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The pyridine nucleotide ß-NA D+ induces increase in intracellular Ca2+ and relaxation of the human urinary bladder smooth muscle
2007-01-01
Novel pyridine containing ligands as models for the copper centres in nitrite reductase
This thesis is concerned with the synthesis of a series of novel pyridine containing ligands and their copper co-ordination chemistry. The aim was to design ligands which would produce copper complexes which model the active sites within certain copper-containing Nitrite Reductase enzymes. The first chapter reviews previous work in this area and details the promising nature of pyridine-containing ligands. The remainder of this thesis is concerned with the synthesis and characterisation of some novel pyridine-containing ligands and their copper chemistry. The synthetic routes developed during this work enabled tris(pyrid-2-yl)methylamine ligands to be produced and studied which were tripodal in form but which had a primary amine group at the cap which could be further elaborated. Additional substituents were also placed on the pyridine rings to investigate their impact on the chemistry of their copper complexes. These ligands showed a variety, counter ion dependent chemistry. The structures of number of the copper complexes formed during these studies have been determined by X-ray crystallography. These showed the ligand system to exhibit various modes of co-ordination. The exploitation of the synthetic approaches developed to these tripyridyl tripodal ligands has enabled the basic ligand to be elaborated to incorporate thiol, protected thiol and/or thioether groups. As part of this study the X-ray crystal structure of a copper complex from an N sub 2 S sub 2 ligand was determined. The synthesis of more sophisticated ligand systems which have both N sub 3 and N sub 2 S sub 2 donor sets within the same molecule have also been investigated.
Controlled Synthesis of β-cyclodextrin Derivatives in Pyridine
2008-01-01
The swelling of a low-rank coal in benzene-pyridine and toluene-pyridine mixtures
1995-10-01
A low-rank coal is examined for swelling in benzene-pyridine and toluene-pyridine mixtures. In each case, swelling is shown to be mainly due to the pyridine, the action of which is specific and not amenable to interpretation by the solubility parameter approach to understanding coal swelling.
X - Band EPR Study on Poly(Li-2-Hydroxyethyl Methacrylate)-Co-Poly(4-Vinly Pyridine)
2008-01-01
Some copolymers have important properties that it is alter rapidly from a liquid to a solid state when an external electric field is applied. In this study, the polymer was synthesized by six ionomers with different molar masses. The polymer has been irradiated with 60Co - gamma rays at room temperature along three days. After irradiation, the material has been investigated by X-band Electron Spin Resonance (ESR) spectrometer at various conditions. A very intensity ESR peaks have been observed at temperature between 130-450K along with that displayed, this ESR peaks were changed with temperature and produced radical was stable
Formation of composite nanomaterial MnPS3 layered structure intercalated with pyridine
2009-01-01
Intercalated compound of pyridine into layered MnPS3 has been synthesized and characterized by X-ray powder diffraction (XRD), Infrared (IR) and Scanning Electron Microscopy connected with chemical analysis (SEM-EDEX). It is found that leaving the intercalated compound in open atmosphere for a number of days influences the existing phase and the arranged orientation of the pyridine in the interlayer gap (6.4A) of the MnPS3 lattice. The estimated crystallite size varied with leaving the intercalated sample in open atmosphere and reached a lowest value of about 26nm. Three phases coexisted together as confirmed by XRD: the 001' phase (with lattice spacing 9.6A); the 001'' phase (with lattice spacing of 10.7A); and other phase with lattice spacing of 7.3A. The phase transformation occurs betw...
2010-01-01
Pyridinium ion was formed from pyridine, which had been bound to Lewis acid sites on Pt/SO4^2^--ZrO2 and Zn/H-ZSM5 by contact with pentane vapor. Protonic acid sites were generated on these surfaces by contact with pentane. The protonic acid sites generated in the presence of pentane were eliminated when pentane was removed from gas phase. The generation of the protonic acid sites occurred above 350K for Pt/SO4^2^--ZrO2 and above room temperature for Zn/H-ZSM5.
2009-01-01
Fe(III), Cr(III), Fe(II), Co(II) and Ni(II) chloride complexes supported by 2,6-bis[1-(iminophenyl)ethyl]pyridine have been synthesized and characterized along with single crystal X-ray diffraction. These complexes, in combination with MAO, have been examined in butadiene polymerization. The catalytic activity and regioselectivity are strongly controlled by metal center and cocatalyst (MAO/Co ratio dependent in the case of Co(II) complex). The activity decreases in the order of Fe(III)>Co(II)>Cr(III)Ni (II) complexes, in consistent with the space around the metal center. Polybutadiene with different microstructure content, from high trans-1,4 units (88-95% for iron(III) and Cr(III)), medium trans-1,4 and cis-1,4 units (55% and 35%, respectively, for iron(II)) to high cis-1,4 units 79% for ...
Deconjugation of N-glucuronide conjugated metabolites with hydrazine hydrate - Biomarkers for exposure to the food-borne carcinogen 2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)
2007-01-01
The metabolism of the carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) has been investigated in rabbit liver S9. Two phase I metabolites, N-2-OH-PhIP and 4'-OH-PhIP were identified based on UV and mass spectra and co-elution with reference standards. Fortification of the incubation with UDGPA resulted in a complete glucuronidation of PhIP and N-2-OH-PhIP, while 4'-OH-PhIP was only partly glucuronidated. Also, the PhIP metabolite 5-OH-PhIP was completely glucuronidated by rabbit liver S9, while 5-OH-PhIP was a poor substrate for CYP mediated hydroxylation. The glucuronic acid conjugates of PhIP metabolites were unsusceptible to treatment with beta-glucuronidase indicating that these are N-glucuronides. Treatment of the conjugates with hydrazine hydrate, however, resulted in complete hydrolysis of the glucuronic acid conjugates as well as in reduction to the parent amine of metabolites hydroxylated in the exocyclic amino group. Urine was collected from a male volunteer following consumption of fried chicken. Treatment of the urine with beta-glucuronidase/sulfatase resulted in release of 4'-OH-PhIP, while treatment with hydrazine hydrate in addition resulted in release of substantial amounts of PhIP and 5-OH-PhIP. The data show that hydrazine hydrate can hydrolyse N-glucuronides of metabolites of PhIP, glucuronides that are unsusceptible to enzymatic hydrolysis. In addition the data indicate that humans metabolise a large fraction of ingested PhIP to genotoxic metabolites. The chemical hydrolysis of glucuronide conjugates of PhIP metabolites with hydrazine hydrate observed in this study may also be a useful approach in the development of biomarkers for exposure and effect of other xenobiotics.
Modulation of neurotoxicant-induced increases in intracellular calcium by phytoestrogens differ for amyloid beta peptide (Abeta) and 1-methyl-4-phenyl-pyridine (MPP(+))
2009-01-01
Neurotoxicant-induced elevation of intracellular calcium (Ca(2+)) and modulation by phystoestrogens were examined in vitro using human neuroblastoma SH-SY5Y cells cultured with amyloid beta-peptide (Abeta) and 1-methyl-4-phenyl-pyridine (MPP+). Although Abeta itself did not increase Ca(2+), it exacerbated the effects of carbachol. The elevation of Ca(2+) caused by the agents in combination could be reduced by pretreatment with the phytoestrogens equol and genistein, as well as by the L-type Ca(2+) channel blocker nifedipine. MPP+ exposure also elevated Ca(2+), an effect blocked by nifedipine but not by the phytoestrogens. As opposed to phytoestrogens, nifedipine was also able to significantly reduce cell death caused by higher concentrations of MPP(+) in the LDH viability assay. The results suggest that phytoestrogens are unlikely to serve as general cellular protectants for neurotoxicants with different mechanisms of action. The concentrations of Abeta and MPP(+) affecting Ca(2+) release did not inhibit cell viability as measured with the LDH release assay. This indicates that mechanisms involved with toxicity can be studied at doses that are not lethal. Copyright (c) 2008 John Wiley & Sons, Ltd.
2010-01-01
Maintenance of the reduced state of luminal pyridine nucleotides in the endoplasmic reticulum - an important pro-survival factor in the cell - is ensured by the concerted action of glucose-6-phosphate transporter and hexose-6-phosphate dehydrogenase. The mechanism by which the redox imbalance leads to cell death was investigated in HepG2 cells. The chemical inhibition of the glucose-6-phosphate transporter, the silencing of hexose-6-phosphate dehydrogenase and/or the glucose-6-phosphate transporter, or the oxidation of luminal NADPH by themselves did not cause a significant loss of cell viability. However, these treatments caused ER calcium store depletion. If these treatments were supplemented with the administration of a subliminal dose of the oxidizing agent menadione, endoplasmic retic...
Bis(oxazoline) Lewis Acid Catalyzed Aldol Reactions of Pyridine N-Oxide Aldehydes-Synthesis of Optically Active 2-(1-Hydroxylalkyl)pyridine Derivatives: Development, Scope, and Total Synthesis of an Indolizine Alkaloid
2006-01-01
A novel preparation of pyridine-urea hybrids and elucidation of their structures
2009-01-01
A mechanistically unique and serendipitously discovered reaction providing a variety of pyridine-urea hybrids via the thiophenol-initiated uracil ring opening and pyridine ring-forming process was reported. The identification process of the hybrids and the pathway through which they were formed were also briefly described. Copyright 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:362-368, 2009; Published online in Wiley InterScience (). DOI 10.1002/hc.20560
Removal of Cr6+ ions on new pyridine ion exchangers bearing different functional groups
2009-01-01
(No abstract available)
The cycloauration of pyridine-2-thiocarboxamide ligands
2010-01-01
Reactions of H[AuCl4] with N-substituted 2-pyridine thiocarboxamide ligands 2-(C5H4N)C(S)NHR (R=p-C6H4Me, CH2Ph, Me, p-C6H4OMe) gave cycloaurated derivatives {(C5H4N)C(S)NR}AuCl2, with the ligand bonded as the thiol tautomer through the deprotonated SH group and the pyridine N atom to give a five-membered metallacyclic ring. The X-ray structure determination of the R=CH2Ph derivative shows a square-planar gold(III) complex that dimerises in the solid state by weak AuS intermolecular interactions. In contrast, in the reaction of H[AuCl4] with 2-(C5H4N)C(S)NHR where R=2-pyridyl, the ligand was oxidised to give a 1,2,4-thiadiazolo[2,3-a]pyridinium heterocyclic ring that was crystallographically characterised.
The effect of substituents in pyridine ring on extraction of zinc(II) from chloride solutions
2009-01-01
(No abstract available)
Characterization of plasma-polymerized 4-vinyl pyridine with silver nanoparticies on poly(ethylene terephthalate) film for anti-microbial properties
2006-01-01
4-vinyl pyridine was polymerized on poly(ethylene terephthalate) (PET) film by using lower energy pulsed AC plasma under low pressure in Ar atmosphere. The plasma polymerized coating was characterized by ATR Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Different thicknesses Of poly(4-vinyl pyridine) coating under different plasma polymerization conditions were studied. Silver nanoparticles with diameter around 50nm deposit were precipitated on the poly(4-vinyl pyridine) coating by UV irradiation in Silver nitride water solution, in order to enhance the anti-microbial properties. Different kinds of modified PET films were tested for anti-microbial properties against yeast (Debaryomyces hansenii) by using microbiological analyser mu-4200 and direct microscopic count method.
{sup 13}C NMR spectroscopy of pyridine and alkylpyridines sorbed onto coal
1993-12-31
Heterocyclic compounds such as pyridine and alkylpyridines sorbed onto coals can be examined by cross-polarization (CP) nuclear magnetic resonance (NMR) techniques in which signals from both the coal and the pyridine are seen. The addition of one methyl group to pyridine has little effect on the intensity of the observed spectrum, but two methyl groups show a decreased signal intensity of the pyridine carbons, especially for the 2,5-substitution pattern. Larger alkyl groups result in a much-reduced signal intensity for the sorbed molecule. In the case of pyridine sorption of the coals studied, those coals with carbon contents greater than 85% showed the weakest pyridine signals in the CP spectrum. A proposed model for the pyridine bonding is one in which surface-immobilized molecules are bonded to a number of additional pyridine molecules. These bonded molecules constitute the bulk of the CP pyridine signal observed in the spectrum. 28 refs., 6 figs., 2 tabs.
2009-01-01
The design, synthesis, and characterization of the 10 linear and bent acentric ligands 1-10 (tectons) based on the differentiation of two divergently disposed coordinating poles is reported. The nature of the two poles and their distance are varied by the use of different linear spacers. For these molecules, a monodentate coordinating site, i.e., a pyridine ring, and a tridentate coordinating site, i.e., a pyridine moiety bearing at the 2 and 6 positions either two thioether groups or two dimethylamino units (PySMe and PyN(Me2)2 type, resp.), a terpyridine, or a pyridine ring bearing two optically pure dihydrooxazole units, are combined.
{2,6-Bis[bis(2-pyridylmethyl)aminomethyl]pyridine}manganese(II) bis(perchlorate) 0.435-hydrate
2007-01-01
Bisoxazoline-Lewis Acid Catalyzed Direct-Electron Demand Oxo-Hetero-Diels-Alder Reactions Pyridine-N-Oxide Aldehyde and Ketone Derivatives
2007-01-01
{2,6-Bis[bis(2-pyridylmethyl)aminomethyl]-pyridine}cobalt(II) bis(perchlorate) 0.365-hydrate
2007-01-01
2009-01-01
A family of thieno[3,2-b]pyridine based small molecule inhibitors of c-Met and VEGFR2 were designed based on lead structure 2. These compounds were shown to have IC50 values in the low nanomolar range in vitro and were efficacious in human tumor xenograft models in mice in vivo.
2010-01-01
A series of new p-tert-butyl thiacalix[4]arenes with o-, m-, p-amido and o-, m-, p-(amidomethyl)pyridine substituents at the lower rim in cone, partial cone, and 1,3-alternate conformations were synthesized. The ability of the obtained compounds to recognize the a-hydroxy (glycolic, tartaric) and dicarboxylic (oxalic, malonic, succinic, fumaric, and maleic) acids was investigated by UV-vis spectroscopy. Also, the efficiency and selectivity of binding, the association constants logKa (102 to 107M-1) and the stoichiometry were determined for the complexes of p-tert-butyl thiacalix[4]arenes with the acids. The receptors based on p-tert-butyl thiacalix[4]arenes with (amidomethyl)pyridine substitutes are most efficient in complexation in many cases.
Scientific Opinion of the Panel on Food Additives, Flavourings, Processing Aids and Materials in contact with Food (AFC): Pyridine, pyrrole, indole and quinoline derivatives from chemical group 28 Flavouring Group Evaluation 24, Revision 1 : Question No EFSA-Q-2003-167B
2008-01-01
Biomonitoring of urinary metabolites of 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) following human consumption of cooked chicken
2008-01-01
Human risk assessment of exposure to 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) through the diet may be improved by conducting biomonitoring studies comparing metabolism in humans and rodents. Eleven volunteers ingested a meal of cooked chicken containing 4-OH-PhIP and PhIP in amounts of 0.6 and 0.8 mu g/kg, respectively and urine was collected for the next 16 h. The large number of PhIP metabolites was by treatment of the urine samples with hydrazine hydrate and hydrolytic enzymes reduced to three substances, 4'-OH-PhIP, PhIP and 5-OH-PhIP of which the first is a biomarker for detoxification and the last a biomarker for activation. The eleven volunteers eliminated large amounts of 4'-OH-PhiP in the urine. The majority of which Could be accounted for by the presence of 4'-OH-PhIP in the fried chicken, showing that PhIP only to a small extent (11%) was metabolised to 4'-OH-PhIP. A larger fraction of the PhIP exposure, 38%, was recovered as PhIP and the largest fraction (51%) was recovered as 5-OH-PhIP Suggesting that PhIP in humans to a large extent is metabolised to reactive Substances. In rats, less than 1% of the dose of PhIP was eliminated as 5-OH-PhIP, Suggesting that human cancer risk from exposure to PhIP is considerable higher than risk estimations based on extrapolation from rodent bioassays. (C) 2008 Elsevier Ltd. All rights reserved.
2008-02-22
Pyridine hydrogenation in the presence of a surface monolayer consisting of cubic Pt nanoparticles stabilized by tetradecyltrimethylammonium bromide (TTAB) was investigated by sum frequency generation (SFG) vibrational spectroscopy using total internal reflection (TIR) geometry. TIR-SFG spectra analysis revealed that a pyridinium cation (C{sub 5}H{sub 5}NH{sup +}) forms during pyridine hydrogenation on the Pt nanoparticle surface, and the NH group in the C{sub 5}H{sub 5}NH{sup +} cation becomes more hydrogen bound with the increase of the temperature. In addition, the surface coverage of the cation decreases with the increase of the temperature. An important contribution of this study is the in situ identification of reaction intermediates adsorbed on the Pt nanoparticle monolayer during pyridine hydrogenation.
