Bone 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... 

Liden, K., Takahasi, C. and Nelson, D.E. 1995 The effects of lipids in stable carbon isotope analysis and the effects of NaOH treatment on the composition of extracted bone collagen. Journal ofArchaeological Science 22 321-326. 

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. 

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). 

In conclusion, nitrogen/carbon ratios combined with quantitative amino acid analyses could determine the level of impurities that may co-exist with fossil bone collagen and could help in selecting the optimum method of collagen separation. An extraction method may be successful in some cases but could fail to remove the impurities from bone collagen in other samples. Chemical analysis of the impurities and their radiocarbon dates also should be obtained. 

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