Cyameluric Acid as Anion-π Type Receptor for ClO₄⁻ and NO₃⁻: π-Stacked and Edge-to-Face Structures

Based on the binding energies at high levels of ab initio theory including coupled cluster theory at the complete basis limit, we show that cyameluric acid (C6N7O3H3) is a potent receptor for ClO4− and NO3− anions through the anion-π interactions. In contrast, cyanuric acid (C3N3O3H3) binds Cl−, NO3−, and ClO4− with the hydrogen bonding type structures, while their anion-π type structures show slightly weaker binding. Consequently, the cyameluric acid having the C3h symmetric C6N7 nucleus with electron withdrawing oxygen atoms is a novel anion-π type receptor for trigonal-planar and tetrahedral anions. The structures of the cyameluric acid interacting with Cl− and ClO4− are considered as the π stacking type. For the cyameluric acid interacting with NO3−, the π(edge) type complex is only slightly more favored over the π(stack) type in the gas phase, but the π(stack) type is likely to be as stable as the π(edge) type in the solvent phase

Snail is upregulated under extracellular matrix (ECM)-mediated signals.

<p>(A) Western blot analysis showing Snail expression on immobilized ECM. After HUVECs were transfected with siCon or siSnail, the transfectants were reseeded and cultured on PLL (20 μg/mL)-, FN (20 μg/mL)-, or CI (20 μg/mL)-coated culture dishes for 2 h. PLL, poly-L-lysine; FN, fibronectin; CI, collagen type I. (B) Time-course expression pattern of Snail on immobilized ECM. Confluent HUVECs were reseeded and cultured on PLL-, FN- or CI-coated dishes for the indicated time points. Snail expression was evaluated by western blot (upper) and quantitative RT-PCR (lower) analyses. (C) Western blot analysis showing the induction of phosphorylated Akt (p-Akt) and phosphorylated extracellular-regulated kinase 1/2 (p-Erk1/2) in HUVECs that were cultured on FN-coated dishes. (D) Snail expression on immobilized ECM after MK2206 treatment. Confluent HUVECs or human retinal endothelial cells (HRECs) were pre-exposed to 10 μM PP2 (a Src kinase inhibitor) or 1 μg/mL MK2206 (an allosteric Akt inhibitor) for 1 h, followed by reseeding and culture on PLL-, FN-, or CI-coated dishes for 2 h (western blot) or 1 h (quantitative RT-PCR).</p

Comprehensive Energy Analysis for Various Types of π-Interaction

We have investigated various types of π-interactions, where one of the interacting π-systems is represented by an aromatic benzene molecule. The system includes Rg-π, CH-π, π-π(D), π-π(T), H-π(T), π+-π(D), π+-π(T), H+-π(T), π+2-π(D), M+-π, and M+2-π complexes, where Rg denotes a rare gas or noble atom, M denotes a metal, and D/T indicates displaced-stacked/T-shaped structure. The microsolvation effect is also considered. We note that the interaction between a cationic π system and a neutral π system (πcation-π interaction) is so far ambiguously considered as either π-π or cation-π interaction. In terms of total binding energy, the πcation-π interaction is weaker than the cation−π interaction, but much stronger than the π-π interaction. When the hydrophilic (N−H)+ or (C−H)+ group in a singly charged π+ system (as in protonated histidine, arginine, pyridine, or dimethyl imidazolium) interacts with a π-system, the complex favors a T-shaped form [π+-π(T) complex]. However, in the presence of polar solvating molecules or counteranions, these species interact with the (N−H)+/(C−H)+ group, while the π+ system interacts with the neutral aromatic ring. Then, the displaced-stacked form [π+-π(D) complex] is favored or otherwise nearly isoenergetic to the π+-π(T) form. The π+-π systems are stabilized mainly by both dispersion and electrostatic energies. Ternary diagrams using either attractive energy components or both attractive and repulsive energy components show that the π+-π(D) complexes have more contribution from dispersion energy but less contribution from induction energy than the π+-π(T) complexes, while both complexes have similar percentage contributions from electrostatic and exchange energy components. In particular, the π+-π(D) complexes are found to be distinctly different from the π-π complexes and the non-π organic or metallic cation-π complexes

Methane-Assisted Chemical Vapor Deposition Yielding Millimeter-Tall Single-Wall Carbon Nanotubes of Smaller Diameter

