From LiNiO₂ to Li₂NiO₃ : Synthesis, Structures and Electrochemical Mechanisms in Li-Rich Nickel Oxides

The Li−Ni−O phase diagram contains a variety of compounds, most of which are electrochemically active in Li-ion batteries. Other than the well-known LiNiO2, here we report a facile solid-state method to prepare Li2NiO3 and other Li-rich Ni oxides of composition Li1+xNi1−xO2 (0 ≤ x ≤ 0.33). We characterize their crystal and electronic structure, exhibiting a highly oxidized Ni state and defects of various nature (Li−Ni disorder, stacking faults, oxygen vacancies). We then investigate the use of Li2NiO3 as a cathode active material and show its remarkably high specific capacity, which however fades quickly. While we demonstrate that the initial capacity is due to irreversible O2 release, such process stops quickly in favor of more classical reversible redox mechanisms that allow cycling the material for >100 cycles. After the severe oxygen loss (∼15−20%) and prolonged cycling, the Bragg reflections of Li2NiO3 disappear. Analysis of the diffracted intensities suggests the resulting phase is a disordered rock salt-type material with high Li content, close to Li0.5Ni0.5O, never reported to date and capable of Li diffusion. Our findings demonstrate that the Li−Ni−O phase diagram has not been fully investigated yet, especially concerning the preparation of new promising materials by out-of-equilibrium methods

Cumulative contributions of weak DNA determinants to targeting the Drosophila dosage compensation complex

Fine-tuning of X chromosomal gene expression in Drosophila melanogaster involves the selective interaction of the Dosage Compensation Complex (DCC) with the male X chromosome, in order to increase the transcription of many genes. However, the X chromosomal DNA sequences determining DCC binding remain elusive. By adapting a ‘one-hybrid’ assay, we identified minimal DNA elements that direct the interaction of the key DCC subunit, MSL2, in cells. Strikingly, several such novel MSL2 recruitment modules have very different DNA sequences. The assay revealed a novel, 40 bp DNA element that is necessary for recruitment of DCC to an autosomal binding site in flies in the context of a longer sequence and sufficient by itself to direct recruitment if trimerized. Accordingly, recruitment of MSL2 to the single 40 bp element in cells was weak, but as a trimer approached the power of the strongest DCC recruitment site known to date, the roX1 DH site. This element is the shortest MSL2 recruitment sequence known to date. The results support a model for MSL2 recruitment according to which several different, degenerate sequence motifs of variable affinity cluster and synergise to form a high affinity site

The DNA binding CXC domain of MSL2 is required for faithful targeting the Dosage Compensation Complex to the X chromosome

Dosage compensation in Drosophila melanogaster involves the selective targeting of the male X chromosome by the dosage compensation complex (DCC) and the coordinate, ∼2-fold activation of most genes. The principles that allow the DCC to distinguish the X chromosome from the autosomes are not understood. Targeting presumably involves DNA sequence elements whose combination or enrichment mark the X chromosome. DNA sequences that characterize ‘chromosomal entry sites’ or ‘high-affinity sites’ may serve such a function. However, to date no DNA binding domain that could interpret sequence information has been identified within the subunits of the DCC. Early genetic studies suggested that MSL1 and MSL2 serve to recognize high-affinity sites (HAS) in vivo, but a direct interaction of these DCC subunits with DNA has not been studied. We now show that recombinant MSL2, through its CXC domain, directly binds DNA with low nanomolar affinity. The DNA binding of MSL2 or of an MSL2–MSL1 complex does not discriminate between different sequences in vitro, but in a reporter gene assay in vivo, suggesting the existence of an unknown selectivity cofactor. Reporter gene assays and localization of GFP-fusion proteins confirm the important contribution of the CXC domain for DCC targeting in vivo

The Volume-Regulated Anion Channel LRRC8 is Involved in the Initiation of Epidermal Differentiation and is Deregulated in Psoriasis

Recent studies have shown that LRRC8A, the essential subunit of the volume-regulated anion channel LRRC8, which is responsible for mediating cell volume regulation during hypotonic stress, is predominantly localized in the basal layer of the epidermis. This prompted us to investigate whether LRRC8A plays a role in maintaining epidermal homeostasis by regulating key processes initiated in this layer, such as cell proliferation and/or differentiation.LRRC8A was found to be strongly upregulated in transiently amplifying cells at the onset of differentiation. While LRRC8A mRNA remains high when keratinocytes mature further, the LRRC8A protein is drastically downregulated. Interference with LRRC8A expression at this step inhibits the transition of keratinocyte stem cells into transiently amplifying cells and impairs terminal differentiation. As psoriasis is a common chronic inflammatory skin disease characterized by disturbed epidermal differentiation and aberrant function of transiently amplifying cells, we investigated the involvement of LRRC8A in this disease. Indeed, LRRC8A was strongly decreased in lesional psoriatic skin, which could also be mimicked in vitro using Th1/Th17 cytokine mixes. Thus, our data suggest that LRRC8 could serve as a therapeutic target for the topical treatment strategies of psoriatic lesions by restoring the capacity of keratinocytes to initiate differentiation

An <i>in situ</i> structural study on the synthesis and decomposition of LiNiO₂

High-resolution in situ synchrotron XRD shades new light on structural evolution during solid-state synthesis and decomposition processes in LiNiO2.</p