Who hasn’t been amazed by the beauty and wild colors of bird feathers? Yet the diverse range of colors seen across the animal kingdom is made possible by surprisingly few molecular building blocks. It is these molecules, referred to collectively as melanins, that are understood to provide the pigmentation that confers color to animal skin, hair, and feathers. So, how is nature able to achieve such a wide variety of colors with so few components? Recent work at the ALS by Musahid Ahmed, Shirley Liu, Tyler Troy, and Dula Parkinson in collaboration with Matt Shawkey (University of Akron), have found that is the proportions in which these molecular components come together that makes all the difference.
In their experiments, melanin samples extracted from a variety of bird plumage were gently vaporized by a laser under high-vacuum conditions. The sample vapor is then exposed to synchrotron radiation, causing the molecules to lose an electron to form a charged ion which is then detected by the beamline’s mass spectrometer.
During this process however, some ions fall apart to form many smaller pieces which are also detected, making it difficult to determine what each mass peak represents. As a result, a computer algorithm was developed to interpret and categorize the mass spectra matching specific patterns to the color of the sampled bird feather. The algorithm can now be applied to samples for which the plumage color is unknown.
Peak probability contrasts (PPC) analysis projected onto three dimensions for black, brown, grey, and peacock (green) feathers. Where relevant, red arrows indicate the pigment extraction location.
In addition to deciphering the chemical structures of melanin, this work will help paleontologists to derive the colors and patterns of furs, feathers, and skins of ancient beasts using only their fossil remains.
Work performed on ALS Beamline 9.0.2.
Citation: S. Y. Liu, M. D. Shawkey, D. Parkinson, T. P. Troy, and M. Ahmed, “Elucidation of the chemical composition of avian melanin,” RSC Adv. 4, 40396 (2014), doi:10.1039/c4ra06606e.