Diamond Annual Review 2023/24

38 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 3 / 2 4 How a chemical reaction used by cooks helped create life on Earth A chemical process used in the browning of food to give it its distinct smell and taste is probably happening deep in the oceans, where it helped create the conditions necessary for life. Known as the Maillard reaction after the French scientist who discovered it, the process converts small molecules of organic carbon into bigger molecules known as polymers. In the kitchen, it is used to create flavours and aromas out of sugars. A research team led by Professor Caroline Peacock at the University of Leeds argues that on the sea floor, the process has had a more fundamental effect, where it has helped to raise oxygen and reduce carbon dioxide levels in the atmosphere, to create the conditions for complex life forms to emerge and thrive on Earth. The team used Diamond’s I08 beamline for this research. As part of the study, the scientists modelled how much organic carbon has been locked into the seabed because of the Maillard reaction. They estimate it has resulted in around 4 million tonnes of organic carbon each year being locked into the seabed. To test their theory, the researchers looked at what happened to simple organic compounds when mixed with different forms of iron and manganese in the laboratory at 10 degrees Celsius, the temperature of the seabed. Analysis revealed that the“chemical fingerprint”of the laboratory samples - which had undergone the Maillard reaction - matched those from sediment samples taken from seabed locations around the world. Understanding the complex processes affecting the fate of organic carbon that is deposited on the seafloor is crucial to pinpointing how Earth’s climate changes in response to both natural processes and human activity, and helping humanity better manage climate change, since the application and long-term success of carbon capture technologies relies on carbon being locked away in stable forms rather than being transformed into carbon dioxide. Moore, O.W. et al . DOI: 10.1038/s41586-023-06325-9 Micro-CT can take us back in time to the dawn of jaws More than 99% of living vertebrate species, including ourselves, are jawed vertebrates (gnathostomes). However, how and when jaws and teeth evolved remains a contentious issue. Placoderms were among the earliest jawed vertebrates, and many features of their anatomy can still be seen in modern fish and other animals. During this period, the skeletons of many animals were comprised of cartilage, which doesn’t preserve as well as bone. A team of researchers used X-ray micro- Computed Tomography (micro-CT) at the I12 beamline to examine a near-complete acanthothoracid upper jaw discovered in western Mongolia. The high-resolution micro- CT scans allowed the team to see both the actual surface of the jaw hinge and the overall shape of the cavity where the jaw muscle would have been. They could also see the course of the lateral line canals on the outside of the jaw. Their results suggest jaw morphology was phylogenetically conserved across most placoderms, and bring a step closer to understanding the origin and evolution of jaws and teeth in vertebrates. Brazeau, M.D. et al. DOI:10.1098/ rsos.221452 Imaging and Microscopy Science Highlights Figure: C and N 1s NEXAFS data plotted as energy (eV) versus normalized absorbance (presented in arbitrary units (a.u.)). Grey bands show energy regions in which spectral features associated with Maillard reaction products are expected to appear. The presence of peaks or other spectral content in these regions in both our experimental and sediment samples indicates that geopolymerization by means of a Maillard-type reaction is a likely formation pathway for persistent organics in marine sediments. Figure: Upper jaw complex in virtual three-dimensional rendering from synchrotron tomography.