Mode of Coordination and Chemical Reactivity of Alpha-Imine Hydrasone Ligands

Interaction of nickel(I1) and copper(I1) complexes of 4,9-dimethy1-5,8-diazadodeca-4,8diene-2,1 ldione, Ni(baen) and 4,6,9-trimethyl-5, 8diazadodeca-4,8-diene-2,ll-dione, Ni(bapn), with arene diazonium chlorides in buffered solutions of methanol yielded metal derivatives of glyoxaliminearylhydrazones. This typical electrophilic addition at the 3-carbon of the complex occurs owing to the pseudo aromatic behaviour of the chelate ring. A mechanism which predicts the attack of the diazonium cation through the coordination shell of the metal is well documented from the available experimental evidences. The chemical reactivity of a few complexes with a single residual non-substituted y-carbon is reasonably manifested by their reaction with phenyl isocyanate.

Nonlinear transport in semiconducting polymers at high carrier densities

Conducting and semiconducting polymers are important materials in the development of printed, flexible, large-area electronics such as flat-panel displays and photovoltaic cells. There has been rapid progress in developing conjugated polymers with high transport mobility required for high-performance field-effect transistors (FETs), beginning(1) with mobilities around 10(-4) cm(2) V-1 s(-1) to a recent report(2) of 1 cm(2) V-1 s(-1) for poly(2,5-bis(3-tetradecylthiophen-2-yl) thieno[3,2-b] thiophene) (PBTTT). Here, the electrical properties of PBTTT are studied at high charge densities both as the semiconductor layer in FETs and in electrochemically doped films to determine the transport mechanism. We show that data obtained using a wide range of parameters (temperature, gate-induced carrier density, source-drain voltage and doping level) scale onto the universal curve predicted for transport in the Luttinger liquid description of the one-dimensional `metal'.

Complexes of lanthanide perchlorates with two new O,N,O ligands derived from antipyraldehyde and acetic and benzoic acid hydrazides

Antipyrine is a well known ligand for lanthanides (I). A forage through the organic literature of pyrazolones reveals that the 4-position of antipyrine is amenable to a wide variety of organic reactions. It should thus be possible to introduce suitable functional groups at this position and design new multidentate ligands for metal ions. It is also found that the coordination chemistry of lanthanides is much less well developed and far fewer ligands have been used for complexation with lanthanide ions compared to that of the d-transition metal ions. Keeping these points in view we have reported earlier, complexes of lanthanides with a bidentate ligand N,N-diethyl-antipyrine-4-carboxamide (2). In this communication we report the synthesis of two new ligands from Schiff base condensation of antipyraldehyde and the hydrazides of acetic and benzoic acids and the complexes formed by these hydrazones with lanthanide perchlorates.

A criterion for existence of low frequency pure surface magnetoplasmon modes in the Faraday configuration

The low frequency surface magnetoplasmon-type polaritons in the Faraday configuration will propagate as generalized surface modes if 4ε∞/(ε∞ − 1)2 greater-or-equal, slanted μ2 and as pure surface modes if this inequality is reversed. The possibility of using the low frequency surface waves as a suitable probe for measuring the carrier concentration of a given sample is discussed.

Metal chelates in vinyl polymerization: Kinetics and mechanism of acrylonitrile polymerization initiated by Cu(II) imine complexes

The free radical polymerization of acrylonitrile (AN) initiated by Cu(II) 4-anilino 2-one [Cu(II) ANIPO] Cu(II), 4-p-toluedeno 3-pentene 2-one [Cu(II) TPO], and Cu(II) 4-p-nitroanilino 3-pentene 2-one [Cu(II) NAPO] was studied in benzene at 50 and 60°C and in carbon tetrachloride (CCl4), dimethyl sulfoxide (DMSO), and methanol (MeOH) at 60°C. Although the polymerization proceeded in a heterogeneous phase, it followed the kinetics of a homogeneous process. The monomer exponents were 2 at two different temperatures and in different solvents. The square-root dependence of Rp on initiator concentration and higher monomer exponents accounted for a 1:2 complex formation between the chelate and monomer. The complex formation was shown by ultraviolet (UV) study. The activation energies, kinetics, and chain transfer constants were also evaluated.

