Variability in the preservation of the isotopic composition of collagen from fossil bone

Abstract

Collagen from bone was prepared by several methods. For modern and well-preserved bone the δ 13 C and δ 15 N of collagen replicas obtained after HCl or EDTA demineralization were similar to those obtained with a gelatinization procedure. However, in more poorly preserved fossil bone the δ 13 C and δ 15 N varied among the different protein extracts. The yield of collagen obtained with EDTA demineralization was consistently higher than extraction procedures that used HCl. The δ 13 C of individual amino acids separated from the collagen of modern and fossil whale bone varied up to 17%., and the δ 15 N from the same amino acids ranged over 47%. The δ 13 C and δ 15 N of most amino acids clustered closely to the average of the HCl insoluble collagen. The δ 13 C of the major amino acid in collagen, glycine, differed from the average HCl insoluble collagen by approximately 8%. in the fossil whale and 14%. in the modern whale. The δ 15 N of glycine differed from the average HCl insoluble values by approximately 4%. in the fossil whale and 7%. in the modern whale. Thus, diagenetic changes that alter the ratio of glycine to other amino acids in bone can be expected to perturb the values for carbon and nitrogen isotopes.