Laser desorption ionization mass spectrometry in the study of natural and synthetic melanins. I--Tyrosine melanins.

Nine synthetic, biosynthetic and natural tyrosine melanins, together with dopa and catechol melanins, have been studied by means of laser desorption ionization mass spectrometry. The results obtained have shown that all the melanins under study consist of homogeneous sets of oligomers and have led to definitive information on their molecular weight distribution (from 500 to 30,000 Da). A deeper analysis of the spectra, in terms of mass differences among the various oligomers, allowed the identification of some monomeric units, identical or analogous to those already proposed in the literature.