Dr. Schurr:

I appreciate the time you've taken to answer my query.  The comments that
were especially helpful were made by Dr. Bocherens and yourself.  I believe
the conflicts are beginning to sort themselves out.  It is always a humbling
experience to realize how much one DOESN'T know!

Again, I appreciate your time and citations.  I think you have saved us much
in the way of time and effort.

Michael


At 09:16 AM 1/16/98 -0500, you wrote:
>In response to Michael Jacoby's request about collagen purity in extinct
>bears:
>
>  A number of different criteria have been used to evaluate the purity of
>collagen (or the reliability of isotope ratios obtained from them).  These
>include C:N ratio - empirically between 2.9 - 3.6 (DeNiro 1985), the yield
>of collagen extracted from bone and combustion yields of carbon and
>nitrogen gas (Ambrose 1990), and amino acid analysis (Schwarcz 1985 is a
>typical archaeological example, I am sure there are many others).  You
>could also add amino acid racemization, for which I do not have a handy
>citation.
>
>  From what I have been able to gather, amino acid analysis is not all that
>helpful, unless you fear contamination by proteins other than collagen.  If
>anyone is aware of an example where a collagen sample was rejected solely
>on the basis of its amino acid profile, I would enjoy hearing about it.  In
>my personal opinion, amino acid analysis is not worth the trouble and
>expenses of being a routine test, unless of course one happens to already
>be doing them routinely anyway.
>
>  Extraction yields and C:N ratio are very useful.  In general, samples
>producing less than about 2% yields of collagen are probably going to give
>poor isotope ratios.  Samples with C:N ratios far outside the empirical
>range of 2.9 - 3.6 are also likely to be poor.  The nice thing about these
>tests are that if you are extracting and running isotope ratios on your
>samples, you can get this kind of information with just a little extra
>effort, and there is not need to turn to an outside lab.  And if someone
>else is doing your isotope ratios, they should be able to provide this info
>with the delta values
>
>Regards,
>  -Mark Schurr
>
>Ambrose, S. H.
>1990  Preparation and Characterization of Bone and Tooth Collagen for
>Isotopic Analysis. Journal of Archaeological Science 17:431-451.
>
>DeNiro, M. J.
>1985  Postmortem Preservation and Alteration of Invivo Bone Collagen
>Isotope Ratios in Relation to Paleodietary Reconstruction. Nature 317:806-809.
>
>Schwarcz, H. P., J. Melbye, M. A. Katzenberg, and M. Knyf
>1985  Stable Isotopes in Human Skeletons of Southern Ontario:
>Reconstructing Paleodiet.  Journal of Archaeological Science 12:187-206.
>
>
>**************************************************************
>Mark R. Schurr                                  Phone:  (219) 631-7638
>Assistant Professor                             FAX:     (219) 631-8209
>Department of Anthropology
>University of Notre Dame
>Notre Dame, IN  46556 USA
>
>
___________________________

Michael Jacoby
Department of Zoology
Washington State University
PO Box 644236
Pullman, WA  99164-4236

phone: (509)335-4715
email: [log in to unmask]
fax: (509) 335-3184