51 research outputs found
IMPACT-Global Hip Fracture Audit: Nosocomial infection, risk prediction and prognostication, minimum reporting standards and global collaborative audit. Lessons from an international multicentre study of 7,090 patients conducted in 14 nations during the COVID-19 pandemic
Provenance and tectonic significance of the Palaeoproterozoic metasedimentary successions of central and northern Madagascar
New detrital zircon U-Pb age data obtained from various quartzite units of three spatially
separated supracrustal packages in central and northern Madagascar, show that these units were
deposited between 1.8 and 0.8 Ga and have similar aged provenances. The distribution of detrital
zircon ages indicates an overwhelming contribution of sources with ages between 2.5 and 1.8 Ga.
Possible source rocks with an age of 2.5 Ga are present in abundance in the crustal segments
(Antananarivo, Antongil and Masora Domains) either side of a purported Neoproterozoic suture
("Betsimisaraka Suture Zone"). Recently, possible source rocks for the 1.8 Ga age peak have been
recognised in southern Madagascar. All three supracrustal successions, as well as the Archaean blocks
onto which they were emplaced, are intruded by mid-Neoproterozoic magmatic suites placing a
minimum age on their deposition. The similarities in detrital pattern, maximum and minimum age of
deposition in the three successions, lend some support to a model in which all of Madagascar's
Archaean blocks form a coherent crustal entity (the Greater Dharwar Craton), rather than an
amalgamate of disparate crustal blocks brought together only during Neoproterozoic convergence.
However, potential source terranes exist outside Madagascar and on either side of the Neoproterozoic
sutures, so that a model including a Neoproterozoic suture in Madagascar cannot be dispelled outright
Pretectonic tholeiitic volcanism and related transitional plutonism in the Kidal assemblage (Iforas Pan-African Belt, Mali)
Geochemistry, geochronology and Hf isotope of granitoids in the Chinese Altai: Implications for Paleozoic tectonic evolution of the Central Asian Orogenic Belt
Petrogenesis of the Devonian high-Mg rock association and its tectonic implication for the Chinese Altai orogenic belt, NW China
The Late Carboniferous to Early Permian high silica magmatism in the Southern Mongolia: Implications for tectonic evolution and continental growth
Carboniferous bimodal volcanic rocks in the Eastern Tianshan, NW China: Evidence for arc rifting
Reconstructing multiple arc-basin systems in the Altai–Junggar area (NW China): Implications for the architecture and evolution of the western Central Asian Orogenic Belt
Functional evolution of scorpion venom peptides with an inhibitor cystine knot fold
The ICK (inhibitor cystine knot) defines a large superfamily of polypeptides with high structural stability and functional diversity. Here, we describe a new scorpion venom-derived K+ channel toxin (named lambda-MeuKTx-1) with an ICK fold through gene cloning, chemical synthesis, nuclear magnetic resonance spectroscopy, Ca2+ release measurements and electrophysiological recordings. lambda-MeuKTx-1 was found to adopt an ICK fold that contains a three-strand anti-parallel beta-sheet and a 3(10)-helix. Functionally, this peptide selectively inhibits the Drosophila Shaker K+ channel but is not capable of activating skeletal-type Ca2+ release channels/ryanodine receptors, which is remarkably different from the previously known scorpion venom ICK peptides. The removal of two C-terminal residues of lambda-MeuKTx-1 led to the loss of the inhibitory activity on the channel, whereas the C-terminal amidation resulted in the emergence of activity on four mammalian K+ channels accompanied by the loss of activity on the Shaker channel. A combination of structural and pharmacological data allows the recognition of three putative functional sites involved in channel blockade of lambda-MeuKTx-1. The presence of a functional dyad in lambda-MeuKTx-1 supports functional convergence among scorpion venom peptides with different folds. Furthermore, similarities in precursor organization, exon-intron structure, 3D-fold and function suggest that scorpion venom ICK-type K+ channel inhibitors and Ca2+ release channel activators share a common ancestor and their divergence occurs after speciation between buthidae and non-buthids. The structural and functional characterizations of the first scorpion venom ICK toxin with K+ channel-blocking activity sheds light on functionally divergent and convergent evolution of this conserved scaffold of ancient origin
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