A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time

Marine, Earth, and Atmospheric Sciences, North Carolina State University, , Campus Box 8208, Raleigh, NC 27695, USA, North Carolina Museum of Natural Sciences, , 11 West Jones Street, Raleigh, NC 27601, USA, Museum of Paleontology, University of California, , Berkeley, CA 94720, USA, Department of Material Sciences and Engineering, University of California, , Berkeley, CA 94720, USA, CHORI (Children's Hospital Oakland Research Institute), , 5700 Martin Luther King, Jr. Way, Oakland, CA 94609, USA, Department of Molecular and Structural Biochemistry, North Carolina State University, , Raleigh, NC 27695-7622, USA, Advanced Light Source, Lawrence Berkeley National Laboratory, , Berkeley, CA 94720, USA.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.05). 01/2014; 281(1775):20132741. DOI: 10.1098/rspb.2013.2741
Source: PubMed


The persistence of original soft tissues in Mesozoic fossil bone is not explained by current chemical degradation models. We identified iron particles (goethite-αFeO(OH)) associated with soft tissues recovered from two Mesozoic dinosaurs, using transmission electron microscopy, electron energy loss spectroscopy, micro-X-ray diffraction and Fe micro-X-ray absorption near-edge structure. Iron chelators increased fossil tissue immunoreactivity to multiple antibodies dramatically, suggesting a role for iron in both preserving and masking proteins in fossil tissues. Haemoglobin (HB) increased tissue stability more than 200-fold, from approximately 3 days to more than two years at room temperature (25°C) in an ostrich blood vessel model developed to test post-mortem 'tissue fixation' by cross-linking or peroxidation. HB-induced solution hypoxia coupled with iron chelation enhances preservation as follows: HB + O2 > HB - O2 > -O2 ≫ +O2. The well-known O2/haeme interactions in the chemistry of life, such as respiration and bioenergetics, are complemented by O2/haeme interactions in the preservation of fossil soft tissues.

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    ABSTRACT: Exceptionally preserved organic remains are known throughout the vertebrate fossil record, and recently, evidence has emerged that such soft tissue might contain original components. We examined samples from eight Cretaceous dinosaur bones using nano-analytical techniques; the bones are not exceptionally preserved and show no external indication of soft tissue. In one sample, we observe structures consistent with endogenous collagen fibre remains displaying ~67 nm banding, indicating the possible preservation of the original quaternary structure. Using ToF-SIMS, we identify amino-acid fragments typical of collagen fibrils. Furthermore, we observe structures consistent with putative erythrocyte remains that exhibit mass spectra similar to emu whole blood. Using advanced material characterization approaches, we find that these putative biological structures can be well preserved over geological timescales, and their preservation is more common than previously thought. The preservation of protein over geological timescales offers the opportunity to investigate relationships, physiology and behaviour of long extinct animals.
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