The solvent effect on the isotropic hyperfine interaction in some aliphatic polyamine copper(II) complexes

ESR and optical absorption studies are described for a number of copper(II) chelates with aliphatic polyamines, exhibiting both square pyramidal and square bipyramidal coordination around the copper ion. The complexes studied were bis(N,N′-dimethylethylenediamine)copper(II) sulphate tetrahydrate, bis(N,N′-diethylethylenediamine)copper(II) nitrate, diaquosulphato(N,N,N′,N′-tetramethylethylenediamine)copper(II) hydrate, dinitrato(N,N,N′,N′-tetramethylethylenediamine)copper(II), dichloro(N,N,N′,N′-tetramethylethylenediamine)copper(II) and dithiocyanato(N,N,N′,N′-tetramethylethylenediamine)copper(II). The ESR measurements were carried out in methanol, dimethyl sulphoxide, dimethylformamide and pyridine, at room and liquid nitrogen temperatures. The molecular orbital coefficients were estimated assuming an axial symmetry. The parameter χ proportional to the hyperfine constants shows a variation with the solvent for all these complexes. The χ values in solution are lower than the corresponding average χ values reported in the solid state for each complex. The solvent effect and the influence of 4s character in the ground state are discussed. The χ values, either calculated or reported, for a number of copper complexes for [4O], [3O, N], [2O, 2N], [O, 3N] and [4N] environments around copper(II) are presented.     

Evaluation of the Probiotic Characteristics of Newly Isolated Lactic Acid Bacteria

Lactic acid bacteria were isolated from fermented vegetables, sour dough, milk products, sheep and human excreta. The newly isolated cultures were evaluated for a number of probiotic characteristics like bile salt resistance, salt tolerance in general, survival in low pH, hydrophobicity of the cell surface, resistance to low phenol concentration, antimicrobial activity and susceptibility pattern against vancomycin and erythromycin. The selected cultures were further screened for their ability to produce the nutraceticals such as folic acid and exopolysaccharide (EPS). Two potent isolates, CB2 (from cabbage) and SD2 (from sour dough) were found to produce both extracellular and intracellular folate. One of the isolates from yogurt (MC-1) and the one from whey (W3) produced significant amount of EPS with a maximum production of 8.79 +/- 0.05 g/l by MC-1.     

Reduced Graphene Oxide Non‐covalent Functionalized with Zinc Tetra Phenyl Porphyrin Nanocomposite for Electrochemical Detection of Dopamine in Human Serum and Rat Brain Samples

We described the use of a nanocomposite consisting of reduced graphene oxide and zinc tetraphenylporphyrin (RGO/Zn‐TPP) for electrochemical sensing of dopamine (DA). The surface of RGO was homogeneously functionalized with Zn‐TPP via non‐covalent π‐π interaction. The nanocomposite was characterized by scanning electron microscopy, UV‐Vis spectrometry, nuclear magnetic resonance spectroscopy and electrochemical impedance spectroscopy. The electroanalysis behavior of the nanocomposite was studied by cyclic voltammetry and amperometry. The excellent electrocatalytic activity is found for oxidation of DA, best at working voltage of 0.214 V (vs. Ag/AgCl) and linear response range of 0.04–238.8 μM. The sensitivity and detection limit were of 0.665 μA µM^?1 cm^?2 and 3 nM, respectrively. The electrode is well reproducible, stable, and represents a viable platform for the analysis of DA in DA injection, human serum and rat brain sample.     

Preparation of alkylidene indane and related scaffolds and their further elaboration to novel chemotypes

Alkylidene indane and ring-expanded scaffolds have been prepared using an enantioselective crotylation/Heck cyclization sequence. Further diversification using consecutive cyclopropanation-Cope rearrangement affords novel chemotypes including spiroindane frameworks.     

On some boundary element methods for the heat equation

Summary The object of this paper is to study some boundary element methods for the heat equation. Two approaches are considered. The first, based on the heat potential, has been studied numerically by previous authors. Here the convergence analysis in one space dimension is presented. In the second approach, the heat equation is first descretized in time and the resulting elliptic problem is put in the boundary formulation. A straight forward implicit method and Crank-Nicolson's method are thus studied. Again convergence in one space dimension is proved.     

Tumor cell toxicity of hypericin and related analogs

A series of hypericin analogs were found to differ in their cytotoxic activity induced by ambient light levels. These analogs vary in their ability to partition into cells, to generate singlet oxygen as well as in other photophysical properties. The data suggest that the biological activity of hypericin is due to a combination of factors whose roles may vary under different circumstances.     

