Enhanced Electrocatalytic Activity of Ni‐CNT Nanocomposites for Simultaneous Determination of Epinephrine and Dopamine

A promising electrochemical sensor based nickel‐carbon nanotube (Ni‐CNT) modified on glassy carbon (GC) electrode had been developed and the properties of the modified electrode were characterized by multispectroscopic analysis. The fabricated sensor (GC/Ni‐CNT) electrode was utilized to determine the catecholamines such as epinephrine and dopamine simultaneously. Differential pulse voltammetry and amperometry were used to verify the electrochemical behavior of the studied compounds. The GC/Ni‐CNT based amperometric sensor showed a wide linear range and low detection limit with high analytical sensitivity of 8.31 and 6.61 μA μM^?1 for EP and DA, respectively which demonstrates better characteristics compared to other electrodes reported in the literature. Further, no significant change in amperometric current response was observed in presence of biological interference species such as glucose, cysteine, citric acid, uric acid and ascorbic acid in the detection of EP and DA. The utility of this GC/Ni‐CNT electrode was well established for the determination of EP and DA in human urine samples.     

Lewis acid-catalyzed one-pot, three-component route to chiral 3,3'-bipyrroles

3,3'-Bipyrroles 3 could be synthesized using a double Michael addition reaction involving diaroyl acetylene 1 and the appropriate 1,3-dicarbonyls 2 using ammonium acetate as a nitrogen source. The axial chirality of bipyrrole was anticipated from the X-ray crystal structure and DFT calculations and confirmed by separating the racemates on a chiral column and subsequent CD spectra of the enantiomers. The absolute configuration of the enantiomers was achieved by theoretical CD spectra calculation using the ZINDO method.     

Fully automated molecular mechanics based induced fit protein-ligand docking method

We describe a method for docking a ligand into a protein receptor while allowing flexibility of the protein binding site. The method employs a multistep procedure that begins with the generation of protein and ligand conformations. An initial placement of the ligand is then performed by computing binding site hotspots. This initial placement is followed by a protein side-chain refinement stage that models protein flexibility. The final step of the process is an energy minimization of the ligand pose in the presence of the rigid receptor. Thus the algorithm models flexibility of the protein at two stages, before and after ligand placement. We validated this method by performing docking and cross docking studies of eight protein systems for which crystal structures were available for at least two bound ligands. The resulting rmsd values of the 21 docked protein-ligand complexes showed values of 2 A or less for all but one of the systems examined. The method has two critical benefits for high throughput virtual screening studies. First, no user intervention is required in the docking once the initial binding site selection has been made in the protein. Second, the initial protein conformation generation needs to be performed only once for a given binding region. Also, the method may be customized in various ways depending on the particular scenario in which dockings are being performed. Each of the individual steps of the method is fully independent making it straightforward to explore different variants of the high level workflow to further improve accuracy and performance.     

Detection of electrophoretically separated cytochromes P450 by element-labelled monoclonal antibodies via laser ablation inductively coupled plasma mass spectrometry

Numerous structurally and enzymatically similar cytochromes P450 (CYPs) are involved in the metabolism of xenobiotics and are present in different amounts and with different enzyme profiles in human tissues and cells. Analysis of their adaptively regulated and individually variable patterns is a peculiar analytical challenge. We developed a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) based method for concomitant detection and semiquantitative determination of electrophoretically separated and blotted CYPs. The first results are given here for the two enzymes CYP1A1 and CYP2E1. Specific monoclonal antibodies directed against the enzymes were differentially labelled with europium via a covalently linked chelator and with iodine, respectively. Analysis of the modified antibodies shows that both europium and iodine are coupled to the heavy and the light chains of the antibodies. Also, the antibodies maintained their antigen-binding properties after labelling as demonstrated by LA-ICP-MS-analysed immunoblots. The method allowed us to detect specifically and concomitantly both CYP enzymes in complex biological samples, i.e. microsomes of rat liver and minipig duodenum, which are characterized by different levels and proportions of the two CYP enzymes. A strong CYP1A1 signal is found in liver microsomes of 3-methylcholanthrene-treated rats, while it is (nearly) absent in liver microsomes of rats treated with isonocotinic acid hydrazide (isoniazid). The constitutively expressed CYP2E1 is found in microsomes of both treatment groups. Duodenal microsomes of minipigs orally exposed to polycyclic aromatic hydrocarbons show a clear CYP1A1 signal. Low levels of CYP2E1 can also be detected in these microsomes. The LA-ICP-MS method allows concomitant determination of CYPs, thereby exhibiting sensitivity similar to that of conventional chemoluminescence detection via peroxidase-labelled secondary antibodies. The latter method allows readout of a single CYP protein in a 1D separation. Although the results presented here are only for labelling by use of the elements iodine and europium, the same strategy can be applied also for other lanthanide elements in combination with chelating compounds, so LA-ICP-MS of western blots offers a new capability to be applied for highly multiplexed CYP determinations via labelled antibodies.     

