THE POWER OF THE HELIX: HYDRATION, BOUND WATER AND HYDROGEN EXCHANGE

In the collagen molecule, the amount of hydrogen exchange and the potential alteration of in vivo isotopic values have been shown to be extensive and complex. Two different parameters, one physical and one molecular, can have a significant impact on apparent hydrogen exchange. The rapid rehydration of protein during sample preparation can now be largely controlled with continuous flow systems, and careful handling of samples can decrease the error contributed from adsorbed water. The range of molecular integrity that exists in collagen from fossil and subfossil bone spans the gamut from completely insoluble, unaltered protein to hydrolyzed, deaminated, decarboxylated, racemic remnant polymer. The amount of hydrogen exchanged during collagen preparation from bone varies significantly as a function of protein preservation, specifically helical content. The impact of widely disparate collagen preservation states on the observed hydrogen isotopic values in bone collagen is shown for a midHolocene burial site in east central Florida, where clear trends between human and faunal collagens can be seen through the noise of different amounts of hydrogen exchange.