Metabolism of DL-(+/-)-phenylalanine by Aspergillus niger.

A fungus capable of degrading DL-phenylalanine was isolated from the soil and identified as Aspergillus niger. It was found to metabolize DL-phenylalanine by a new pathway involving 4-hydroxymandelic acid. D-Amino acid oxidase and L-phenylalanine: 2-oxoglutaric acid aminotransferase initiated the degradation of D- and L-phenylalanine, respectively. Both phenylpyruvate oxidase and phenylpyruvate decarboxylase activities could be demonstrated in the cell-free system. Phenylacetate hydroxylase, which required reduced nicotinamide adenine dinucleotide phosphate, converted phenylacetic acid to 2- and 4-hydroxyphenylacetic acid. Although 4-hydroxyphenylacetate was converted to 4-hydroxymandelate, 2-hydroxyphenylacetate was not utilized until the onset of sporulation. During sporulation, it was converted rapidly into homogentisate and oxidized to ring-cleaved products. 4-Hydroxymandelate was degraded to protocatechuate via

Studies in terpenoids. Part XXXI. Synthesis of pyrocurzerenone, a furosesquiterpenoid from Curcuma zedoaria

7-Acetonyloxy-5-methyl--tetralone (Vc) was cyclodehydrated to 7,8-dihydro-1,5-dimethylnaphtho[2,1-b]furan-9(6H)-one (VIa), the structure of which was established by an independent synthesis from methyl 4-(4-acetonyloxy-2-methylphenyl)butyrate (IXd). Similarly, 7-acetonyloxy-2,5-dimethyl--tetralone (Vf), synthesized via 4-(5-isopropyl-4-methoxy-2-methylphenyl)-2-methylbutyric acid (XIIb) and 7-methoxy-2,5-dimethyl--tetralone (Vd), was cyclodehydrated to 7,8-dihydro-1,5,8-trimethylnaphtho[2,1-b]furan-9(6H)-one (VIb), which on reduction and dehydration furnished pyrocurzerenone (6,7-dihydro-1,5,8-trimethylnaphtho[2,1-b]furan)(I). The deisopropylation and cyclodehydration of (XIIb) to (Vd) were effected in one step by treatment with polyphosphoric acid.

Instability of Combustion

THE following equations governing the phenomenon of intrinsic instability of combustion, leading to low frequency oscillations in a rocket motor using a single liquid propellant, were derived and investigated by L. Crocco.

New ternary copper(II) complexes of L-alanine and heterocyclic bases: DNA binding and oxidative DNA cleavage activity

Four new ternary copper(II) complexes of alpha-amino acid having polypyridyl bases of general formulation [Cu(L-ala)(B)(H2O)](X)(1-4), where L-ala is L-alanine, B is an N,N-donor heterocyclic base, viz. 2,2'-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2) and 5,6-phenanthroline dione (dione, 3), dipyrido[3,2:2',3'-f] quinoxaline (dpq, 4), and X = ClO4-/NO3- are synthesized, characterized by various spectroscopic and X-ray crystallographic methods. The complexes show a distorted square-pyramidal (4 + 1) CuN3O2 coordination geometry. The one-electron paramagnetic complexes (1-4) display a low energy d-d band near 600 nm in aqueous medium and show a quasi-reversible cyclic voltammetric response due to one-electron Cu(II)/Cu(I) reduction near - 100 mV (versus SCE) in DMF-0.1 M TBAP. Binding interactions of the complexes with calf thymus DNA (CT-DNA) were investigated by UV-Vis absorption titration, ethidium bromide displacement assay, viscometric titration experiment and DNA melting studies. All the complexes barring the complexes 1 and 3 are avid binder to the CT-DNA in the DNA minor groove giving an order: 4 > 2 >>>1, 3. The complexes 2 and 4 show appreciable chemical nuclease activity in the presence of 3-mercaptopropionic acid (MPA) as a reducing agent. Hydroxyl radical was investigated to be the DNA cleavage active species. Control experiments in the presence of distamycin-A show primarily minor groove-binding propensity for the complexes 2 and 4 to the DNA.

