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Functionalized ITO electrodes are used to regenerate NADH using [Cp*Rh(bpy)(H2O)]2+ (Cp* = pentamethylcyclopentadienyl, bpy = 2,2′-bipyridine) electrochemically in a buffer solution. Amino- and mercapto-functionalized electrodes featured higher activity and stability for electrocatalytic generation of NADH than a bare ITO electrode. Effect of metal nanoparticles was also studied on modified ITO electrodes and the addition of platinum nanoparticles even resulted in improved activity. The electrochemical regeneration was somewhat affected in the presence of dioxygen, but not significantly. In addition, a conversion of carbon dioxide was carried out utilizing the electrochemically generated NADH and formate dehydrogenase to produce formic acid.

A phenol-pyridylimine probe was utilized as an optical sensor to quantify the presence of aluminum ions using a turn-on fluorescence enhancement approach. The high sensitivity was the result of FRET amplification of the receptor subunit fluorescence emission. The complex stability constant (Ks) for the stoichiometric 1:1 complex of the sensor with aluminum ions was obtained by fluorimetric titration. Remarkably, fluorescence output was not significantly affected by other trivalent cations, particularly Ga3+ and In3+.

In this study, an assay to quantify the presence of magnesium ions with a chemosensor of bispicolylamine covalently attached to coumarin as a fluorephore was developed using a ratiometric fluorescence enhancement approach. Upon treatment with magnesium ions, the fluorescence wavelength of the chemosensor at 367 nm was shifted to 413 nm and the intensity was also enhanced. The formation of a 1:2 complex between the chemosensor and magnesium ions was confirmed based on the spectral changes of UV–vis, fluorescence and NMR as well as Job's plot. An appreciable enhancement in the luminescence intensity for the emission band at 413 nm was evident when magnesium ions were added progressively. The maximum wavelength and intensity of the emission of the complex with Mg2+ were discriminated from those of other metal ions, such as Ca2+ and Zn2+.

The catabolic acetolactate synthase (cALS) of Enterococcus faecalis V583 was cloned, expressed in Escherichia coli, and purified to homogeneity. The purified protein had a molecular weight of 60 kDa. The cALS of E. faecalis is highly homologous with other cALSs, while sharing low homology with its anabolic counterparts. The cALS of E. faecalis exhibits optimum activity at a temperature of 37 °C and pH 6.8. Based on the enzyme characterization, the apparent Km for pyruvate was calculated to be 1.37 mM, while the Kc for thiamin diphosphate (ThDP) and Mg2+ were found to be 0.031 μM and 1.27 mM, respectively. Negligible absorbance at 450 nm and lack of activity enhancement upon addition of flavin adenine dinucleotide (FAD) to the assay buffer suggest that the cALS of E. faecalis is not FAD-dependent. The enzyme showed extreme stability against the organic solvent dimethyl sulfoxide (DMSO), whereas the activity decreased to less than 50% in the presence of acetone and ethanol.

Oxaliplatin, a platinum-based anti-cancer drug, induces peripheral neuropathy as a side effect and causes cold hyperalgesia in cancer patients receiving anti-cancer chemotherapy. In oxaliplatin-treated mice, aluminum was accumulated in the dorsal root ganglia (DRG), and accumulated aluminum in DRG or other organs aggravated oxaliplatin-induced neuropathic pain. To investigate whether aluminum oxalate, which is the compound of aluminum and oxaliplatin, might be the peripheral neuropathy inducer, the withdrawal responses of mice to coldness, the expression of transient receptor potential ankyrin 1 and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays in DRG were analyzed in mice administered with aluminum oxalate. In addition, the concentrations of aluminum in aluminum oxalate-treated mice were significantly increased compared to those of mice treated with aluminum chloride. To alleviate neuropathic pain, glutathione (GSH), known as an antioxidant and a metal chelator, was injected into oxaliplatin-treated mice. The concentrations of aluminum in the DRG were decreased by the chelation action of GSH. Taken together, behavioral and molecular analyses also supported that aluminum accumulation on the DRG might be a factor for neuropathic pain. This result also suggested that the aluminum chelation by GSH can provide an alleviatory remedy of neuropathic pain for cancer patients with oxaliplatin-induced neuropathic pain.

We demonstrate a facile wet chemical approach for fabricating spherical metal/metal-oxide core@mesoporous silica shell hybrid nanoparticles with different core and shell thicknesses. Vertically aligned mesoporous silica (mSiO(2)) shells were fabricated over the pre-synthesized spherical SiO(2) nanoparticles through a three-step strategy: 1) synthesis of core materials, 2) covering the core with an organic-inorganic composite layer, and 3) removing the organic template through calcinations in air. The mechanisms of hybrid structure formation are proposed. The multifunctional nature of the hybrid structures could be induced by incorporating guest ions/molecules, such as Ag, Mn, and TiO(2), into the pores of an mSiO(2) shell. Mn and TiO(2) cluster-incorporated composite structures have been tested to be antioxidizing agents and effective photocatalysts through electron spin resonance, radical scavenging tests, and the photocatalytic degradation of rhodamine B. The possibility of incorporating several hetero-element guest clusters in these mesoporous composite particles makes them highly attractive for multifunctional applications.

