Geology Club Seminar

Theme: Biosignature Detection and the Origins of Life

Complex organic molecules are ubiquitous in our solar system and within all life on Earth. These molecules form through diverse metabolic and abiotic synthesis pathways, potentially leaving unique isotope signatures behind. For decades, stable carbon isotope ratios (¹²C/¹³C) have provided a powerful means of linking organic molecules to their origins, with applications spanning geosciences, planetary science, chemical forensics, and drug testing. Traditionally, these ratios are reported as averages, whether across mixtures or individual compounds, potentially obscuring the carbon isotope distribution across specific molecular sites.

Position-specific isotope analysis is an emerging field of research that seeks to uncover isotope ratios at distinct atomic sites within molecules, offering a detailed molecular fingerprint that was previously masked. Nuclear magnetic resonance (NMR) spectroscopy has the potential to play a key role within this field of research by allowing isotope information to be gathered from complex mixtures without the need to fragment the molecule, and by directly measuring absolute (rather than relative) isotope ratios. We have developed several NMR-based tools for position-specific ¹³C/¹²C analysis, leveraging indirect detection methods with nuclei like ¹H, ¹⁹F, and ³¹P. With these tools, we have characterized intramolecular carbon isotope distributions across a variety of compounds, including amino acids and organofluorine molecules.

Position-specific isotope analysis opens new pathways for studying isotope fractionation in (bio)geochemical processes and ecological systems. However, the lack of comprehensive data and limited understanding of the natural intramolecular distribution of stable carbon isotopes currently limits our interpretations. This talk will present our NMR methodology and its diverse applications, from autotroph-derived molecular fingerprints that can be utilized to improve our ability to interpret position-specific isotope data to forensic analyses that reveal synthesis pathways for specific anthropogenic compounds.

For more information, please contact Will Lawrence by email at [email protected].