title: Evaluating uncertainty in the calculation of non-exchangeable hydrogen fractions within organic materials.
abstract: We calculated the fraction of exchangeable hydrogen atoms in proteinaceous materials commonly analyzed for stable isotopic composition related to the region-of-origin of an animal. These included several types of alpha- and beta-keratin, and muscle tissue. We find that the fraction of H atoms in keratin available for exchange at a biologically relevant temperature (25 degrees C) averaged 9% across a range of ground organic materials, but was as high as approximately 17% in cut hair; muscle tissue has approximately 12% exchangeable H atoms. Under most analysis conditions, the difference in exchangeable fractions due to physical sample processing has a minimal effect on the calculated delta2H values of the non-exchangeable H atoms within a keratin-containing tissue (<2 per thousand). However, extreme mismatches between sample and reference material types could affect delta2H values.
authors.affiliation: Biology Department, University of Utah, Salt Lake City, UT 84112, USA. chesson@biology.utah.edu
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Chesson
authors.forename: David W
authors.initials: DW
authors.lastname: Podlesak
authors.forename: Thure E
authors.initials: TE
authors.lastname: Cerling
authors.forename: James R
authors.initials: JR
authors.lastname: Ehleringer
mesh_terms: D000818:Animals; D002417:Cattle; D006801:Humans; D006859:Hydrogen / Q000032:analysis*; D007553:Isotope Labeling / Q000379:methods*; D007633:Keratins / Q000032:analysis*; D009132:Muscles / Q000737:chemistry*; D012015:Reference Standards; D012756:Sheep; D013696:Temperature; D035501:Uncertainty; D053800:beta-Keratins / Q000032:analysis*
chemical_list: D053800:beta-Keratins; D007633:Keratins; D006859:Hydrogen