Calcium/Calmodulin Dependent Protein Kinase II Bound to NMDA Receptor 2B Subunit Exhibits Increased ATP Affinity and Attenuated Dephosphorylation

Calcium/calmodulin dependent protein kinase II (CaMKII) is implicated to play a key role in learning and memory. NR2B subunit of N-methyl-D-aspartate receptor (NMDAR) is a high affinity binding partner of CaMKII at the postsynaptic membrane. NR2B binds to the T-site of CaMKII and modulates its catalysis. By direct measurement using isothermal titration calorimetry (ITC), we show that NR2B binding causes about 11 fold increase in the affinity of CaMKII for ATP gamma S, an analogue of ATP. ITC data is also consistent with an ordered binding mechanism for CaMKII with ATP binding the catalytic site first followed by peptide substrate. We also show that dephosphorylation of phospho-Thr(286)-alpha-CaMKII is attenuated when NR2B is bound to CaMKII. This favors the persistence of Thr(286) autophosphorylated state of CaMKII in a CaMKII/phosphatase conjugate system in vitro. Overall our data indicate that the NR2B- bound state of CaMKII attains unique biochemical properties which could help in the efficient functioning of the proposed molecular switch supporting synaptic memory.

Role of lattice defects and crystallite morphology in the UV and visible-light-induced photo-catalytic properties of combustion-prepared TiO2

The physico-chemical, photo-physical and micro-structural properties responsible for the strikingly different photocatalytic behavior of combustion-prepared TiO2 (c.TiO2) and Degussa P25 (d.TiO2) samples are elucidated in this study. Electron microscopy and selected area electron diffraction micrographs revealed that the two samples exhibited different morphologies. The grains of c.TiO2 were spherical and comprised of 5-6 nm size primary particle. On the other hand, d.TiO2 consisted of large (0.5-3.0 mu m) size and irregular shape aggregates having primary particles of 15-40 nm cross-sectional diameter. The ESR study revealed that the presence of certain defect states in c.TiO2 helped in stabilization of O-. and Ti3+-OH type species during room-temperature UV-irradiation. No such paramagnetic species were however formed over d.TiO2 under similar conditions. C1s and Ti 2p XPS spectra provide evidence for the presence of some lattice vacancies in c.TiO2 and also for the bulk Ti4+ -> Ti3+ conversion during its UV-irradiation. Compared to d.TiO2, c.TiO2 displayed considerably higher activity for discoloration of methyl orange but very poor activity for splitting of water, both under UV and visible light radiations. This is attributed to enhanced surface adsorption of dye molecules over c.TiO2, because of its textural features and also the presence of photo-active ion-radicals. On the other hand, the poor activity of c.TiO2 for water splitting is related to certain defect-induced inter-band charge trapping states in the close vicinity of valence and conduction bands of c.TiO2, as revealed by thermoluminescence spectroscopy. Further, the dispersion of nanosize gold particles gave rise to augmented activity of both the catalysts, particularly for water splitting. This is explained by the promotional role of Au-0 or Au-0/TiO2 interfacial sites in the adsorption and charge-adsorbate interaction processes. (C) 2011 Elsevier B.V. All rights reserved.

An Efficient Simulated Annealing With a Valid Solution Mechanism For TDMA Brodcast Scheduling problem

This paper presents an efficient Simulated Annealing with valid solution mechanism for finding an optimum conflict-free transmission schedule for a broadcast radio network. This is known as a Broadcast Scheduling Problem (BSP) and shown as an NP-complete problem, in earlier studies. Because of this NP-complete nature, earlier studies used genetic algorithms, mean field annealing, neural networks, factor graph and sum product algorithm, and sequential vertex coloring algorithm to obtain the solution. In our study, a valid solution mechanism is included in simulated annealing. Because of this inclusion, we are able to achieve better results even for networks with 100 nodes and 300 links. The results obtained using our methodology is compared with all the other earlier solution methods.

Reactivity and catalytic activity of layered YBA2CU3O7-delta (123) type defect perovskites

The chemical modifications of structure, reactivity and catalytic properties of layered triple perovskite oxides, related to the YBa2Cu3O7-delta (123) system, have been briefly reviewed. These oxides form a versatile family of materials with wide-ranging chemical and physical properties. The multiple sites available for chemical doping, and the ability to reversibly intercalate oxygen at the defect sites have rendered these oxides important model systems in the area of oxide catalysis. An attempt has been made to comprehend the hitherto known catalytic reactions and correlate them to various factors like structure, oxygen diffusional limitations, different geometries adopted by various substituents, oxidative non-stoichiometry and activation energy for oxygen desorption. In particular, results on the enhanced catalytic activity of cobalt-substituted 123 oxide systems towards the selective catalytic oxidation of ammonia to nitric oxide and carbon monoxide to carbon dioxide are presented.

