Discriminantal arrangement, 3 × 3 minors of Plücker matrix and hypersurfaces in Grassmannian Gr(3,n)

We show that points in specific degree-2 hypersurfaces in the Grassmannian $Gr(3,n)$ correspond to generic arrangements of n hyperplanes in ${\mathbb{C}}^3$ with associated discriminantal arrangement having intersections of multiplicity three in codimension two.     

Binding of metal ions by pyrimidine base pairs in DNA duplexes

Pyrimidine base pairs in DNA duplexes selectively capture metal ions to form metal ion-mediated base pairs, which can be evaluated by thermal denaturation, isothermal titration calorimetry, and nuclear magnetic resonance spectroscopy. In this critical review, we discuss the metal ion binding of pyrimidine bases (thymine, cytosine, 4-thiothymine, 2-thiothymine, 5-fluorouracil) in DNA duplexes. Thymine-thymine (T-T) and cytosine-cytosine (C-C) base pairs selectively capture Hg(II) and Ag(I) ions, respectively, and the metallo-base pairs, T-Hg(II)-T and C-Ag(I)-C, are formed in DNA duplexes. The metal ion binding properties of the pyrimidine-pyrimidine pairs can be changed by small chemical modifications. The binding selectivity of a metal ion to a 5-fluorouracil-5-fluorouracil pair in a DNA duplex can be switched by changing the pH of the solution. Two silver ions bind to each thiopyrimidine-thiopyrimidine pair in the duplexes, and the duplexes are largely stabilized. Oligonucleotides containing these bases are commercially available and can readily be applied in many scientific fields (86 references).     

Design and fabrication of teflon-coated tungsten nanorods for tunable hydrophobicity

The nature of water interaction with tungsten nanorods (WNRs) fabricated by the glancing-angle deposition technique (GLAD)-using RF magnetron sputtering under various Ar pressures and substrate tilting angles and then subsequent coating with Teflon-has been studied and reported. Such nanostructured surfaces have shown strong water repellency properties with apparent water contact angles (AWCA) of as high as 160°, which were found to depend strongly upon the fabrication conditions. Variations in Ar pressure and the substrate tilting angle resulted in the generation of WNRs with different surface roughness and porosity properties. A theoretical model has been proposed to predict the observed high AWCAs measured at the nanostructure interfaces. The unique pyramidal tip geometry of WNRs generated at low Ar pressure with a high oblique angle reduced the solid fraction at the water interface, explaining the high AWCA measured on such surfaces. It was also found that the top geometrical morphologies controlling the total solid fraction of the WNRs are dependent upon and controlled by both the Ar pressure and substrate tilting angle. The water repellency of the tungsten nanorods with contact angles as high as 160° suggests that these coatings have enormous potential for robust superhydrophobic and anti-icing applications in harsh environments.     

Quantitative determination of imatinib in human plasma with high-performance liquid chromatography and ultraviolet detection

A simple and sensitive high-performance liquid chromatography (HPLC) method was developed to quantitate imatinib in human plasma. Imatinib and the internal standard dasatinib were separated using a mobile phase of 0.5% KH(2)PO(4) (pH3.5)-acetonitrile-methanol (55:25:20, v/v/v) on a CAPCELL PAK C18 MG II column (250 mm × 4.6 mm) at a flow rate of 0.5 mL/min and measurement at UV 265 nm. Analysis required 100 μL of plasma and involved a solid phase extraction with an Oasis HLB cartridge, which gave recoveries of imatinib from 73% to 76%. The lower limit of quantification for imatinib was 10 ng/mL. The linear range of this assay was between 10 and 5000 ng/mL (regression line r(2) > 0.9992). Inter- and intra-day coefficients of variation were less than 11.9% and accuracies were within 8.3% over the linear range. The plasma concentrations of imatinib obtained by our present method were almost the same as those assayed by an LC-MS-MS method at the Toray Research Center, Inc. This method can be applied effectively to measure imatinib concentrations in clinical samples.     

Multiple proton ionizable calixarene derivatives with different ring sizes and complexation ability as efficient ionophores for complexation and solvent extraction of trivalent indium

The solvent extraction behavior of multiple proton ionizable p-tert-butylcalix[4]arene and [6]arene carboxylic acid derivatives towards indium has been investigated along with an acyclic monomeric analogue from weakly acidic media into chloroform. The extraction mechanism is ion exchange and carboxylic acid groups are adequate ligating sites for extraction. The cyclic structure of calixarene ligands to accommodate the potential guest species and the cooperativity effect of multifunctional groups significantly affect the complexation behavior and calixarene derivatives are found to be excellent extractants over the monomeric analogue. The composition of the extracted complex depends on the solution pH and attempts to determine the composition of the extracted complex for the extraction of indium have been stymied by complications arising from the formation of polynuclear species of indium and bridged polymeric species of calixarene carboxylic acid derivatives. One mole of calix[4]arene derivative extracts 2.5 moles of indium whereas the calix[6]arene derivative tends to extract 4.0 moles of indium. The loaded indium is back extracted with 1 mol dm(-3) hydrochloric acid solution. Though quantitative back extraction of indium was achieved from the fully loaded calix[6]arene derivative, it was only achieved up to 85% in the case of the calix[4]arene derivative.     

