Abnormal (Hydroxy)proline Deuterium Content Redefines Hydrogen Chemical Mass

Area of Science:

• Biogeochemistry
• Paleontology
• Biomolecular analysis

Background:

• Deuterium (²H) stable isotope analysis is crucial for understanding ecological processes.
• Previous studies indicate that an organism's diet primarily dictates its isotopic composition.
• Vertebrate bone collagen is a valuable archive for reconstructing past environments and diets.

Purpose of the Study:

• To investigate the deuterium (²H) values in individual amino acids of vertebrate bone collagen.
• To identify potential anomalies in deuterium incorporation into specific amino acid residues.
• To explore the implications of observed deuterium enrichment for established ecological principles.

Main Methods:

• Extraction and purification of bone collagen from vertebrate samples.
• High-precision analysis of deuterium (²H) stable isotope ratios in individual amino acids using gas chromatography-isotope ratio mass spectrometry.
• Comparison of ²H values in amino acids with environmental water (seawater) and dietary sources.

Main Results:

• Unexpectedly high deuterium (²H) enrichment, exceeding seawater values by over twofold, was observed in proline and hydroxyproline residues from some vertebrate bone collagen samples, notably seals.
• These proline and hydroxyproline ²H values were at least four times higher than any previously reported biogenic samples.
• Dietary analysis could not account for the observed anomalous deuterium enrichment in these specific amino acids.

Conclusions:

• The findings challenge the conventional understanding that an organism's isotopic signature is solely determined by its diet.
• Anomalous deuterium enrichment in specific amino acids suggests novel biological or environmental processes at play.
• This research necessitates a re-evaluation of how isotopic data from bone collagen is interpreted in ecological and paleoclimatic studies.