Rh(I)-Catalyzed Direct Arylation of Pyridines and Quinolines
2008-07-29
The pyridine and quinoline nuclei are privileged scaffolds that occupy a central role in many medicinally relevant compounds. Consequently, methods for their expeditious functionalization are of immediate interest. However, despite the immense importance of transition-metal catalyzed cross-coupling for the functionalization of aromatic scaffolds, general solutions for coupling 2-pyridyl organometallics with aryl halides have only recently been presented. Direct arylation at the ortho position of pyridine would constitute an even more efficient approach because it eliminates the need for the stoichiometric preparation and isolation of 2-pyridyl organometallics. Progress towards this goal has been achieved by activation of the pyridine nucleus for arylation via conversion to the corresponding pyridine N-oxide or N-iminopyridinium ylide. However, this approach necessitates two additional steps: activation of the pyridine or quinoline starting material, and then unmasking the arylated product. The use of pyridines directly would clearly represent the ideal situation both in terms of cost and simplicity. We now wish to document our efforts in this vein, culminating in an operationally simple Rh(I)-catalyzed direct arylation of pyridines and quinolines. We recently developed an electron-rich Rh(I) system for catalytic alkylation at the ortho position of pyridines and quinolines with alkenes. Therefore, we initially focused our attention on the use of similarly electron-rich Rh(I) catalysts for the proposed direct arylation. After screening an array of electron-rich phosphine ligands and Rh(I) salts, only marginal yields (<20%) of the desired product were obtained. Much more efficient was an electron-poor Rh(I) system with [RhCl(CO){sub 2}]{sub 2} as precatalyst (Table 1). For the direct arylation of picoline with 3,5-dimethyl-bromobenzene, addition of P(OiPr){sub 3} afforded a promising 40% yield of the cross coupled product 1a (entry 1). The exclusion of phosphite additive proved even more effective, with the yield of 1a improving to 61% (entry 2). Further enhancement in yield was not observed upon the inclusion of other additives such as MgO (entry 3), various organic bases (entries 4, 5), or a protic acid source (entry 6). Absolute concentration proved very important, with the best results being obtained at relatively high concentrations of the aryl bromide (compare entries 7 and 8). A marginal improvement was observed upon running the reaction with 6 equivalents of 2-methyl pyridine (entry 9). The reaction temperature could also be increased to 175 or 190 C while maintaining reaction yield, to enable the reaction time to be reduced to 24 h (entries 10 and 11). In summary, we have developed a Rh(I)-catalyzed strategy for the direct arylation of pyridines and quinolines. The heterocycle is used without the need for prefunctionalization, and all reaction components are inexpensive and readily available. The strategy represents an expeditious route to an important class of bis(hetero)aryls and should be of broad utility.
Thermodynamics of the solvent swelling of coal
1990-01-01
Sorption of pyridine by the pyridine-extracts of three premium Argonne coals was studied at several relative vapor pressures at 50{degree}C. The amount of pyridine sorbed by each extract increases linearly with pyridine vapor pressure. The extrapolated lines do not pass through the origin. At low pressures, a dual-mode sorption mechanism is proposed, whereby pyridine concurrently fills holes (microvoids) and dissolves into the extract. At higher pressures, we propose that the holes are saturated and that only dissolution is occurring. Dissolution thus increases linearly with pressure of pyridine. Not all pyridine can be desorbed from the extract. The amount remaining corresponds closely to the intercept of the straight-line curve. This result suggests that pyridine cannot be desorbed from the holes at the experimental temperature. 1 ref., 4 figs., 1 tab.
Thermodynamics of the solvent swelling of coal
1990-01-01
Sorption of pyridine by the pyridine-extracts of three premium Argonne coals was studied at several relative vapor pressures at 50{degree}C and 70{degree}C. The amount of pyridine sorbed by each extract increases linearly with pyridine vapor pressure. Heat of dilution were calculated from the slopes of the straight-line portions of the curves. In a related experiment, the pyridine sorption isotherms of the pyridine-extract, pyridine-insoluble residue, and the whole coal were determined at 50{degree}C. For all materials, the amount of pyridine sorbed increases linearly with pressure of pyridine, with similar slopes. However, the intercepts are different for each material. Finally, the sorption of benzene vapors by O-alkylated Illinois {number sign}6 coals were studied at 30{degree}C. The rate of benzene sorption increases dramatically upon O-methylation, indicating that coal-coal hydrogen bonds play a dominant role in controlling the rate of benzene sorption. 2 refs., 3 figs., 1 tab.
Molecular accessibility in solvent swelled coals. Quarterly report, [September--November, 1993]
1993-11-01
This quarter, experiments were performed on the use of binary swelling solvents in molecular accessibility in coal conversion. These experiments consisted of accessibility measurements of spin probe VII (TEMPAMINE) in Toluene swelled Illinois No. 6 APCS coal. The toluene was spiked with amounts of pyridine which ranged in concentration from 500 ppm to 10%. The experiments were done in triplicate to gain information about the experimental error involved in the procedure. It was shown that oscillations occur in the concentration of spin probe retained as the amount of pyridine that is added to the swelling solvent is increased. These oscillations decrease in intensity as the concentration of pyridine in the solvent solution is increased up to 2% pyridine (0.2mLs pyridine in 10mLs toluene). From a 2% pyridine concentration to a 5% concentration, there is no significant change in the retention of spin probe VII. An increase in retention is observed when the concentration of pyridine is increased to 6% and 7% successively, followed by a large decrease at 8% and 9% pyridine. The largest changes in spin probe retention are observed for concentrations of pyridine less than 0.5%. A three fold increase in spin probe retention is observed upon the addition of 500 ppm pyridine in the toluene swelling solvent, which indicates that small amounts of a strong swelling solvent could be used to improve molecular accessibility 91% in coals swelled in an otherwise weak swelling solvent.
http://eprints.utas.edu.au/2923/1/AJC1976_2C_1383.pdf
Methylmercuric nitrate reacts with pyridine-2(lH)-thione (C5H5NS) in acetone to give methyl(pyridine-2(1H)-thione)mercury(II) nitrate, [MeHg(C5H5NS)]NO3. This complex reacts with sodium bicarbonate in acetone to give methyl(pyridine-2-thiolato)mercury(II), MeHg(C5H4NS). Infrared, Raman, and nuclear magnetic resonance spectra indicate that MeHg(II) is bonded to sulphur in both complexes, and that protonation of nitrogen occurs on reaction of MeHg(C5H4NS) with nitric acid to give [MeHg(C5H5NS)]NO3. Format: application/pdf Other identifier: Canty, AJ and Marker, A (1976) Methylmercury(II) Derivatives of Pyridine-2(1H)-thione. Australian Journal of Chemistry, 29 (6). pp. 1383-1387. ISSN 0004-9425
2009-01-01
A series of europium(III) and terbium(III) complexes of three 1,4,7-triazacyclononane-based pyridine containing ligands were synthesized. The three ligands differ from each other in the substitution of the pyridine pendant arm, namely they have a carboxylic acid, an ethylamide, or an ethyl ester substituent, i.e., these ligands are 6,6prime,6Prime-[1,4,7-triazacyclononane-1,4,7-triyltris(methylene)]tri- s[pyridine-2-carboxylic acid] (H3tpatcn), -tris[pyridine-2-carboxamide] (tpatcnam), and -tris[pyridine-2-carboxylic acid] triethyl ester (tpatcnes) respectively. The quantum yields of both the europium(III) and terbium(III) emission, upon ligand excitation, were highly dependent upon ligand substitution, with a ca. 50-fold decrease for the carboxamide derivative in comparison to the picolin...
Design of a high activity and selectivity alcohol catalyst
1992-02-07
Results of the pyridine adsorption, studies on native and K-doped alumina provide fundamental grounding for the observed methanol dehydration activity of these samples. Both the reactor studies and the pyridine adsorption studies support the conclusion that the K-doped sample had reduced Lewis acidity. Moreover, we were able to measurably alter the acidity of the support surface by our ion exchange treatment. More significantly, when reactor results for transition-metal loaded samples are reconsidered in combination with their surface characteristics suggested by our pyridine adsorption studies, our hypothesis that Rh and Mo have ultimately titrated the support surface seems all the more convincing. Hence, in light of the pyridine adsorption results, the attenuation of a transition-metal based decomposition pathway for methanol on the metal-loaded samples-as seen in the reactor testing-is all the more reasonable.
Investigation of coal structure. Quarterly report, January 1, 1993--March 31, 1993
1993-04-01
The goal of the present work is to conduct multi-stage sequences of extraction experiments and direct solvent swelling measurements of raw and extracted coal to study in a greater depth the role of intra- and intermolecular interactions in the structure of coal. One of the possible ways to investigate the structure of coal is to extract it with a series of procedures. The individual extraction step chosen will be such that it weaken or disrupt intra- and intermolecular interactions that are particular to the rank of the test coal. To date, we attempted to extract raw and pyridine extracted (PI) DECS 16 coal with two solvents; 1:1 volume percent carbon disulfide & 1-methyl-2-pyrrolidinone (NMEP) mixed solvent and 1:3 volume percent 1M tetrabutylammonium hydroxide (TBAH) in methanol & pyridine. Also, raw DECS 16 coal was o-butylated followed by pyridine extraction in a soxhlet apparatus and the ultimate extraction yields were compared with o-butylated pyridine extracted coal.
1992-02-07
Results of the pyridine adsorption, studies on native and K-doped alumina provide fundamental grounding for the observed methanol dehydration activity of these samples. Both the reactor studies and the pyridine adsorption studies support the conclusion that the K-doped sample had reduced Lewis acidity. Moreover, we were able to measurably alter the acidity of the support surface by our ion exchange treatment. More significantly, when reactor results for transition-metal loaded samples are reconsidered in combination with their surface characteristics suggested by our pyridine adsorption studies, our hypothesis that Rh and Mo have ultimately titrated the support surface seems all the more convincing. Hence, in light of the pyridine adsorption results, the attenuation of a transition-metal based decomposition pathway for methanol on the metal-loaded samples-as seen in the reactor testing-is all the more reasonable.
Shale oil value enhancement research. Fourth quarterly report, 1996
1997-09-01
Concurrent activities are ongoing in all key areas, namely, (a) construction and startup of a flow THDA reactor system, (b) development of KPX product slate, and (c) conducting industrial liaison for assembly of the KPX consortium. Excellent progress is being made in all cases. Our market analysis and industrial feedback have caused us to focus on pyridine itself. We are concentrating our effort toward increasing the yield of pyridine at present. To produce sufficient quantity of sample for marketing purpose, we needed an in- house flow THDA unit. This unit is in its startup phase. The completion of the flow THDA unit will allow us to produce pyridine effectively. The liaison with potential industrial partners is continuing. At the present time, we have a confidentiality agreement with many of the major target companies. Follow-up work has been initiated and excellent progress has been made. To expedite the process, we reached an agreement with Mr. David Purpi as a consultant to assist on the industrial liaison. Mr Purpi has served many years as a marketing executive for a major pyridine manufacturer and has extensive experience in pyridine production and marketing. His appointment to work on this project has been approved by the DOE.
http://espace.library.uq.edu.au/view/UQ:141159
FVT of 2-(2-diazoacetyl)pyridine (1) yields 2-pyridylketene (3) (largely in the s-Z form 32), which dimerizes to quinazolinone 5. Matrix photolysis of 1 (largely in the EZ form 1EZ) yields the carbene-pyridine ylide 6, which on further photolysis at lambda > 320 nm is converted to (mainly) the s-E ketene 3E. Continued photolysis of 3E at 320 nm converts it to 3Z, and this process is reversed on photolysis at 254 nm. Publisher: American Chemical Society Relation: isMemberOf School of Biological Sciences Publications
http://espace.library.uq.edu.au/view/UQ:72437
Several tetrazolo[1,5-a] pyridines/2-azidopyridines undergo photochemical nitrogen elimination and ring expansion to 1,3-diazacyclohepta-1,2,4,6-tetraenes (7,10,13,16,19,22) as well as ring cleavage to cyanovinylketenimines (8,17,20b) in low temperature Ar matrices. 6,8-Dichlorotetrazolo[1,5-a] pyridine/2-azido-3,5-dichloropridine 6 undergoes ready exchange of the chlorine in position 8 (3) with ROH/RONa. 8-Chloro-6-trifluoromethyltetrazolo[1,5-a] pyridine 15 undergoes solvolysis of the CF3 group to afford 8-chloro-6-methoxycarbonyltetrazolo[1,5-a] pyridine 18. Several tetrazolopyridines/2-azidopyridines afford 1H- or 5H-1,3-diazepines in good yields on photolysis in the presence of alcohols or amines (11,14,23,25). 5-Chlorotetrazolo[1,5-a] pyridines/2-azido-6-chloropyridines 21 and 38 undergo a rearrangement to 1H- and 3H-3-cyanopyrroles 27 and 45, respectively. The mechanism of this rearrangement was investigated by N-15-labelling and takes place via transient 1,3-diazepines. The structures of 6,8-dichloro-tetrazolo[1,5-a] pyridine 6T, 6-chloro-8-ethoxytetrazolo[1,5-a] pyridine 9Tb, dipyrrolylmethane 28, and 2-isopropoxy-4-dimethylamino-5H-1,3-diazepine 25b were determined by X-ray crystallography. In the latter case, this represents the first reported X-ray crystal structure of a 5H-1,3-diazepine. Publisher: Royal Society of Chemistry Relation: isMemberOf School of Chemistry and Molecular Biosciences; isMemberOf Excellence in Research Australia (ERA) - Collection
Studies of coupled chemical and catalytic coal conversion methods
1989-01-01
C-Alkylation has been utilized in the solubilization of various coals. Low rank, high oxygen Illinois No. 6 coal was alkylated with different alkylating agents under different conditions to determine the most suitable reaction conditions. A new method of alkylating coal with n-butyl lithium and potassium tertiary butoxide in refluxing heptane has been studied. The influence of the solvent for alkylation on the pyridine solubility of the product was studied. The pyridine solubility of the products obtained with n-butyl iodide ranged from 39% for the reaction in heptane to 5l% for the reaction in tetrahydropyran. Tetrahydrofuran, in contrast, produced only 33% pyridine soluble product. The reactivity pattern for alkylation was determined by deuterium and carbon NMR spectroscopy of the products that were obtained with deuterium and carbon-13 labelled alkylating agents.
Molecular accessibility in solvent swelled coal
1990-11-01
Research continued on the swelling of coal. Changes in the size and number distribution of the accessible regions in five Argonne Premium Coal Samples (APCS No.3, No.4, No.5, No.6, and No.8) upon swelling with the solvents, cyclohexane, toluene, nitrobenzene and pyridine were examined by an EPR spin probe method. It was found that as the basicity of the solvent increased the number and length of the cylindrical pores increased with decreasing rank. The number of cylindrical pores also increased with oxygen content (with decreasing rank) suggesting a destruction of the hydrogen-bond network upon swelling with pyridine. 6 refs.
1989-12-31
C-Alkylation has been utilized in the solubilization of various coals. Low rank, high oxygen Illinois No. 6 coal was alkylated with different alkylating agents under different conditions to determine the most suitable reaction conditions. A new method of alkylating coal with n-butyl lithium and potassium tertiary butoxide in refluxing heptane has been studied. The influence of the solvent for alkylation on the pyridine solubility of the product was studied. The pyridine solubility of the products obtained with n-butyl iodide ranged from 39% for the reaction in heptane to 5l% for the reaction in tetrahydropyran. Tetrahydrofuran, in contrast, produced only 33% pyridine soluble product. The reactivity pattern for alkylation was determined by deuterium and carbon NMR spectroscopy of the products that were obtained with deuterium and carbon-13 labelled alkylating agents.
http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=118131
Reaction of 2,6-bis(3-butylbenzimidazol-1-ium)pyridine dibromide with silVer oxide affords a dinuclear complex of the type [L2Ag2]2+ [L ) 2,6-bis(3-butylbenzimidazolin-2-ylidene)pyridine]. 1H NMR spectroscopic studies suggest that the dinuclear structure is also present in solution. Transmetalationof the silVer-NHC complex with PdCl2(CH3CN)2 yields a mononuclear palladium complex of the type [LPdCl]+, with a chelating C,N,C pincer ligand. Publisher: Nanochemistry Research Institute (Research Institute) Other identifier: PUB-SE-NRI-BT-48181
Development of high energy polymers systems: 6th monthly status report
1969-07-09
The major objective of the current program is the preparation of high energy hydroxyl-terminated polyester prepolymers from combinations of energetic diols and dicarboxylic acid chlorides. The initial work was based on the reactions of 4,4-dinitropimeloyl chloride (DNPCl) with 2,2,8,8-tetranitro-4,6-dioxa-1,9-nonanediol (DINOL) and 3(dinitrofluoro- ethoxy)-1,2-propanediol (REX-18). In an effort to develop a smooth and rapid polyester polymerization method, reactions between DNPCl and both DINOL and REX-18 have been carried out in THF containing pyridine. It was expected that the pyridine would act as an HCl acceptor, permitting room temperature polymerizations. This was indeed shown to be the case. In fact, when the glycol and DNPCl were dissolved in THF and pyridine added rapidly, a very exothermic reaction took place, with copious quantities of pyridine hydrochloride being precipitated. Slow addition of pyridine to the reaction mixture also resulted in an exotherm. In both cases, brown polymers were produced and they were very difficult to work-up. The next series of polymerizations will be carried out at 0{degrees}C in an effort to control the polymerizations more carefully and avoid color formation. The diacid chloride of 2-fluoro-2,2-dinitroethoxyfumaric acid has apparently been synthesized. Reactions of the acid with thionyl chloride at 50-60{degrees} for several days followed by a one-hour reflux produced a white solid. It was filtered, washed with hexane and dried in a vacuum dessicator over KOH. The powder melted at 104-106{degrees}. After it is recrystallized, it will be submitted for elemental analyses. Should it prove to be the diacid chloride, it will be reacted with DINOL and REX-18.