The photocatalyst-enzyme coupled system for artificial photosynthesis process is one of the most promising methods of solar energy conversion for the synthesis of organic chemicals or fuel. Here we report the synthesis of a novel graphene-based visible light active photocatalyst which covalently bonded the chromophore, such as multianthraquinone substituted porphyrin with the chemically converted graphene as a photocatalyst of the artificial photosynthesis system for an efficient photosynthetic production of formic acid from CO(2). The results not only show a benchmark example of the graphene-based material used as a photocatalyst in general artificial photosynthesis but also the benchmark example of the selective production system of solar chemicals/solar fuel directly from CO(2).

Mesoporous titania with crystalline pore walls and controlled pore sizes was fabricated through triblock copolymer (pluronic series) templated sol-gel process by changing the copolymer concentration and by adjusting their calcination temperature. Compared with mesoprous silicate, the synthetic condition of mesoporous titania would be sensitive to calcination temperature. Their pore arrangement and pore size depend strongly on the concentration of copolymer used as a template. Their arrangement of pores and specific surface area increases with the increase of calcination temperature up to critical limit, 320 degrees C. Beyond the critical temperature, the orderness of pores and specific surface area decreases due to the collapse of the pore walls. The specific surface area, pore size and pore orderness can be controlled by optimizing calcination temperature as well as polymer concentration. We demonstrate the mechanism of pore formation and their collapse in the sol-gel synthesis of mesoporous titania.

Single-stranded oligonucleotides (ssDNA) containing guanine bases in their sequences were adsorbed onto gold nanoparticles (AuNPs) by electrostatic interaction. Cyclic voltammetry of Ru(bpy)32+ in the presence of the ssDNA-AuNP complex resulted in an enhanced anodic current due to the oxidation of the guanine bases of DNA. The current obtained with ssDNA-AuNP appeared much smaller than the corresponding ssDNA alone. This current reduction was due to the decrease in solvent accessibility of the guanines in ssDNA immobilized to AuNPs. A progressive decrease in the current was observed in the titration of AuNPs to ssDNA, and a minimum current was eventually obtained, indicating complete binding of ssDNA. The size dependences of AuNPs on the interaction between ssDNA and AuNP were also studied, and the ssDNA adsorbed to 5 nm AuNPs was more solvent-accessible for the Ru mediator than 13 and 30 nm AuNPs.

In this study, an assay to quantify the presence of aluminum ions with a receptor containing naphthol and quinoline moieties was developed using a turn-on fluorescence enhancement approach. Upon treatment with aluminum ions, the fluorescence of the receptor was enhanced at 510 nm due to the formation of a complex between the ligand and aluminum ions at room temperature. As the concentration of Al3+ was increased, the fluorescence gradually increased. Other metal ions, such as K+, Ag+, Ca2+, Mg2+, Zn2+, Mn2+, Co2+, Ni2+, Cu2+, Cd2+, Cr3+, Fe3+, In3+, had no significant effect on the fluorescence.

To quantify the presence of mercuric ions in aqueous solution, double-stranded DNA (dsDNA) of poly(dT) was employed using a light switch compound, (1) which is reported to intercalate into dsDNA of a right-handed B-form. Addition of mercuric ions induced the dehybridization of poly(dT)poly(dA) duplexes to form a hairpin structure of poly(dT) at room temperature and the metal-to-ligand charge transfer emission derived from the intercalation of 1 was reduced due to the dehybridization of dsDNA. As the concentration of was increased, the emission of 1 progressively decreased. This label-free emission method had a detection limit of 0.2 nM. Other metal ions, such as , , , , , , , , , , , , had no significant effect on reducing emission. This emission method can differentiate matched and mismatched poly(dT) sequences based on the emission intensity of dsDNA.

The protective antigen (PA) of Bacillus anthracis is a secreted protein that functions as a critical virulence factor. Protective antigen has been selected as a biomarker in detecting bacterial infection. The in vitro selection method, systematic evolution of ligands by exponential enrichment (SELEX), was used to find single-stranded DNAs that were tightly bound to PA. After 8 rounds of the SELEX process with PA, 4 different oligonucleotides (referred to as aptamers) that contain a 30-residue ssDNA sequence were identified. Dissociation constant (K(d)) values with Cy3-attached aptamers were determined via fluorophotometry to be within a nanomolar range. The authors attempted to visualize the detection of PA using an aptamer-based enzyme-linked immunosorbent assay method, which has proven to be successful within a nanomolar K(d) value range. Furthermore, 2 of the 4 aptamers exhibited specificity to PA against bovine serum albumin and bovine serum. The results of this study demonstrate the analytical potential of an oligonucleotide-based biosensor for a wide variety of applications, particularly in diagnosing disease through specific protein biomarkers.

