Two major groups of contaminants exist; humic and non-humic substances.Humic substances are dark coloured acids moderately high-molecular-weight polymers of indefinite structure.
Initially analyses were carried out on whole bone, later the organic (collagen) or inorganic component of bone (hydroxyapatite) were separated and dated.
A lack of success saw the dating of different fractions obtained during bone pretreatment, including the acid soluble (humics) as well as the "collagen" (acid insoluble component). 1989; Gurfinkel 1987); specific amino acids, for example hydroxyproline and proline (Wand 1981 in Taylor 1992; Stafford et al. 1984); a series of individual amino acids (Hare and Estep 1983 in Stafford et al. 1988); larger or smaller (peptide) parts of collagen (Brown et al.
hydrophobic reaction) (Woodhead-Galloway 19, 23-24, 38). All amino acids, except glycine, exhibit optical activity, existing in the natural state as laevo-rotary compounds, a property apparently restricted to amino acids of a biological origin (Wyckoff 19), a property which is exploited in amino acid racemisation dating (e.g. In general the composition of mammalian collagens shows little variability (see Hare 199). Hydroxyproline is found rarely in other proteins but comprises about 10% of all amino acids in collagen.
Of special significance to recent AMS works is the amino acid hydroxyproline (i.e. However, from a practical point of view the use of hydroxyproline for 14C analysis is limited as it does not occur in large quantities in fossil bones, has been detected in natural waters (Long et al.
The substitution mechanisms that occur in the hydroxyapatite of bone include intercrystalline exchange and a recrystallisation due to dissolution and reformation of crystals, with the addition of new ions into the crystal structure replacing Ca2 or being adsorbed on the crystal surfaces (Smith et al. The tooth is constructed of three layers; the pulp cavity, containing blood vessels and nerves; this is covered with the dentine; where the tooth is exposed the dentine is covered by enamel; and the submerged roots are covered with cementum.
The cementum closely resembles cortical bone in composition, except that dentine is hard and dense, being almost 75% mineral but with a higher collagen content than bone (30% compared to 15% in bone).
Non-humic substances include all classes of organic compounds.
The major contaminants are polyphenols, polysaccharides, lignins as well as degraded collagen and other broken down bone components (Morrison 199-60).
The enamel is denser and harder and is almost 98% mineral with the hydroxyapatite crystals being much larger than those of dentine, cementum or bone and consequently more resistant.Tags: Adult Dating, affair dating, sex dating