A simple spectrophotometric method for the determination of zirconium in U–Zr alloy samples in presence of fluoride ions

Journal of Radioanalytical and Nuclear Chemistry - A spectrophotometric method, circumventing interference from F− ions, during estimation of Zr in U-Zr alloy fuel, has been developed....     

Nematogens containing oxyethylene units at a lateral or terminal position and their mixtures with salts

Short terminal polyoxyethylene chains may be introduced into mesogens containing lateral substituents such as two hexyloxy chains or a crown-ether fragment. These compounds have a large nematic range near room temperature and can dissolve large amounts of the salt LiBF₄ without destroying the nematic arrangment. In the nematic phase, the ions are ordered and the quadrupolar splitting associated with these ions can allow this ordering to be monitored. Increasing the salt concentration does not seem to change the ordering of the individual ions. The ¹³C thermal evolution of the field-induced chemical shift in the oxyethylene (OE) units with or without salt does not show any real difference, indicating that the interaction between the ions and the mesogen is small. This means that there is very little change in conformation in the OE unit when adding salt to the mesogen.     

Electrochemical impedance spectroscopic studies of copper dissolution in arginine–hydrogen peroxide solutions

Anodic dissolution of copper in arginine and hydrogen peroxide-based medium suitable for chemical mechanical planarization slurry formulation was investigated using electrochemical impedance spectroscopy. Potentiodynamic polarization and impedance data were acquired for copper dissolving in hydrogen peroxide and arginine solution. Reaction mechanism analysis (RMA) was employed to determine the mechanistic pathway of copper dissolution. RMA analysis indicates that a stable passivating film does not form on the copper surface, and the direct dissolution of copper was also ruled out. A two-step mechanism involving cupric oxide as an intermediate species is proposed. The data were also fit to an electrical equivalent circuit to obtain insight into the variation of the parameters with the overpotential. The modeled data for the two-step mechanism captures the essential features of the impedance spectra at various overpotentials.     

Determination of mitragynine in plasma with solid-phase extraction and rapid HPLC–UV analysis, and its application to a pharmacokinetic study in rat

A new solid phase extraction method for rapid high performance liquid chromatography–UV determination of mitragynine in plasma has been developed. Optimal separation was achieved with an isocratic mobile phase consisting of acetonitrile–ammonium acetate buffer, 50 mM at pH 5.0 (50:50, v/v). The method had limits of detection and quantification of 0.025 and 0.050 μg/mL, respectively. The method was accurate and precise for the quantitative analysis of mitragynine in human and rat plasma with within-day and between-day accuracies between 84.0 and 109.6%, and their precision values were between 1.7 and 16.8%. Additional advantages over known methods are related to the solid phase extraction technique for sample preparation which yields a clean chromatogram, a short total analysis time, requires a smaller amount of plasma samples and has good assay sensitivity for bioanalytical application. The method was successfully applied in pharmacokinetic and stability studies of mitragynine. In the present study, mitragynine was found to be fairly stable during storage and sample preparation. The present study showed for the first time the detailed pharmacokinetic profiles of mitragynine. Following intravenous administration, mitragynine demonstrated a biphasic elimination from plasma. Oral absorption of the drug was slow, prolonged and was incomplete, with a calculated absolute oral bioavailability value of 3.03%. The variations observed in previous pharmacokinetic studies after oral administration of mitragynine could be attributed to its poor bioavailability rather than to the differences in assay method, metabolic saturation or mitragynine dose.     

TUD-1: synthesis and application of a versatile catalyst, carrier, material…

The three-dimensional sponge-like mesoporous material TUD-1 is straightforward to prepare. Its synthesis can readily be modified to introduce metals into the framework of TUD-1, imparting many different catalytic activities. M-TUD-1 catalysts have proven to be very active, unlimited by diffusion and very stable. By combining two metals into one TUD-1 catalyst, synergy between Lewis and Br?nsted acid sites could be induced; incorporation of zeolites similarly gave rise to synergy. In addition to successful applications in redox-, acid- and photo-catalysis TUD-1 proved to be an excellent carrier material for catalysts, enabling new applications. TUD-1 was used as a contrast agent and drug delivery system, indicating that this material is but at the beginning of its potential applications.     

Ligand-Based Pharmacophore Screening Strategy: a Pragmatic Approach for Targeting HER Proteins

Targeting ErbB family of receptors is an important therapeutic option, because of its essential role in the broad spectrum of human cancers, including non-small cell lung cancer (NSCLC). Therefore, in the present work, considerable effort has been made to develop an inhibitor against HER family proteins, by combining the use of pharmacophore modelling, docking scoring functions, and ADME property analysis. Initially, a five-point pharmacophore model was developed using known HER family inhibitors. The generated model was then used as a query to screen a total of 468,880 compounds of three databases namely ZINC, ASINEX, and DrugBank. Subsequently, docking analysis was carried out to obtain hit molecules that could inhibit the HER receptors. Further, analysis of GLIDE scores and ADME properties resulted in one hit namely BAS01025917 with higher glide scores, increased CNS involvement, and good pharmaceutically relevant properties than reference ligand, afatinib. Furthermore, the inhibitory activity of the lead compounds was validated by performing molecular dynamic simulations. Of note, BAS01025917 was found to possess scaffolds with a broad spectrum of antitumor activity. We believe that this novel hit molecule can be further exploited for the development of a pan-HER inhibitor with low toxicity and greater potential.     

Nonnegative Moore-Penrose Inverse of Gram Matrices in an Indefinite Inner Product Space

In this paper, we derive necessary and sufficient conditions for the nonnegativity of the Moore-Penrose inverse of a Gram matrix defined in an indefinite inner product space using indefinite matrix multiplication. These conditions include the acuteness of a pair of closed convex cones.     

Synthesis of secondary amines by titanium-mediated transfer of alkenyl groups from alcohols

Reaction of Ti(NMe2)4 with allyl alcohols and primary amines leads to the selective formation of secondary allylic amines. The allyl transfer from the alcohol to the amine occurs with selective allylic transposition. Due to substituent effects in the reactions, we postulate that the reaction occurs through a [2 + 2]/retro-[2 + 2]-cycloaddition mechanism. It was also found that a similar reaction could be accomplished with homoallylic alcohol. In this case, the more complex mechanism leads to the formation of 1-aza-spiro[5.5]undecane. Possible pathways for the homoallylic transfer and cyclization are discussed.