LASER-DESORPTION IONIZATION MASS-SPECTROMETRY IN THE STUDY OF NATURALAND SYNTHETIC MELANINS .11. SEROTONIN MELANINS

Various biosynthetic melanins obtained by enzymic oxidation of seroton in with polyphenol oxidase from Psalliota campestris mushroom or potat o, and with tyrosinase from Sepia officinalis or from Sigma were studi ed by means of laser desorption ionization mass spectrometry. Various oligomeric clusters were evidenced, proving that the examined melanins are composed of sets of different oligomers, the production of which strongly depends on the enzyme reaction. While serotonin melanins obta ined with polyphenol oxidase from potato showed wide species distribut ion with molecular weights ranging from 2008 to 13 000 Da, the same me lanins obtained from mushroom showed oligomer distributions ham 1505 t o 9000 Da. Serotonin melanins prepared with tyrosinase from Sepia show ed oligomers from 1636 to 18 000 Da. A dopa-melanin obtained with mush room polyphenol oxidase showed oligomer species from 1709 to 17 874 Da . Comparison of molecular weight distributions of the various oligomer sets in serotonin melanins with those in tyrosine melanins revealed c lear differences, which are investigated and discussed.