Rearrangements in the cerium(IV) and manganese(III) oxidations of substituted naphthalenes and the nih shift mechanism

Ceric ammonium sulphate oxidation of 1- and 1,4- disubstituted naphthalenes gives 2- and/or 2,3- disubstituted 1,4- naphthoquinones through migration of substituents (D, Br, Ph). Similar rearrangements are also observed in the manganese(III) oxidation and also in the anodic oxidation of these substrates. The results are consistent with the proposal that these oxidations go through the formation of radical cation followed by reaction with H2O and further oxidation of the radical to the carbocationic intermediate on the way to the corresponding 1,4-naphthoquinone. Oxidation of 1,4-diphenylnaphthalene gives 2,3-diphenyl-1,4-naphthoquinone or 4-hydroxy- 2,4- diphenyl - 1(4)R - naphthalenone. The results are in accordance with the conclusion that such rearrangements do not require prior formation of arene oxide intermediates, originally proposed for the NM shift mechanism.

The Reaction of a Nitro-Capped Cobalt(III) Cage Complex With Base: the Crystal Structure of a Contracted Cage Complex, and the Mechanism of Its Formation

The synthesis, properties and crystal structure of the cage complex (1-hydroxy-8-methyl-3,6,10,13,15,18-hexaazabicyclo[6.6.5]nonadecane)cobalt(III) chloride hydrate ([Co(Me,OH-absar)] C13.H2O) are reported. The mechanism of the formation of this contracted cavity cage from a nitro-capped hexaazabicycloicosane type cage has been investigated. Treatment of (1-methyl-8-nitro-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane)cobalt(III) chloride ([Co(Me,NO2-sar)] 3+) with excess base in aqueous solution leads initially to rapid (t1/2 < 1 ms) and reversible deprotonation of one coordinated secondary amine. This species undergoes a retro-Mannich type reaction and imine hydrolysis (t1/2 almost-equal-to 90 s). Quenching the reaction with acid gives rise to a pair of isomeric intermediate species which have been isolated and characterized. They have a pendant arm macrocyclic structure, resulting from the loss of a methylene unit from one of the arms of the cap. Heating either isomer in aqueous solution gives the new cage compound with the contracted cap. It is postulated that this occurs through a Nef reaction, resulting in the formation of a ketone which then condenses with the coordinated primary amine. A comparison with the corresponding bicycloicosane analogue indicates a reduced chromophoric cavity size for the contracted cage. The reduction potential of the cobalt(III)/cobalt(II) couple is 170 mV more negative for the smaller cage, and, in the electronic spectrum of the cobalt(III) complex, the d-d transitions are both shifted to higher energy, corresponding to a stronger ligand field.

High-Throughput Study of the Cu(CH3COO)(2)center dot H2O-5-Nitroisophthalic Acid Heterocyclic Ligand System: Synthesis, Structure, Magnetic, and Heterogeneous Catalytic Studies of Three Copper Nitroisophthalates

A high-throughput screening was employed to identify new compounds in Cu(CH3COO)(2)center dot H2O-NIPA-heterocyclic ligand systems. Of the compounds identified, three compounds, Cu-3{(NO2)-C6H3-(COO)(2)}(3)(C3N6H6)] (1), Cu-2(mu(3)-OH)(H2O){(NO2)-C6H3-(COO)(2)}(CN4H)]center dot-(H2O) (II), and Cu-2(mu(3)-OH)(H2O){(NO2)-C6H3-(COO)(2}-)(CN5H2)]center dot 2(H2O) (III), have been isolated as good quality single crystals by employing conventional hydrothermal methods. Three other compounds, Cu-2{(NO2)-C6H3-(COO)(2)}-(CN4H)(H2O) (IIa), Cu-2{(NO2)-C6H3-(COO)(2)}(CN5H2) (IIIa), and Cu-2{(NO2)-C6H3-(COO)(2)}{(CN5H2)(2)}2H(2)O (IIIb), were identified by a combination of elemental analysis, thermogravimetric analysis (TGA), and IR spectroscopic studies, although their structures are yet to be determined. The single crystalline compounds were also characterized by elemental analysis, TGA, IR, UV vis, magnetic, and catalytic studies. The structures of the compounds have paddle wheel (I) and infinite Cu 0(H) Cu chains (II and HI) connected with NLPA and heterocyclic ligands forming two-(II) and three-dimensional (I and III) structures. The bound and lattice water molecules in 11 and 111 could be reversibly removed/inserted without affecting the structure. In the case of II, the removal of water gives rise to a structural transition, but the dehydrated phase reverts back to the original phase on prolonged exposure to atmospheric conditions. Magnetic studies indicate an overall antiferromagnetism in all of the compounds. Lewis acid catalytic studies indicate that compounds II and HI are active for cyanosilylation of imines.

