The second phase of polymerization is characterized by self-assembling of the different units up to achieve graphite structures of the type shown in the table 4. Other discrepancy is the fact that the particle possesses groups OH, COOH and cationic centers able to bind acids like HCl. All the melanins are insoluble salts. For example, Sepia officinalis ink melanin is a Ca and Mg salt. The corresponding melanic acid loose CO 2 by bland heating, .
Melanins are sensitive to light, pressure, oxygen and peroxides.
All these variables render difficult melanin's study. In fact a giant fullerene is essentially a monostrate of hexagons with sp2 carbons that bend over among 12 pentagonal cusps necessary for the closing. Interstitial compounds could be formed in the proposed structures also with gases. O could suggest new mechanism and biological functions. Melanins must have had an important role in the pre-enzymatic era.