In studies that mimic natural photosynthesis, a system containing three inde-pendent components, a photosensitizer, electron relay, and catalyst, has been used with a sacrificial electron donor. In this study, we created a novel system for the photocatalytic generation of NADH from aqueous protons using only Pt nanoparticles without any additional photosensitizer, electron relay, and homogeneous organometallic catalyst. We found that irradiation of the Pt nanoparticle solution with visible light converts NAD+ to NADH with a high yield of 86% in the presence of triethanolamine as a sacrificial electron donor. The rate of NADH photogeneration depended on the concentration of PtNPs and TEOA. The rate of NADH generation also increased with NAD+ concentration at low values and reached a plateau.

Highly ordered macroporous silica films with a monolayer thickness and regular array of spherical pores with diameters of about 305 nm are prepared using templates self-assembled by polymethyl methacrylate (PMMA) spheres on solid surfaces by spin coating. The macropores are uniform in size and completely exposed on the bottom surface of the film after the PMMA spheres are etched out. Based on electrochemical experiments, the film allows for easy mass transport of Ru(bpy)(3)(2+) to the ITO surface. Electrochemical detection of DNA hybridization was also carried out in model oligonucleotide hybrids immobilized on the macroporous silica film. Refereed/Peer-reviewed

A simple scheme to fabricate 2-D arrays of Au/titania hybrid nanopatterns is presented, using polystyrene-block-poly(ethylene oxide) diblock copolymer (PS-b-PEO) as templates coupled with sol-gel chemistry. Both the functionalized Au nanoparticles (NPs) and titania precursors are selectively incorporated into the PEO domain. A series of morphologies ranging from nanodot to nanowire arrays is formed and the mechanism of morphological evolution is discussed. Such hybrid films exhibit characteristic localized surface plasmon resonance bands originating from the coupling between neighboring Au NPs spatially located in a controlled manner.

Fructose-1,6-bisphosphate (FBP) aldolase, is a glycolytic enzyme that catalyzes the reversible condensation reaction of FBP to dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P). The aldolase gene from Aquifex aeolicus was subcloned, overexpressed in E. coli and purified to 95% homogeneity. The purified enzyme was activated by high concentrations of NH 4 + and low concentrations of Co 2+ . The native molecular weight of the purified FBP aldolase was identified as 67 kDa (dimer) by gel filtration chromatography. The enzyme exhibits optimum pH at 6.5 and temperature at 90 °C. Based on the kinetic characterizations, the apparent K m was calculated to be 4.4 ± 0.07 mM, while V max was found to be 100 ± 0.02 μM min −1 mg protein −1 . The recombinant protein showed extreme heat stability; no activity loss was observed even at 100 °C for 2 h. In addition, the thermophilic enzyme also showed higher stability against several organic solvents viz . acetonitrile, 1,4-dioxane, and methanol. With higher stability against both heat and organic solvents than any other class II aldolase, the A. aeolicus FBP aldolase is an attractive enzyme for use as a biocatalyst for industrial applications.

A general synthetic method capable of producing a kind of water-soluble gold nanoparticles possessing single-phase synthetic route, high concentration, small size under control, easy store, and excellent thermal, pH and salt stability, was demonstrated. The combined studies with transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and UV-visible spectra clearly show that the gold nanoparticles modified by thioethyl-pendant ligand exist.

The nanoporous chromium carboxylate MIL-101 with coordinatively unsaturated chromium sites has been shown to be active in the sulfoxidation of aryl sulfides with H2O2 to selectively produce the corresponding sulfoxides. Interestingly, the electron-releasing groups in the oxygenation reaction of para-X-phenylmethyl sulfoxides (X-Ph-S-CH3, X = CH3, H, NO2, and CN) enhanced the oxidation reactivity in 1:1 mixtures of X-Ph-S-CH3:H-Ph-S-CH3. Moreover, the 18O-labeled experiments to understand the source of oxygen in sulfoxide products proved that the oxygen atom in the sulfoxide product was entirely derived from H2O2.

A novel O-butyryl chitosan (OBCS)-grafted polypyrrole (PPy) film was described. The immobilization was accomplished by photocrosslinking the OBCS onto PPy films under ultraviolet light irradiation. The surfaces of OBCS-grafted PPy film were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and electron spectroscopy for chemical analysis (ESCA). The blood compatibility of the OBCS-grafted PPy film was evaluated by platelet-rich plasma (PRP) contacting experiments and protein adsorption experiments in vitro. These results have demonstrated that the surface with immobilized OBCS shows much less platelet adhesive and fibrinogen adsorption compared to the control surface. The bulk conductivity values of PPy films were measured by a modified four-probe method. The composite films have both good blood compatibility and high electrical conductivity that make them suitable for using as potential biomaterials, such as electrically conducting blood vessel and functionally haemocompatible substrate of biosensor used directly in whole blood.