Kinetics and mechanism for dye degradation with ionic Pd-substituted ceria

The degradation of the dye, Orange G, was carried out in the presence of H2O2 and Pd-substituted/impregnated CeO2. The effects of pH, initial dye concentration, initial H2O2 concentration, temperature, catalyst loading, and Pd content in the catalyst on the degradation of the dye were investigated. Eight to twelve percent degradation of the dye was obtained in 1 h when the reaction was carried out in the presence of CeO2 or H2O2 or Pd-substituted/impregnated CeO2 while 17% and 97% degradation was obtained when H2O2 was used with Pd-impregnated CeO2 and Pd-substituted CeO2, respectively. This difference clearly indicated that the ionic substitution of Pd played a key role in the degradation of the dye. A mechanism for the reaction was proposed based upon the catalyst structure and the electron transfer processes that take place in the metal ion substituted system in a reducible oxide. The reaction was found to follow first order kinetics and the influence of all the parameters on the degradation kinetics was compared using the rate constants. (c) 2011 Elsevier B.V. All rights reserved.

Mechanism of ?-cleavage in the excited states of keto sulfides

The beta-cleavage process in photoexcited ketones of structure RCOCH2X (X = CH2CH3, OCH3, SCH3; R = CH3, Ph) has been studied using the configuration interaction procedure within the framework of MINDO/3. The results explain qualitatively why the beta-cleavage process is faster than the alpha-cleavage process in keto sulfides while in keto ethers the reverse is true.

Catalytic current polarographic determination of traces of titanium in water after preconcentration by coflotation

A new method is reported for the determination of trace levels of Ti(IV) in water by coflotation and polargraphy. Ti(IV) is preconcentrated and separated by coflotation using aluminium hydroxide as coprecipitant and sodium oleate as surfactant. Polarographic determination of titanium content in the froth is based on the catalytic wave of Ti(IV) in the presence of chlorate and oxalate. The effect of various cations and anions on the flotation and determination of titanium has been investigated. The method has been applied to estimation of titanium in natural fresh water samples.

Mechanism of protonic conduction in defect pyrochlore HNbWO6.xH(2)O using MAS NMR

We have carried out H-1 Magic Angle Spinning (MAS) NMR measurements at various spinning speeds (1-12 kHz) on HNbWO(6)xH(2)O (x = 0 and 1) defect pyrochlore systems. The variation of the line width with the spinning speed in the two systems points towards the presence of motions with different time scales. We conclude that the mechanism of conduction in both the compounds are similar except that the proton hopping in hydrated form is assisted by the water of hydration.

Mechanism of growth inhibition of intraerythrocytic stages of Plasmodium falciparum by 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR)

Purine nucleotide synthesis in Plasmodium falciparum takes place solely by the purine salvage pathway in which preformed purine base(s) are salvaged from the host and acted upon by a battery of enzymes to generate AMP and GMP. Inhibitors of this pathway have a potent effect on the in vitro growth of P. falciparum and are hence, implicated as promising leads for the development of new generation anti-malarials. Here, we describe the mechanism of inhibition of the intraerythrocytic growth of P. falciparum by the purine nucleoside precursor, 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR). Our results show that AICAR toxicity is mediated through the erythrocyte in which AICAR is phosphorylated to its nucleotide, ZMP. Further, purine metabolite labeling of the parasitized erythrocytes by H-3]-hypoxanthine, in the presence of AICAR, showed a significant decrease in radioactive counts in adenylate fractions but not in guanylate fractions. The most dramatic effect on parasite growth was observed when erythrocytes pretreated with AICAR were used in culture. Pretreatment of erythrocytes with AICAR led to significant intracellular accumulation of ZMP and these erythrocytes were incapable of supporting parasite growth. These results implicate that in addition to the purine salvage pathway in P. falciparum, AICAR alters the metabolic status of the erythrocytes, which inhibits parasite growth. As AICAR and ZMP are metabolites in the human serum and erythrocytes, our studies reported here throw light on their possible role in disease susceptibility, and also suggests the possibility of AICAR being a potential prophylactic or chemotherapeutic anti-malarial compound. (C) 2011 Elsevier B.V. All rights reserved.

Relationship between nonlinear resistivity and the varistor forming mechanism in ZnO ceramics

The use of a number of perovskite phases M� M�O3-x, as the only forming additive in ZnO ceramics, produces a high nonlinearity index, ?(up to 45), where M� is a multivalent transition?metal ion and M� is an alkaline earth or a rare?earth ion. From this study, the formation parameters crucial to high nonlinearity, such as nonstoichiometry in the as?received ZnO powder, low x values of the additives and fast cooling rate after the sintering, are explainable on the basis of a depletion layer formation at the presintering stage. This is because of the surface states arising out of the chemisorbed oxygen. The depletion layer is retained during sintering as a result of the higher valence state of M� ions, preferentially present at the grain?boundary regions. The fast cooling freezes in the high?temperature concentration of donor?type defects, thereby decreasing the depletion layer width.

Synthesis and catalytic properties of cobalt- and molybdenum-containing mesoporous MCM-41 molecular sieves

Mesoporous MCM-41 type silicas containing molybdenum and cobalt have been prepared with pore sizes in the range 30-38 Angstrom and 54-59 Angstrom. Catalytic properties of these materials have been examined with respect to the oxidation of cyclooctene and aniline.