We examined the use of low purity H₂ (96 vol % H₂ with 4 vol % CH₄) in chemical vapor deposition (CVD) using a C₂H₂ feedstock, and obtained vertically aligned single-wall carbon nanotubes (VA-SWCNTs) with unexpectedly smaller diameters, larger height, and higher quality compared with those grown using pure H₂. During the catalyst annealing, carbon deposited at a small amount from CH₄ on the Fe particles, which kept them small and dense. During CVD, CH₄ prevented the Fe particles from coarsening, resulting in an enhanced growth lifetime and suppressed diameter increase of growing SWCNTs. These effects were observed only for CH₄, and not for C₂H₄ or C₂H₂. CH₄-assisted CVD is an efficient and practical method that uses H₂ containing CH₄ that is available as a byproduct in chemical factories

Snail upregulates VEGFR3 transcripts via cooperating with Egr-1.

<p>(A) <i>VEGFR3</i> promoter activity after the exposure of HRECs to immobilized FN. HRECs were transfected with the human <i>VEGFR3</i> promoter_luciferase (hVEGFR3_Luc) reporter (wildR3) and then reseeded at a density of 2–2.5×10⁴ cells/cm² on FN-coated dishes. (B) Schematic illustration of the location of putative Snail and the Egr-1-binding site in the human <i>VEGFR3</i> promoter. WildR3, human <i>VEGFR3</i> promoter_luciferase (hVEGFR3_Luc) reporter; mutR3(Snail), mutation in the putative E-box. Broken line, Egr-1-binding elements; thick line, putative E-box; Luc, luciferase. (C) Western blot analysis showing the effect of Egr-1 knockdown on VEGFR3. HRECs were reseeded after transfections with siCon or siEgr-1 on FN-coated dishes. Arrow, an Egr-1 band; *, a non-specific band. (D) <i>VEGFR3</i> promoter activity after the knockdown of Snail or Egr-1. HRECs were co-transfected with the indicated siRNA and the wildR3 reporter and then reseeded and cultured on FN-coated dishes for 16 h. (E) Mutant <i>VEGFR3</i> promoter activity. HRECs were transfected with the indicated wildR3 and mutR3 (Snail) reporters and then reseeded on FN-coated dishes for 16 h. (F) Immunoprecipitation assay demonstrating the complex association between Snail and Egr-1. HRECs were seeded on FN-coated dishes. After 2 h, the cell lysates were immunoprecipitated (IP) with immunoglobulin G (IgG) or anti-Egr-1 antibody (α-Egr-1). (G) Chromatin immunoprecipitation analysis of the <i>VEGFR3</i> promoter in HUVECs. HUVECs were transfected with flag-Snail (Snail) and immunoprecipitated using anti-Snail antibodies (α-Snail). PCR was performed to detect the <i>VEGFR3</i> promoter region containing the putative E box.</p

Solvent-Driven Structural Changes in Anion−π Complexes

Among the π interactions, the anion−π interaction has been a novel type of interaction. In the cases of halide−π complexes, which are the most typical examples of the anion−π interaction, the theoretically predicted and experimentally observed structures in the gas phase are quite different from the most frequently observed crystal structures. We here investigate the structural changes in complexation of the F−/Cl− ion with triazine (TAz) as the number of water/acetonitrile molecules increases from 1 to 4. Both the covalent bonding type for F−−TAz and the hydrogen-bonding type for Cl−−TAz, which are the lowest-energy structures in the gas phase, change to the solvent-mediated anion−π-type or displaced anion−π-type complexes. This study explains why the (displaced) anion−π-type complexes with some flexible orientations are most common in many crystal structures

Electrodynamically Sprayed Thin Films of Aqueous Dispersible Graphene Nanosheets: Highly Efficient Cathodes for Dye-Sensitized Solar Cells

