Synthesis, antimicrobial evaluation and QSAR studies of 3-ethoxy-4-hydroxybenzylidene/4-nitrobenzylidene hydrazides

A series of 3-ethoxy-4-hydroxybenzylidene/4-nitrobenzylidene hydrazides (1–20) was synthesized and tested for in vitro antimicrobial activity. The results of antimicrobial studies indicated that the compounds having dinitro, methoxy, hydroxy and nitro substituents on phenyl ring of the aromatic acids were most active ones. The QSAR investigation indicated the importance of the topological parameter, third order molecular connectivity index (³χ) in describing the antimicrobial activity of synthesized hydrazides.     

One-pot synthesis of aryl oxime analogues from methyl arenes using NBS and hydroxyl amine hydrochloride

The one-pot synthesis of aryl oximes is reported by the reaction of methyl arenes with NBS using hydroxyl amine hydrochloride. The direct conversion of methyl group into oxime group has been achieved under mild reaction conditions in the presence of sensitive functional groups including chloro, bromo, cyano, hydroxy, fluoro, dioxaborolane, esters, and trifluoro methyl substituents with excellent yields. The simple experimental procedure and easy purification make this protocol advantageous.     

Isolation, enzyme-bound structure, and activity of platensimycin A1 from Streptomyces platensis

Inhibition of fatty acid synthesis is emerging as a valuable target for antibacterial agents. Platensimycin and platencin are novel natural products that were reported recently to inhibit the FabF and FabF/FabH condensing enzymes, respectively, present in the fatty acid biosynthetic pathway. Selective inhibition of these enzymes by platensimycin and platencin accounts for their potent antibiotic activity. We have continued our quest to find additional members of this class of compounds leading to discovery of platensimycin A₁, a hydroxylated congener. We report herein the isolation, structure, antibacterial and enzymatic activities, and co-crystal structure bound to Escherichia coli FabF. The lower activity of platensimycin A₁ suggests that substitution at C-14 is detrimental for the activity.     

Reconfigurable virtual electrowetting channels

Lab-on-a-chip systems rely on several microfluidic paradigms. The first uses a fixed layout of continuous microfluidic channels. Such lab-on-a-chip systems are almost always application specific and far from a true "laboratory." The second involves electrowetting droplet movement (digital microfluidics), and allows two-dimensional computer control of fluidic transport and mixing. The merging of the two paradigms in the form of programmable electrowetting channels takes advantage of both the "continuous" functionality of rigid channels based on which a large number of applications have been developed to date and the "programmable" functionality of digital microfluidics that permits electrical control of on-chip functions. In this work, we demonstrate for the first time programmable formation of virtual microfluidic channels and their continuous operation with pressure driven flows using an electrowetting platform. Experimental, theoretical, and numerical analyses of virtual channel formation with biologically relevant electrolyte solutions and electrically-programmable reconfiguration are presented. We demonstrate that the "wall-less" virtual channels can be formed reliably and rapidly, with propagation rates of 3.5-3.8 mm s(-1). Pressure driven transport in these virtual channels at flow rates up to 100 μL min(-1) is achievable without distortion of the channel shape. We further demonstrate that these virtual channels can be switched on-demand between multiple inputs and outputs. Ultimately, we envision a platform that would provide rapid prototyping of microfluidic concepts and would be capable of a vast library of functions and benefitting applications from clinical diagnostics in resource-limited environments to rapid system prototyping to high throughput pharmaceutical applications.     

Catalytic intermolecular enal-alkyne [3 + 2] reductive cycloadditions

A catalytic, intermolecular [3 + 2] reductive cycloaddition of enals and alkynes has been developed. The method provides a nickel-catalyzed strategy for combining two simple acyclic pi-systems into a five-membered ring product by effecting a net two-electron reduction of the starting materials mediated by triethylborane as the reducing agent. The use of a protic solvent is a key feature of the process.     

DFT and MD studies on the influence of the orientation of ester linkage groups in banana-shaped mesogens

The influence of the direction of ester linkage groups on the structural and electronic properties of five-ring banana-shaped molecules with a central 1,3-phenylene unit has been investigated including hexyloxy and dodecyloxy terminal chains. DFT studies on the B3LYP/6-31G(d) level were performed on the conformational behaviour of the ten isomers in a systematic way. The one- and two-fold potential energy scans show that the flexibility of the wings significantly depends on the orientation of the carboxyl linkage groups. Moreover, the different directions of the carboxyl groups between the aromatic rings cause remarkable changes on the dipole moment and its components of the molecules. These findings are supported by investigations on the global charge pattern of the molecules calculated from electrostatic potential group charges. The bending angle alpha obtained from a simple model for the five-ring bent-core molecules is a characteristic structural parameter which can be correlated with experimental findings. Calculations on the bent-core molecules in an external electric dipole field related to the direction of their polar axis show remarkable effects with respect to the flexibility and polarity of the isomers. First molecular dynamics simulations on the banana-shaped molecules were carried out within the AMBER 7 package. The trajectories of relevant structural parameters support the findings of the DFT studies. The results concerning the structure and polarity revealed from the DFT and MD calculations of the ten isomers can be correlated with data from dielectric measurements and mesophase properties.     

