Inclusion complexation of 4,4′-dihydroxybenzophenone and 4-hydroxybenzophenone with α- and β-cyclodextrins

The inclusion complexation behaviours of 4,4′-dihydroxybenzophenone (DHBP) and 4-hydroxybenzophenone (HBP) with α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) were investigated using UV–visible fluorescence, time-resolved fluorescence, molecular modelling, scanning electron microscopy (SEM), FTIR, differential scanning calorimeter, X-ray diffraction, ¹H NMR and molecular modelling techniques. In both molecules, biexponential decay was observed in water, whereas triexponential decay was observed in the CD medium. The DSC thermogram of the DHBP/α-CD and DHBP/β-CD inclusion complex nanomaterials shows the endothermic peak at 60.8, 101.9, 119.6 and 112.8°C. The upfield chemical shift observed for HBP protons reveal that the phenyl ring (without hydroxyl substitution) entered the CD cavity and the hydroxyl group of HBP is exposed outside the CD cavity. The SEM image of DHBP appears as needle-shaped crystals on the micrometre scale, whereas the irregular bar shape was observed for HBP. Transmission electron microscopy images show that both guest molecules formed nano vesicles with α-CD and formed nano rods with β-CD.     

Studies directed toward the synthesis of caylobolide A: convergent synthesis of C21–C40 subunit

Stereoselective synthesis of the C21–C40 core segment of caylobolide A has been achieved following a highly efficient convergent strategy. The key reactions featured in the synthesis are Prins cyclization, reductive radical cyclization, Sharpless asymmetric epoxidation and olefin cross metathesis.     

Monolithically Integrated Spinel MxCo3−xO4 (M=Co,Ni, Zn) Nanoarray Catalysts: Scalable Synthesis and Cation Manipulation for Tunable Low‐Temperature CH4 and CO Oxidation

A series of large scale M_xCo_3?xO₄ (M=Co, Ni, Zn) nanoarray catalysts have been cost‐effectively integrated onto large commercial cordierite monolithic substrates to greatly enhance the catalyst utilization efficiency. The monolithically integrated spinel nanoarrays exhibit tunable catalytic performance (as revealed by spectroscopy characterization and parallel first‐principles calculations) toward low‐temperature CO and CH₄ oxidation by selective cation occupancy and concentration, which lead to controlled adsorption–desorption behavior and surface defect population. This provides a feasible approach for scalable fabrication and rational manipulation of metal oxide nanoarray catalysts applicable at low temperatures for various catalytic reactions.     

Evolution of an Adenine–Copper Cluster to a Highly Porous Cuboidal Framework: Solution‐Phase Ripening and Gas‐Adsorption Properties

The synthesis and directed evolution of a tetranuclear copper cluster, supported by 8‐mercapto‐N9‐propyladenine ligand, to a highly porous three‐dimensional cubic framework in the solid state is reported. The structure of this porous framework was unambiguously characterized by X‐ray crystallography. The framework contains about 62 % solvent‐accessible void; the presence of a free exocyclic amino group in the porous framework facilitates reversible adsorption of gas and solvent molecules. Oriented growth of framework in solution was also tracked by force and scanning electron microscopy studies, leading to identification of an intriguing ripening process, over a period of 30 days, which also revealed formation of cuboidal aggregates in solution. The elemental composition of these cuboidal aggregates was ascertained by EDAX analysis.     

Optimization and validation of RP-HPLC-UV method with solid-phase extraction for determination of buparvaquone in human and rabbit plasma: application to pharmacokinetic study

A simple, sensitive and specific reversed-phase high-performance liquid chromatographic method with UV detection at 251 nm was developed for quantitation of buparvaquone (BPQ) in human and rabbit plasma. The method utilizes 250 microL of plasma and sample preparation involves protein precipitation followed by solid-phase extraction. The method was validated on a C18 column with mobile phase consisting of ammonium acetate buffer (0.02 m, pH 3.0) and acetonitrile in the ratio of 18:82 (v/v) at a flow rate of 1.1 mL/min. The calibration curves were linear (correlation coefficient>or=0.998) in the selected range. The method is specific and sensitive with limit of quantitation of 50 ng/mL for BPQ. The validated method was found to be accurate and precise in the working calibration range. Stability studies were carried out at different storage conditions and BPQ was found to be stable. Partial validation studies were carried out using rabbit plasma and intra- and inter-day precision and accuracy were within 7%. This method is simple, reliable and can be routinely used for preclinical pharmacokinetic studies for BPQ.     

