Hydrogen bonding and coordination in normal and supercritical water from X-ray inelastic scattering

A direct measure of hydrogen bonding in water under conditions ranging from the normal state to the supercritical regime is derived from the Compton scattering of inelastically-scattered X-rays. First, we show that a measure of the number of electrons $n_e$ involved in hydrogen bonding at varying thermodynamic conditions can be directly obtained from Compton profile differences. Then, we use first-principles simulations to provide a connection between $n_e$ and the number of hydrogen bonds $n_{HB}$. Our study shows that over the broad range studied the relationship between $n_e$ and $n_{HB}$ is linear, allowing for a direct experimental measure of bonding and coordination in water. In particular, the transition to supercritical state is characterized by a sharp increase in the number of water monomers, but also displays a significant number of residual dimers and trimers.Comment: 14 pages, 5 figures, 1 tabl

Phonon dispersion and lifetimes in MgB2

We measure phonon dispersion and linewidth in a single crystal of MgB_2 along the Gamma-A, Gamma-M and A-L directions using inelastic X-Ray scattering. We use Density Functional Theory to compute the effect of both electron-phonon coupling and anharmonicity on the linewidth, obtaining excellent agreement with experiment. Anomalous broadening of the E_2g phonon mode is found all along Gamma-A. The dominant contribution to the linewidth is always the electron-phonon coupling.Comment: 4 pages, 3 figure

Cardiac microtissues from human pluripotent stem cells recapitulate the phenotype of long-QT syndrome

Background: Human induced pluripotent stem cells (hiPSCs) and their derivative cardiomyocytes (hiPSCCMs) have been successfully used to study the electrical phenotype of cardiac ion channel diseases. However, strategies to mature CMs and more comprehensive systems recapitulating the heart complexity are required to advance our ability to capture adult phenotypes. Methods: We differentiated wild-type (WT) and long QT syndrome type 1 (LQT1) hiPSCs into CMs, endothelial cells and cardiac fibroblasts. The three cell types were combined to form three-dimensional (3D) spheroids, termed "cardiac microtissues" (cMTs) and the electrophysiological properties were measured using 96-well multi-electrode arrays. Results: LQT1 cMTs displayed prolonged field potential duration compared to WT controls, thus recapitulating the typical feature of LQTS. Isoprenaline caused a positive chronotropic effect on both LQT1 and WT cMTs. The 96-well multi-electrode array format proved suitable to detect electrical changes directly in the 3D tissues. Conclusions: 3D hiPSC cMTs are a scalable tool that can be used to identify LQT electrical hallmarks and drug responses. We anticipate this tool can be adopted by pharmaceutical companies to screen cardioactive compounds. (c) 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Stem cells & developmental biolog

Functional conservation of the grapevine candidate gene INNER NO OUTER for ovule development and seed formation

Seedlessness represents a highly appreciated trait in table grapes. Based on an interesting case of seedless fruit production described in the crop species Annona squamosa, we focused on the Vitis vinifera INNER NO OUTER (INO) gene as a candidate. This gene encodes a transcription factor belonging to the YABBY family involved in the determination of abaxial identity in several organs. In Arabidopsis thaliana, this gene was shown to be essential for the formation and asymmetric growth of the ovule outer integument and its mutation leads to a phenotypic defect of ovules and failure in seed formation. In this study, we identified in silico the V. vinifera orthologue and investigated its phylogenetic relationship to INO genes from other species and its expression in different organs in seeded and seedless varieties. Applying cross-species complementation, we have tested its functionality in the Arabidopsis ino-1 mutant. We show that the V. vinifera INO successfully rescues the ovule outer integument growth and seeds set and also partially complements the outer integument asymmetric growth in the Arabidopsis mutant, differently from orthologues from other species. These data demonstrate that VviINO retains similar activity and protein targets in grapevine as in Arabidopsis. Potential implications for grapevine breeding are discussed

Bid in plants: characterization of plants expressing the animal pro-apoptotic protein Bid

Programmed cell death (PCD) is a crucial process in all the living organisms. Similarities and substantial differences are present in control, signaling and execution of this program in plants and animals. The major regulators of the commitment to PCD in animal cells are the BCL-2 protein family. Homologous proteins are absent in plants. Among these, the BH3-only protein Bid is crucial for both life and death of the animal cells. We have constitutively expressed this pro-apoptotic protein, Bid from mouse, in Arabidopsis thaliana and in Nicotiana tabacum to explore the possible cross-talk between the apoptotic signaling pathway and the plant PCD pathway. This protein has been inserted in its full-length form, flBid, and not in its caspase-processed active form, tBid. For this reason, it requires an activation signal to exert its action on mitochondria that can be either a caspase-like processing activity or the binding of specific signal molecules (i.e. lysolipid molecules). Transgenic plants show no differences with wild-type in growth and development. They were treated with different abiotic stress conditions to activate the PCD signaling cascade and to study the possible involvement of responses able to induce flBid activation within plant cells. No significant differences were observed when Bid plants and WT plants were treated either with NO or H2O2 as PCD inducer. Small differences are observed in necrotic death induction: Bid plants leaves appear to be more sensitive to oxidative stress when compared to the wild-type ones. Caspase-like activity on Bid protein is absent in these conditions. In root hair cells, we have observed a reduction in the number of apoptotic cells due to an increase of the necrotic ones after 24 hours from H2O2 treatment. These results indicated that full length Bid do not significantly change PCD response to H2O2 and NO stress in plants