ESR study of hair and melanin–keratin mixtures – the effects of temperature and light

Abstract

Synopsis The ESR spectrum of hair presents a symmetrical absorption band with the same characteristics as pure melanin (g= 2.0030; deltaH= 5 G). Between 250 degrees K and 490 degrees K, the intensity of the signal increases as for pure melanin. This variation may be explained by a change in the moisture content of hair as function of the temperature. Below 250 degrees K, in a frozen medium, melanin-water interactions remain constant and the number of radicals is no longer a function of temperature. Under exposure to light of hair, melanin-derived radicals were formed. Stable and short-lived radicals were observed at lambda > 345 nm; only unstable radicals were formed at lambda > 450 nm. At shorter wavelengths (lambda > 280 nm), a new asymmetric signal (g= 2.0065H= 20 G) appeared on UV exposure of black, grey or white hair; this signal was attributed to radicals formed in the direct excitation of keratin amino acids.

Electron Spin Resonance Study of Photoinduced Radicals in Various Eumelanins in Solid Matrix

“…It is recalled that the ESR signal of 1.3 x lO-'mg human hair eumelanin dispersed in 250 mg KBr varied when the pellet was exposed to a polychromatic light of wavelengths longer than 295 nm (Arnaud et al, 1984). In the presence of air, the ESR signal increased until a stationary value was reached (see curve a, Fig.…”

“…), ESR spectrometry has been of a special interest since the various melanins contain stable free radicals and short-lived radicals can be formed photochemically (Felix et al, 1979;Kalyanaraman et al, 1984;Sarna and Sealy, 1984;Sealy et al, 1980). In a series of recent papers on eumelanin, we have emphasized the advantages of the coupling of photochemical techniques and ESR analysis in a solid ionic matrix (Arnaud et al, 1983(Arnaud et al, ,1984Bibang et al, 1989 [this issue]). As opposite to suspensions in water, which do not favour the observation of photoinduced radicals, KBr matrices increase the formation rate of radicals issued from ionic photochemical processes (like electron photo-ejection) and inhibits biradicalar recombination (through immobilization of macroradicals).…”

ESR study of photoinduced free radicals by visible light in hair and the effects of ascorbic acid (vitamin C)

“…There are many studies about melanin contained in hair, skin and eyes [4–9]. The ESR method is one of the most productive methods in the study of melanin contained in hair and skin.…”

“…The ESR method is one of the most productive methods in the study of melanin contained in hair and skin. [5, 8–21]…”

Towards an insight on photodamage in hair fibre byUV‐light: An experimental and theoretical study

“…In hair, the estimated content for the Trp ranges from 0.2% to 1.0% [3,35], but this amino acid plays a significant role in the photochemistry of keratins and proteins in general (as discussed above). In this respect, Pande and Jachowicz [7] monitored the photodegradation of hair by a spectroscopic technique as a function of the relative concentration of Trp.…”