Influence of binary swelling solvents: Mechanism of action
1995-12-31
This study addresses the dramatic up-take of a poor swelling solvent in Argonne Premium Coal Samples (APCS), Illinois No. 6, Beulah-Zap and Lewiston-Stockton when such a solvent is spiked with various amounts of the strong swelling solvent, pyridine. The unexpected up-take can be explained in terms of four different processes: (1) disruption of weak hydrogen bonds which isolate the interconnected micropore system; (2) disruption of weak hydrogen bonds which protect individual micropores; (3) competition of pyridine for the active sites involved in the hydrogen bonds or the {open_quotes}poisoning{close_quotes} of active sites; and (4) disruption of stronger hydrogen bonds within the macromolecules which causes an opening of the structure. When more than 5% pyridine is used, no additional disruption of the hydrogen-bonded network occurs. The structural changes were monitored by spin probe incorporation which was measured by EPR spectroscopy.
Kinetics of coal conversion to soluble products. Final technical report
1994-04-12
The objectives of this work are (1) to measure the kinetics of the conversion of coals to soluble products under model liquefaction conditions using GPS techniques to count the number of bonds broken; (2) to analyze these data using kinetic schemes based on the behavior of crosslinked macromolecular networks. The product was Soxhlet extracted with pyridine until the pyridine solution was clear. A gel permeation chromatogram of the pyridine soluble is shown in Figure 2A. The improved mass sensitive detector system requires only about 500 ng to acquire a chromatogram having fairly good S/N ratio. Apparently, no disturbance is caused by the remaining tetralin and naphthalene formed by dehydrogenation of tetralin. These seriously affect the lower molecular weight region when IR or UV detectors are used. It is a notable advantage of the mass sensitive detector that suitable adjustment of the nebulizer and of the evaporator completely suppressed the contribution of solvent to the chromatogram. The molecular weight distribution of liquefaction product appears to be almost unimodal if the small shoulder at the lower elution volume side is neglected.
http://eprints.qut.edu.au/17944/
Poly(ethylene oxide) (PEO)/2,6-bis (N-pyrazolyl) pyridine (BNPP) polymer electrolyte based photoelectrochemical cells have been fabricated with [cis-dithiocyanato-N, N-bis (2,2 bipyridyl-4, 4 dicarboxylic acid)ruthenium(II)] dihydrate (N3 dye) dye complex as the sensitizer and nanoporous TiO2 film as photo anode. The introduction of 2,6-bis (N-pyrazolyl) pyridine into the poly (ethylene oxide) matrix reduces the crystallinity of the polymer and enhances the mobility of I−/I3− redox couple resulting in an improved performance with a higher conversion efficiency of 8.8% in terms of light energy to electric energy when compared to that of the corresponding dye-sensitized nanocrystalline TiO2 solar cell. Publisher: Elsevier Relation: DOI:10.1016/j.electacta.2008.05.071; Ganesan, S. and Achari, Muthuraaman Bhagavathi and Madhavan, J. and Vinod, Mathew and Maruthamuthu, P. and Suthanthiraraj, Austin (2008) The use of 2,6-bis (N-pyrazolyl) pyridine as an efficient dopant in conjugation with poly(ethylene oxide) for nanocrystalline dye-sensitized solar cells. Electrochimica Acta, 53(27). pp. 7903-7907. Format: application/pdf Rights: Copyright 2008 Elsevier
Temperature effects on chemical structure and motion in coal. Quarterly report, April--June, 1995
1995-06-30
As described in previous reports, the effects of moderate temperatures (up to 230 C) is to increase molecular/macromolecular mobility in coals, as determined by {sup 1}H CRAMPS (Combined Rotation And Multiple Pulse Spectroscopy) measurements, especially dipolar-dephasing experiments. Pyridine-saturated coals have also been studied with the same kinds of NMR experiments. The author found that thermal activation and solvent saturation promote the molecular mobility of coals in quite different ways. These results have provided some new insight into the molecular/macromolecular structure and dynamics of coals. In this report, the author compares {sup 1}H CRAMPS results obtained on the original (untreated) Argonne Premium coal 601 with those obtained on the pyridine extraction residue of coal 601. These results are consistent with previous results and provide further information on the structure and dynamics of coals.
2010-01-01
Four octamolybdate-based compounds, that is, CuII2(L1)4(Mo8O26) (1), CuII2(HL2)4(Mo8O26)2 (2), [CuIIL2(H2O)(Mo8O26)0.5]2H2O (3) and [CuIIL2(H2O)(Mo8O26)0.5]2H2O (4) (L1=2-(2-pyridyl)imidazole, L2=2-(1-(pyridine-3-ylmethyl)-1H-imidazol-2-yl)pyridine), have been hydrothermally synthesized via changing the reaction conditions and structurally characterized by single-crystal X-ray diffraction. With L1 ligand, we obtained compound 1, which is a 0D molecule and extends to a 3D supramolecular structure via hydrogen-bonding interactions. By using L2 instead of L1 ligand, compound 2 comes into being which is as well a discrete molecule and further extended to a 3D supramolecular structure by hydrogen bonds. Intriguingly, compounds 3 and 4 are supramolecular isomers: the former is a 2D 4-connected n...
http://hdl.handle.net/10072/25001
Mixed base pyridine (py)/triphenylphosphine adducts of the silver(I) halides, AgX (X = Cl, Br, I), have been synthesized for 1 : 1 : 1 stoichiometry. The three complexes are isomorphous and isostructural, being monoclinic, P21/c, a ≈ 11.2, b ≈ 16.8, c ≈ 16.5 Å , β ≈ 122 º ; the complexes are centrosymmetric µ, µ?- dihalo -bridged dimers , [(PPh3)( py )AgX2Ag( py )(PPh3)1 (Z = 2 dimers ). Although the stoichiometry of the complex itself is as above, an additional unit of pyridine per silver atom is found as solvent in the lattice, implying the unlikelihood of the existence of an independent 1 : 2 : 1 AgX : py : PPh3 molecular series. In addition, the iodide has been isolated as a different C2/m (?) disordered polymorph. Publisher: http://www.publish.csiro.au/nid/51/paper/CH9890923.htm; CSIRO Publishing; Collingwood, Vic.; http://www.publish.csiro.au/nid/51.htm Relation: Australian Journal of Chemistry; 923; 931; N; 42 Other identifier: 0004-9425 Language: en_AU Rights: Copyright 1989 CSIRO. Please refer to the journal's website for access to the definitive, published version.; Y
Thermodynamics of the solvent swelling of coal
1991-10-10
Sorption of benzene by the pyridine-extracts of premium Argonne Illinois {number sign}6 coal was studied at several relative vapor pressures at 50{degrees}C and 70{degrees}C. The amount of benzene sorbed by the extract increases linearly or nearly linearly with benzene vapor pressure. The extrapolated lines do not pass through the origin. At low pressures, a dual-mode sorption mechanism is proposed, whereby benzene concurrently fills holes (microvoids) and dissolves into the extract. At higher pressures, we propose that the holes are saturated and that only dissolution is occurring. Dissolution thus increases linearly with pressure of benzene. The heat of dilution, calculated from the change in slope of the curve with temperature, is positive, indicating a endothermic process. This result is in distinct contrast to results obtained previously using pyridine as solvent. The O-methylated extract absorbs considerably more benzene at 50{degrees}C compared to the extract. Again, the sorption curve is linearly, with a slope 1.5 times that of the extract. The increase in slope is consistent with the disruption of hydrogen bonds by O-methylation. 3 refs., 2 figs., 1 tab.
1996-07-01
This report presents the results of the outstanding studies on olefin product purities, pyridine recovery, and absorber offgas utilization. Other reports issued since the May 2 technical review meeting in Grangemouth evaluated the impact of the new VLE data on the solution stripping operation and the olefin loadings in the lean and rich solutions. This report completes the bulk of Stone & Webster`s engineering development of the absorber/stripper process for Phase I. The final feasibility study report (to be issued in August) will present an updated design and economics.
Strictly hetero-dinuclear compounds containing U4+ and Cu2+ or Ni2+ ions
2007-01-01
Treatment of [M(H2Li)] with UCl4 in pyridine led to the formation of the dinuclear complexes [MLi(py)UCl2(py)2] and/or [Hpy]-[MLi(py)UCl3] [Li=N,N'-bis(3-hydroxy-salicylidene)-R, R = 1,2-phenylene-diamine (i = 1), Rtrans-1,2-cyclohexane-diamine (i = 2), R = 2-amino-benzyl-amine (i = 3), R1,3-propane-diamine (i = 4), R = 2,2-dimethyl-1,3-propane-diamine (i = 5). MCu or Ni]. The crystal structures show that the 3d and 5f ions occupy, respectively, the N2O2, and O4 cavities of the Schiff base ligand, the U4+ ion adopting a dodecahedral or pentagonal bipyramidal configuration in the neutral and anionic complexes, respectively. (authors)
http://hdl.handle.net/10072/16965
Irradiation of benzoyl azide 1 at 254 nm in the presence of some amines produces aminimides: in the presence of pyridine the aminimide 13 can be isolated in 41% yield; in the presence of N,N-dimethylaniline a CH insertion product 7 is obtained via an intermediate aminimide 12. This is the first reported synthesis of aminimides from a benzoyl azide. Publisher: http://dx.doi.org/10.1071/CH07027; CSIRO Publishing; Australia; http://www.publish.csiro.au/nid/51.htm Relation: 3; Australian Journal of Chemistry; 214; 217; N; 60 Other identifier: 0004-9425 Language: en_AU Rights: Y
Rhodium-Catalyzed Decarbonylation of Aldoses
2007-01-01
A catalytic procedure is described for decarbonylation of unprotected aldoses to afford alditols with one less carbon atom. The reaction is performed with the rhodium complex Rh(dppp)2Cl in a refluxing diglyme - DMA solution. A slightly improved catalyst turnover is observed when a catalytic amount of pyridine is added. Under these conditions most hexoses and pentoses undergo decarbonylation into the corresponding pentitols and tetrols in isolated yields around 70%. The reaction has been applied as the key transformation in a five-step synthesis of L-threose from D-glucose.
Trinuclear Schiff base complexes with uranium(V) and copper(II) or zinc(II) ions
2007-01-01
Treatment of the uranium(IV) complexes [left braceML1(py)right brace2U(IV)] (M = Cu, Zn. L1 = N, N'-bis(3-hydroxy-salicylidene)-1,3-propane-diamine) with silver nitrate in pyridine led to the formation of the corresponding cationic uranium(V) species which were found to be thermally unstable and were converted back into the parent U(IV) complexes. No electron transfer was observed in solution between the U(IV) and U(V) compounds. In the crystals of [left braceML1(py)right brace2U(IV)][left braceML1(py)right brace2U(V)][NO3], the neutral U(IV) and cationic U(V) species are clearly identified by the distinct U-O distances. Similar reaction of [left ... >>
Theoretical study of N-complexes in carbon nanotubes
2007-01-24
We have made a systematic theoretical study to determine which are the most stable structures for substitutional nitrogen defects in carbon nanotubes, by making total energy calculations via DFT. These calculations were made for a (5,5) and a (8,0) nanotube to check the influence of chirality and for a graphene sheet, to check the limit of infinite diameter. In all these systems, we found that either substitutional nitrogen or structures containing two vacancies surrounded by four pyridine-like rings have the lowest formation energy, depending on the value of the nitrogen chemical potential. These defects have lower formation energies in nanotubes than in the graphene sheet.
http://hdl.handle.net/1947/1777
This paper describes a scanning fluorometer which produces images in real time of the distribution of pyridine nucleotide or flavoprotein fluorescence at the surface of tissues in vivo. The basic difference between this device and others reported in the literature is that fluorescence changes at any selected point within the image can be quantified as they occur. We suggest that the apparatus has potential application in those areas of surgery where vascular replacement or repair is required and where it would be advantageous to have an immediate measure of the cellular response to a return of blood flow. Other identifier: Journal of Biomedical Engineering 8 (4), pp. 334-340, 1986 Language: en_US
Modulation of the Reactivity, Stability and Substrate- and Enantioselectivity of an Epoxidation Catalyst by Noncovalent Dynamic Attachment of a Receptor Functionality - Aspects on the Mechanism of the Jacobsen-Katsuki Epoxidation Applied to a Supramolecular System
2006-01-01
The synthesis of the components of the dynamic supramolecular hydrogen-bonded catalytic system 2 + 3 is described. The catalytic performance and substrate- and enantioselectivity of Mn(salen) catalyst 2 were investigated in the presence and absence of the Zn(porphyrin) receptor unit 3. The effects of pyridine and pyridine N-oxide donor ligands were also studied. Some aspects on the mechanism of the JacobsenâKatsuki epoxidation, based on literature observations, are introduced as a means to analyse the behaviour of 2 and its modulation by the formation of macrocycle 1 with 3. A complete association model of the metal-free system 4 + 5 refutes the earlier assumption that macrocycle 1 is the predominant form of catalyst 2 under the standard epoxidation reaction conditions with 2 + 3. Evidence are provided that receptor-binding substrates and nonbinding substrates, respectively, are epoxidised by two different catalytic species, or two distinct distributions of species in competitive epoxidations using catalytic system 2 + 3. The two species are assigned to the endo and exo faces of the Mn(salen) catalyst in macrocycle 1, and to equivalently folded oligomeric structures with monomers 2 and 3 in adjacent positions.
http://hdl.handle.net/10072/25035
Mixed base pyridine (py)/triphenylphosphine adducts of the copper(1) halides, CuX, have been synthesized for 1 : 1 : 1 stoichiometry for X = chloride and iodide; single-crystal X-ray structure determinations of these show them to be isomorphous and isostructural with that of the bromide recorded elsewhere, being µ,µ′- dihalo-bridged dimers , [(PPh3)( py )CuX2Cu( py )(PPh3)], monoclinic, C2/c, a ≈ 26.2, b ≈ 14.3, c ≈ 11 .2 Å , β ≈ 95, Z = 4 dimers. The bromide has been isolated as a new monoclinic C 2/m polymorph, a 11 .279(8), b 14.268(6), c 13.858(4) Å, β 109.33(6)º, Z=4 dimers, and details of its structure are also recorded. The structures of their pyridine-4-carbonitrile (pycn) analogues have also been determined and found to be also binuclear, with no cyano-copper interactions; these also are an isomorphous, isostructural series, monoclinic P21/n, a ≈ 15.4, b ≈ 8.1, c ≈ 17.9 Å , β ≈ 101 º, Z = 2 dimers. In each series of dimers, one half of the dimer is crystallographically independent, the generators of the other half being twofold rotor (C2/c phase), mirror (C2/m phase) and inversion centre (P21/n phase) respectively. Publisher: http://www.publish.csiro.au/nid/51/paper/CH9890913.htm; CSIRO Publishing; Collingwood, Vic.; http://www.publish.csiro.au/nid/51.htm Relation: Australian Journal of Chemistry; 913; 922; N; 42 Other identifier: 0004-9425 Language: en_AU Rights: Copyright 1989 CSIRO. Please refer to the journal's website for access to the definitive, published version.; Y
Nitrogen doping of metallic single-walled carbon nanotubes: n-type conduction and dipole scattering
2006-01-23
The charge transport properties of individual, metallic nitrogen doped, single-walled carbon nanotubes are investigated. It is demonstrated that n-type conduction can be achieved by nitrogen doping. Evidence was obtained by appealing to electric-field effect measurements at ambient condition. The observed temperature dependencies of the zero-bias conductance indicate a disordered electron system with electric-dipole scattering, caused mainly by the pyridine-type nitrogen atoms in the honeycomb lattice. These results illustrate the possibility of creating all-metallic molecular devices, in which the charge carrier type can be controlled.
http://hdl.handle.net/1959.3/5407
The miscibility of poly(hydroxyether terephthalate ester) (PHETE) with poly(4-vinyl pyridine) (P4VP) was established on the basis of thermal analysis. Differential scanning calorimetry showed that each blend displayed a single glass-transition temperature (Tg), which is intermediate between those of the pure polymers and varies with the composition of blend. The T g-composition relationship can be well described with Kwei equation with k = 1 and q = -30.8 (K), suggesting the presence of the intermolecular specific interactions in the blend system. To investigate the intermolecular specific interactions in the blends, the model compounds such as 1,3-diphenoxy-2-propanol, 4-methyl pyridine, and ethyl benzoate were used to determine the equilibrium constants, according to Coleman and Painter model, to account for the association equilibriums of several structural moieties, using liquid Fourier transform infrared difference spectroscopy. In terms of the difference in the association equilibrium constant, it is proposed that there are the competitive specific interactions in the blends, which were confirmed by means of Fourier transform infrared spectroscopy of the blends. It is observed that upon adding P4VP to the system, the ester carbonyls of PHETE that were H-bonded with the hydroxyl groups were released because of the formation of the stronger interchain association via the hydrogen bonding between the hydroxyls of PHETE and tertiary nitrogen atoms of P4VP. Publisher: John Wiley & Sons Format: 1618-1626 Other identifier: swin:5407 Language: English Source: Journal of Polymer Science, Part B : Polymer Physics, Vol. 44, no. 11 (2006), p. 1618-1626 Rights: Copyright © 2006 Wiley Periodicals, Inc.