The reactivity of an isolated, well-characterized nonheme iron(IV)-oxo complex, [(TMC)FeIV O]2+ (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), has been examined in the oxidation of hydroquinones. This complex has been shown to oxidize a series of hydroquinones, resulting in the production of the corresponding quinone products. Kinetic studies performed with substituted hydroquinones revealed a good correlation between reaction rates of the iron(IV)-oxo complex and the electron-donating ability of the substituents and the bond dissociation energy (BDE) of substrate O–H bonds. These results with a kinetic isotope effect (KIE) of 2.7 led us to propose a hydrogen-atom abstraction mechanism for the oxidation of hydroquinones by the nonheme iron(IV)-oxo species.

Acetohydroxyacid synthase (AHAS, EC 2. 2. 1. 6) is the enzyme that catalyses the first step in the common pathway of the biosynthesis of the branched chain amino acids, valine, leucine and isoleucine. For the first time, the AHAS gene from Bacillus anthracis was cloned into the expression vector pET28a(+), and was expressed in the E. coli strain BL21(DE3). The purified enzyme was checked on 12% SDS-PAGE to be a single band with molecular weight of 65 kDa. The optimum pH and temperature for B. anthracis AHAS was at pH 7.5 and 37 °C, respectively. Kinetic parameters of B. anthracis were as follows: K m for pyruvate, K 0.5 for ThDP and Mg 2+ was 4.8, 0.28 and 1.16 mM respectively. AHAS from B. anthracis showed strong resistance to three classes of herbicides, Londax (a sulfonylurea), Cadre (an imidazolinone), and TP (a triazolopyrimidine). These results indicated that these herbicides could be used in the search for new anti-bacterial drugs.

High-valent iron-oxo species have been frequently employed in heme and nonheme iron enzymes to carry out catalytic oxygenation reactions. In heme-based systems, biological and synthetic oxoiron(IV) porphyrin π-cation radicals are believed to carry out the catalytic oxidations of organic substrates. In the nonheme iron enzymes, oxoiron(IV) intermediates have recently been identified by spectroscopic methods in the catalytic cycle of taurine dioxygenase, and synthetic nonheme oxoiron(IV) species bearing tetradentate and pentadentate ligands were also isolated and characterized. In addition, it has been demonstrated that the nonheme oxoiron(IV) species were capable of conducting the conversion of diverse organic subsatrates such as PPh3, thioanisole, alcohol, and alkanes. The molecular mechanisms of oxidative N-demethylation of N,N-dimethylanilines by heme enzymes such as peroxidases and cytochrome P-450 have been studied for the past twenty years. However, two possible mechanisms, electron transfer followed by proton transfer and hydrogen transfer from α-C-H bonds of the methyl group in N,Ndimethylanilines, are still under debate. Recently, we also reported the oxidative N-dealkylation of N,N-dialkylanilines and demonstrated that the oxidative N-dealkylation reactions occurred via a proton-coupled electron transfer process. Meanwhile, secondary amine substrates bearing a cyclopropyl group have been used in the relation to a mechanismbased inactivation of heme enzymes, and the formation of a highly reactive carbon-centered radical was reported in the oxidation of heteroatom-containing cyclopropyl substrates. Relatively, a few studies for the oxidation of Nmethylanilines as substrate were reported using iron, cobalt, and copper complexes. However, no detailed mechanistic study in the oxidation of secondary amines with nonheme Fe(IV)-oxo species has been reported until now. Presented in this study is a kinetic examination of the oxidation of N-methylanilines with [(tmc)Fe=O] (tmc = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), which yields N,N'-dimethyl-N,N'-diphenylhydrazine formed by the coupling of two N-methylaniline molecules. By determining the rate constants for the step of electron transfer from N-methylaniline to the iron(IV)-oxo species, we suggest that the oxidation of N-methylaniline occurs via an electron transfer. Experimental Procedure

A series of structurally-related [Cu(R-benzyl-dipicolylamine)(NO3)2] complexes, where R=methoxy- (1), methyl- (2), H- (3), fluoro- (4), and nitro-group (5), were synthesized, and their activity on DNA cleavage was investigated by linear dichroism (LD) and electrophoresis. The addition of a benzyl group to the dipicolylamine ligand of the [Cu(dipicolylamine)(NO3)2] complex (A), i.e., the [Cu(benzyl-dipicolylamine)(NO3)2] complex (3), caused significant enhancement in the efficiency of oxidative cleavage of both super-coiled (sc) and double stranded (ds) DNA, as evidenced by the electrophoresis pattern and faster decrease in the LD intensity at 260nm. The efficiency in DNA cleavage was also altered with further modifications of the benzyl group by the introduction of various substituents at the para-position. The cleavage efficiency appeared to be the largest when the methyl group was attached. The order of efficiency in DNA cleavage was methyl>methoxy≈H>fluoro≈nitro group. When an electron-withdrawing group was introduced, the cleavage efficiency decreased remarkably. The reactive oxygen species involved in the cleavage process were the superoxide radical and singlet oxygen. A possible mechanism for this variation in the DNA cleavage efficiency was proposed.

