Uranium isotope analysis of the Triassic-Jurassic boundary section at Csővár

INST: L_200A kutatásom célja egy új uránizotóp-adatsor előállítása volt csővári Vár-hegy triász-jura határszelvényéből, melynek elemzése, valamint dinamikus modellezése hozzájárul annak megértéséhez, hogy az anoxia milyen szerepet játszott a triász végi tömeges kihalási esemény elindításában, illetve az ökoszisztéma helyreállásának késleltetésében

Uranium isotope evidence for extensive seafloor anoxia after the end-Triassic mass extinction

The end-Triassic extinction (ETE) ranks as one of the ‘Big Five’ biotic crises of the Phanerozoic and is thought to be triggered by volcanism of the Central Atlantic Magmatic Province (CAMP). However, the proximal causes of the extinction and the factors responsible for the delayed biotic recovery remain debated. Here we use uranium isotopes and geochemical models to constrain the evolution of global seafloor anoxia during the latest Triassic and earliest Jurassic. We document a major negative uranium isotope anomaly from carbonates in a western Tethyan continuous marine Triassic-Jurassic boundary section. The onset of the δ238U anomaly is coincident with the initial negative carbon isotope anomaly that is correlative with the extinction horizon and a major pulse of intrusive CAMP volcanism. The U isotope values remain low throughout most of the Hettangian indicating persistent, widespread anoxia. Our coupled C-P-U Earth system and U-cycle box model results show that the maximum extent of anoxia (∼13%) was reached 200–250 kyr after the extinction, probably as a consequence of extrusive CAMP pulses. The anoxic extent remained high (1–6%) throughout the Hettangian. We suggest that the continuing volcanic activity, recorded by the successive negative carbon isotope anomalies and Hg peaks in the section, inhibited any rapid recovery from anoxia. Our results indicate that the spread of marine anoxia and the ETE have a common cause rather than a cause-and-effect relationship but anoxia played a key role in hindering the biotic recovery of benthic ecosystems following the extinction.ISSN:0012-821XISSN:1385-013

19F multiple-quantum coherence NMR spectroscopy for probing protein–ligand interactions

A new 19F NMR method is presented which can be used to detect weak protein binding of small molecules with up to mM affinity. The method capitalizes on the synthetic availability of unique SF5 containing compounds and the generation of five-quantum coherences (5QC). Given the high sensitivity of 5QC relaxation to exchange events (i.e. reversible protein binding) fragments which bind to the target with weak affinity can be identified. The utility of the method in early stage drug discovery programs is demonstrated with applications to two model proteins, the neurotoxic NGAL and the prominent tumor target β-catenin