Laser Desorption/Ionisation Mass Spectrometry in the Study of Natural and Synthetic Melanins. III. Human Hair Melanins

Four samples of natural melanin extracted from red, fair, black and brown human head hair were studied by both laser desorption/ionisation (LDI) and matrix-assisted laser desorption/ionisation (MALDI) methods. Clear differences were found among the LDI and MALDI mass spectra of the four melanins. In red hair melanin, there was a major peak at m/z 842 attributed to an oligomeric cluster, together with lower-intensity peaks in the range 4000–5000 Da. In fair hair melanin, only species with molecular masses from 300 to 600 Da were evidenced. In black hair melanin, clusters up to 25,000 Da were detectable, and in brown hair melanin, there were two main oligomeric clusters in the ranges 600–900 Da and 3000–5000 Da, respectively, and a large oligomer distribution from 11,000 to 16,000 Da. It is concluded that there is an increase in relative molecular masses of melanins on passing from fair to black hair, suggesting that in “dark” hair the colour is related to melanins with a higher degree of polymerisation.