Diastereoselective syntheses of pyrazolyl isoxazolidines via 1,3-dipolar cycloaddition

Synthesis of novel 2,3,4,5-tetrasubstituted isoxazolidine and 2,3,5-trisubstituted isoxazolidine by 1,3-dipolar cycloaddition of nitrones with electron-deficient and electron-rich olefins is described. 1,3-Dipolar cycloaddition of nitrones with β-nitrostyrene, gives exclusively endo-diastereoisomer of isoxazolidine and with ethyl vinyl ether, gives exo-diastereoisomer of isoxazolidine with de >95%. The stereochemistry of the products were assigned using extensive NMR studies.     

The physical and electrochemical properties of poly(vinylidene chloride-co-acrylonitrile)-based polymer electrolytes prepared with different plasticizers

Lithium ion-conducting membranes with poly(ethylene oxide) (PEO)/poly(vinylidene chloride-co-acrylonitrile) (PVdC-co-AN)/lithium perchlorate (LiClO₄) were prepared by solution casting method. Different plasticizers ethylene carbonate (EC), propylene carbonate (PC), gamma butyrolactone (gBL), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dibutyl phthalate (DBP) were complexed with the fixed ratio of PEO/PVdC-co-AN/LiClO₄. The preparation and physical and electrochemical properties of the gel polymer electrolytes have been briefly elucidated in this paper. The maximum ionic conductivity value computed from the ac impedance spectroscopy is found to be 3?×?10^?4 S cm^?1 for the EC-based system. From DBP-based system down to EC-based system, a decrease of crystallinity and an increase of amorphousity are depicted by X-ray diffraction technique, the decrease of band gap energy is picturized through UV–visible analysis, the decrease of glass transition temperature is perceived from differential scanning calorimetry plots, and the reduction of photoluminescence intensity is described through photoluminescence spectroscopy study at an excitation wavelength of 280 nm. Atomic force microscopic images of EC-based polymer electrolyte film show the escalation of micropores. Fourier transform infrared spectroscopy study supports the complex formation and the interaction between the polymers, salt, and plasticizer. The maximum thermal stability is obtained from thermogravimetry/differential thermal analysis, which is found to be 222 °C for the sample complexed with EC. The cyclic voltagram of the sample having a maximum ionic conductivity shows a small redox current at the anode, and cathode and the chemical stability is confirmed by linear sweep voltammetry.     

Bioactives of Microbes Isolated from Western Ghat Belt of Kerala Show β-Lactamase Inhibition along with Wide Spectrum Antimicrobial Activity

The present study describes the exploitation of microbial biodiversity from Western Ghats of Kerala for screening of bioactives having β-lactamase inhibitory activities. A total of 700 pure cultures were isolated and were screened for antibacterial activity against a β-lactam resistant Bacillus cereus strain (PL 10) isolated from the same niche. Bioactive extracts made from 45 isolates showed inhibitory activities against PL 10, of which two strains showed inhibition of extended spectrum β-lactamase (ESBL) producing Klebsiella ESBL1101 and three strains inhibited methicillin-resistant Staphylococcus aureus (MRSA) strain MRSA831. All these five strains showed wide spectrum antimicrobial activity against various fungi and bacteria. These five cultures were identified by 16S rRNA sequencing and biochemical tests and the preliminary characterizations of their bioactive extracts were carried out. This study suggests the potential of bioactives from two inhibitor–producer strains, NII 167 and NII 1054, for being developed as inhibitors against wide spectrum β-lactam resistant strains.     

An aldol-based build/couple/pair strategy for the synthesis of medium- and large-sized rings: discovery of macrocyclic histone deacetylase inhibitors

An aldol-based build/couple/pair (B/C/P) strategy was applied to generate a collection of stereochemically and skeletally diverse small molecules. In the build phase, a series of asymmetric syn- and anti-aldol reactions were performed to produce four stereoisomers of a Boc-protected γ-amino acid. In addition, both stereoisomers of O-PMB-protected alaninol were generated to provide a chiral amine coupling partner. In the couple step, eight stereoisomeric amides were synthesized by coupling the chiral acid and amine building blocks. The amides were subsequently reduced to generate the corresponding secondary amines. In the pair phase, three different reactions were employed to enable intramolecular ring-forming processes: nucleophilic aromatic substitution (S(N)Ar), Huisgen [3+2] cycloaddition, and ring-closing metathesis (RCM). Despite some stereochemical dependencies, the ring-forming reactions were optimized to proceed with good to excellent yields, providing a variety of skeletons ranging in size from 8- to 14-membered rings. Scaffolds resulting from the RCM pairing reaction were diversified on the solid phase to yield a 14?400-membered library of macrolactams. Screening of this library led to the discovery of a novel class of histone deacetylase inhibitors, which display mixed enzyme inhibition, and led to increased levels of acetylation in a primary mouse neuron culture. The development of stereo-structure/activity relationships was made possible by screening all 16 stereoisomers of the macrolactams produced through the aldol-based B/C/P strategy.