Infrared and water sorption studies of the hydration structure and mechanism in natural and synthetic melanin.

Although water is a structural and functional determinant in melanins, a direct study of the interaction between water and melanin is still lacking and is the subject of the present work. Melanin forms in cells and organisms' colloidal particles deriving from the hierarchical aggregation of smaller subunits such as protomolecules, stacking units, and small aggregates: its functions must be interpreted in terms of solid-state and surface properties. They are strictly connected to the porosity of the particles when they interact with water and other chemicals.

An XAS study of the sulfur environment in human neuromelanin and its synthetic analogs.

Neuromelanin is a complex molecule accumulating in the catecholaminergic neurons that undergo a degenerative process in Parkinson's disease. It has been shown to play either a protective or a toxic role depending on whether it is present in the intraneuronal or extraneuronal milieu. Understanding its structure and synthesis mechanisms is mandatory to clarify the reason for this remarkable dual behavior.

New melanic pigments in the human brain that accumulate in aging and block environmental toxic metals.

Neuronal pigments of melanic type were identified in the putamen, cortex, cerebellum, and other major regions of human brain. These pigments consist of granules 30 nm in size, contained in organelles together with lipid droplets, and they accumulate in aging, reaching concentrations as high as 1.5-2.

Photophysical properties of pyrene in interaction with the surface of melanin particles.

Melanins perform their biological activity (photoprotection and light enhanced chemical reactivity) under the form of porous aggregates on which ions and neutral molecules can be adsorbed. For this reason, the photochemistry of natural and synthetic melanins must be investigated in the framework of the physico-chemical theory of the heterogeneous reactions and a detailed knowledge of the surface properties, is therefore, necessary. In this work, some surface characteristics of melanin particles have been investigated taking advantage of the photophysical behaviour of pyrene, a dye widely used in studies of the interface properties of micelles and colloidal semiconductors.