title: Nanostructure and mechanics of mummified type I collagen from the 5300-year-old Tyrolean Iceman.
abstract: Skin protects the body from pathogens and degradation. Mummified skin in particular is extremely resistant to decomposition. External influences or the action of micro-organisms, however, can degrade the connective tissue and lay the subjacent tissue open. To determine the degree of tissue preservation in mummified human skin and, in particular, the reason for its durability, we investigated the structural integrity of its main protein, type I collagen. We extracted samples from the Neolithic glacier mummy known as 'the Iceman'. Atomic force microscopy (AFM) revealed collagen fibrils that had characteristic banding patterns of 69 +/- 5 nm periodicity. Both the microstructure and the ultrastructure of dermal collagen bundles and fibrils were largely unaltered and extremely well preserved by the natural conservation process. Raman spectra of the ancient collagen indicated that there were no significant modifications in the molecular structure. However, AFM nanoindentation measurements showed slight changes in the mechanical behaviour of the fibrils. Young's modulus of single mummified fibrils was 4.1 +/- 1.1 GPa, whereas the elasticity of recent collagen averages 3.2 +/- 1.0 GPa. The excellent preservation of the collagen indicates that dehydration owing to freeze-drying of the collagen is the main process in mummification and that the influence of the degradation processes can be addressed, even after 5300 years.
authors.affiliation: Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, Theresienstrasse 41, 80333 Munich, Germany.
authors.forename: Marek
authors.initials: M
authors.lastname: Janko
authors.forename: Albert
authors.initials: A
authors.lastname: Zink
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Gigler
authors.forename: Wolfgang M
authors.initials: WM
authors.lastname: Heckl
authors.forename: Robert W
authors.initials: RW
authors.lastname: Stark
mesh_terms: D024042:Collagen Type I / Q000648:ultrastructure*; D055119:Elastic Modulus; D006801:Humans; D018625:Microscopy, Atomic Force; D009106:Mummies; D049329:Nanostructures / Q000648:ultrastructure*; D012867:Skin / Q000648:ultrastructure*; D013059:Spectrum Analysis, Raman
chemical_list: D024042:Collagen Type I