Microspectroscopic Evidence of Cretaceous Bone Proteins
Johan Lindgren1*, Per Uvdal2,3*, Anders Engdahl2, Andrew H. Lee4, Carl Alwmark1, Karl-Erik Bergquist5, Einar Nilsson5, Peter Ekström6, Magnus Rasmussen7, Desirée A. Douglas6¤, Michael J. Polcyn8, Louis L. Jacobs8
1 Division of Geology, Department of Earth and Ecosystem Sciences, Lund University, Lund, Sweden, 2 MAX-lab, Lund University, Lund, Sweden, 3Chemical Physics, Department of Chemistry, Lund University, Lund, Sweden,4 Department of Anatomy, Midwestern University, Glendale, Arizona, United States of America, 5 Division of Organic Chemistry, Department of Chemistry, Lund University, Lund, Sweden, 6 Department of Biology, Lund University, Lund, Sweden, 7 Division of Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden, 8 Roy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, Texas, United States of America
Abstract
Low concentrations of the structural protein collagen have recently been reported in dinosaur fossils based primarily on mass spectrometric analyses of whole bone extracts. However, direct spectroscopic characterization of isolated fibrous bone tissues, a crucial test of hypotheses of biomolecular preservation over deep time, has not been performed. Here, we demonstrate that endogenous proteinaceous molecules are retained in a humerus from a Late Cretaceous mosasaur (an extinct giant marine lizard). In situ immunofluorescence of demineralized bone extracts shows reactivity to antibodies raised against type I collagen, and amino acid analyses of soluble proteins extracted from the bone exhibit a composition indicative of structural proteins or their breakdown products. These data are corroborated by synchrotron radiation-based infrared microspectroscopic studies demonstrating that amino acid containing matter is located in bone matrix fibrils that express imprints of the characteristic 67 nm D-periodicity typical of collagen. Moreover, the fibrils differ significantly in spectral signature from those of potential modern bacterial contaminants, such as biofilms and collagen-like proteins. Thus, the preservation of primary soft tissues and biomolecules is not limited to large-sized bones buried in fluvial sandstone environments, but also occurs in relatively small-sized skeletal elements deposited in marine sediments.
Citation: Lindgren J, Uvdal P, Engdahl A, Lee AH, Alwmark C, et al. (2011) Microspectroscopic Evidence of Cretaceous Bone Proteins. PLoS ONE 6(4): e19445. doi:10.1371/journal.pone.0019445
Editor: Anna Stepanova, Paleontological Institute of Russian Academy of Science, United States of America
Received: February 10, 2011; Accepted: March 29, 2011; Published: April 29, 2011
Copyright: © 2011 Lindgren et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This research was supported by the Swedish Research Council, the Crafoord Foundation and the Royal Swedish Academy of Sciences. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
* E-mail: johan.lindgren@geol.lu.se (JL); per.uvdal@chemphys.lu.se (PU)
¤ Current address: Developmental Biology Division, Institution for Experimental Medicine, Lund University, Lund, Sweden
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