical properties of skin that may affect this intensity. One such factor might just be the shape of the analyzed melanin EPR signal of murine C57BL/6 skin/hair shafts [8][9][10][35][36][37][38][39], i.e. its linewidth and hyperfine structure.…”

“…2A. The signal was a single, slightly asymmetric line around g = 2.004 (the g value of the free-radical standard DPPH is 2.0037), without hyperfine structure typical of pheomelanin [35][36][37][38][39]50]. The average line widths of each of the group (4.58 AE 0.16, 4.69 AE 0.09 and 4.71 AE 0.13 Gs for S1, D2 and S2, respectively; means AE S.D.)…”

“…As melanin is a substance with stable paramagnetic free-radical centres deeply embedded in the polymer structure, EPR has become a main research tool to study this pigment [32][33][34]. On the other hand, as melanogenesis in murine truncal skin occurs exclusively in the pigmentary units of anagen III-VI hair follicles, and is thus a completely hair cycle-coupled phenomenon [7,11,12], EPR has proven to be a fast, accurate and instructive biophysical technique for analyzing hair growth-and pigmentation-associated phenomena [8][9][10][34][35][36][37][38][39]. In light of this, we have asked in the current study (a) whether EPR spectroscopy is also by any means useful for hair research when no melanin is generated (i.e.…”

Preservation of Eumelanin Hair Pigmentation in Proopiomelanocortin-Deficient Mice on a Nonagouti (a/a) Genetic Background

“…5), but there was no statistically significant difference between the hybrid 129;B6 Pomc Ϫ/Ϫ and C57BL/6J mice. The presence of a hyperfine structure of the EPR signal of pigments containing a contribution of pheomelanin originates from the difference in the chemical character of pheomelanin-like paramagnetic centers being of a semiquinonimine rather than semiquinone character (43) and is considered a sine qua non for the presence of pheomelanin in biological samples (47). Conversely, the lack of this structure in a signal strongly suggests the lack of pheomelanin in an investigated material but does not represent an absolute proof because trace amounts of pheomelanin might be effectively masked by a strong eumelanin-like signal.…”