Nonheme and heme iron monooxygenases participate in oxidative N-dealkylation reactions in nature, and high-valent oxoiron(IV) species have been invoked as active oxidants that effect the oxygenation of organic substrates. The present study describes the first example of the oxidative N-dealkylation of N,N-dialkylamines by synthetic nonheme oxoiron(IV) complexes and the reactivity comparisons of nonheme and heme oxoiron(IV) complexes. Detailed mechanistic studies were performed with various N,N-dialkylaniline substrates such as para-substituted N,N-dimethylanilines, para-chloro-N-ethyl-N-methylaniline, para-chloro-N-cyclopropyl-N-isopropylaniline, and deuteriated N,N-dimethylanilines. The results of a linear free-energy correlation, inter- and intramolecular kinetic isotope effects, and product analysis studied with the mechanistic probes demonstrate that the oxidative N-dealkylation reactions by nonheme and heme oxoiron(IV) complexes occur via an electron transfer-proton transfer (ET-PT) mechanism.

Crack-free Nb-doped Bi 4 Ti 3 O 12 (Nb-BIT-p) ferroelectric thin films were fabricated utilizing nonionic block copolymer, HO(CH 2 CH 2 O) 20 (CH(CH 3 )CH 2 O) 70 (CH 2 CH 2 O) 20 H (EO 20 PO 70 EO 20 ), on Pt/Ti/SiO 2 /Si substrates by a processing route of metalorganic solution deposition. The Nb-BIT-p films after calcination showed only a Bi 4 Ti 3 O 12 -type crystalline phase with a random orientation and small grains ( P r ) and the coercive field ( E c ) values of Nb-BIT-p capacitors were unusually high, such as 42 ± 3 μC/cm 2 and 72 ± 5 kV/cm, respectively, at a maximum applied field of 160 kV/cm. After 1.5 × 10 10 read/write cycles with ± 8 V amplitude (160 kV/cm) at 1 MHz frequency, the 2 P r value was partially reduced, but recoverable close to the original one by repeated switching at a high field.

La- or Nd-substituted bismuth titanate (BLT or BNT) and Nb-cosubstituted bismuth titanate (Nb-BLT or Nb-BNT) thin films were prepared in the presence of nonionic surfactants, poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (EO x PO y EO x ) triblock copolymers, added as additives to the sol solution. For Nb-BLT films prepared with EO 106 PO 70 EO 106 , the (200) orientation relative to (117) was dominant as compared with Nb-BLT films produced without surfactant or with EO 20 PO 70 EO 20 , and the remanent polarization ( P r ) of the Nb-BLT film was 22 μC/cm 2 , which was superior to 10 and 15 μC/cm 2 of Nb-BLT films prepared without surfactant or with EO 20 PO 70 EO 20 . The additional Nb cosubstitution in BLT and BNT affected particle orientation in the films and resulted in higher ferroelectricity than those of the BLT and BNT films. The Nb-BNT/EO 106 PO 70 EO 106 film showed the best ferroelectric properties; its remanent polarization was 30 μC/cm 2 and the polarization ( P *– P ˄) shows no significant change up to 8 × 10 8 switching cycles.

There is an intriguing, current controversy on the involvement of iron(III)-hydroperoxo species as a "second electrophilic oxidant" in oxygenation reactions by heme and non-heme iron enzymes and their model compounds. In the present work, we have performed reactivity studies of the iron-hydroperoxo species in nucleophilic and electrophilic reactions, with in situ-generated mononuclear non-heme iron(III)-hydroperoxo complexes that have been well characterized with various spectroscopic techniques. The intermediates did not show any reactivities in the nucleophilic (e.g., aldehyde deformylation) and electrophilic (e.g., oxidation of sulfide and olefin) reactions. These results demonstrate that non-heme iron(III)-hydroperoxo species are sluggish oxidants and that the oxidizing power of the intermediates cannot compete with that of high-valent iron(IV)-oxo complexes. We have also reported reactivities of mononuclear non-heme iron(III)-peroxo and iron(IV)-oxo complexes in the aldehyde deformylation and the oxidation of sulfides, respectively.

