Isolation of eupatorin (3′,5-dihydroxy-4′,6,7-trimethoxyflavone) from Albizia odoratissima and its application for l-tryptophan sensing

Research on Chemical Intermediates - A simple fluorescence sensor for selective detection of L-Tryptophan (Trp) was developed by isolation of naturally occurring flavone Eupatorin...     

Efficient Synthesis of N‐Oxide Derivatives: Substituted 2‐(2‐(Pyridyl‐N‐oxide)methylsulphinyl)benzimidazoles

Different substituted 2‐chloromethylpyridyl derivatives (6a–d) were oxidized with mCPBA to give the respective 2‐chloromethylpyridine‐N‐oxide derivatives (7a–d) at low temperature, which on condensation with 2‐mercapto‐1H‐benzimidazole (8a–c) in the presence of aprotic solvents give the 2‐[[(pyridin‐2‐yl‐1‐oxide)methyl]sulfanyl]‐1H‐benzimidazole (9a–d) in good yield. Finally, 9a–d oxidized with mCPBA in chlorinated solvent gives a mixture of 2‐[[(pyridin‐2‐yl‐1‐oxide)methyl]sulfonyl]‐1H‐benzimidazole (3a–d, 10%) and 2‐[[(pyridin‐2‐yl‐1‐oxide) methyl]sulfinyl]‐1H‐benzimidazole (4a–d, 90%) derivatives.     

Boolean Logic Networks Mimicked with Chimeric Enzymes Activated/Inhibited by Several Input Signals

Reactions catalyzed by artificial allosteric enzymes, chimeric proteins with fused biorecognition and catalytic units, were used to mimic multi-input Boolean logic systems. The catalytic parts of the systems were represented by pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH). Two biorecognition units, calmodulin or artificial peptide-clamp, were integrated into PQQ-GDH and locked it in the OFF or ON state respectively. The ligand-peptide binding cooperatively with Ca²⁺ cations to a calmodulin bioreceptor resulted in the enzyme activation, while another ligand-peptide bound to a clamp-receptor inhibited the enzyme. The enzyme activation and inhibition originated from peptide-induced allosteric transitions in the receptor units that propagated to the catalytic domain. While most of enzymes used to mimic Boolean logic gates operate with two inputs (substrate and co-substrate), the used chimeric enzymes were controlled by four inputs (glucose – substrate, dichlorophenolindophenol – electron acceptor/co-substrate, Ca²⁺ cations and a peptide – activating/inhibiting signals). The biocatalytic reactions controlled by four input signals were considered as logic networks composed of several concatenated logic gates. The developed approach allows potentially programming complex logic networks operating with various biomolecular inputs representing potential utility for different biomedical applications.     

A Simple and Highly Sensitive Electrochemically Reduced p‐Nitrobenzoic Acid Film Modified Sensor for Determination of Mercury

Herein, a simple electrochemical sensor was fabricated for sensing Hg²⁺ ions by using electrochemically reduced p‐nitrobenzoic acid molecules modified (ERpNBA) glassy carbon electrode (GCE). The modified electrode was applied for the determination of Hg²⁺ ions by using differential pulse anodic stripping voltammetry (DPASV). Experimental parameters such as concentration of p‐nitrobenzoic acid used for electrode modification, pH, accumulation time and deposition potential used for the determination of Hg²⁺ ions were optimized. The strong interaction between the Hg²⁺ ions and the lone pair of electrons on the nitrogen atoms of ERpNBA molecules leads to highly selective adsorption of Hg²⁺ ions on the modified electrode. Under the optimum experimental conditions, the sensor showed higher sensitivity and very low detection limit for Hg²⁺ ions than other metal ions such as Cd²⁺, Pb²⁺ and Zn²⁺ ions. The LOD for Hg²⁺ ions was 240 pM which is below the guideline value given by the World Health Organization and the earlier reports.     