Metabolic fate of menthofuran in rats. Novel oxidative pathways

Metabolic fate of menthofuran (II) in rats was investigated. Menthofuran (II) was administered orally (200 mg/kg of the body weight/day) to rats for 3 days. The following metabolites were isolated from the urine of these animals: p-cresol (VI), 5-methyl-2-cyclohexen-1- one (VII), 3-methylcyclohexanone (VIII), 3-methylcyclohexanol (IX), 4- hydroxy-4-methyl-2-cyclohexen-1-one (V), geranic acid (XI), neronic acid (XII), benzoic acid (XIII), and 2-[2'-keto-4'- methylcyclohexyl]propionic acid (X). Incubation of menthofuran (II) with phenobarbital-induced rat liver microsomes in the presence of NADPH and oxygen resulted in the formation of a metabolite tentatively identified as 2-Z-(2'-keto-4'-methylcyclohexylidene)propanal (III; alpha,beta-unsaturated-gamma-keto-aldehyde). The structure assigned was further supported by trapping this metabolite (III) as a cinnoline derivative. Phenobarbital-induced rat liver microsomes also converted 4- methyl-2-cyclohexenone (IV) to 4-hydroxy-4-methyl-2-cyclohexenone (V) and p-cresol (VI) in the presence of NADPH and oxygen. On the basis of both in vivo and in vitro studies, a possible mechanism for the formation of p-cresol from menthofuran has been proposed.

Role of Bacillus subtilis BacB in the Synthesis of Bacilysin

Bacilysin is a non-ribosomally synthesized dipeptide antibiotic that is active against a wide range of bacteria and some fungi. Synthesis of bacilysin (L-alanine-[2,3-epoxycyclohexano-4]-L-alanine) is achieved by proteins in the bac operon, also referred to as the bacABCDE (ywfBCDEF) gene cluster in B. subtilis. Extensive genetic analysis from several strains of B. subtilis suggests that the bacABC gene cluster encodes all the proteins that synthesize the epoxyhexanone ring of L-anticapsin. These data, however, were not consistent with the putative functional annotation for these proteins whereby BacA, a prephenate dehydratase along with a potential isomerase/guanylyl transferase, BacB and an oxidoreductase, BacC, could synthesize L-anticapsin. Here we demonstrate that BacA is a decarboxylase that acts on prephenate. Further, based on the biochemical characterization and the crystal structure of BacB, we show that BacB is an oxidase that catalyzes the synthesis of 2-oxo-3-(4-oxocyclohexa-2,5-dienyl)propanoic acid, a precursor to L-anticapsin. This protein is a bi-cupin, with two putative active sites each containing a bound metal ion. Additional electron density at the active site of the C-terminal domain of BacB could be interpreted as a bound phenylpyruvic acid. A significant decrease in the catalytic activity of a point variant of BacB with a mutation at the N-terminal domain suggests that the N-terminal cupin domain is involved in catalysis.

Co(II) and Cr(III) complexes of formate-formamide mixed ligands: synthesis, structures, single crystal-to-single crystal transformation and magnetic behaviour

Solvothermal treatment of an equimolar mixture of Co(NO3)(2)center dot 6H(2)O, HCONH2 and NaN3 in MeOH at 100 degrees C yielded a three-dimensional NaCl type network Co(HCOO)(2)(HCONH2)(2) center dot HCONH2 (1a) containing formamides in the pores of the structure. Solvated pink 1a undergoes single crystal-to-single crystal (SCSC) transformation at 215 degrees C to form the desolvated dark brown product Co(HCOO)(2)-( HCONH2)(2) (1b) with the retention of the original framework. Reversible single crystal-to-single crystal transformation of 1b (brown) to 1a (pink) in the presence of excess formamide was also established at room temperature. The coordination environment around Co(II) in both 1a and 1b is octahedral with a CoN2O4 coordination composition. A similar reaction replacing Co(II) by Cr(III) produced a heterometallic 3D extended network Na[Cr(HCOO)(4)(HCONH2)(2)]center dot 2H(2)O (2a) at 100 degrees C. An increase in reaction temperature to 150 degrees C produced a simple mononuclear complex Cr(HCOO)(3)(HCONH2)(3) center dot 3H(2)O (2b). Variable temperature magnetic studies revealed the presence of a canting phenomena in both 1a and 1b, and hysteresis loop in the field dependent magnetisation plot at 2 K whereas complex 2a is simply paramagnetic in nature.

