Elemental characterisation of melanin in feathers via synchrotron X-ray imaging and absorption spectroscopy
Nicholas P. Edwards, Arjen van Veelen, Jennifer Anné, Phillip L. Manning, Uwe Bergmann, William I. Sellers, Victoria M. Egerton, Dimosthenis Sokaras, Roberto Alonso-Mori, Kazumasa Wakamatsu, Shosuke Ito & Roy A. Wogelius
Scientific Reports 6, Article number: 34002 (2016)
Analytical chemistry Biochemistry
Received: 15 June 2016 Accepted: 02 September 2016 Published online: 23 September 2016
Melanin is a critical component of biological systems, but the exact chemistry of melanin is still imprecisely known. This is partly due to melanin’s complex heterogeneous nature and partly because many studies use synthetic analogues and/or pigments extracted from their natural biological setting, which may display important differences from endogenous pigments. Here we demonstrate how synchrotron X-ray analyses can non-destructively characterise the elements associated with melanin pigment in situ within extant feathers. Elemental imaging shows that the distributions of Ca, Cu and Zn are almost exclusively controlled by melanin pigment distribution. X-ray absorption spectroscopy demonstrates that the atomic coordination of zinc and sulfur is different within eumelanised regions compared to pheomelanised regions. This not only impacts our fundamental understanding of pigmentation in extant organisms but also provides a significant contribution to the evidence-based colour palette available for reconstructing the appearance of fossil organisms.
Funding was provided by a UK Natural Environment Research Council grant NE/J023426/1. Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource (CA, USA), a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. Portions of this research were also carried out at Diamond Light Source (UK, allocation SP11865 and SP12948). We thank support staff at SSRL and DLS. PLM thanks the Science and Technology Facilities Council for their support (ST/M001814/1). We also thank the Live Animal Center (LAC) at The Academy of Natural Sciences of Drexel University (Philadelphia, PA, USA) and the Wild Wings Birds of Prey education and rehabilitation centre (UK) for supply of feathers from bird under their care.
University of Manchester, School of Earth and Environmental Sciences, Williamson Research Centre for Molecular Environmental Science, M13 9PL, UK
Nicholas P. Edwards, Arjen van Veelen, Jennifer Anné, William I. Sellers & Roy A. Wogelius
University of Manchester, School of Earth and Environmental Sciences, Interdisciplinary Centre for Ancient Life, Manchester M13 9PL, UK
Nicholas P. Edwards, Arjen van Veelen, Jennifer Anné, Phillip L. Manning, William I. Sellers, Victoria M. Egerton & Roy A. Wogelius
College of Charleston, Department of Geology and Environmental Geosciences, Charleston, SC, 29424, USA
Phillip L. Manning & Victoria M. Egerton
Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
Linac Coherent Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
Department of Chemistry, Fujita Health University, School of Health Sciences, Toyoake, Aichi 470–1192, Japan
Kazumasa Wakamatsu & Shosuke Ito
N.P.E., A.V.V., J.A., P.L.M., U.B., W.I.S., V.M.E., D.S., R.A.-M. and R.A.W. all participated in the synchrotron analyses. N.P.E. and J.A. composed the experimental design with guidance from R.A.W. K.W and S.I. conducted the melanin identification and quantification experiments. N.P.E. processed the synchrotron image, quantitative and sulfur XAS data, created all the figures, and composed the manuscript. A.V.V. processed and fit the Zn EXAFS data. All co-authors gave critical input to the text.
The authors declare no competing financial interests.
Correspondence to Nicholas P. Edwards or Roy A. Wogelius.