2010-01-01
Electronic spectra of Ni(acac)2 were studied in acetone, DMF, and some other solvents for the purpose of identifying the cis/trans isomers from the spectra (acac-=acetylacetonate anion). The spectral components were investigated in the spin-allowed transition bands, and a relationship was found between the spectral pattern and the cis/trans isomers. According to this relationship, it was concluded that the cis isomer was formed in DMF and in N-methylformadide, whereas the trans isomer was formed in acetone and in pyridine. Based on the DFT computation, the cis-[Ni(acac)2(DMF)2] was found to be stabilized by intramolecular hydrogen bonds between acetylacetonate and DMF.
Electron Paramagnetic Resonance Investigation of Some 11-Tungstoruthenate(III) Polyoxoanions
2009-01-01
EPR spectra of three Keggin structure polyoxotungstates containing ruthenium(III), [PW11O39Ru(L)]4- (L = H2O, pyridine, dimethyl sulfoxide), have been recorded at 77 K and yield details of the symmetry and ligand field parameters of the embedded low-spin d5 ruthenium cation. The magnitudes of the g tensors and 99,101Ru hyperfine coupling constants of the dmso derivative show that the unpaired electron occupies a dxy-type orbital as a result of the axial component of the ligand field with D(dxy - dxz,dyz) 6200 cm-1. A weak broad absorption in the electronic spectrum at ca. 5600 cm-1 is consistent with this interpretation. A smaller rhombic component imposed by the polytungstate ligand further splits the dxz and dyz orbitals (
Tb3+ and Eu3+ luminescence in imidazolium ionic liquids
2009-01-01
The luminescence properties of Tb3+ and Eu3+ dissolved in ionic liquids are studied. Solutes in this study include simple lanthanide compounds (e.g., EuBr3, TbCl3) and lanthanide complexes (e.g., Eu(dpa)33- where dpa=2,6 pyridine dicarboxylate dianion) dissolved in a 1-butyl-3-methylimidazolium bromide(BMIBr)/water mixture. Emission, excitation, and time-resolved emission measurements are utilized to characterize the spectroscopic properties. It is well established in the literature that the solubility and spectroscopic properties of lanthanides in ionic liquids are highly dependent upon environmental factors including purity, and water content [K. Binnemans, Chemical Reviews (2007); I. Billard, S. Mekki, C. Gaillard, P. Hesemann, C. Mariet, G. Moutiers, A. Labet, J.-C.G. Bunzli, European ...
New water-soluble iminecalix[4]arene with a deep hydrophobic cavity
2009-01-01
We report the synthesis of a new water-soluble iminecalix[4]arene host 4c with a deep hydrophobic cavity. The negatively charged four carboxylate functions on the top of the cavity play a major role in the recognition of charged molecular species. The 1H NMR titration experiments revealed that host 4c binds with cationic (10-12) and neutral guests (6-9) in water with high binding constants in the order of 104-105M-1. Cationic guest 9 showed highest binding constant of 2.81x105M-1 with host 4c amongst all tested guests. Selectivity over anionic guests (13-17) is established by the presence of negative charges at the top of the deep hydrophobic cavity, as guests 15 and 17 were not recognized by host 4c. Neutral pyridine derivatives with hydrophobic chains at para positions showed high bindin...
Acidity of MCM-58 and MCM-68 zeolites in comparison with some other 12-ring zeolites
2010-01-01
Two novel zeolites MCM-58 and MCM-68 with 12-ring channels and containing the cages in the structure were investigated with respect to their acidic properties and compared with other two 12-ring zeolites, namely Beta and ZSM-12. The main objective was to characterize the accessibility and acid strength of Lewis and Bronsted sites using FTIR spectroscopy. Pyridine adsorption allowed for quantification of Bronsted and Lewis acid centres and pointed out that while in the structure of MCM-58 nearly all Al atoms form acidic SiOHAl bridges, only about half of Al is a source of the Bronsted acidity in MCM-68. The special attention was devoted to the origin and location of the hydrogen-bonded OH groups in the MCM-58 zeolite. The frequency lowering is caused by the across-the-ring interaction with ...
2009-01-01
The dimeric CoW5 Lindqvist-type anion [{CoW5O18H}2]6- (1) has been obtained as a tetrabutylammonium (TBA) salt by addition of either [Co(MeCN)4(H2O)2]2+ or CoCl2 to a "virtual" W5O186- precursor generated by non-aqueous hydrolysis of a mixture of (TBA)2WO4 and WO(OMe)4. Analysis of the X-ray crystal structure of (TBA)71(BF4) by using the Bond Valence Sum (BVS) method reveals that cobalt is present as CoII and that two protons are associated with CoOW bridging oxygen atoms, one of which is located in a hydrogen bond between the two CoW5O18 units, whereas the other is disordered between an adjacent oxygen atom and its symmetry-related site on the other CoW5O18 unit. Treatment with pyridine cleaves dimer 1 to give [(py)CoW5O18H]3- (2), and the single protonated CoOW site was identified by BVS...
2010-01-01
Styrene polymerization via generation of activators by monomer addition (GAMA) for atom transfer radical polymerization (ATRP) has been examined extensively with bulk FeX3 and FeX2 at 110 degreeC in conjunction with various phosphorus-bearing ligands. It was found that GAMA possesses advantages over normal ATRP. Most importantly, narrower polydispersity index (PDI) values were observed from the styrene polymerizations with Fe(III) over those with Fe(II). Every instance of 2-(diphenylphosphino)-N,Nprime-dimethyl-[1,1prime-biphenyl]-2-amine and 2-(diphenylphosphino) pyridine with the Fe(III) system were controlled excellently without addition of any radical initiator or reducing agent additives. Initiator type was found to exert a significant factor to influence on the controllability of pol...
Stilbazolium Merocyanine Dye Determination in Different Solutions, Concentrations and Colloids Using SERS
2006-01-01
Surface Enhanced Raman Scattering (SERS) measurements were carried out on stilbazolium merocyanine dye in methanol and pyridine solvents. Both solutions were measured in series of concentrations, covering a range of 5·10-5 M to 5·10-8 M. In these measurements Ag and Au colloids were used and the results have shown that Ag colloids yield better enhancement in the Raman spectra of this dye. Moreover, the effect of adding NaCl solution to the SERS samples was also studied. All measurements were carried out using the state-of-the-art ChiralRaman instrument, which utilizes a 532 nm laser source. We report here on the success of using SERS to obtain Raman spectra of merocyanine dye at very low concentration in an attempt of new approach, which can be used for further investigations of the dye. The SERS spectra will here be reported and the results from different solutions, colloids, concentrations and pH values will be compared.
2010-01-01
Absolute rate constants (keff) for the chemical reactions of Cu(II)2(3,5-di-iso-propylsalicylate)4(H2O)3, Cu(II)2(3,5-di-tert-butylsalicylate)4, Cu(II)2(3,5-di-tert-butylsalicylate)4(H2O)4, Cu(II)2(3,5-dimethylsalicylate)4(H2O)3, Cu(II)2(3-ethylsalicylate)4(H2O), Cu(II)2(3-phenylsalicylate)4, and Cu(II)(3,5-di-iso-propylsalicylate)2(pyridine)2 with tert-butylperoxyl radical were determined using kinetic electron paramagnetic resonance measurements in 10% toluene in the hexane medium at temperatures ranging from -63degreeC to 2degreeC. These antioxidant (AO) chelates were ranked by their reactivity as follows: 2,6-di-tert-butyl-4-methylphenol Cu(II)2(3,5-di-tert-butylsalicylate)4 Cu(II)2(3-phenylsalicylate)4 > Cu(II)2(3,5-di-iso-propylsalicylate)4(H2O)3 Cu(II)2(3,5-di-tert-butylsalicylate)4...
2010-01-01
An improved medium scale synthesis of 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP), a selective and potent metabotropic glutamate subtype 5 (mGlu5) antagonist, has allowed thorough characterisation of the crystal structures of the free base and the previously unreported hydrochloride (MTEP.HCl). Hirshfeld surface analysis has revealed that molecules in crystalline MTEP are weakly polar, and aggregate through nonclassical C H Formula Not Shown N hydrogen bonds. A strong ionic N H+ Formula Not Shown Cl- hydrogen bond dominates the crystal packing in MTEP.HCl. Despite significant differences in the crystal packing, the molecular structures of MTEP and MTEP.HCl are very similar. The acid dissociation constants for MTEP were investigated using 1H NMR spectroscopy. The second acid disso...
Density functional study of the adsorption and van der Waals binding of aromatic and conjugated compounds on the basal plane of MoS2
2009-01-01
Accurate calculations of adsorption energies of cyclic molecules are of key importance in investigations of, e.g., hydrodesulfurization (HDS) catalysis. The present density functional theory (DFT) study of a set of important reactants, products, and inhibitors in HDS catalysis demonstrates that van der Waals interactions are essential for binding energies on MoS2 surfaces and that DFT with a recently developed exchange-correlation functional (vdW-DF) accurately calculates the van der Waals energy. Values are calculated for the adsorption energies of butadiene, thiophene, benzothiophene, pyridine, quinoline, benzene, and naphthalene on the basal plane of MoS2, showing good agreement with available experimental data, and the equilibrium geometry is found as flat at a separation of about 3.5 A for all studied molecules. This adsorption is found to be due to mainly van der Waals interactions. Furthermore, the manifold of adsorption-energy values allows trend analyses to be made, and they are found to have a linear correlation with the number of main atoms.
The crystal structure of the low-temperature phase (LTP) of the title compound was determined at 220 K (monoclinic, P2 sub 1 sub / sub c). The 4-aminopyridinium cations (4-NH sub 2 C sub 5 H sub 4 NH sup +) were found to be ordered in LTP, while being severely disordered in the room-temperature phase (monoclinic, C2/c). The tetrabromoantimonate anions (SbBr sub 4 sup -) were incorporated into the infinite polyanion chains of irregular SbBr sub 6 octahedra with two-edges sharing. The trans-Br-Sb-Br moiety in the SbBr sub 4 sup - anion was approximately symmetric differing from the asymmetric Br-Sb centre dot centre dot centre dot Br moiety found in LTP of pyridinium tetrabromoantimonate (3). The N-H moieties in both of the pyridine ring and the amino (-NH sub 2) group participate in the formation of N-H centre dot centre dot centre dot Br hydrogen bonds. It was shown that the sup 8 sup 1 Br NQR spectrum of LTP is closely related to the anion structure and the hydrogen bonds. The distinctive anion structures, as well as the different types of phase transitions, exhibited by the PyH and 4-APyH salts, seemed to be attributable to the difference in the hydrogen bond scheme between them. (author)
Ni+ reactions with aminoacetonitrile, a potential prebiological precursor of glycine
2008-02-29
The gas-phase reactions between Ni+ (2D5/2) and aminoacetonitrile, a molecule of prebiological interest as possible precursor of glycine, have been investigated by means of mass spectrometry techniques. The mass-analyzed ion kinetic energy (MIKE) spectrum reveals that the adduct ions [NCCH2NH2, Ni+] spontaneously decompose by loosing HCN, H2, and H2CNH, the loss of hydrogen cyanide being clearly dominant. The structures and bonding characteristics of the aminoacetonitrile-Ni+ complexes as well as the different stationary points of the corresponding potential energy surface (PES) have been theoretically studied by density functional theory (DFT) calculations carried out at B3LYP/6-311G(d,p) level. A cyclic intermediate, in which Ni+ is bisligated to the cyano and the amino group, plays an important role in the unimolecular reactivity of these ions, because it is the precursor for the observed losses of HCN and H2CNH. In all mechanisms associated with the loss of H2, the metal acts as hydrogen carrier favoring the formation of the H2 molecule. The estimated bond dissociation energy of aminoacetonitrile-Ni+ complexes (291 kJ mol-1) is larger than those measured for other nitrogen bases such as pyridine or pyrimidine and only slightly smaller than that of adenine.
2009-09-29
The paper demonstrates possibility of giant enhancement of Surface Enhanced Hyper Raman Scattering on the base of qualitative consideration of electromagnetic field near some models of rough metal surfaces and of some features of the dipole and quadrupole light-molecule interaction, such as it was made in the dipole-quadrupole SERS theory. Consideration of symmetrical molecules permits to obtain selection rules for their SEHR spectra and establish such regularity as appearance of the bands, caused by the totally symmetric vibrations, transforming after the unitary irreducible representation in molecules with C2h,D and higher symmetry groups, which are forbidden in usual HRS spectra. Analysis of literature data on trans-1,2-bis (4-pyridyle) ethylene and pyridine molecules demonstrates that their SEHR spectra can be explained by the SEHRS dipole-quadrupole theory, while analysis of the SEHR spectrum of pyrazine reveals appearance of the strong forbidden bands, caused by vibrations transforming after the unitary irreducible representation that strongly confirms this theory which permits to interpret the whole SEHR spectrum in detail. The results corroborate this common mechanism of Surface Enhanced optical processes on molecules adsorbed on rough metal surfaces.
http://espace.library.uq.edu.au/view/UQ:61725
The synthesis, spectroscopic properties, and chemical reactions of the stable (neopentylimino)-, (mesitylimino)-, and (o-tert-butylphenylimino)propadienones (6) are reported. Nucleophilic addition of amines affords the malonic amidoamidines 7 and 8. 3,5-Dimethylpyrazole reacts analogously to form 9b. Addition of 1,2-dimethylhydrazine produces pyrazolinones 10-12. Addition of N,Y'-dimethyldiaminoethane, -propane, and -butane gives diazepine, diazocine, and diazonine derivatives 13-15, respectively (X-ray structures of 13c, 14a, and 15a are available). The mesoionic pyridopyrimidinium olates IS are obtained by addition of 2-(methylamino)pyridine (X-ray structure of 18b available). Primary 2-aminopyridines afford the pyridopyrimidininones 20-29 and 31 (X-ray structure of 21a available), and 2-aminopyrimidines and 2-aminopyrazine afford pyrimidopyrimidinones and pyrazinopyrimidinones 33-35. Pyrimidoisoquinolinone 36 results from 1-aminoisoquinoline and pyridoquinolinone 40 from 8-aminoquinoline. 2-Aminothiazoline and 2-aminothiazole afford thiazolopyrimidinone derivatives 41-43 (X-ray structure of 43a available). Publisher: American Chemical Society Relation: isMemberOf School of Chemistry and Molecular Biosciences; isMemberOf Excellence in Research Australia (ERA) - Collection
http://hdl.handle.net/10072/14338
The title compound, C2H10N22+·C7H3NO42−·2H2O, forms a three-dimensional hydrogen-bonded framework structure in which both of the amine groups of ethylenediamine are protonated and participate in a total of six hydrogen-bonding interactions with carboxylate O-atom acceptors of the anions as well as the water molecules. The cations lie on crystallographic inversion centres and adopt extended conformations, while the anions have twofold rotational symmetry. This results in the pyridine N atom and its ortho-related CH group being disordered over two 50% occupancy sites. Publisher: http://dx.doi.org/10.1107/S1600536806024263; Blackwell Munksgaard; Copenhagen, Denmark; http://journals.iucr.org/e/journalhomepage.html Relation: 2006; 7; Acta crystallographica. Section E, Structure reports online; 3124; 3126; N; 62 Format: 195777 bytes; 10029 bytes; application/pdf; text/plain Other identifier: 1600-5368 Language: en_AU Rights: Copyright remains with the authors 2006. For information about this journal please refer to the journal's website. All articles published in Acta Crystallographica Section E are open access and distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. See http://creativecommons.org/licenses/by/2.0/uk/legalcode; N
MGlu5 antagonism impairs exploration and memory of spatial and non-spatial stimuli in rats.