Electrochemical behaviour of zinc gluconate complexes

Voltammetric studies revealed that under transient conditions in the pH range 3.7 to 5.0, the deposition of zinc from ZnSO₄ solutions involves the formation of adsorbed monovalent zinc. The conversion of divalent zinc to monovalent is a slow step. In the presence of gluconate, the reduction of divalent complex involves the monovalent zinc complex and the second electron transfer is slow. In the pH range 10 to 12.5, the zinc complex may be [(Zn(GH₄)₄]2^- and is found to vary with gluconate and OH^- ions. The conversion of [Zn(GH₄)(OH)_abs ^-] to Zn(OH)₂ or Zn(GH₄)₂ is the slow step in the reduction of the complexes. In strong alkali solutions sodium gluconate forms zinc hydroxy gluconate complexes. [Zn(OH)₃(GH₄)]^2- to adsorbed [Zn(OH)(GH₄)]^- is the slow step in the reduction.     

Characterization of alpha helices interacting with nucleic acids

Protein-nucleic acid interactions play a vital role in most genetic processes. An enhanced insight into such interactions can be obtained from the structure database of these complexes. Here, we report an overall survey on the geometry of alpha helices which interact with nucleic acids through hydrogen bonds and/or non-bonded interactions. Using the program RADIL based on an algorithm developed from this laboratory, 161 alpha helices in 70 non-redundant nucleic acid binding protein chains solved using X-ray crystallography are analysed. The helical geometry has been characterized as bent, canonical, terminally or completely distorted. The analysis reveals that approximately 70% of the alpha helices possess distortions of any one kind, viz., bend, terminal distortion or complete distortion. Nearly one-third of the total helices possess bends, with a majority of the bending occurring in 5-15 degrees range. In addition, a majority of the bent helices approach the nucleic acid helix in a perpendicular direction. The program RADIL has been useful in characterizing the nucleic acid-induced structural variations in alpha helices, however small they may be.     

Structural and thermal characterization of a semiorganic NLO material: L-alanine cadmium chloride

L-Alaninium cadmium chloride (LACC), a semiorganic nonlinear optical material has been synthesized and its single crystal grown and characterized for its thermal, structural, linear and second order nonlinear optical properties. Powder SHG study shows that LACC is 1.5 times efficient as KDP. Its optical transparency goes down to 200 nm comparable to the typical borate crystals like potassium pentaborate.     

Fabrication of Nickel Tetrasulfonated Phthalocyanine Functionalized Multiwalled Carbon Nanotubes on Activated Glassy Carbon Electrode for the Detection of Dopamine

The nickel tetrasulfonated phthalocyanine (NiTsPc) functionalized multiwalled carbon nanotube (MWCNT) nanocomposite was prepared by a simple sonochemical method. Here, NiTsPc served as a dispersing agent for MWCNT via π? π interaction between MWCNT and NiTsPc. The activated glassy carbon electrode (AGCE) modified with MWCNT‐NiTsPc composite exhibited a good electrocatalytic ability toward dopamine and displayed a good linear dependence in the concentration range of 20 nM–1.384 mM with a sensitivity of 0.17 µA µM^?1 cm^?2. The detection limit is 1 nM based on the signal‐to‐noise ratio of 3.     

Competition between binary fission,ternary fission,cluster radioactivity and alpha decay of 281Ds

Journal of Radioanalytical and Nuclear Chemistry - The competition between different decay modes such as binary fission, ternary fission, cluster and alpha decay modes finds an important role in...     

New hexaphosphane ligands 1,3,5-C6H3{p-C6H4N(PX2)2}3 [X = Cl, F, C6H3OMe(C3H5)]: synthesis, derivatization and palladium(II) and platinum(II) complexes

A novel dodecachlorohexaphosphane, 1,3,5-C(6)H(3)[p-C(6)H(4)N(PCl(2))(2)](3) (1) was synthesized by reacting 1,3,5-tris(4'-anilino)benzene with phosphorus trichloride. Fluorination of 1 with SbF(3) produces 1,3,5-C(6)H(3)[p-C(6)H(4)N(PF(2))(2)](3) (2). The derivatization of chlorohexaphosphane with an aryloxy substituent and its palladium(II) and platinum(II) complexes are also described.