Methods in Melanin Research

Despite intense research efforts, melanins can be still regarded as the most enigmatic pigments/biopolymers found in Nature. This state of affairs is due to the adverse physicochemical properties; the instability to acids, alkali, oxidizing agents and UV radiation; the lack of standardized materials and protocols to be used for investigative purposes; reliance on assumptions and speculations that have never been proven on experimental grounds; incomplete biochemical characterization of the melanogenic pathway(s). It is thus difficult to compare data on the same pigment or melanogenic protein obtained in different laboratories, and it is unclear whether the range of synthetic systems studied are appropriate to investigate the structure and function of natural pigments or if various mammalian and invertebrate melanins are accurate models for the human pigment. Furthermore, there is a lack of consensus on melanin “structure”, and several unwarranted models are still found in scientific literature. This situation has engendered much disagreement in the pigment cell community and contributed to some extent to slow down progress in the various fields of melanin research. Objective of this Concurrent Session is to discuss and eventually propose a consensus document addressing crucial issues in melanin research: 1. Definition, classification and terminology (e.g. should all black insoluble pigments of plant origin be classified as melanins?) 2. Recommended protocols for preparation, isolation, purification, spectral and chemical analysis of both natural and synthetic melanins. 3. Recommended protocols for utilization of enzymes for studies of melanin properties in cell cultures and other in vitro systems. 4. Preparation and/or assessment of standard compounds for melanin research, including commercially available pigments and enzymes. These objectives will be pursued through: a) survey of literature and definition of criteria that should guide classification and terminology; b) critical discussion of current methods and identification of best protocols, protocols to avoid, effects of experimental approaches on melanin structure and properties, best criteria for determination of purity, selection of "best practices" for sample preparation and spectral analysis, scope and limitations of chemical degradation methods for analysis and quantitation. Realization of these goals should enable the creation of a set of recommended procedures for investigative