2008-01-01
Metabotropic glutamate receptor subtype 5 (mGlu5) has been implicated in memory processing in some but not all learning tasks. The reason why this receptor is involved in some tasks but not in others remains to be determined. The present experiments using rats examined effects of the mGlu5-antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) - applied systemically i.p. (1-10 mg/kg) or bilaterally into the prelimbic cortex (1-10 µg) - on the ability of rats to explore and remember new stimuli. A cross-maze, open field, and object recognition task were used to evaluate exploration and memory and it was found that: 1) Locomotion during exploration of spatial environments and exploration time at novel objects were reduced by i.p. but not by prelimbic administration of MPEP, 2) spatial short-term memory was impaired in cross-maze and object discrimination was reduced after both types of administration, 3) long-term retention of spatial conditioning in the cross-maze was inhibited after i.p. applications which 4) also inhibited spontaneous alternation performance during maze-exploration. Reduced exploratory locomotion and exploration time after i.p. injections may have contributed to the observed retention impairments. However, the fact that prelimbic administration of MPEP inhibited retention without reducing exploration shows that memory formation was also impacted directly by prelimbic mGlu5 in both spatial and non-spatial learning.
The monomeric compounds [Fe(abpt) sub 2 (NCX) sub 2] (X= S (1), Se (2) and abpt 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) have been synthesized and characterized. They crystallize in the monoclinic P2 sub 1 /n space group with a 11.637(2) Aa, b = 9.8021(14) Aa, c = 12.983 8(12) Aa, beta = 101.126(14) sup o , and Z= 2 for 1, and a = 11.601(2) Aa, b = 9.6666 (14) Aa, c = 12.883(2) Aa, beta = 101.449(10) sup o , and Z= 2 for 2. The unit cell contains a pair mononuclear [Fe(abpt) sub 2 (NCX) sub 2] units related by a center of symmetry. Each iron atom, located at a molecular inversion center, is in a distorted octahedral environment. Four of the six nitrogen atoms coordinated to the Fe(11) ion belong to the pyridine-N(1) and triazole-N (2) rings of two abpt ligands. The remaining trans positions are occupied by two nitrogen atoms, N(3), belonging to the two pseudo-halide ligands. The magnetic susceptibility measurements at ambient pressure have revealed that they are in the high-spin range in the 2 K-300 K temperature range. The pressure study has revealed that compound 1 remains in high-spin as pressure is increased up to 4.4 kbar, where an incomplete thermal spin crossover appears at around T sub 1 sub / sub 2 = 65 K. Quenching experiments at 4.4 kbar have shown that the incomplete character of the conversion is a consequence of slow kinetics. Relatively sharp spin transition takes place at T sub 1 sub / sub 2 = 106, 152 and 179 K, as pressure attains 5.6, 8.6 and 10.5 kbar, respectively. (author)
http://espace.library.uq.edu.au/view/UQ:160929
Recent studies have revealed the effectiveness of 2-methyl-6-(phenylethynyl)pyridine (MPEP), a highly selective antagonist of metabotropic glutamate receptors subtype 5 (mGluR5), in conditioned drug reward. In a previous study we showed that MPEP blocks expression of context-conditioned morphine- but not cocaine reward in the rat. The present study now examines the effectiveness of MPEP in the expression of context-conditioned food, MDMA ('ecstasy’) or amphetamine reward. Therefore, three groups of rats were conditioned either to food, MDMA or amphetamine in the conditioned place preference (CPP) paradigm. After conditioning, CPP expression and locomotion were determined simultaneously in the presence and absence of the respective reward (i.e. food or drug), or after application of 50mg/kg MPEP (the dose that was most effective in reducing morphine CPP expression in our previous study). As a result, MPEP reduced locomotion in all groups. Furthermore, only expression of amphetamine CPP was inhibited by MPEP, while expression of food and MDMA CPP was not affected, suggesting that the MPEP-induced inhibition of amphetamine CPP expression was not causally linked to the reduction of locomotion. Overall, we conclude that MPEP reduces expression of context-conditioned amphetamine but not MDMA or food reward. Publisher: Wiley Inter Science Relation: isMemberOf Institute for Molecular Bioscience - Publications; isMemberOf Excellence in Research Australia (ERA) - Collection
http://hdl.handle.net/1959.13/28865
In this paper, we report the use of an NIR fiber-optic spectrometer with a high-speed diode array for calibration-free monitoring and modeling of the reaction of acetic anhydride with butanol using the catalyst 4-(dimethylamino)pyridine in a microscale batch reactor. Acquisition of spectra at 5 ms/scan gave information relevant for modeling these fast batch processes with a single multibatch kinetic model. Nonlinear fitting of a first-principles model directly to the reaction spectra gave calibration-free estimates of time-dependent concentration profiles and pure component spectra. The amount of catalyst was varied between different batches to permit accurate estimation of its effect in the multiway model. A wide range of different models with increasing complexity could be fit to each batch individually with low residuals and apparent low lack of fit. However, only one model properly estimated the concentration profiles when all five batches were fitted simultaneously in a multiway kinetic model. Inclusion of on-line temperature measurements and use of an Arrhenius model for the estimated rate constant gave significantly improved model fits compared to an isothermal kinetic model. Augmentation of prerun batches with data from an additional batch permitted model-based forecasts of reaction trajectories, reaction yield, reaction end points, and process upsets. One batch with added water to simulate a process upset was easily detected by the calibration free process model. Publisher: American Chemical Society Relation: Analytical Chemistry Vol. 76, Issue 9, p. 2575-2582; 10.1021/ac035356i Other identifier: ISSN:0003-2700 Language:
Full Text Available.Nicotinamide phosphoribosyltransferase (Nampt) inhibitors such as FK866 are potent inhibitors of NAD+ synthesis that show promise for the treatment of different forms of cancer. Based on Nampt upregulation in activated T lymphocytes and on preliminary reports of lymphopenia in FK866 treated patients, we have investigated FK866 for its capacity to interfere with T lymphocyte function and survival. Intracellular pyridine nucleotides, ATP, mitochondrial function, viability, proliferation, activation markers and cytokine secretion were assessed in resting and in activated human T lymphocytes. In addition, we used experimental autoimmune encephalomyelitis (EAE) as a model of T-cell mediated autoimmune disease to assess FK866 efficacy in vivo. We show that activated, but not resting, T lymphocytes undergo massive NAD+ depletion upon FK866-mediated Nampt inhibition. As a consequence, impaired proliferation, reduced IFN-γ and TNF-α production, and finally autophagic cell demise result. We demonstrate that upregulation of the NAD+-degrading enzyme poly-(ADP-ribose)-polymerase (PARP) by activated T cells enhances their susceptibility to NAD+ depletion. In addition, we relate defective IFN-γ and TNF-α production in response to FK866 to impaired Sirt6 activity. Finally, we show that FK866 strikingly reduces the neurological damage and the clinical manifestations of EAE. In conclusion, Nampt inhibitors (and possibly Sirt6 inhibitors) could be used to modulate T cell-mediated immune responses and thereby be beneficial in immune-mediated disorders.
Magnetic circular dichroism spectroscopy of weakly exchange coupled transition metal dimers: A model study
2009-01-01
A detailed study of the magnetic circular dichroism (MCD) spectra of weakly exchange coupled transition metal heterodimers is reported. The systems consist of three isostructural complexes of the type [LM(III)(PyA)(3)M(II)](ClO4)(2) where L represents 1,4,7-trimethyl-1,4,7-triazacyclonanane and PyA- is the monoanion of pyridine-2-aldoxime. The trivalent metal ion M(III) is either diamagnetic Ga(III) or paramagnetic Cr(III) (S-Cr = 3/2). The divalent metal ion M(II) is either diamagnetic Zn(II) or paramagnetic Ni(II) (S-Ni = 1). The three systems 1 (CrZn), 2 (GaNi) and 3 (CrNi) have been structurally and magnetically characterized through magnetic susceptibility measurements. For I the zero-field splitting is D = 0.6 cm(-1) while for 2 the value D = 3.5 cm(-1) was found. These values have been fixed in analyzing 3 which was found to be characterized by an antiferromagnetic interaction Of J(CrNi) = -8.4 cm(-1) (H = -2JS(A)S(B)). These values served as benchmarks in the MCD analysis. The zero-field splitting of I and 2 was qualitatively recovered using a multi-wavelength analysis of the variable-temperature variable-field (VTVH) MCD data. The observed ligand field bands were assigned to individual d(3) and d(8) multiplets. Using an extension of an earlier developed theory of the nonlinear MCD response, the stunningly complex multiwavelength VTVH-MCD curves of 3 could be quantitatively reproduced with only the relative transition polarizations as input into the fitting procedure. Interestingly, the MCD bands of the minority spin Ni(II) ligand field bands were observed to change sign relative to the parent complex 2. This behavior has been analyzed. The present work hence provides a benchmark study for the application of MCD spectroscopy to weakly interacting transition metal dinners. (C) 2008 Elsevier B.V. All rights reserved
http://hdl.handle.net/1959.13/33321
Interaction between tetramethylcucurbit[6]uril (TMeQ[6], host) with hydrochloride salts of 2-phenylpridine (G1), 2-benzylpyridine (G2), and 4-benzylpyridine (G3) (guests) have been investigated by using ¹H NMR spectroscopy and electronic absorption spectroscopy and theoretical calculations. The ¹H NMR spectra analysis established an interaction model in which the host selectively included the phenyl moiety of the HCl salt of the above three guests, and formed inclusion complexes with a host−guest ratio of 1:1. Absorption spectrophotometric analysis allowed quantitative measurement of the stability of these host−guest inclusion complexes. Particularly, we have established a competitive interaction in which one host−guest inclusion complex pair is much more stable than another host−guest inclusion complex pair. The stability constants for the three host−guest inclusion complexes of TMeQ[6]-G1, TMeQ[6]-G2, and TMeQ[6]-G3 are 2 × 10⁶, 60.7, and 19.9 mol⁻¹·L, respectively. To understand how subtle differences in the structure of the title guests lead to a significant difference in the stability of the corresponding host−guest inclusion complexes with the TMeQ[6], ab initio theoretical calculations have been performed, not only for the gas phase but also the solution phase (water as solvent) in all cases. The calculation results revealed that when the phenyl moiety of the three pyridine derivate guests was included, the host−guest complexation reached the minimum, and the corresponding energy differences for the formation of the title host−guest inclusion complexes are qualitatively consistent with the experimental results. Publisher: American Chemical Society Relation: Journal of Physical Chemistry A Vol. 111, Issue 14, p. 2715-2721; 10.1021/jp066031j Other identifier: ISSN:1089-5639 Language:
Full Text Available.BackgroundAliphatic molecules containing free carboxyl groups are important intermediates in many metabolic and signalling reactions, however, they accumulate to low levels in tissues and are not efficiently ionized by electrospray ionization (ESI) compared to more polar substances. Quantification of aliphatic molecules becomes therefore difficult when small amounts of tissue are available for analysis. Traditional methods for analysis of these molecules require purification or enrichment steps, which are onerous when multiple samples need to be analyzed. In contrast to aliphatic molecules, more polar substances containing free carboxyl groups such as some phytohormones are efficiently ionized by ESI and suitable for analysis by LC-MS/MS. Thus, the development of a method with which aliphatic and polar molecules -which their unmodified forms differ dramatically in their efficiencies of ionization by ESI- can be simultaneously detected with similar sensitivities would substantially simplify the analysis of complex biological matrices.ResultsA simple, rapid, specific and sensitive method for the simultaneous detection and quantification of free aliphatic molecules (e.g., free fatty acids (FFA)) and small polar molecules (e.g., jasmonic acid (JA), salicylic acid (SA)) containing free carboxyl groups by direct derivatization of leaf extracts with Picolinyl reagent followed by LC-MS/MS analysis is presented. The presence of the N atom in the esterified pyridine moiety allowed the efficient ionization of 25 compounds tested irrespective of their chemical structure. The method was validated by comparing the results obtained after analysis of Nicotiana attenuata leaf material with previously described analytical methods.ConclusionThe method presented was used to detect 16 compounds in leaf extracts of N. attenuata plants. Importantly, the method can be adapted based on the specific analytes of interest with the only consideration that the molecules must contain at least one free carboxyl group.
Methods for Shortening and Extending the Carbon Chain in Carbohydrates
1900-01-01
Carbohydrates play a central role in a variety of physiological and pathological processes such as HIV, cancer and diabetes. The understanding of these processes and the development of specific therapeutic agents is relying on the ability to chemically synthesize unnatural sugars, glycoconjugates and carbohydrate mimetics. Such polyhydroxylated compounds are conveniently synthesized from carbohydrates, however, due to the scarcity of many sugars from nature, efficient methods for transformation of readily available carbohydrates into valuable chiral building blocks are required. The work presented in this thesis focuses on the development and application of transition metal mediated methods for shortening and extending the carbon chain in carbohydrates thereby providing access to lower and higher sugars.A new catalytic procedure for shortening unprotected sugars by one carbon atom has been developed. By means of a rhodium-catalyzed decarbonylation of the aldehyde functionality, aldoses are converted into their corresponding lower alditols in yields around 70%. The reaction is performed with 8% of the catalyst Rh(dppp)2Cl in the presence of small amounts of pyridine to facilitate mutarotation. The procedure has been employed as the key step in a short five-step synthesis of the unnatural sugar L-threose in 74% overall yield from D-glucose. A zinc-mediated one-pot fragmentation-allylation reaction has been used to elongate D-glucose and D-ribose by three carbon atoms thereby producing carbohydrate-derived α,Ï-dienes, which have been converted into the natural products calystegine A3 and gabosine A. The glycosidase inhibitor calystegine A3 was produced by two similar routes from commercially available methyl α-D-glucopyranoside in 13 and 14 steps with 8.3 and 5.3% overall yield, respectively. The present work thereby constitutes the shortest synthesis of enantiomerically pure calystegine A3, and furthermore, it enables the absolute configuration of the natural product to be determined. Gabosine A has been prepared in nine steps and 13.9% overall yield from D-ribose, and this synthesis provides the first route to gabosine A from an abundant carbohydrate precursor.During an external stay at University of Oxford, the metabolism of nonsteroidal anti-inflammatory drugs (NSAIDs) has been investigated. It was found that known acyl glucuronide metabolites of ibuprofen and several analogues modify human plasma protein under conditions encountered in therapy. Two different kinds of protein modification occur depending on the structure of the parent drug. The obtained results strongly suggest that irreversible modification of human proteins takes place during treatment with carboxylic acid containing drugs such as NSAIDs. Furthermore, the observed reactivity of these metabolites with respect to protein modification may provide an explanation for the severe toxicity that has led to the withdrawal of certain carboxylate drugs.