<Emphasis Type="Italic">Prosopis juliflora</Emphasis>—A green corrosion inhibitor for reinforced steel in concrete

The corrosion of reinforced steel in concrete in 3.5 % NaCl without and with Prosopis juliflora extract at different time intervals has been studied using various techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization study (PDS) and atomic force microscopy (AFM). The results obtained by electrochemical measurements (EIS and PDS) showed that the extract inhibited corrosion by forming a protective layer on the surface of the embedded steel and by altering the reactions of the cathodic and anodic sites of the steel. Further, the AFM images supported the formation of the protective layer over the surface of the embedded steel by inhibitor molecules. The adsorption of the inhibitor molecules over the surface of the embedded steel obeyed the Temkin isotherm. Density functional theory (DFT) calculations for major ingredients of the extract have been carried out. From the results of the DFT calculations, the influence of major ingredients on the anti–corrosion potential of the plant extract has been correlated. The mechanism of inhibitive action of the P. juliflora extract has also been proposed.     

A Simple and Efficient Approach for Estimating Recovery of a Preparative Reversed Phase HPLC Purification

The widely applied reversed phase high-performance liquid chromatography (RP-HPLC) is an indispensable purification technique in drug discovery. During drug discovery, recovery was usually calculated based on the weight of the purified product after drying over the weight of the crude material multiplied by the assumed purity from HPLC/UV area percent of the product. Such a purity assumption can be off significantly when the crude material contains water, solvents, other UV-inactive impurities and inorganic salts. In this paper, we report a simple and efficient way to estimate recovery of preparative HPLC purification process. It is based on the ratio of the HPLC/UV peak area measured for the product in the crude solution and that in the final collected fraction with both accounted for their volumes. This approach eliminates not only the need for drying of the collected fraction to calculate recovery but also the inaccuracy associated with the true content in the crude sample using the traditional method. A systematic study was conducted to verify this method using caffeine mixed with various UV-active and -inactive impurities. The calculated recoveries using this approach were found to be consistent within 4% with the true recoveries based on dry weight estimation. The approach has been successfully applied for our in-house purifications. Furthermore, the approach was extended to library purifications, where in many cases heart-cutting the desired peaks is used to meet the purity requirements.

     

Ag‐CNT Architectures for Attomolar Dopamine Detection and 100‐Fold Fluorescence Enhancements with Cellphone‐Based Surface Plasmon‐Coupled Emission Platform

We report cellphone‐based detection of dopamine with attomolar sensitivity in clinical samples with the use of a surface plasmon‐coupled emission (SPCE) platform. To this end, silver‐coated carbon nanotubes were used as spacer and cavity materials on SPCE substrates to obtain up to 100‐fold fluorescence enhancements. The presence of silver on the carbon nanotubes helped to overcome fluorescence quenching arising due to π–π interactions between the carbon nanotube and rhodamine 6G. The competing adsorption of dopamine versus rhodamine 6G on graphene oxide was utilized to develop this sensing platform.     

Generalized fabrication of two-dimensional non-close-packed colloidal crystals

In this paper we report a generalized templating approach for fabricating wafer-scale, two-dimensional, non-close-packed (ncp) colloidal crystals. Polymer nanocomposites consisting of monolayer ncp colloidal crystals prepared by a spin-coating process are used as sacrificial templates. After removal of the colloidal silica templates, the voids in the polymer matrix are infiltrated with other materials. By plasma-etching the polymer matrix, wafer-scale ncp colloidal crystals from a variety of functional materials can be made. This technique is scalable and compatible with standard microfabrication. Two-component colloidal arrays with complex micropatterns can also be fabricated by combining microfabrication with this templating approach. Normal-incidence reflectivity spectra of replicated titania ncp arrays agree well with theoretical prediction using Scalar Wave Approximation.