Meeting Abstract

35.6  Friday, Jan. 4  Melanin chemistry and color in feathers SHAWKEY, MD*; D’ALBA, L; VINTHER, J; AHMED, M; LIU, S; University of Akron; College of Wooster; University of Bristol; Lawrence Berkeley National Lab; Lawrence Berkeley National Lab shawkey@uakron.edu

Melanin has great potential as a uniquely multifunctional material because of its high light absorption and conversion efficiency, its physical toughness that enables it to persist for millions of years in unaltered form and its likely high refractive index (estimated at ~1.8-2.0) that enables it to produce strong optical effects. However, our understanding of the chemistry of melanin remains limited, primarily based on samples from human hair and squid ink sacs and stuck in an overly simplified eumelanin/pheomelanin paradigm. Avian melanosomes have an unparalleled diversity of form that almost certainly mirrors a diversity in chemistry. However, their chemistry remains virtually unstudied, even though it is critical to understanding questions of both fundamental and applied interest. We are using Vacuum Ultraviolet Laser Desorption Mass Spectrometry (VUV-LDMS) to determine the chemical structure of melanin from samples of melanic non-iridescent (black, brown, grey) and iridescent feathers. The mass distributions of these samples are determined on an imaging mass spectrometer coupled to VUV synchrotron radiation, and the probable chemical arrangements and structure determined by comparing fragmentation patterns upon varying photon energy and using bioinformatics and electronic structure calculations. While there is considerable variation, the spectral data for each of the color categories are relatively consistent (see Fig. 3), indicating that they have distinct chemical signatures. These data suggest a direct correspondence between molecular color and structure in avian melanin and suggest that our method is useful for reconstructing color of fossilized feathers.