Stability and selectivity of alkaline proteases in hydrophilic solvents
2008-01-01
Hydrophilic, organic solvents can be used as co-solvents with water to produce one phase systems sustaining optimal mass transfer of substrates and products of mixed polarity in biocatalysed processes. At concentrations below 50 % hydrophilic solvents can even have a stabilising effect on alkaline proteases, but at higher concentrations and particularly in anhydrous systems most enzymes including alkaline proteases will denature and consequently loose activity [1]. However, partial denaturing and increased structural flexibility due to the interaction between hydrophilic solvents and alkaline proteases has been agued as the primary reasons for increasing activity, influencing regio-selectivity and improving the enantio-selectivity of these enzymes [2]. Alkaline proteases have been shown to be active not only on peptides, but on a wide range of renewable resources for synthesis of biologically active molecules and carriers, and in synthesis of carbohydrate derivatives with designed functional properties. When it comes to regio-selectivity of alkaline proateses on carbohydrates both the properties of the particular enzyme and the influence of the solvent is determining for the position of substitution. Some of the most abundant hexoses were all substituted at the primary hydroxyl group at the C-6 position in processes catalysed by different alkaline proteases [3,4,5]. However by adding DMSO to the reaction medium the regio-selectivity in a Streptomyces sp protease catalysed reaction was shifted from the primary hydroxyl to the secondary hydroxyl group at the C-2 position of galactose [3]. Subtilisins from B. subtilis showed regio-selectivity towards the primary hydroxyl group situated at the non reducing end of three important reducing disaccharides, respectively [4,6,7]. Sucrose monoesters were synthesised in anhydrous DMF and pyridine, respectively with different acyl donors and a number of different subtilisins as biocatalysts - in all cases the 1'-O-monoester was the major product [6,7,8,9]. But the alkaline protease AL89 revealed regio-selectivity towards the C-2 position of sucrose [10]. This way acylation of a secondary hydroxyl group situated on the glucose moiety of sucrose was obtained. The initial reaction rate of acylation was not effected by the fatty acid chain length of the acyl donor. The half life of the enzyme in de-ioniset water was 4 minutes whereas in 100% DMF it was 10 minutes. The activity was effected by the solvation of the enzyme in both DMSO and DMF [11]. Literature  [1]          H. Ogino, H. Ishikawa, J. Biosci. Bioeng. 2001, 91, 109. [2]          K. Watanabe, S. Ueji, Biotechnol. Lett. 2000, 22, 599. {3]          M. Kitagawa, H. Fan, T. Raku, S. Shibatani, Y. Maekawa, Y. Hiraguri, R. Kurane, Y. Tokiwa, Biotechnol. Lett.1999, 21, 355. [4]          S. Riva, J. Chopineau, A.P.G. Kieboom, A. Klibanov, J. Am. Chem. Soc.,1988, 110, 584. [5]          T. Watanabe, R. Matsue, Y. Honda, M. Kuwahara, Carbohydr. Res., 1995, 275, 215. [6]          P. Potier, A. Bouchu, G. Descotes, Y. Queneau, Tetrahedron: Lett. 2000, 41, 3597. [7]          Q. Wu, N. Wang, Y.M. Xiao, D.S. Lu, X.F. Lin, Carbohydr. Res., 2004, 339, 2059. [8]          H.G. Park, H.N. Chang, Biotechnol. Lett. 2000, 22, 39 [9]          S. Riva, M. Nonini, G. Ottolina, B. Danieli, Carbohydr. Res., 1998, 314, 259. [10]        N.R. Pedersen, R. Wimmer, R. Matthiesen, L.H. Pedersen, A. Gessesse, Tetrahedron: Asymmetry 2003, 14, 667. [11]        L. H. Pedersen, S. Ritthitham and M. Kristensen (2008) in Modern Biocatalysis Eds W. D. Fessner and T. Anthonsen, Wiley-VCH in press
http://espace.library.uq.edu.au/view/UQ:61686
Quinolizine-2,4-diones 11 are obtained by ash vacuum thermolysis (FVT) of 3-acyl-1,2,3-triazolo[1,5-a]pyridines 7. The reaction takes place via methyl- and phenyl(2-pyridyl)ketenes 10, which are directly observable by infrared spectroscopy in low temperature matrices. FVT of 11 regenerates the ketenes 10. Publisher: The Royal Society of Chemistry Relation: isMemberOf School of Chemistry and Molecular Biosciences
http://hdl.handle.net/2440/20675
[Typescript]208 leaves : ill.Title page, contents and abstract only. The complete thesis in print form is available from the University Library.Thesis (Ph.D.)--University of Adelaide, Dept. of Agricultural Chemistry, 1964 Publisher: Adelaide, Language: en_US
http://espace.library.uq.edu.au/view/UQ:65618
Flash vacuum thermolysis (FVT) of 1-(dimethylamino)pyrrole-2,3-diones 5 causes extrusion of CO with formation of transient hydrazonoketenes 7. The transient ketenes 7 are observable in the form of weak bands at 2130 (7a) or 2115 cm(-1) (7b) in the Ar matrix IR spectra resulting from either FVT or photolysis of either 5 or 1,1- dimethylpyrazolium-5- oxides 8, and these absorptions are in excellent agreement with B3LYP/6-31G* frequency calculations. Under FVT conditions the ketenes 7 cyclize to pyrazolium oxides 8, which undergo 1,4-migration of a methyl group to yield 1,4-dimethyl-3-phenylpyrazole-5(4H)-one 9a and 1,4,4-trimethyl-3-phenylpyrazole-5(4H)-one 9b. All three tautomers of 9a have been characterized, viz. the CH form 9a (most stable form in the gas phase, the solid state and solvents of low polarity), the OH form 9a' (metastable solid at room temperature) and the NH form 9a (stable in aprotic dipolar solvents). The isomeric 1,4-dimethyl-5-phenylpyrazole-3(2H)-one 12 tautomerizes to the 3-hydroxypyrazole 12'. The crystal structure of the hydrochloride 14 of 9a'/9a is reported, representing the first structurally characterised example of a protonated 5-hydroxypyrazole. Publisher: Royal Society of Chemistry Relation: isMemberOf School of Chemistry and Molecular Biosciences; isMemberOf Excellence in Research Australia (ERA) - Collection
http://espace.library.uq.edu.au/view/UQ:36226
To test the hypothesis that the sulfotransferase gene plays a role in the phase II bioactivation of PhlP, a heterocyclic amine found in cooked meats, we transfected the UV5P3 cell line with cDNA plasmids of human aryl sulfotransferases (HAST1 and MASTS). UV5P3 is a nucleotide excision repair-deficient and P4501A2-expressing CHO cell line that we have previously developed. Functionally transformed clones were identified by the differential cytotoxicity (DC) assay that used PhlP as the cytotoxic agent. Two clones designated 5P3H1 and 5P3H3, expressing HAST1 and HAST3, respectively, were chosen for further characterization. Correct fragment sizes of the sulfotransferase cDNAs were identified in both cell lines by polymerase chain reaction. Immunoblot analysis confirmed the expression of the sulfotransferase proteins. The addition of the sulfotransferase inhibitor DCNP decreased the cytotoxic effects of PhlP in a dose-dependent manner. The increase in cell growth was 6.5-fold for 5P3H1 and 2.4-fold for 5P3H3, relative to values obtained without DCNP. Based on D-50 values, the dose that reduced the survival to 50% relative to untreated controls, the cytotoxic effect of PhlP was increased threefold For 5P3H1 and 1.87-fold for 5P3H3 cell lines over the parental UV5P3 line. There was also a small increase in the mutation response at the aprt locus. These newly established 5P3H1 and 5P3H3 sulfotransferase-expressing cells provide valuable mechanistic information of the bioactivation of PhlP and related compounds. Published 2000 Wiley-Liss, Inc.(dagger). Relation: isMemberOf Faculty of Science Publications
http://espace.library.uq.edu.au/view/UQ:123215
We have investigated an unusual nucleotide that accumulates, with precursors, in the erythrocytes of patients in uraemia. This nucleotide is related chemically to the NAD breakdown product, N1-methyl-2-pyridone-5-carboxamide (Me2Py), found in high concentrations in the plasma of uraemic patients. Both Me2Py and the nucleotide accumulate to high concentrations in the blood during uraemia: our investigations of samples from renal out-patients have provided information on a plausible link between the two compounds. Publisher: Marcel Dekker Inc Relation: isMemberOf School of Pharmacy Publications; isMemberOf Excellence in Research Australia (ERA) - Collection
Understanding the Electronic Structure of Metal/SAM/Organic−Semiconductor Heterojunctions
2009-11-24
Full Text Available.Computational modeling is used to describe the mechanisms governing energy level alignment between an organic semiconductor (OSC) and a metal covered by various self-assembled monolayers (SAMs). In particular, we address the question to what extent and under what circumstances SAM-induced work-function modifications lead to an actual change of the barriers for electron and hole injection from the metal into the OSC layer. Depending on the nature of the SAM, we observe clear transitions between Fermi level pinning and vacuum-level alignment regimes. Surprisingly, although in most cases the pinning occurs only when the metal is present, it is not related to charge transfer between the electrode and the organic layer. Instead, charge rearrangements at the interface between the SAM and the OSC are observed, accompanied by a polarization of the SAM.
Understanding the Electronic Structure of Metal/SAM/Organic−Semiconductor Heterojunctions
2009-11-24
Computational modeling is used to describe the mechanisms governing...Full Text Available
The Super-ACO storage ring FEL, covering the UV range down to 300 nm with a high average power (300 mW at 350 nm) together with a high stability and long lifetime, is a unique tool for the performance of users applications. We present here the first pump-probe two color experiments on biological species using a storage ring FEL coupled to the synchrotron radiation. The intense UV pulse of the Super-ACO FEL is used to prepare a high initial concentration of chromophores in their first singlet electronic excited state. The nearby bending magnet synchrotron radiation provides, on the other hand a pulsed, white light continuum (UV-IR), naturally synchronized with the FEL pulses and used to probe the photochemical subsequent events and the associated transient species. We have demonstrated the feasibility with a dye molecule (POPOP) observing a two-color effect, signature of excited state absorption and a temporal signature with Acridine. Applications on various chromophores of biological interest are carried out, such as the time-resolved absorption study of the first excited state of Acridine.
Vitamin B1 is in its active form thiamine pyrophosphate (TPP), an essential cofactor for several key enzymes in the carbohydrate metabolism. Mammals must salvage this crucial nutrient from their diet...Full Text Available
Full Text Available.Vitamin B1 is in its active form thiamine pyrophosphate (TPP), an essential cofactor for several key enzymes in the carbohydrate metabolism. Mammals must salvage this crucial nutrient from their diet in order to complement the deficiency of de novo synthesis. In the human pathogenic bacterium Staphylococcus aureus, two operons were identified which are involved in vitamin B1 metabolism. The first operon encodes for the thiaminase type II (TenA), 4-amino-5-hydroxymethyl-2-methylpyrimidine kinase (ThiD), 5-(2-hydroxyethyl)-4-methylthiazole kinase (ThiM) and thiamine phosphate synthase (ThiE). The second operon encodes a phosphatase, an epimerase and the thiamine pyrophosphokinase (TPK). The open reading frames of the individual operons were cloned, their corresponding proteins were recombinantly expressed and biochemically analysed. The kinetic properties of the enzymes as well as the binding of TPP to the in vitro transcribed RNA of the proposed operons suggest that the vitamin B1 homeostasis in S. aureus is strongly regulated at transcriptional as well as enzymatic levels.
The Impact of Water Deficiency on Leaf Cuticle Lipids of Arabidopsis1[W][OA]
2009-12-01
Full Text Available.Arabidopsis (Arabidopsis thaliana) plants subjected to water deficit, sodium chloride (NaCl), or abscisic acid treatments were shown to exhibit a significant increase in the amount of leaf cuticular lipids. These stress treatments led to increases in cuticular wax amount per unit area of 32% to 80%, due primarily to 29% to 98% increases in wax alkanes. Of these treatments, only water deficit increased the total cutin monomer amount (by 65%), whereas both water deficit and NaCl altered the proportional amounts of cutin monomers. Abscisic acid had little effect on cutin composition. Water deficit, but not NaCl, increased leaf cuticle thickness (by 49%). Electron micrographs revealed that both water-deprived and NaCl-treated plants had elevated osmium accumulation in their cuticles. The abundance of cuticle-associated gene transcripts in leaves was altered by all treatments, including those performed in both pot-grown and in vitro conditions. Notably, the abundance of the ECERIFERUM1 gene transcript, predicted to function in alkane synthesis, was highly induced by all treatments, results consistent with the elevated alkane amounts observed in all treatments. Further, this induction of cuticle lipids was associated with reduced cuticle permeability and may be important for plant acclimation to subsequent water-limited conditions. Taken together, these results show that Arabidopsis provides an excellent model system to study the role of the cuticle in plant response to drought and related stresses, and its associated genetic and cellular regulation.
The Impact of Water Deficiency on Leaf Cuticle Lipids of Arabidopsis1[W][OA]
2009-12-01
Arabidopsis (Arabidopsis thaliana) plants subjected to water deficit, sodium chloride (NaCl), or abscisic acid treatments were shown to exhibit a significant increase in the amount...Full Text Available
Síntese e caracterização de copolímeros de estireno e divinilbenzeno clorometilados
2004-01-01
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Síntese de novas fitotoxinas derivadas do 8-oxabiciclo[3.2.1]oct-6-en-3-ona
2005-06-01
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SYNTHESIS OF NOVEL TRYPTOPHAN DERIVATIVES OF POTENTIAL BIOLOGICAL ACTIVITY
2009-06-01
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SANS studies of critical phenomena in ternary mixtures
Critical behaviour of a quasi-binary liquid mixture is investigated by small-angle neutron scattering. Analysis of the changes of the critical parameters, caused by addition of a small amount of electrolyte into the binary mixture 3-methylpyridine-heavy water, shows that the third component does not change the 3D Ising-type behaviour of the system; a crossover towards the mean-field behaviour is not observed. (orig.)
QENS and NMR studies of 3-picoline-water solutions
Quasi-elastic neutron scattering measurements were performed on aqueous solutions of 3-picoline (3-methylpyridine) at room temperature. H-D substitution on both the solute and the water was used to separate the dynamics of the two species. The analysis of the translational diffusive motion at different concentrations shows that at high picoline content the diffusion coefficient of water decreases strongly and becomes similar to that of the solute, indicating strong coupling between the motions of the solute and the solvent. Activation energies characteristic of the dynamic behavior of the methyl group were determined from sup 1 H spin-lattice relaxation rate measurements for H sub 2 O and D sub 2 O solutions of 3-picoline above 310 K. (orig.)
Prevention of selenite-induced cataractogenesis by rutin in Wistar rats
PurposeTo investigate whether rutin retards selenite-induced cataractogenesis in Wistar rat pups.MethodsOn postpartum day ten, Group I rat pups received...Full Text Available
Prevention of selenite-induced cataractogenesis by rutin in Wistar rats
Full Text Available.PurposeTo investigate whether rutin retards selenite-induced cataractogenesis in Wistar rat pups.MethodsOn postpartum day ten, Group I rat pups received an intraperitoneal injection of saline. Group II and III rat pups received a subcutaneous injection of sodium selenite. Group III also received an intraperitoneal injection of rutin once daily on postpartum days 9–14. Both eyes of each pup were examined from day 16 up to postpartum day 30. After sacrifice, extricated pup lenses were analyzed for mean activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione S-transferase, and glutathione reductase. In addition, the mean concentrations of reduced glutathione (GSH) and of malondialdehyde were analyzed in samples of lenses and hemolysate.ResultsThere was dense lenticular opacification in all of Group II, minimal opacification in 33.3% of Group III, no opacification in 66.7% of Group III, and no opacification in Group I. Significantly lower mean activities of lenticular antioxidant enzymes were noted in Group II, compared to Group I and III. Significantly lower mean concentrations of GSH and higher mean concentrations of malondialdehyde were noted in samples of hemolysate and lens from Group II, compared to the values in Group I and III.ConclusionRutin prevents experimental selenite-induced cataractogenesis in rat pups, possibly by preventing depletion of antioxidant enzymes and of GSH, and by inhibiting lipid peroxidation.
Positron annihilation studies of some charge transfer molecular complexes
Positron annihilation lifetimes were measured for some solid charge transfer (CT) molecular complexes of quinoline compounds (2,6-dimethylquinoline, 6-methoxyquinoline, quinoline, 6-methylquinoline, 3-bromoquinoline and 2-chloro-4-methylquinoline) as electron donor and picric acid as an electron acceptor. The infrared spectra (IR) of the solid complexes clearly indicated the formation of the hydrogen-bonding CT-complexes. The annihilation spectra were analyzed into two lifetime components using PATFIT program. The values of the average and bulk lifetimes divide the complexes into two groups according to the non-bonding ionization potential of the donor (electron donating power) and the molecular weight of the complexes. Also, it is found that the ionization potential of the donors and molecular weight of the complexes have a conspicuous effect on the average and bulk lifetime values. The bulk lifetime values of the complexes are consistent with the formation of stable hydrogen-bonding CT-complexes as inferred from the IR-spectral data.
Physiochemical property space distribution among human metabolites, drugs and toxins
Full Text Available.BackgroundThe current approach to screen for drug-like molecules is to sieve for molecules with biochemical properties suitable for desirable pharmacokinetics and reduced toxicity, using predominantly biophysical properties of chemical compounds, based on empirical rules such as Lipinski's "rule of five" (Ro5). For over a decade, Ro5 has been applied to combinatorial compounds, drugs and ligands, in the search for suitable lead compounds. Unfortunately, till date, a clear distinction between drugs and non-drugs has not been achieved. The current trend is to seek out drugs which show metabolite-likeness. In identifying similar physicochemical characteristics, compounds have usually been clustered based on some characteristic, to reduce the search space presented by large molecular datasets. This paper examines the similarity of current drug molecules with human metabolites and toxins, using a range of computed molecular descriptors as well as the effect of comparison to clustered data compared to searches against complete datasets.ResultsWe have carried out statistical and substructure functional group analyses of three datasets, namely human metabolites, drugs and toxin molecules. The distributions of various molecular descriptors were investigated. Our analyses show that, although the three groups are distinct, present-day drugs are closer to toxin molecules than to metabolites. Furthermore, these distributions are quite similar for both clustered data as well as complete or unclustered datasets.ConclusionThe property space occupied by metabolites is dissimilar to that of drugs or toxin molecules, with current drugs showing greater similarity to toxins than to metabolites. Additionally, empirical rules like Ro5 can be refined to identify drugs or drug-like molecules that are clearly distinct from toxic compounds and more metabolite-like. The inclusion of human metabolites in this study provides a deeper insight into metabolite/drug/toxin-like properties and will also prove to be valuable in the prediction or optimization of small molecules as ligands for therapeutic applications.