Discrete transfer method applied to radiative transfer in a variable refractive index semitransparent medium

Application of the discrete transfer method (DTM) has been extended to the analysis of radiative heat transfer in a variable refractive index participating medium. To validate the DTM formulation, radiative heat transfer in an absorbing, emitting and isotropically scattering planar medium was considered. The participating medium was assumed to be in radiative equilibrium. For both constant and variable refractive indices of the medium, the DTM results were compared with those available in the literature. The DTM was found to provide accurate results.     

Determination of the Natural Dissolved Concentration of Zirconium in Seawater by Adsorptive Stripping Voltammetry

A voltammetric method was developed for zirconium determination as Zr(IV)‐cupferron‐oxalate‐diphenylguanidine complex based on adsorptive accumulation at the HMDE (E_peak=?0.95 V). The supporting electrolyte was a mixture of acetate/acetic acid (pH 4.6) and ammonium acetate (pH 5.7) solutions. E_ads=?0.6 V (vs. Ag/AgCl), t_ads=400 s, 10 mV s^?1 scan rate, and DP mode were the main parameters. The linear range was 0.033 to 3.3×10^?9 mol L^?1, and the LOD and LOQ (t_ads=400 s) were 0.77 and 1.6×10^?11 mol L^?1, respectively. The method was adequate for seawater samples, although not sufficiently sensitive for surface waters.     

Synthesis,Characterization, and X-Ray Structures of 2-(3,5-Dimethylpyrazol-1-Yl)Phenyl-Based Organoselenium Compounds and Their Glutathione Peroxidase (Gpx) Like Activity

Abstract

The synthesis of a series of 2-(3,5-dimethylpyrazol-1-yl)phenyl-based organoselenium compounds, (dmpzC₆H₄Se)₂ (1), dmpzC₆H₄SeR (dmpz = 3,5-dimethylpyrazol-1-yl; R = (CH₂)_nY; Y = OH, NH₂, and COOH), and dmpzC₆H₄SeX (X = Cl, Br, or I) is described. The compounds are characterized by IR, NMR (¹H, ¹³C{¹H}, ⁷⁷Se{¹H}), and mass spectral (MS) data. The molecular structures of (dmpzC₆H₄Se)₂, dmpzC₆H₄SeCH₂COOH, and dmpzC₆H₄SeCH₂CH₂OH have been established by X-ray crystallography. The two latter compounds are associated in the solid state through intermolecular hydrogen bonding between the OH proton and the pyrazolyl nitrogen atom of the adjacent molecule. Glutathione peroxidase (GPx) like catalytic activity of these compounds has been evaluated by using hydrogen peroxide (H₂O₂) as substrate and dithiothreitol (DTT^red) as thiol cofactor in CD₃OD, and the progress of the reaction was monitored by ¹H NMR spectroscopy. All the compounds exhibited the GPx-like catalytic activity. Among these, the ones containing alkylamino groups showed the best activity.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Quantum chemical studies on the conformational behaviour of substituted banana-shaped mesogens with a central 1,3-phenylene unit

Ab initio and DFT calculations on the HF/STO-3G and B3LYP/6-31G(d) level were performed on the conformational behaviour of isolated banana-shaped molecules of 1,3-phenylene bis[4-(4-n-hexyloxyphenyliminomethyl)benzoate] systems (P-6-O-PIMB). The influence of small substituents in both the central phenyl ring and the external phenyl rings on the shape, polarity and flexibility of these molecules was investigated by one- and two-fold relaxed potential energy scans in a systematic way. The effect of substituents on the global polarity of banana-shaped mesogens was analysed by the magnitude and direction of the dipole moment and its components in relation to the long axis of the molecules. Moreover, a simple model for the calculation of the bending angle was tested for banana-shaped molecules with a central 1,3-phenylene unit. The findings for the isolated banana-shaped molecules are correlated with solid state X-ray and liquid crystalline state NMR results. Banana-shaped molecules with both hexyloxy (P-6-O-PIMB) and hexyl (P-6-PIMB) terminal chains are included to study the effect of substituents in the external phenyl rings on the flexibility of these chains. An attempt will be made to correlate the results with experimental findings on banana-shaped mesogens.