High-valent iron(IV)-oxo species have been invoked as the key reactive intermediates in the catalytic cycles of nonheme iron enzymes involved in dioxygen metabolism. Direct experimental evidence for such intermediates has been obtained in the chemistry of methane monooxygenase and taurine-2-oxoglutarate dioxygenase. To gain insight into this interesting chemistry, we have made much effort in the design and synthesis of functional models for such systems. Recently, it has been reported that synthetic mononuclear oxoiron(IV) complexes were generated using tetradentate N4 ligands such as macrocyclic TMC and tripodal TPA ligands and pentadentate N5 ligands such as N4Py and Bn-tpen. While the TMC oxoiron(IV) intermediate can effect oxygen-atom transfer to PPh3 and the TPA complex is able to epoxidize cyclooctene, the N4Py and Bn-tpen complexes are capable of activating C-H bonds of alkanes. As the TMC ligand provides relatively weak reactivity to oxoiron(IV) species, we have tried to modify cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) with other substituents on nitrogens of the ligand, in order to understand the effect of ligand environment by cyclam derivatives on the spectroscopic properties and reactivities of oxoiron(IV) species. We now report the synthesis and characterization of an Fe(IV)-oxo complex bearing a tetradentate macrocyclic TBC (TBC = 1,4,8,11-tetrabenzyl-1,4, 8,11-tetraazacyclotetradecane) which has benzyl groups instead of methyl on TMC. This new Fe=O species exhibits an ability to oxidize a variety of organic substrates such as triphenylphosphine, thioanisole, N,N-dimethylaniline, and triphenylmethane. The tetradentate TBC ligand (1) was prepared from cyclam by alkylation with benzyl bromide (Scheme 1). After purification by column chromatography, the TBC ligand was obtained in 60% yield. Reaction of 1 with Fe(OTf)2 afforded white powder of [Fe(TBC)(CH3CN)2](OTf)2 (2). Complex 2 collected by recrystallization was subjected to comprehensive spectroscopic analysis. We then tried to test the generation of oxoiron(IV) species

Alkynes were oxidized by hydrogen peroxide and tert-butyl hydroperoxide catalyzed by nonheme iron complexes under aerobic and anaerobic conditions: the formation of diketone and a;b-acetylenic oxidation products was significantly affected by the oxidants, and product yields were markedly influenced by the presence of O2. 2004 Elsevier B.V. All rights reserved.

A novel thiazolothiazole-based Cu(2+) colorimetric and fluorescent sensor is reported. A highly selective colorimetric change from yellow to dark green was observed among various metal ions after adding Cu(2+). Unique radical formation can engender these highly selective colorimetric and fluorescent changes.

The catalytic epoxidation of cyclohexene by iron(III) porphyrin complexes and H2O2 has been investigated in alcohol solvents to understand factors affecting the catalyst activity in protic solvents. The yields of cyclohexene oxide and the Fe(III/II) reduction potentials of iron porphyrin complexes were significantly affected by the protic solvents, and there was a close correlation between the product yields and the reduction potentials of the iron porphyrin catalysts. The role of alcohol solvents was proposed to control the electronic nature of iron porphyrin complexes that determines the catalyst activity in the epoxidation of olefins by H2O2. We have also demonstrated that an electron-deficient iron porphyrin complex can catalyze the epoxidation of olefins by H2O2 under conditions of limiting substrate with high conversion efficiency in a solvent mixture of CH3OH and CH2Cl2.

Nb-doped Bi4Ti3O12 (Nb-BIT) ferroelectric thin films were prepared in the presence of a nonionic surfactant (pluronic P123) added as an additive to the sol solution and by rapid thermal annealing (RTA). The film annealed at the relatively low temperature of 600 °C was well crystallized and showed good ferroelectricity. The switching charge of capacitors with polarization reversal rapidly increased with a large amplitude and low frequency of the applied pulse, and gradually decreased with a small amplitude and high frequency. The remanent polarization (2Pr) after subjecting the Nb-BIT capacitors to 108 read/write cycles was 46 μC/cm2, which is remarkably higher than 20 μC/cm2 observed in the initial state. These phenomena seem to appear by the presence of space charges trapped after heat treatment by the RTA process.

Randall-Sundrum scenario with all the standard model (SM) fermions and gauge bosons in the bulk is phenomenologically studied. Even though the simple assumption of universal bulk fermion mass m_\psi leads to the same Kaluza-Klein (KK) mass spectrum for all the SM fermions and thus suppresses new contributions to Flavor-Changing-Neutral-Current and the \rho parameter, large Yukawa coupling of the top quark generates its KK mode mixing and breaks the degeneracy: unacceptably large contribution to \Delta \rho occurs. With a different bulk fermion mass to SU(2) singlet bottom quark, we demonstrate that there exists some parameter space to satisfy the \Delta \rho constraint., Comment: Contributed to 31st International Conference on High Energy Physics (ICHEP 2002), Amsterdam, The Netherlands, 24-31 Jul 2002

Ferroelectric properties of W-doped Bi 4 Ti 3 O 12 (W-BIT) thin film were investigated in comparison with those of undoped Bi 4 Ti 3 O 12 (BIT), which were prepared by sol–gel method and spin-coating technique. X-ray diffraction (XRD) measurements showed layered perovskite structures with a single phase in both films. The W-BIT film appeared to have superior ferroelectric properties to the undoped film prepared under the same conditions. The remanent polarization (2 P r ) and the coercive field (2 E c ) of the W-BIT film were 20 μC/cm 2 and 90 kV/cm, respectively, with a maximum applied field of 170 kV/cm. In addition, the W-BIT film showed a fatigue-free behavior up to 4.5×10 10 read/write cycles.

