Progetti di ricerca

Atmospheric mineral dust (hereby ’dust’) is a key component of the Earth system and has widespread climatic impacts. Dust affects the global climate and environment through, for example, radiative forcing, cloud formation, and nutrient cycles1,2, but its parametrisation in global climate and… Leggi tutto Earth system models is defective3-5. Recently, the current net effect of dust direct radiative forcing on global climate was calculated as most likely negative, although potentially slightly positive given the large uncertainty on this estimate (-0.2 ± 0.5 W m-2 with 90% confidence interval5 ). Many uncertainties remain in such calculations, largely caused by incomplete data on the chemical and physical properties of dust particles, and on the meteorological processes and driving mechanisms behind dust emission, transport, and deposition (‘dust cycle’). While climate models have become increasingly complex, the parametrisation of dust processes, although also improving, lags behind this development, and its uncertainties amplify as models get more sophisticated4 . This limits our understanding on the Earth system as a whole and hampers the ability of models to predict the effects of climate changes on the natural world and societies. A necessary first step to enhance models is to have more observational data on dust properties. The arid and semi-arid East Asia is one of the key global dust sources, but, for example, observational studies on East Asian dust mineralogy were ~50% less than those from the northern African region by 20156 . Compared to other major global dust sources, East Asia is unique in that it also hosts a globally exceptional geologic archive of windblown dust from the past ~25 million years, the Chinese Loess Plateau (CLP; Fig. 1). Extensive research, especially provenance studies, on the CLP dust deposits has been a key in revealing the long-term, two-way link between dust and climate changes in the Earth’s history7-10 . Dust provenance analysis is, in fact, one of the few methods that simultaneously provide information on all the steps of the dust cycle (emission, transport, deposition). Because of the scarcity of interdisciplinary studies involving both atmospheric scientists and geologists, the CLP region has much unused potential to establish a link between past and present dust activity to better understand both and to enhance the modelling aspects of dust11-13 . In this project, I study the properties and provenance of dust collected by active and passive samplers in East Asia during 2019–2023.

Exploring Nature’s mechanisms for CO2 fixation is an important and timely research topic, considering the current environmental crisis linked to increased levels of greenhouse gasses. Anaerobic microorganisms use nickel-iron carbon monoxide dehydrogenase (NiFe-CODH) metalloenzymes to catalyze CO2 reduction and CO oxidation. NiFe-CODHs… Leggi tutto play key physiological roles, such as enabling growth using the reducing power of CO and fixing CO2 to generate acetylCoA(1). However, these enzymes proved difficult to study and their catalytic mechanism remains unclear. Although only a tiny fraction of the vast biodiversity of NiFe-CODHs has been explored, it has already revealed their intriguing functional biodiversity. Interestingly, these enzymes have the same inorganic active site, surrounded by conserved residues, but homologous NiFe-CODHs have different catalytic properties (i.e. catalytic rates, substrate affinities, and, most importantly, oxygen resistance). These properties must be determined by the protein scaffold, in a way that is still unknown. The host laboratory showed how informative quantum and molecular mechanics methods are to investigate redox metalloenzymes such as NiFe-CODHs and hydrogenases(2,3), paving the way for this project. Focusing on three model enzymes, and using a computational approach, this project has two main objectives: first, fully elucidate the catalytic mechanism of NiFe-CODHs and the protein scaffold’s role in controlling catalytic properties; second, clarify the O2 inhibition mechanisms, still poorly understood, and identify the key residues involved in O2 resistance. These findings will contribute to the understanding of the NiFe-CODH’s physiological functions, and will help in designing catalysts to fix CO2.