Physiochemical property space distribution among human metabolites, drugs and toxins
BackgroundThe current approach to screen for drug-like molecules is to sieve for molecules with biochemical properties suitable for desirable pharmacokinetics and reduced toxicity,...Full Text Available
Optically nonlinear Langmuir Blodgett films
A series of novel amphiphilic molecules plus a new class of chevron-shaped materials, without aliphatic tails, were designed, synthesised and non-centrosymmetrically aligned by the Langmuir-Blodgett technique. Their LB films exhibited optical second-harmonic generation (SHG). The chevron-shaped molecules have a central cationic acceptor and two pi-bridged donor groups with an angle of ca. 120 deg between the charge-transfer axes of the D-pi-(A sup +)-pi-D unit. A monolayer LB film of a representative example, 1-butyl-2,6-bis[2- (4-dibutylaminophenyl)vinyl]pyridinium iodide, has an effective susceptibility, chi sup ( sup 2 sup ) sub e sub f sub f , of 120 pm V sup - sup 1 at 1064 nm, a thickness of 1.16 nm and an area in contact with the substrate of 0.91 nm sup 2 molecule sup - sup 1. The second-harmonic intensity (1.6 x 10 sup - sup 4 versus quartz) is similar to those of the extensively studied conventional amphiphilic hemicyanines but as a result of non-centrosymmetric alignment, without the need for long aliphatic tails, the susceptibility is significantly higher. The LB film has an absorbance of 0.014 at the second-harmonic wavelength (532 nm). Other chevron-shaped examples, for instance, 1-butyl-2,6-bis[2-(7-diethylamino-2-oxo-2H-chromen-3-yl)vinyl]pyridinium iodide, show similar properties with a chi sup ( sup 2 sup ) sub e sub f sub f of 110 pm V sup - sup 1 , a thickness of 1.23 nm, a contact area of 0.85 nm sup 2 molecule sup - sup 1 and an absorbance at 532 nm of 0.013. Other dyes investigated included 7-diethylamino-2-oxo-2H-chromen-3-ylmethylene- 5,6,7,8-tetrahydroisoquinolinium octadecylsulfate and (E)-4-[2- (bis(octadecylsulfanyl)tetrathiafulvalenyl)ethenyl]-1-methylpyridinium iodide. Alternate-layer LB films of the former, interleaved with poly(tert-butylmethacrylate), PtBM, exhibit a quadratic dependence in second-harmonic intensity with the number of bilayers. The 95 bilayer LB film has a chi sup ( sup 2 sup ) sub e sub f sub f of 45 pm V su ss of 3.9 nm bilayer sup - sup 1 , a contact area of 0.50 nm sup 2 molecule sup - sup 1 and an absorbance at 532 nm of 1.1 x 10 sup - sup 3 bilayer sup - sup 1. Monolayer LB films of the latter, on the other hand, has a chi sup ( sup 2 sup ) sub e sub f sub f of 70 pm V sup - sup 1 , a thickness of 2.1 nm, a contact area of 0.50 nm sup 2 molecule sup - sup 1 and an absorbance at 532 nm of 1.7 x 10 sup - sup 3. Unconventional amphiphilic benzopyrylium compounds in which the electron donor and electron acceptor groups are not directly opposite each other, the molecules not being rod-like, were also obtained as monolayer and multilayer LB films. For example, a monolayer of 7-docosyl-3-methoxy-5,6-dihydro(naphtha[1,2-b]-1-benzopyrylium octadecylsulfate has a chi sup ( sup 2 sup ) sub e sub f sub f of 28 pm V sup - sup 1 , a layer thickness of 3.0 nm, a contact area of 0.44 nm sup 2 molecule sup - sup 1 and very slight absorbance of 3 x 10 sup - sup 4 at 532 nm. Furthermore, its alternate-layer LB films interleaved with PtBM exhibit a quadratic dependence of the second-harmonic intensity with the number of bilayers.
Novel Nucleoside Analogues with Fluorophores Replacing the DNA Base
2009-12-15
We describe the preparation and fluorescence properties of a set of new nucleosides in which a known hydrocarbon or oligothiophene fluorophore replaces the DNA base at C(1) of the deoxyribose...Full Text Available
Novel Nucleoside Analogues with Fluorophores Replacing the DNA Base
2009-12-15
Full Text Available.We describe the preparation and fluorescence properties of a set of new nucleosides in which a known hydrocarbon or oligothiophene fluorophore replaces the DNA base at C(1) of the deoxyribose moiety (see 3a – f). These compounds are potentially useful as probes in the study of the structure and dynamics of nucleic acids and their complexes with proteins. In addition, they may find use as fluorescent labels for nucleic-acid-based biomedical diagnostics methods. The fluorophores conjugated to deoxyribose at C(1) in the α-d-form include terphenyl, stilbene, terthiophene, benzoterthiophene, and pyrene. Also included is a non-fluorescent spacer in which cyclohexene replaces the DNA base. The nucleosides are derived from brominated fluorophore precursors and Hoffer’s 2-deoxy-3,5-di-O-(p-toluoyl)-d-ribofuranosyl chloride. The emission maxima of the free nucleosides range from 345 to 536 nm. Also described are the 5′-(dimethoxytrityl) 3′-O-phosphoramidite derivatives 5a – f, suitable for incorporation into oligonucleotides by automated synthesizers.
2008-01-01
This work deals with new aspects of the chemistry of the uranyl(VI) ion left braceUO2right brace2+ in anhydrous polar organic solvents such as the activation of the reputedly inert U-Oyl bond and the controlled reduction of this species which represent a particularly active field of research that attracts much attention for both its fundamental aspects and applications. Treatment of uranyl(VI) compounds UO2X'2 (X' = I, OTf, Cl) with Me3SiX (X = Cl, Br, I) reagents, in various anhydrous polar organic solvents, has been first considered. In most cases, reduction into tetravalent species with complete de-oxygenation of the uranyl left braceUO2right brace2+ ion is observed. The reaction is particularly efficient in ... >>
Métodos de preparação e atividade biológica do ácido quinolínico e derivados
2003-01-01
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Multiple Functions of Nm23-H1 Are Regulated by Oxido-Reduction System
Nucleoside diphosphate kinase (NDPK, Nm23), a housekeeping enzyme, is known to be a multifunctional protein, acting as a metastasis suppressor, transactivation activity on c-myc, and regulating endocytosis....Full Text Available
Multiple Functions of Nm23-H1 Are Regulated by Oxido-Reduction System
Full Text Available.Nucleoside diphosphate kinase (NDPK, Nm23), a housekeeping enzyme, is known to be a multifunctional protein, acting as a metastasis suppressor, transactivation activity on c-myc, and regulating endocytosis. The cellular mechanisms regulating Nm23 functions are poorly understood. In this study, we identified the modifications and interacting proteins of Nm23-H1 in response to oxidative stress. We found that Cys109 in Nm23-H1 is oxidized to various oxidation states including intra- and inter-disulfide crosslinks, glutathionylation, and sulfonic acid formation in response to H2O2 treatment both in vivo and in vitro. The cross-linking sites and modifications of oxidized Nm23-H1 were identified by peptide sequencing using UPLC-ESI-q-TOF tandem MS. Glutathionylation and oxidation of Cys109 inhibited the NDPK enzymatic activity of Nm23-H1. We also found that thioredoxin reductase 1 (TrxR1) is an interacting protein of Nm23-H1, and it binds specifically to oxidized Nm23-H1. Oxidized Nm23 is a substrate of NADPH-TrxR1-thioredoxin shuttle system, and the disulfide crosslinking is reversibly reduced and the enzymatic activity is recovered by this system. Oxidation of Cys109 in Nm23-H1 inhibited its metastatic suppressor activity as well as the enzymatic activities. The mutant, Nm23-H1 C109A, retained both the enzymatic and metastasis suppressor activities under oxidative stress. This suggests that key enzymatic and metastasis suppressor functions of Nm23-H1 are regulated by oxido-reduction of its Cys109.
Full Text Available.BackgroundRoux-en-Y gastric bypass (RYGB) surgery is associated with weight loss, improved insulin sensitivity and glucose homeostasis, and a reduction in co-morbidities such as diabetes and coronary heart disease. To generate further insight into the numerous metabolic adaptations associated with RYGB surgery, we profiled serum metabolites before and after gastric bypass surgery and integrated metabolite changes with clinical data.Methodology and Principal FindingsSerum metabolites were detected by gas and liquid chromatography-coupled mass spectrometry before, and 3 and 6 months after RYGB in morbidly obese female subjects (n = 14; BMI = 46.2±1.7). Subjects showed decreases in weight-related parameters and improvements in insulin sensitivity post surgery. The abundance of 48% (83 of 172) of the measured metabolites changed significantly within the first 3 months post RYGB (p<0.05), including sphingosines, unsaturated fatty acids, and branched chain amino acids. Dividing subjects into obese (n = 9) and obese/diabetic (n = 5) groups identified 8 metabolites that differed consistently at all time points and whose serum levels changed following RYGB: asparagine, lysophosphatidylcholine (C18:2), nervonic (C24:1) acid, p-Cresol sulfate, lactate, lycopene, glucose, and mannose. Changes in the aforementioned metabolites were integrated with clinical data for body mass index (BMI) and estimates for insulin resistance (HOMA-IR). Of these, nervonic acid was significantly and negatively correlated with HOMA-IR (p = 0.001, R = −0.55).ConclusionsGlobal metabolite profiling in morbidly obese subjects after RYGB has provided new information regarding the considerable metabolic alterations associated with this surgical procedure. Integrating clinical measurements with metabolomics data is capable of identifying markers that reflect the metabolic adaptations following RYGB.
BackgroundRoux-en-Y gastric bypass (RYGB) surgery is associated with weight loss, improved insulin sensitivity and glucose homeostasis, and a reduction in co-morbidities such as...Full Text Available
ObjectiveCrush injury to the sciatic nerve causes oxidative stress. Alfa Lipoic acid (a-LA) is a neuroprotective metabolic antioxidant. This study was designed to investigate the...Full Text Available
Full Text Available.ObjectiveCrush injury to the sciatic nerve causes oxidative stress. Alfa Lipoic acid (a-LA) is a neuroprotective metabolic antioxidant. This study was designed to investigate the antioxidant effects of pretreatment with a-LA on the crush injury of rat sciatic nerve.MethodsForty rats were randomized into four groups. Group I and Group II received saline (2 ml, intraperitoneally) and a-LA (100 mg/kg, 2 ml, intraperitoneally) in the groups III and IV at the 24 and 1 hour prior to the crush injury. In groups II, III and IV, the left sciatic nerve was exposed and compressed for 60 seconds with a jeweler's forceps. In Group I (n = 10), the sciatic nerve was explored but not crushed. In all groups of rats, superoxide dismutase (SOD) and catalase (CAT) activities, as well as malondialdehyde (MDA) levels were measured in samples of sciatic nerve tissue.ResultsCompared to Group I, Group II had significantly decreased tissue SOD and CAT activities and elevated MDA levels indicating crush injury (p < 0.05). In the a-LA treatment groups (groups III and IV), tissue CAT and SOD activities were significantly increased and MDA levels significantly decreased at the first hour (p < 0.05) and on the 3rd day (p < 0.05). There was no significant difference between a-LA treatment groups (p > 0.05).ConclusionA-LA administered before crush injury of the sciatic nerve showed significant protective effects against crush injury by decreasing the oxidative stress. A-LA should be considered in the treatment of peripheral nerve injuries, but further studies are needed to explain the mechanism of its neuroprotective effects.
In vivo administration of BL-3050: highly stable engineered PON1-HDL complexes
Full Text Available.BackgroundSerum paraoxonase (PON1) is a high density lipoprotein (HDL)-associated enzyme involved in organophosphate (OP) degradation and prevention of atherosclerosis. PON1 comprises a potential candidate for in vivo therapeutics, as an anti-atherogenic agent, and for detoxification of pesticides and nerve agents. Because human PON1 exhibits limited stability, engineered, recombinant PON1 (rePON1) variants that were designed for higher reactivity, solubility, stability, and bacterial expression, are candidates for treatment. This work addresses the feasibility of in vivo administration of rePON1, and its HDL complex, as a potentially therapeutic agent dubbed BL-3050.MethodsFor stability studies we applied different challenges related to the in vivo disfunctionalization of HDL and PON1 and tested for inactivation of PON1's activity. We applied acute, repetitive administrations of BL-3050 in mice to assess its toxicity and adverse immune responses. The in vivo efficacy of recombinant PON1 and BL-3050 were tested with an animal model of chlorpyrifos-oxon poisoning.ResultsInactivation studies show significantly improved in vitro lifespan of the engineered rePON1 relative to human PON1. Significant sequence changes relative to human PON1 might hamper the in vivo applicability of BL-3050 due to adverse immune responses. However, we observed no toxic effects in mice subjected to repetitive administration of BL-3050, suggesting that BL-3050 could be safely used. To further evaluate the activity of BL-3050 in vivo, we applied an animal model that mimics human organophosphate poisoning. In these studies, a significant advantages of rePON1 and BL-3050 (>87.5% survival versus <37.5% in the control groups) was observed. Furthermore, BL-3050 and rePON1 were superior to the conventional treatment of atropine-2-PAM as a prophylactic treatment for OP poisoning.ConclusionIn vitro and in vivo data described here demonstrate the potential advantages of rePON1 and BL-3050 for treatment of OP toxicity and chronic cardiovascular diseases like atherosclerosis. The in vivo data also suggest that rePON1 and BL-3050 are stable and safe, and could be used for acute, and possibly repeated treatments, with no adverse effects.
In vivo administration of BL-3050: highly stable engineered PON1-HDL complexes
BackgroundSerum paraoxonase (PON1) is a high density lipoprotein (HDL)-associated enzyme involved in organophosphate (OP) degradation and prevention of atherosclerosis. PON1 comprises...Full Text Available
Identification of excited states in conjugated polymers
This thesis reports quasi steady state photoinduced absorption measurements from three conjugated polymers: polypyridine (PPy), polyfluorene (PFO) and the emeraldine base (EB) form of polyaniline. The aim of these experiments was to determine the nature of the photoexcited states existing in these materials in the millisecond time domain, as this has important consequences for the operation of real devices manufactured using these materials. The results from the photoinduced absorption experiments are closely compared with published results from pulse radiolysis experiments. In all cases there is very good correspondence between the two data sets, which has enabled the photoexcited states to be assigned with a high degree of confidence. Quasi steady-state photoinduced absorption involves the measurement of the change in absorption of a material in response to optical excitation with a laser beam. The changes in absorption are small, so a instrument was developed and optimised for each different sample. Lock-in techniques were used to recover the small signals from the samples. The samples involved were thin films of the polymer spin coated onto sapphire substrates in the cases of PPy and EB. Solution state experiments were conducted on EB. The experiments on PFO were conducted on aligned and unaligned thin films provided by Sony. In the case of the aligned PFO samples, the photoinduced absorption spectrometer was modified to enable polarisation-sensitive data collection. In PPy, both triplet excitons and polarons have been shown to be long-lived photoexcitations, with photoinduced absorption features at 2.29 eV (triplet exciton transition), 1.5 eV and 0.8 eV (polaron transitions). In PFO, the one observed photoinduced band at 1.52 eV is assigned to a triplet exciton. Two photoinduced absorption bands are observed in EB, at 1.4 eV and 0.8 eV. These are assigned to a self-trapped CT singlet exciton and triplet exciton, respectively.
2009-12-01
The cuticle covering plants' aerial surfaces is a unique structure that plays a key role in organ development and protection against diverse stress conditions. A detailed analysis of the tomato colorless-peel...Full Text Available
2009-12-01
Full Text Available.The cuticle covering plants' aerial surfaces is a unique structure that plays a key role in organ development and protection against diverse stress conditions. A detailed analysis of the tomato colorless-peel y mutant was carried out in the framework of studying the outer surface of reproductive organs. The y mutant peel lacks the yellow flavonoid pigment naringenin chalcone, which has been suggested to influence the characteristics and function of the cuticular layer. Large-scale metabolic and transcript profiling revealed broad effects on both primary and secondary metabolism, related mostly to the biosynthesis of phenylpropanoids, particularly flavonoids. These were not restricted to the fruit or to a specific stage of its development and indicated that the y mutant phenotype is due to a mutation in a regulatory gene. Indeed, expression analyses specified three R2R3-MYB–type transcription factors that were significantly down-regulated in the y mutant fruit peel. One of these, SlMYB12, was mapped to the genomic region on tomato chromosome 1 previously shown to harbor the y mutation. Identification of an additional mutant allele that co-segregates with the colorless-peel trait, specific down-regulation of SlMYB12 and rescue of the y phenotype by overexpression of SlMYB12 on the mutant background, confirmed that a lesion in this regulator underlies the y phenotype. Hence, this work provides novel insight to the study of fleshy fruit cuticular structure and paves the way for the elucidation of the regulatory network that controls flavonoid accumulation in tomato fruit cuticle.
