Abnormal (Hydroxy)proline Deuterium Content Redefines Hydrogen Chemical Mass

Analyzing the δ²H values in individual amino acids of proteins extracted from vertebrates, we unexpectedly found in some samples, notably bone collagen from seals, more than twice as much deuterium in proline and hydroxyproline residues than in seawater. This corresponds to at least 4 times higher δ²H than in any previously reported biogenic sample. We ruled out diet as a plausible mechanism for such anomalous enrichment. This finding puts into question the old adage that "you are what you eat".