A novel method for the preparation of structurally diverse fullerene derivatives, which relies on the use of single electron transfer (SET)-promoted photochemical reactions between fullerene C60 and α-trimethylsilylamines, has been developed. Photoirradiation of 10% EtOH-toluene solutions containing C60 and α-silylamines leads to high-yielding, regioselective formation of 1,2-adducts that arise through a pathway in which sequential SET-desilylation occurs to generate α-amino and C60 anion radical pair intermediates, which undergo C-C bond formation. Protonation of generated α-aminofullerene anions gives rise to formation of monoaddition products that possess functionalized α-aminomethyl-substituted 1,2-dihydrofullerene structures. Observations made in this effort show that the use of EtOH in the solvent mixture is critical for efficient photoproduct formation. In contrast to typical thermal and photochemical strategies devised previously for the preparation of fullerene derivatives, the new photochemical approach takes place under mild conditions and does not require the use of excess amounts of substrates. Thus, the method developed in this study could broaden the scope of fullerene chemistry by providing a simple photochemical strategy for large-scale preparation of highly substituted fullerene derivatives. Finally, the α-aminomethyl-substituted 1,2-dihydrofullerene photoadducts are observed to undergo photoinduced fragmentation reactions to produce C60 and the corresponding N-methylamines.

The air-stable complex [Fe(6-Me3-TPA) (O2CAr)]+ [1; 6-Me3-TPA = tris(6-methyl-2-pyridylmethyl)amine] has been synthesized as a model for the iron(II) site of lipoxygenase. This iron(II) complex reacts with 0.5 equiv ROOH to form a yellow species, which has been formulated as [FeIII(OH)(6-Me3-TPA) (O2CAr)]+ (2) by electrospray mass spectrometry. Addition of more ROOH converts 2 into a purple species, which is characterized by electrospray ionization mass spectrometry and resonance Raman spectroscopy as [FeIII(OOR)(6-Me3-TPA)(O2CAr)]+. The purple species is metastable and decomposes via Fe-O bond homolysis to regenerate the starting iron(II) complex. These metal-centered transformations parallel the changes observed for lipoxygenase in its reaction with its product hydroperoxide.

Colloidal crystal-templating methods have been used to prepare inverse opal photonic crystal films of La-doped bismuth titanate, Bi3.25La0.75Ti3O12 (BLT). Ordered arrays of uniformly sized polymer spheres were deposited on glass substrates by a unidirectional deposition method. By carefully controlling the synthetic procedures, macroporous films exhibiting photonic crystal properties were obtained. Bragg diffractions from the planes produced photonic stop bands in the visible spectra of these films.

The complex Pt2(pop)44− abstracts hydrogen atoms and electrons from DNA upon photolysis into the d σ ∗ → p σ excited state (pop = P2O5H22−). In duplex DNA, the hydrogen atoms are abstracted from the 4′- and 5′- positions of the deoxynbose functionality, and electrons are abstracted by tunneling from the guanine nucleobase. At high Mg2+ concentrations, the Pt2(pop)44− tetraanion can associate more intimately with the duplex, and both hydrogen atom and electron transfer are efficient; however, at low Mg2+ concentrations, the complex is situated far from the duplex so that the only efficient pathway is electron tunneling. Therefore, the guanine/sugar ratio decreases with increasing Mg2+. The electron transfer pathway can also be examined in the absence of the hydrogen transfer pathway in thermal reactions where the electron is abstracted from guanine by Ru(bpy)33+ (bpy = 2,2′-bipyridine). These reactions can be initiated electrochemically by potentiation of the complex to the 3 + form, which produces catalytic enhancements in cyclic voltammograms. These enhancements show that guanine multiplets are more reactive than dispersed guanines. Finally, binding of DNA to the HhaI methyltransferase causes flipping of a cytosine into the active site of the enzyme, leaving behind an unpaired guanine residue that is more reactive towards electron transfer than the paired guanine, an effect visible in high-resolution electrophoresis gels after photolysis in the presence of Pt2(pop)44−.

