Understanding the role of atmospheric CO 2 during past climate changes requires clear knowledge of how it varies in time relative to temperature. Antarctic ice cores preserve highly resolved records ...of atmospheric CO 2 and Antarctic temperature for the past 800,000 years. Here we propose a revised relative age scale for the concentration of atmospheric CO 2 and Antarctic temperature for the last deglacial warming, using data from five Antarctic ice cores. We infer the phasing between CO 2 concentration and Antarctic temperature at four times when their trends change abruptly. We find no significant asynchrony between them, indicating that Antarctic temperature did not begin to rise hundreds of years before the concentration of atmospheric CO 2 , as has been suggested by earlier studies.
Bioconjugates are an important class of therapeutic molecules. To date,
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glycan-based metabolic glycoengineering has had limited use in this field, due to the complexities of the endogenous
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...glycosylation pathway and the lack of an
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glycosylation consensus sequence. Here, we describe the development of a versatile on-demand
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glycosylation system that uses a novel, widely applicable 5 amino acid
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glycosylation tag, and a metabolically engineered UDP-galactose-4-eperimase (GALE) knock-out cell line. Optimization of the primary sequence of the tag enables the production of Fc-based proteins with either single or multiple
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glycans with complexity fully controlled by media supplementation. We demonstrate how the uniformly labeled proteins containing exclusively N-azido-acetylgalactosamine are used for CLICK chemistry-based bioconjugation to generate site-specifically fluorochrome-labeled antibodies, dual-payload molecules, and bioactive Fc-peptides for applications in basic research and drug discovery. To our knowledge, this is the first description of generating a site-specific
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glycosylation system by combining an
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glycosylation tag and a metabolically engineered cell line.
Mott insulators can host a surprisingly diverse set of quantum phenomena when their frozen electrons are perturbed by various stimuli. Superconductivity, metal-insulator transition, and colossal ...magnetoresistance induced by element substitution, pressure, and magnetic field are prominent examples. Here we report strong diamagnetism in the Mott insulator calcium ruthenate (Ca₂RuO₄) induced by dc electric current. The application of a current density of merely 1 ampere per centimeter squared induces diamagnetism stronger than that in other nonsuperconducting materials. This change is coincident with changes in the transport properties as the system becomes semimetallic. These findings suggest that dc currentmay be a means to control the properties of materials in the vicinity of a Mott insulating transition.
Synthesis of FeH Pépin, C. M.; Geneste, G.; Dewaele, A. ...
Science (American Association for the Advancement of Science),
07/2017, Volume:
357, Issue:
6349
Journal Article
Peer reviewed
High pressure promotes the formation of polyhydrides with unusually high hydrogen-tometal ratios. These polyhydrides have complex hydrogenic sublattices. We synthesized iron pentahydride (FeH₅) by a ...direct reaction between iron and H₂ above 130 gigapascals in a laser-heated diamond anvil cell. FeH₅ exhibits a structure built of atomic hydrogen only. It consists of intercalated layers of quasicubic FeH₃ units and four-plane slabs of thin atomic hydrogen. The distribution of the valence electron density indicates a bonding between hydrogen and iron atoms but none between hydrogen atoms, presenting a two-dimensional metallic character. The discovery of FeH₅ suggests a low-pressure path to make materials that approach bulk dense atomic hydrogen.
Bidirectional replication from eukaryotic DNA replication origins requires the loading of two ring-shaped minichromosome maintenance (MCM) helicases around DNA in opposite orientations. MCM loading ...is orchestrated by binding of the origin recognition complex (ORC) to DNA, but how ORC coordinates symmetrical MCM loading is unclear. We used natural budding yeast DNA replication origins and synthetic DNA sequences to show that efficient MCM loading requires binding of two ORC molecules to two ORC binding sites. The relative orientation of these sites, but not the distance between them, was found to be critical for MCM loading in vitro and origin function in vivo. We propose that quasi-symmetrical loading of individual MCM hexamers by ORC and directed MCM translocation into double hexamers acts as a unifying mechanism for the establishment of bidirectional replication in archaea and eukaryotes.
The Kitaev quantum spin liquid (KQSL) is an exotic emergent state of matter exhibiting Majorana fermion and gauge flux excitations. The magnetic insulator α-RuCl3 is thought to realize a proximate ...KQSL. We used neutron scattering on single crystals of α-RuCl3 to reconstruct dynamical correlations in energy-momentum space. We discovered highly unusual signals, including a column of scattering over a large energy interval around the Brillouin zone center, which is very stable with temperature. This finding is consistent with scattering from the Majorana excitations of a KQSL. Other, more delicate experimental features can be transparently associated with perturbations to an ideal model. Our results encourage further study of this prototypical material and may open a window into investigating emergent magnetic Majorana fermions in correlated materials.
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