Biochemical analyses of fossil enamel and dentin

Abstract

Amino acid analyses of undecalcified samples of fossil crocodile and rhinoceros enamel and dentin from mature teeth revealed that the total protein content of these mineralized fossil tissues varied from ~0.01–0.007% by weight. Except in one instance, amino acid analyses of the enamel proteins revealed them to be free of collagen and to have an amino acid composition similar to the proteins obtained from the enamel of mature modern vertebrates. Molecular sieving of the acid soluble enamel proteins demonstrated that the components consisted principally of small peptides and free amino acids, as in the enamel of modern vertebrates.Based on the presence of hydroxyproline (hyp) and hydroxylysine (hyl), collagen was detected in undecalcified mature dentin of fossil rhinoceros, but not in undecalcified crocodile dentin. It was only by sequential extraction procedures that the presence of collagen in the dentin of fossil crocodile was established, emphasizing the utility and importance of analyzing the soluble components in specific extracts of the fossil. Based on these data and the concentrations of hyp and hyl in the material solubilized by the various solvents, the dentin of fossil rhinoceros contained considerably more collagen per weight and as a percentage of the total protein in the dentin than did the dentin of fossil crocodile.As with modern dentin, EDTA and dilute acid solubilize the noncollagenous proteins and peptides found in fossil enamel and dentin, some of which contain O-phosphoserine [Ser(P)], an amino acid unique to mineralized connective tissues. Similar to recent reported findings from fossil bone, less of the original content of the noncollagenous proteins, including those phosphorylated, is degraded and removed from the enamel and dentin during fossilization than the percentage of dentinal collagen and the nonphosphorylated domains of the enamel proteins which are removed. This selective resistance to degradation and removal of the noncollagenous proteins, including phosphoproteins, may reflect the strong interaction of these proteins with the mineral phase of fossilized tissues. The amount and close packing of the inorganic crystals may also inhibit the interaction of the proteins in the interior of the enamel and dentin with the geochemical environment.

Resolving archaeological populations with Sr-isotope mixing models

“…Once childhood tooth mineralization is complete, core enamel is resistant to subsequent isotopic or elemental changes either during an individual's lifetime or during burial, whereas dentine equilibrates with the burial environment (Bocherens et al, 1994;Budd et al, 2000;Glimcher et al, 1990;Hoppe et al, 2003;Montgomery, 2002). To remove soil-derived particulate on the tooth surface, all enamel surfaces were abraded to a depth >100 μm with acidcleaned, tungsten carbide dental burrs.…”

Passports from the past: Investigating human dispersals using strontium isotope analysis of tooth enamel

“…In a large number of biochemical and isotope studies, enamel is considered to be stable and resistant to structural and chemical change over geological (Bocherens et al 1994, Glimcher et al 1990, Horn et al 1994, Kolodny et al 1996, Michel et al 1995, Michel et al 1996, Rink and Schwarcz 1995, Wang and Cerling 1994 as well as archaeological time scales , Elias et al 1982, Ericson 1993, Koch et al 1997, Lee-Thorp and van der Merwe 1991, NielsenMarsh and Hedges 2000, Price et al 2002, Price et al 1994a, Robinson et al 1986, Trickett et al 2003, Vernois et al 1987. Enamel and dentine contain the same carbonate hydroxyapatite mineral phase but their structure, formation process, crystal size and organic content are very different.…”

Soft tissue and cellular preservation in vertebrate skeletal elements from the Cretaceous to the present

“…Likewise, endothelial cell nuclei are identified on intact and aldehyde-fixed vessel surfaces from untreated 14C year post-mortem specimens (Schweitzer et al 2005a). Therefore, for at least a significant initial period, no chemical modification may be required to protect cells, tissues and vessels beyond the intimate association with mineral found in bone Glimcher et al 1990;Sykes et al 1995;Trueman & Martill 2002;MacNamera et al 2006).…”