Spin-Probe ESR Studies on Nanocomposite Polymer Electrolytes

The possibility of using spin-probe electron spin resonance (ESR) as a tool to study glass transition temperature, T g, of polymer electrolytes is explored in 4 hydroxy 2,2,6,6 tetramethylpiperidine N oxyl (TEMPOL) doped composite polymer electrolyte (PEG)46LiClO4 dispersed with nanoparticles of hydrotalcite. The T g is estimated from the measured values of T 50G, the temperature at which the extrema separation 2A zz of the broad powder spectrum decreases to 50 G. In another method, the correlation time τc for the spin probe dynamics was determined by computer simulation of the ESR spectra and T g has been identified as the temperature at which τc begins to show temperature dependence. While both methods give values of T g close to those obtained from differential scanning calorimetry, it is concluded that more work is required to establish spin-probe ESR as a reliable technique for the determination of T g.

Identification and Characterization of a Novel Deoxyhypusine Synthase in Leishmania donovani

Deoxyhypusine synthase, an NAD(+)-dependent enzyme, catalyzes the first step in the post-translational synthesis of an unusual amino acid, hypusine (N-epsilon-(4-amino-2-hydroxybutyl)lysine), in the eukaryotic initiation factor 5A precursor protein. Two putative deoxyhypusine synthase (DHS) sequences have been identified in the Leishmania donovani genome, which are present on chromosomes 20: DHSL20 (DHS-like gene from chromosome 20) and DHS34 (DHS from chromosome 34). Although both sequences exhibit an overall conservation of key residues, DHSL20 protein lacks a critical lysine residue, and the recombinant protein showed no DHS activity in vitro. However, DHS34 contains the critical lysine residue, and the recombinant DHS34 effectively catalyzed deoxyhypusine synthesis. Furthermore, in vivo labeling confirmed that hypusination of eukaryotic initiation factor 5A occurs in intact Leishmania parasites. Interestingly, the DHS34 is much longer, with 601 amino acids, compared with the human DHS enzyme (369 amino acids) and contains several unique insertions. To study the physiological role of DHS34 in Leishmania, gene deletion mutations were attempted via targeted gene replacement. However, chromosomal null mutants of DHS34 could only be obtained in the presence of a DHS34-containing episome. The present data provide evidence that DHS34 is essential for L. donovani and that structural differences in the human and leishmanial DHS enzyme may be exploited for designing selective inhibitors against the parasite.

Solubilities of Some Chlorophenols in Supercritical CO2 in the Presence and Absence of Cosolvents

The solubilities of three chlorophenols, namely, 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol, in supercritical carbon dioxide were determined at temperatures from (308 to 3 18) K in the pressure range of (8.8 to 15.6) MPa. The Solubilities were determined both in the absence of cosolvents and in the presence of two cosolvents, methanol and acetone. The solubilities (in the absence of cosolvents) in mole fraction of 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol at 308 K were in the range of (0.0113 to 0.0215), (0.0312 to 0.0645), and (0.008 to 0.0173), respectively. The Solubilities of the chlorophenols followed the order 2,4-dichlorophenol & 4-chlorophenol & phenol & 2,4,6-trichlorophenol & pentachlorophenol. The solubility data were correlated with the Charstil model and with the Mendez-Santiago and Teja model. The overall deviation between the experimental data and the correlated results Was less than 6 % in averaged absolute relative deviation (AARD) for both of the models.