Model study of CO inhibition of [NiFe]hydrogenase

We propose a modified mechanism for the inhibition of [NiFe]hydrogenase ([NiFe]H(2)ase) by CO. We present a model study, using a NiRu H(2)ase mimic, that demonstrates that (i) CO completely inhibits the catalytic cycle of the model compound, (ii) CO prefers to coordinate to the Ru(II) center rather than taking an axial position on the Ni(II) center, and (iii) CO is unable to displace a hydrido ligand from the NiRu center. We combine these studies with a reevaluation of previous studies to propose that, under normal circumstances, CO inhibits [NiFe]H(2)ase by complexing to the Fe(II) center.     

A combined effective fragment potential-fragment molecular orbital method. II. Analytic gradient and application to the geometry optimization of solvated tetraglycine and chignolin

The gradient for the fragment molecular orbital (FMO) method interfaced with effective fragment potentials (EFP), denoted by FMO∕EFP, was developed and applied to polypeptides solvated in water. The structures of neutral and zwitterionic tetraglycine immersed in water layers of 2.0, 2.5, 3.0, 3.5, 4.0, and 4.5 A? are investigated by performing FMO∕EFP geometry optimizations at the RHF∕cc-pVDZ level of theory for the solutes. The geometries optimized with FMO-RHF∕EFP are compared to those from the conventional RHF∕EFP and are found to be in very close agreement. Using the optimized geometries, the stability of the hydrated zwitterionic and neutral structures is discussed structurally and in terms of energetics at the second-order M?ller-Plesset theory (MP2)∕cc-pVDZ level. To demonstrate the potential of the method for proteins, the geometry of hydrated chignolin (protein data bank ID: 1UAO) was optimized, and the importance of the inclusion of water was examined by comparing the solvated and gas phase structures of chignolin with the experimental NMR structure.     

Molecular-shape selectivity by molecular gel-forming compounds: bioactive and shape-constrained isomers through the integration and orientation of weak interaction sites

A molecular gel system was assembled on carrier particles and the integrated effect of weak interaction sites enabled highly efficient separation of the bioactive and shape-constrained isomers of tocopherols, β-carotene, and polycyclic aromatic hydrocarbons (PAHs) by multiple interaction mechanisms.     

A novel tungsten trioxide (WO3)/ITO porous nanocomposite for enhanced photo-catalytic water splitting

Hybrid nanocomposite films of ITO-coated, self-assembled porous nanostructures of tungsten trioxide (WO(3)) were fabricated using electrochemical anodization and sputtering. The morphology and chemical nature of the porous nanostructures were studied by Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS), respectively. The photoelectrochemical (PEC) properties of WO(3) porous nanostructures were studied in various alkaline electrolytes and compared with those of titania nanotubes. A new type of alkaline electrolyte containing a mixture of NaOH and KOH was proposed for the first time to the best of our knowledge and shown to improve the photocurrent response of the photoanodes. Here, we show that both the WO(3) nanostructures and titania nanotubes (used for comparison) exhibit superior photocurrent response in the mixture of NaOH and KOH than in other alkaline electrolytes. The WO(3) porous nanostructures suffered from surface corrosion resulting in a huge reduction in the photocurrent density as a function of time in the alkaline electrolytes. However, with a protective coating of ITO (100 nm), the surface corrosion of WO(3) porous nanostructures reduced drastically. A tremendous increase in the photocurrent density of as much as 340% was observed after the ITO was applied to the WO(3) porous nanostructures. The results suggest that the hybrid ITO/WO(3) nanocomposites could be potentially coupled with titania nanotubes in a multi-junction PEC cell to expand the light absorption capability in the solar spectrum for water splitting to generate hydrogen.     

The effect of Cl...π interactions on the conformations of 4‐chloro‐5‐(2‐phenoxyethoxy)phthalonitrile and 4‐chloro‐5‐[2‐(pentafluorophenoxy)ethoxy]phthalonitrile

4‐Chloro‐5‐(2‐phenoxyethoxy)phthalonitrile, C₁₆H₁₁ClN₂O₂, (I), and 4‐chloro‐5‐[2‐(pentafluorophenoxy)ethoxy]phthalonitrile, C₁₆H₆ClF₅N₂O₂, (II), show different types of electrostatic interaction. In (I), the phenoxy and phthalonitrile (benzene‐1,2‐dicarbonitrile) moieties are well separated in an open conformation and intermolecular C—H...π interactions are observed in the crystal packing. On the other hand, in (II), the pentafluorophenoxy moiety interacts closely with the Cl atom to form a folded conformation containing an intramolecular halogen–π interaction.