Quantitative measurement of melanin as tyrosine equivalents and as weight of purified melanin.

Previously we reported stoichiometric studies on melanin synthesis in cultures of mouse melanoma cells (1). In this system there was no accumulation of intermediates in the Raper-Mason-Nicolaus pathway for melanin synthesis and the amount of hydroxylated tyrosine was quantitatively related to the release of hydrogen as water from positions 3 and 5 of the benzene ring of tyrosine during the series of reactions involved in melanin synthesis. Therefore, the amount of newly synthesized melanin could be expressed as tyrosine equivalents. The present paper describes a colorimetric method for determination of melanin, using protein-free melanin as standard, and values are compared with those expressed as tyrosine equivalents. For this method, a new procedure was developed to solubilize melanin.