Binuclear ruthenium(III) Schiff base complexes bearing N(4)O(4) donors and their catalytic oxidation of alcohols

An interesting series of binuclear ruthenium(III) Schiff base complexes bearing bis-salophen/bis-naphophen units of the general composition [(EPh(3))(X)Ru-L-Ru(X)(EPh(3))] (where E=P or As; X=Cl or Br; L=binucleating dianionic tetradentate ligands) have been synthesized and characterized by analytical (elemental analysis, magnetic susceptibility measurements), spectral (FT-IR, UV-vis and EPR) and electrochemical methods. These ruthenium(III) complexes have two N(2)O(2) metal binding sites, which are linked to each other with a biphenyl bridge and acts as potential catalyst for oxidation of wide range of primary and secondary alcohols to corresponding aldehydes or ketones with moderate to high conversion in the presence of N-methylmorpholine-N-oxide (NMO). The formation of high-valent Ru(V)=O species as a catalytic active intermediate is proposed for the catalytic processes.     

Design and optimization of photonic crystal based eight channel dense wavelength division multiplexing demultiplexer using conjugate radiant neural network

In this paper, two dimensional photonic crystal, based eight-channel demultiplexer is proposed and designed for DWDM applications. The performance parameters of the demultiplexer such as transmission efficiency, channel spacing, spectral line width, Q factor, and crosstalk have been evaluated. The proposed demultiplexer comprises of bus waveguide, drop waveguide and parellogram resonant cavity (PRC). The bus waveguide transmits light to the PRC and exits through respective drop waveguide. The PRC consists of a parellogram resonator with a nano ring cavity that is used for dropping eight specific wavelength for ITU-T G 694.1 standard with 50 GHz channel spacing. The circular ring resonator is placed above the PRC wherein a resonant air hole (Cr) is positioned for desired channel selection. The channel selection is done by altering the radius of the air hole. In addition, a conjugate radiant neural network is implemented for optimizing the radii of resonant air holes to select the required channel wavelength. The proposed device is very compact and it could be considered for implementing the photonic integrated circuits.     

Hydro­gen bonding in two tetracyclic indole alkaloids

3-Acetyl-1,6,7,12b-tetra­hydro­indolo­[2,3-a]­quinolizin-2(12H)-one, C₁₇H₁₆N₂O₂, consists of two symmetry-independent mol­ecules and each forms a layered structure stabilized by N—H⃛O and C—H⃛O hydrogen bonds. In 3-acetyl-6,7-di­hydro­indolo­[2,3-a]­quinolizin-4(12H)-one monohydrate, C₁₇H₁₄N₂O₂·H₂O, the structure is stabilized by O—H⃛O, N—H⃛O and C—H⃛O hydrogen bonds, with the ordered water mol­ecule playing a crucial role in the self-assembly. Contribution from the weak interactions to the strong hydrogen-bonded network is a common feature in both structures.     

Influence of substrate temperature on the properties of vacuum evaporated InSb films

Indium Antimonide (InSb) thin films were grown onto well cleaned glass substrates at different substrate temperatures (303, 373 and 473 K) by vacuum evaporation. The elemental composition of the deposited InSb film was found to be 52.9% (In) and 47.1% (Sb). X‐ray diffraction studies confirm the polycrystallinity of the films and the films show preferential orientation along the (111) plane. The particle size (D), dislocation density (δ) and strain (ε) were evaluated. The particle size increases with the increase of substrate temperature, which was found to be in the range from 22.36 to 32.59 nm. In Laser Raman study, the presence of longitudinal mode (LO) confirms that the deposited films were having the crystalline nature. Raman peak located at 191.26 cm^–1 shift towards the lower frequencies and narrows with increase in deposition temperature. This indicates that the crystallinity is improved in the films deposited at higher substrate temperatures. Hall measurements indicate that the films were p‐type, having carrier concentration ≅10¹⁶ cm^–3 and mobility (4–7.7) ×10³ cm²/Vs. It is observed that the carrier concentration (N) decreases and the Hall mobility (μ) increases with the increase of substrate temperature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A Novel Stability-Indicating Method for Determination of Related Substances of Montelukast Sodium in a Pharmaceutical Dosage Form Using RP-HPLC

Chromatographia - The main aim is to develop a simple, rugged, and sensitive method for determining the Montelukast Sodium-related impurities in a tablet dosage form using reverse-phase...     

Surface-enhanced Raman scattering from bilayers of polystyrene,diglycidyl ether of bisphenol-A,poly(4-vinyl pyridine), and poly(4-styrene sulfonate)

Surface-enhanced Raman scattering (SERS) has been observed from thin films of polystyrene (PS), diglycidyl ether of bisphenol-A (DGEBA), and poly(4-vinyl pyridine) (PVP) deposited on silver island films Degradation of the polymers occurred rapidly during laser irradiation and was accompanied by the appearance of strong bands near 1375 and 1575 cm-1. These bands were attributed to the formation of graphite-like species by the silver-catalyzed thermal oxidation of the polymers induced by localized laser heating of the substrate. When the thin films of PS, DGEBA, or PVP were overcoated with much thicker films of a second polymer such as polystyrene sulfonate (PSS), the degradation was greatly reduced, and excellent SERS spectra of the PS, DGEBA, and PVP films were obtained. Overlayers reduced degradation within the first films deposited on silver island films by restricting the availability of oxygen at the interface to its solubility in the overlayer polymer or by altering the adsorption of oxygen onto the substrate. SERS was observed for the PS, DGEBA, and PVP films and the PSS overlayers when the films were deposited from relatively dilute solutions. When the PS, DGEBA, and PVP films were deposited from more concentrated solutions, SERS was not observed from the PSS overlayers. It was suggested that most of the SERS was due to a short-range, charge-transfer mechanism associated with sites of atomic scale roughness and that SERS was observed from the overlayer when the first film failed to occupy all of the sites.