Characterization of Proteomes Extracted through Collagen-based Stable Isotope and Radiocarbon Dating Methods

Isotope analyses on “collagen”
extracted from ancient
bone have been routinely used for dietary and chronological inferences
worldwide for decades. These methods involve the decalcification of
biomineralized tissues with acid, often followed by processes to remove
exogenous contaminants, and then gelatinization of what is often described
as the “collagen” fraction. However, little is known
about the relative content of collagen to the many other noncollagenous
proteins (NCPs) potentially present. Some of these NCPs have great
longevity in ancient bone, and some, for example, fetuin-A, are useful
for obtaining better taxonomic information than collagen. This study
uses Orbitrap Elite LC–MS/MS to characterize the proteomes
of the acid-soluble and base-soluble fractions, which are usually
discarded, and the gelatinized “collagen” fraction obtained
from both stable isotope and radiocarbon methods applied to several
ancient bovine bones. The results showed that all fractions tested
contain numerous NCPs, but the base-soluble fraction for both methods
contains the greatest number of NCPs with the highest relative abundances.
This study confirms that not only do the waste fractions obtained
from the “collagen” extraction procedure of stable isotope
or radiocarbon dating methods yield a plentiful resource of NCPs that
is currently being overlooked but that they also provide proteomes
as complex as those obtained from standard proteomics methods.