Highly efficient cathodes for dye-sensitized solar cells (DSSCs) were developed using thin films of graphene nanosheets (GNS), which were fabricated by the electrospray method (e-spray) using aqueous dispersions of chemically driven GNS. The e-sprayed GNS films had the appropriate properties to be an efficient counter electrode (CE) for DSSCs; sufficient electrocatalytic activity for I–/I3– redox couples and low charge transfer resistance (RCT) at the CE/electrolyte interface as characterized by cyclic voltammetry and electrochemical impedance analysis. The performance of the GNS film based CEs was optimized by manipulating the density of surface chemical functional groups and plane conjugation of GNS via post thermal annealing (TA). Upon TA, the oxygen-containing surface functional groups, which have been shown to improve electrocatalytic activity of carbon based materials, were significantly reduced, while the electrical conductivity was enhanced by ∼40 times. The improvement of electrocatalytic activity and fill factor (FF) with reduced RCT of DSSCs after TA was primarily attributed to the increased charge transport within the GNS films, while the chemically prepared GNS typically contained sufficient defects, edges and surface functional groups for electrocatalysis. The performance of the DSSCs using our GNS-CEs was nearly identical (>95%) to the DSSCs using the state-of-the-art CE, thermolytically prepared Pt crystals. Our e-sprayed GNS-CE based DSSCs had a higher FF (69.7%) and cell efficiency (6.93%) when compared previously reported graphene based CEs for DSSCs, demonstrating the outstanding properties of graphene as the electrodes in electrochemical devices

Snail upregulates VEGF receptor 3 (VEGFR3).

<p>(A) Western blot and RT-PCR analyses showing Snail, early growth response protein-1 (Egr-1), VEGF receptor 3 (VEGFR3), and VEGFR2 expression. HRECs were seeded at a density of 2–2.5×10⁴ cells/cm² on FN- (for western blot and RT-PCR) or PLL (for western blot)-coated dishes and cultured for the indicated time points. (B) Western blot analysis showing the effect of Snail knockdown on VEGFR3. HRECs were reseeded after transfections with siCon or siSnail on FN-coated dishes, and cultured for the indicated time. (C) Quantitative RT-PCR analysis showⁱng the effect of Snail knockdown on VEGFR3 expression. SiSnail-transfected ECs were reseeded and cultured on FN-coated dishes for 8 h. *, p<0.01. (D) Western blot and quantitative RT-PCR analyses showing the effect of Snail overexpression on VEGFR3. HUVECs were transfected with Snail. On the next day, the medium was changed, and the transfected cells were cultured for 8 h (quantitative RT-PCR; right) or 16 h (western blot; left). *, p<0.01.</p

Endothelial Snail Regulates Capillary Branching Morphogenesis via Vascular Endothelial Growth Factor Receptor 3 Expression

<div><p>Vascular branching morphogenesis is activated and maintained by several signaling pathways. Among them, vascular endothelial growth factor receptor 2 (VEGFR2) signaling is largely presented in arteries, and VEGFR3 signaling is in veins and capillaries. Recent reports have documented that Snail, a well-known epithelial-to-mesenchymal transition protein, is expressed in endothelial cells, where it regulates sprouting angiogenesis and embryonic vascular development. Here, we identified Snail as a regulator of VEGFR3 expression during capillary branching morphogenesis. Snail was dramatically upregulated in sprouting vessels in the developing retinal vasculature, including the leading-edged vessels and vertical sprouting vessels for capillary extension toward the deep retina. Results from <i>in vitro</i> functional studies demonstrate that Snail expression colocalized with VEGFR3 and upregulated <i>VEGFR3</i> mRNA by directly binding to the <i>VEGFR3</i> promoter via cooperating with early growth response protein-1. Snail knockdown in postnatal mice attenuated the formation of the deep capillary plexus, not only by impairing vertical sprouting vessels but also by downregulating VEGFR3 expression. Collectively, these data suggest that the Snail-VEGFR3 axis controls capillary extension, especially in vessels expressing VEGFR2 at low levels.</p></div

Na Insertion Mechanisms in Vanadium Oxide Nanotubes for Na-Ion Batteries

In this study, we successfully synthesized lamellar-structured Ni_0.1VO_<i>x</i> NTs by a microwave-assisted hydrothermal method and cation exchange reaction. High initial discharge capacity and 100% efficiency were obtained when the Ni_0.1VO_<i>x</i> NTs cathode was used as a cathode material for the Na battery. The intercalation mechanism and capacity fading effect were investigated in detail both experimentally using Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses and theoretically using the ab initio simulation method. During the intercalation of Na⁺ into VO_<i>x</i> NT structures, TEM, XRD, FT-IR, and XPS data revealed the cointercalation of the solvent, resulting in the expansion of the interlayer spacing and carbon and oxygen adsorption. The experimental and simulation results suggest that solvent molecules coordinated the Na insertion mechanisms into the amine interlayer during discharging. These understandings of the Na intercalation mechanism in materials based on Ni_0.1VO_<i>x</i> NTs would be useful to design more stable and high-performance VO_<i>x</i>-based electrodes for Na battery applications