Collagen extraction

The 5 C values of bone and dentine collagen extracted from a mandible and a lower first molar from a Siberian wolf are identical (Table 4.2). On the contrary, the 5 N value of bone collagen is clearly lower (8.2%o) than the 8 N value of dentine collagen (9.8%o). 

In the following description and discussion of our results, various criteria derived from the literature are used to determine whether or not each sample is of adequate preservation to allow it to be confidently included in a stable isotope study. The values applied in the various criteria have been found to be associated with archaeological bone collagen that retained an isotopic composition that was reflective of its diet, while the majority of samples that had values outside of the criteria did not retain an isotopic composition that reflected diet. The values for these criteria may vary slightly depending upon the collagen extraction methodology used, and such criteria are not exact. In this study samples that fall within the criteria values are deemed acceptable, and those that do not are deemed unacceptable. ... 

In addition, our results suggest that removal of hpids improves both yield characteristics and elemental characteristics. Recent work by Liden et al. (1995) suggests that the methanol-chloroform method used here is more effective than other methods, such as treatment with NaOH solution, or the maintenance of an acidic environment and ultrafiltration of products during collagen extraction. It is speculated that the presence of hpids in archaeological bone samples may interfere with the acid hydrolysis of protein during... 

Brown, T.A., Nelson, D.A., Vogel, IS. and Southern, J.A. 1988 Improved collagen extraction by modified Eongin method. Radiocarbon 30 171-177. 

Longin, R. 1971 New method of collagen extraction for radiocarbon dating. Nature 230 241-242. 

Figure 9.2. Amino acid content (mol %) in collagen extract (dark columns) and serum proteins (light columns) from a skeleton from coastal Peru. Due to a prevalence of degraded and soluble collagen, the nonmineral-bound protein fraction shows a collagen amino acid profile.

Figure 9.3. Percentage of non-detectable amino acids in collagen extracts from archaeological human skeletons. Numbers on top of the columns indicate number of carbon atoms per amino acid. XW = weighted mean of % loss (cf. text). Only high-carbon amino acids are more frequently lost than the average.

Since it is possible to differentiate well-preserved from badly preserved collagen through amino acid analysis and gel electrophoresis, it is also possible to determine which bone samples are likely to give erroneous isotopic ratios. At least for 8 C, it should be possible to estimate the in vivo isotopic signature by correcting the changed amino acid concentrations of the collagen extract. This way, a reasonable approach to the reconstruction of pale-odiet should be possible. 

Longin, R., New Method of Collagen Extraction for Radiocarbon Dating, Nature. 1971, 230, 241-242. 

Most of the work discussed so far refers to isotopic measurements (almost always < 13C and < 15N) on collagen extracted from human bone or dentine, or,... 

Archaeological studies have used the stable isotope analysis of collagen extracted from fossil bones to reconsfruct the diet of prehistoric human populations (e.g. Schwarcz et al. 1985). 

Bae, I., Osatomi, K., Yoshida, A., Osako, K., Yamaguchi, A., and , . (2008). Biochemical properties of acid-soluble collagen extracted from the skins of underutilized fishes. Food Chem. 108,49-54. 

Ikoma, T., Kobayashi, H., Tanaka, J., Walsh, D., and Mann, S. (2003). Physical properties of type I collagen extracted from fish scales of Pagrus major and Oreochromis niloticas. Int.. Biol. Macromol. 32, 199-204. 

The increased binding of HA with tissue as a function of age parallels the progressive cross-linking of collagen and the steady loss of collagen extractability with age. Each of these phenomena contributes to the apparent dehydration, atrophy, and loss of elasticity that characterizes aged skin. 

Collagen extracted from residue with 5% trichloroacetic acid (2x 90°)... 

Living, bi-layered skin substitute containing type 1 bovine collagen Extracted and purified from bovine tendons and viable allogeneic human fibroblast and keratinocytes cells isolated from human infant foreskin... 

However, it is clear that some of the more subtle interaction properties do vary between soluble collagens extracted in various ways, and even between fractions of an extract of a single type (e.g., see Fessler, 1960). 

Newly formed collagen extracted with cold, aqueous NaCl solutions consists of three equal-sized chains (a-components) of two different composition types ( -l and -2). The two chains of similar composition are the a-1 chains. The a-2 chain differs from the a-1 in a number of amino acids, particularly hydroxyproline, proline, lysine, and histidine (26). As the collagen molecule matures, the a-chains crosslink intramo-lecularly in pairs this older protein can be readily extracted with acidic solutions such as dilute acetate and citrate buffer, but not with salt solutions. The crosslinked chains are called /3 components the crosslinks are probably covalent bonds (26) that arise by condensation of the side chains of strategic lysyl residues after enzymatic oxidative deamination. Older collageil also forms intermolecular bonds, but the nature of this crosslink has not yet been determined (27). 

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