Identifying infectious organisms, quantitating gene expression, and sequencing genomic DNA on chips all rely on the detection of nucleic acid hybridization. Described here is a novel assay for detection of the hybridization of products of the polymerase chain reaction using electron transfer from guanine to a transition-metal complex. The hybridization assay was modeled in solution by monitoring the cyclic voltammetry of Ru(bpy)3(2+) (bpy = 2,2'-bipyridine) in the presence of a probe strand containing only A, T, and C prior to and after hybridization to a complement that contained seven guanines, which led to high catalytic current due to the oxidation of guanine by Ru(bpy)3(3+). To allow recognition of all four bases in the target sequence, it was shown that inosine 5'-monophosphate was 3 orders of magnitude less reactive than guanosine 5'-monophosphate, suggesting that effective hybridization sensors could be realized by immobilization of probe strands in which inosine was substituted for guanosine; hybridization to guanosine-containing target strands would then provide high catalytic currents. A sensor design was tested in a model system for the detection of a synthetic 21-mer oligonucleotide patterned on the sequence of the ras oncogene, which gave an increase in charge collected of 35 +/- 5 microC after hybridization and of only 8 +/- 5 microC after exposure to noncomplementary DNA. Independent quantitation of probe and target by radiolabeling showed that the hybridized electrode contained 3.0 +/- 0.3 ng of target. New sensor electrodes were then prepared for the detection of PCR-amplified genomic DNA from herpes simplex virus type II, genomic DNA from Clostridium perfringens, and genomic RNA from human immunodeficiency virus and gave an additional charge of 35-65 microC for hybridization to complementary amplicon and of only 2-10 microC after exposure to noncomplementary DNA.

Our efforts to model the oxygen activation chemistry of nonheme iron enzymes have yielded transient intermediates with novel properties. These properties can be dramatically affected by the introduction of a 6-methyl substituent on the pendant pyridines of the tetradentate ligand TPA (TPA = tris(2-pyridylmethyl)amine). A series of Fe(TPA) complexes has thus been synthesized and characterized to provide the structural basis for these dramatic effects. The following complexes have been obtained: [Fe(L)(CH3CN)2](ClO4)2 (1, L = TPA; 2, L = 6-MeTPA; 3, L = 6-Me2TPA; 4, L = 6-Me3TPA) and [Fe(L)(acac)](ClO4)2 (5, L = TPA; 6, L = 5-Me3TPA; 7, L = 6-MeTPA). As indicated by 1H NMR and/or EPR, 1, 5, and 6 with no 6-methyl substituent are low spin, while complexes 2, 3, 4, and 7 with at least one 6-methyl substituent are all high spin, with higher redox potentials than their low-spin counterparts. The ligands with 6-methyl substituents thus favor a metal center with a larger ionic radius, i.e., FeII over FeIII and h...

The hydroxylation of cyclohexane by t-butyl hydroperoxide using [Fe2O(TPA)2(H2O)2]4+ (1, TPA = tris(2-pyridylmethyl)amine) as the catalyst has been investigated with the use of a syringe pump to control the concentration of the alkyl hydroperoxide. Unlike an alkoxy radical-based radical chain autoxidation mechanism, the reaction observed produces only alcohol (no ketone) with a deuterium kinetic isotope effect of 10, similar to heme-catalyzed hydroxylations. An alkylperoxoiron(III) intermediate can be trapped at −40°C and characterized by a number of spectroscopic methods. A mechanistic scheme is proposed involving this intermediate which either serves as the precursor to the metal-based oxidant or oxidizes the substrate directly.

The efficiency of [Cu(2,2′-bipyridine) 2 (NO 3 )]NO 3 , [Cu(2,2′-dipyridylamine) 2 (NO 3 ) 2 ], and [Cu(dipicolylamine) 2 (NO 3 ) 2 ] complexes (complex 1, 2 and 3, respectively) in oxidative DNA cleavage was examined by electrophoresis and linear dichroism (LD). Among the three Cu complexes, complex 1 showed the highest efficiency in super-coiled DNA (scDNA) cleavage in electrophoresis. The presence of tiron, a superoxide radical scavenger, suppressed the reaction almost completely. The LD signal at 260 nm decreased gradually as the time passed. The decrease in LD magnitude was explained best by the sum of the two single exponential curves. This suggests that the cleavage reaction involves two first order kinetic processes; an increase in flexibility due to scission of one of the strands and a shortening in the DNA stem due to cut of both strands of double stranded DNA (dsDNA). In agreement with the electrophoresis data, complex 1 exhibited the highest efficiency with the superoxide radical found to be the essential reactive oxygen species. The order of efficiency in both scDNA and dsDNA was as follows: complex 1 > complex 2 > complex 3. The electrochemical properties alone were insufficient to explain the observed efficiencies, even though reduction of the central Cu ion is essential for the oxidative DNA cleavage. This highlights the importance of an ability to ligate the molecular oxygen (or hydrogen peroxide) to the central Cu ion to produce the superoxide radical, in addition to the reduction of Cu ion, in oxidative DNA cleavage.

Correction for ‘Diiridium(iii) complexes: luminescent probes and sensors for G-quadruplex DNA and endoplasmic reticulum imaging’ by Tikum Florence Anjong et al., New J. Chem., 2017, 41, 377–386.