My research interest is in the application of analytical chemistry to archaeological and geological questions. In particular my focus is on the analysis of proteins: their pathways of degradation, their methods of preservation, of detection, and how these molecules can inform us of an organism’s life and death history. I run the NERC-recognised amino acid dating facility, NEaar.
One key problem is dating in the Quaternary (the last two million years), a crucial period for geological understanding with impacts on both climate change and human evolution. A well-constrained chronology is essential in almost all aspects of Quaternary research, but beyond the limit of radiocarbon dating (~50,000 years) there is no technique that can be applied ubiquitously in the terrestrial environment.
In recent years advances have been made in amino acid racemization geochronology (AAR; Penkman et al., 2007; 2008; 2011), combining the isolation of an 'intra-crystalline' fraction of amino acids by exhaustive bleach treatment of ground shell carbonate (Sykes et al., 1995) with a new Reverse-Phase High Pressure Liquid Chromatography (RP-HPLC) method (Kaufman & Manley, 1998). This combination of techniques results in the analysis of D/L values of multiple amino acids from the chemically-protected protein within the biomineral, enabling both decreased sample sizes and increased reliability. The intra-crystalline protein occurs within a 'closed system' during the burial history of the shell, vital for the application of this technique for geochronological purposes. Amino acid data obtained from the intra-crystalline fraction of calcitic biominerals (Bithynia opercula) indicate this to be a particularly robust repository for the original protein, confirming the antiquity of the early human occupation of northern Europe (Parfitt et al., 2005).
Closed system racemization analysis in shells improves the precision and reliability of AAR as a dating tool in the Quaternary. It also allows developments using laboratory methods and computational chemistry to test non-linear models of decomposition kinetics and to develop methods of internal validation based on other amino acids.
The study of fossil protein also has potential for use as an environmental proxy: research areas include analysing the proteins from speleothems and Greenland ice cores, assessing the microbial contribution to aquatic systems, isolating the stable isotopes of the ‘closed-system’ protein for palaeoclimate studies and looking at protein as a stress biomarker in coral.
A continuous focus of my research has been in ensuring the highest quality amino acid data from fossil samples, whose low concentrations of protein are easily subject to modern contamination. The analytical difficulties of recovering the very low concentrations of useful biomolecules from fossil material require development and refinement, from intensive studies into the best methods of preparation, to the optimization of analytical methods by RP-HPLC.