A new crystal of 2-aminopyridine phosphate (NC sub 4 H sub 4 NH sub 2)centre dot H sub 3 PO sub 4 has been grown and its x-ray structure and physical properties were studied. At room temperature the crystals are monoclinic, space group C2/c. The flat 2-aminopyridine cations are hydrogen bonded to the anionic [PO sub 4 ] groups. The interesting feature of the crystal structure is the three-dimensional network of hydrogen bonds including, among others, two strong, symmetrical O centre dot centre dot centre dot H, H centre dot centre dot centre dot O interactions with disordered proton locations. Symmetrically related PO sub 4 anions linked through these protons form infinite (PO sub 4) subinfinity chains along the crystal a-axis. The anomalies in the temperature dependence of the electric permittivity showed that the crystal undergoes ferroelectric phase transition at T sub c = 103.5 K. The spontaneous polarization takes place along the crystal a-axis, being parallel to the chains of the hydrogen-bonded PO sub 4. The disordered protons, thermally activated at room temperature, can be frozen at their positions in the ferroelectric phase. The order-disorder continuous type of the transition has been evidenced on the basis of the temperature dependences of electric permittivity and spontaneous polarization measurements.
Electrochemical promotion of catalytic reactions with Pt/C (or Pt/Ru/C)//PBI catalysts
2007-01-01
The paper is an overview of the results of the investigation on electrochemical promotion of three catalytic reactions: methane oxidation with oxygen, NO reduction with hydrogen at 135 degrees C and Fischer-Tropsch synthesis (FTS) at 170 degrees C in the [CH4/O-2(or NO/H-2 or CO/H-2)/Ar//Pt(or Pt/Ru)//PBI(H3PO4)/H-2, Ar] fuel cell. It has been shown that the partial methane oxidation to C2H2 and the C-2 selectivity were electrochemically promoted by the negative catalyst polarization. This was also the case in NO reduction with hydrogen for low NO and H-2 partial pressures. In both cases the catalytic reactions have been promoted by the electrochemically produced hydrogen. It has been found that the NO reduction with hydrogen on the Pt/PBI strongly depends on NO and hydrogen partial pressures in the working gas mixture. At higher NO and H-2 partial pressures the catalysis is promoted by the electrochemical pumping of H+ from the catalyst, i.e. at positive polarization. FTS demonstrated the highest methane production rate (11% of CO conversion) at zero fuel cell voltage.
Effects of 1,4-dihydropyridine derivative treatment on base damage in X-irradiated CHO cells
2009-01-01
(No abstract available)
Full Text Available.BackgroundDrug resistance is a primary hindrance for the efficiency of chemotherapy against osteosarcoma. Although chemotherapy has improved the prognosis of osteosarcoma patients dramatically after introduction of neo-adjuvant therapy in the early 1980's, the outcome has since reached plateau at approximately 70% for 5 year survival. The remaining 30% of the patients eventually develop resistance to multiple types of chemotherapy. In order to overcome both the dose-limiting side effects of conventional chemotherapeutic agents and the therapeutic failure incurred from multidrug resistant (MDR) tumor cells, we explored the possibility of loading doxorubicin onto biocompatible, lipid-modified dextran-based polymeric nanoparticles and evaluated the efficacy.MethodsDoxorubicin was loaded onto a lipid-modified dextran based polymeric nano-system. The effect of various concentrations of doxorubicin alone or nanoparticle loaded doxorubicin on KHOS, KHOSR2, U-2OS, and U-2OSR2 cells was analyzed. Effects on drug retention, immunofluorescence, Pgp expression, and induction of apoptosis were also analyzed.ResultsDextran nanoparticles loaded with doxorubicin had a curative effect on multidrug resistant osteosarcoma cell lines by increasing the amount of drug accumulation in the nucleus via Pgp independent pathway. Nanoparticles loaded with doxorubicin also showed increased apoptosis in osteosarcoma cells as compared with doxorubicin alone.ConclusionLipid-modified dextran nanoparticles loaded with doxorubicin showed pronounced anti-proliferative effects against osteosarcoma cell lines. These findings may lead to new treatment options for MDR osteosarcoma.
BackgroundDrug resistance is a primary hindrance for the efficiency of chemotherapy against osteosarcoma. Although chemotherapy has improved the prognosis of osteosarcoma patients...Full Text Available
2010-01-01
The interaction between Leishmania and sand flies has been demonstrated in many Old and New World species. Besides the morphological differentiation from procyclic to infective metacyclic...Full Text Available
2010-01-01
Full Text Available.The interaction between Leishmania and sand flies has been demonstrated in many Old and New World species. Besides the morphological differentiation from procyclic to infective metacyclic promastigotes, the parasite undergoes biochemical transformations in its major surface lipophosphoglycan (LPG). An upregulation of β-glucose residues was previously shown in the LPG repeat units from procyclic to metacyclic phase in Leishmania (Viannia) braziliensis, which has not been reported in any Leishmania species. LPG has been implicated as an adhesion molecule that mediates the interaction with the midgut epithelium of the sand fly in the Subgenus Leishmania. These adaptations were explored for the first time in a species from the Subgenus Viannia, L. (V.) braziliensis with its natural vectors Lutzomyia (Nyssomyia) intermedia and Lutzomyia (Nyssomyia) whitmani. Using two in vitro binding techniques, phosphoglycans (PGs) derived from procyclic and metacyclic parasites were able to bind to the insect midgut and inhibit L. braziliensis attachment. Interestingly, L. braziliensis procyclic parasite attachment was ∼11-fold greater in the midgut of L. whitmani than in L. intermedia. The epidemiological relevance of L. whitmani as a vector of American Cutaneous Leishmaniasis (ACL) in Brazil is discussed.
Corrosion Behaviour of Zn-Al-Cu Alloy in HCl Solution and its Inhibition
2006-01-01
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Coordination polymers assembled through pi-pi interactions
Chapter one is a review of the relevant literature. In chapter two the coordination chemistry of biphenyl-tailed terpyridines with octahedral metal dications is investigated. The effect of different metal ions on their aggregation modes in the solid state is also investigated. In chapter three the coordination chemistry of polyaryl-tailed terpyridines with octahedral metal dications is investigated. The effect of different aryl tails on their aggregation modes in the solid state is investigated. In chapter four the pi-pi aggregation of molecular boxes through biphenyl tails is studied. In chapter five the immobilisation of aryl tailed complexes into polyelectrolyte films has been investigated, and the arrangement of these complexes in the films has been compared with same complexes in the crystal, thus moving from three dimensional aggregation to two dimensions.
Full Text Available.BackgroundThe majority of acute myeloid leukaemia (AML) patients are over sixty years of age. With current treatment regimens, survival rates amongst these, and also those younger patients who relapse, remain dismal and novel therapies are urgently required. In particular, therapies that have anti-leukaemic activity but that, unlike conventional chemotherapy, do not impair normal haemopoiesis.Principal FindingsHere we demonstrate the potent anti-leukaemic activity of the combination of the lipid-regulating drug bezafibrate (BEZ) and the sex hormone medroxyprogesterone acetate (MPA) against AML cell lines and primary AML cells. The combined activity of BEZ and MPA (B/M) converged upon the increased synthesis and reduced metabolism of prostaglandin D2 (PGD2) resulting in elevated levels of the downstream highly bioactive, anti-neoplastic prostaglandin 15-deoxy Δ12,14 PGJ2 (15d-PGJ2). BEZ increased PGD2 synthesis via the generation of reactive oxygen species (ROS) and activation of the lipid peroxidation pathway. MPA directed prostaglandin synthesis towards 15d-PGJ2 by inhibiting the PGD2 11β -ketoreductase activity of the aldo-keto reductase AKR1C3, which metabolises PGD2 to 9α11β-PGF2α. B/M treatment resulted in growth arrest, apoptosis and cell differentiation in both AML cell lines and primary AML cells and these actions were recapitulated by treatment with 15d-PGJ2. Importantly, the actions of B/M had little effect on the survival of normal adult myeloid progenitors.SignificanceCollectively our data demonstrate that B/M treatment of AML cells elevated ROS and delivered the anti-neoplastic actions of 15d-PGJ2. These observations provide the mechanistic rationale for the redeployment of B/M in elderly and relapsed AML.
BackgroundThe majority of acute myeloid leukaemia (AML) patients are over sixty years of age. With current treatment regimens, survival rates amongst these, and also those younger...Full Text Available
Characterisation of molecular thin films grown by organic molecular beam deposition
This work concerns the growth and characterisation of molecular thin films in an ultra high vacuum regime by organic molecular beam deposition (OMBD). Films of three different molecular materials are grown, namely free base phthalocyanine (H sub 2 Pc), perylene 3,4,9,10-tetracarboxylic dianhydride (PTCDA) and aluminium tris-8-hydroxyquinoline (Alq sub 3). The relationship between the growth parameters such as film thickness, growth rate, and substrate temperature during and after growth, and the structural, optical and morphological properties of the film are investigated. These investigations are carried out using various ex-situ techniques. X-ray diffraction, Raman spectroscopy and electronic absorption spectroscopy are used to probe the bulk film characteristics, whilst Nomarski microscopy and atomic force microscopy are used to study the surface morphology. Three different levels of influence of the growth parameters on the film properties are observed. In the case of H sub 2 Pc, two crystal phases are formed, alpha and beta. The alpha-phase occurs for growth at room temperature. The beta-phase, which is formed by growth at elevated substrate temperatures or annealing films grown at room temperature, can be further divided into two sub-phases, beta sub 1 and beta sub 2 , which have very different surface morphologies. The alpha-> beta transition is investigated using AFM and Nomarski microscopy and information is elicited through measurement of the size distribution and number density of the different crystallites and their respective domains. Bilayers of one phase of H sub 2 Pc grown on top of another phase are also investigated and the growth of the second layer is profoundly influenced by the template formed by the first layer. PTCDA films do not show such a phase transition. However, the surface morphology of PTCDA films is influenced by growth conditions. Alq sub 3 films exhibit different behaviour from either H sub 2 Pc or PTCDA films and neither the b
2009-12-01
Full Text Available.A central mechanistic paradigm of cysteine proteases is that the His – Cys catalytic diad forms an ion-pair NH(+)/S(−) already in the catalytically active free enzyme. Most molecular modeling studies of cysteine proteases refer to this paradigm as their starting point. Nevertheless, several recent kinetics and X-ray crystallography studies of viral and bacterial cysteine proteases depart from the ion-pair mechanism, suggesting general base catalysis. We challenge the postulate of the ion-pair formation in free papain. Applying our QM/SCRF(VS) molecular modeling approach, we analyzed all protonation states of the catalytic diad in free papain and its SMe derivative, comparing the predicted and experimental pKa data. We conclude that the His – Cys catalytic diad in free papain is fully protonated, NH(+)/SH. The experimental pKa=8.62 of His159 imidazole in free papain, obtained by NMR controlled titratin and originally interpreated as the NH(+)/S(−) ⇌ N/S(−) equilibrium, is now assigned to the NH(+)/SH ⇌ N/SH equilibrium.
2009-12-01
A central mechanistic paradigm of cysteine proteases is that the His – Cys catalytic diad forms an ion-pair NH(+)/S(−) already in the catalytically active free enzyme. Most molecular...Full Text Available
Nicotinamide phosphoribosyltransferase (Nampt) inhibitors such as FK866 are potent inhibitors of NAD+ synthesis that show promise for the treatment of different forms of cancer. Based...Full Text Available
Bacterial responses to photo-oxidative stress
2009-12-01
Singlet oxygen is one of several reactive oxygen species that can destroy biomolecules, microorganisms and other cells. Traditionally, the response to singlet oxygen has been termed photo-oxidative...Full Text Available
Bacterial responses to photo-oxidative stress
2009-12-01
Full Text Available.Singlet oxygen is one of several reactive oxygen species that can destroy biomolecules, microorganisms and other cells. Traditionally, the response to singlet oxygen has been termed photo-oxidative stress, as light-dependent processes in photosynthetic cells are major biological sources of singlet oxygen. Recent work identifying a core set of singlet oxygen stress response genes across various bacterial species highlights the importance of this response for survival by both photosynthetic and non-photosynthetic cells. Here, we review how bacterial cells mount a transcriptional response to photo-oxidative stress in the context of what is known about bacterial stress responses to other reactive oxygen species.
An optical, electro-optic and thermal characterisation of various organic crystals
The organic materials S - 3 - methyl - 5 - nitro - N - (1 - phenylethyl) - 2 - pyridinamine [3- methyl-MBANP] and S - N - methyl - 5 - nitro - N -(1 - phenylethyl) - 2 - pyridinamine [N- methyl-MBANP] belong to a family of compounds based on the 2-(alpha-methylbenzylamino)-5- nitropyridine molecule and were identified as promising nonlinear optical materials by the powder disk test. Large single crystals were grown from solution for N-methyl-MBANP, which crystallises in a monoclinic space group, and from the melt and solution for 3-methyl-MBANP which crystallises in an orthorhombic space group. Orthoscopic examination of N-methyl-MBANP revealed no dispersion of the dielectric axes unlike the parent molecule and the position of the dielectric axes was correlated with the molecular structure. Preparation of prisms from single crystals of both materials facilitated the measurement of refractive indices in the visible and the near infra-red. The values obtained were correlated with the crystal structure and a Sellmeier equation fitted to each of the dispersion curves. The nonlinear optical properties of both materials were evaluated by use of the Maker fringe technique and phase matched intensities. By means of these two methods, the full nonlinear d sub i sub j tensor was obtained for both materials at a fundamental wavelength of 1064nm. The linear electro-optic properties of N-methyl-MBANP were evaluated using a conoscopic experiment and correlated with the crystal structure together with the magnitude of all non-zero elements in the d sub i sub j tensor. Separately, the thermal properties of N-methylurea (NMU), 4-nitro-4'-methylbenzylidene aniline (NMBA) and Zinc TrisThiourea Sulfate (ZTS) were evaluated and all correlated with the crystal structure and bonding.
BackgroundAliphatic molecules containing free carboxyl groups are important intermediates in many metabolic and signalling reactions, however, they accumulate to low levels in tissues...Full Text Available
2009-12-01
There currently exists a diverse array of molecular probes for the in situ localization of polysaccharides, nucleic acids, and proteins in plant cells, including reporter enzyme strategies (e.g. protein-glucuronidase...Full Text Available
2009-12-01
Full Text Available.There currently exists a diverse array of molecular probes for the in situ localization of polysaccharides, nucleic acids, and proteins in plant cells, including reporter enzyme strategies (e.g. protein-glucuronidase fusions). In contrast, however, there is a paucity of methods for the direct analysis of endogenous glycoside hydrolases and transglycosidases responsible for cell wall remodeling. To exemplify the potential of fluorogenic resorufin glycosides to address this issue, a resorufin β-glycoside of a xylogluco-oligosaccharide (XXXG-β-Res) was synthesized as a specific substrate for in planta analysis of XEH activity. The resorufin aglycone is particularly distinguished for high sensitivity in muro assays due to a low pKa (5.8) and large extinction coefficient (ε 62,000 m−1cm−1), long-wavelength fluorescence (excitation 571 nm/emission 585 nm), and high quantum yield (0.74) of the corresponding anion. In vitro analyses demonstrated that XXXG-β-Res is hydrolyzed by the archetypal plant XEH, nasturtium (Tropaeolum majus) NXG1, with classical Michaelis-Menten substrate saturation kinetics and a linear dependence on both enzyme concentration and incubation time. Further, XEH activity could be visualized in real time by observing the localized increase in fluorescence in germinating nasturtium seeds and Arabidopsis (Arabidopsis thaliana) inflorescent stems by confocal microscopy. Importantly, this new in situ XEH assay provides an essential complement to the in situ xyloglucan endotransglycosylase assay, thus allowing delineation of the disparate activities encoded by xyloglucan endotransglycosylase/hydrolase genes directly in plant tissues. The observation that XXXG-β-Res is also hydrolyzed by diverse microbial XEHs indicates that this substrate, and resorufin glycosides in general, may find broad applicability for the analysis of wall restructuring by polysaccharide hydrolases during morphogenesis and plant-microbe interactions.
5-Fluoro pyrimidines: labels to probe DNA and RNA secondary structures by 1D 19F NMR spectroscopy
2009-12-01
Full Text Available.19F NMR spectroscopy has proved to be a valuable tool to monitor functionally important conformational transitions of nucleic acids. Here, we present a systematic investigation on the application of 5-fluoro pyrimidines to probe DNA and RNA secondary structures. Oligonucleotides with the propensity to adapt secondary structure equilibria were chosen as model systems and analyzed by 1D 19F and 1H NMR spectroscopy. A comparison with the unmodified analogs revealed that the equilibrium characteristics of the bistable DNA and RNA oligonucleotides were hardly affected upon fluorine substitution at C5 of pyrimidines. This observation was in accordance with UV spectroscopic melting experiments which demonstrated that single 5-fluoro substitutions in double helices lead to comparable thermodynamic stabilities. Thus, 5-fluoro pyrimidine labeling of DNA and RNA can be reliably applied for NMR based nucleic acid secondary structure evaluation. Furthermore, we developed a facile synthetic route towards 5-fluoro cytidine phosphoramidites that enables their convenient site-specific incorporation into oligonucleotides by solid-phase synthesis.
5-Fluoro pyrimidines: labels to probe DNA and RNA secondary structures by 1D 19F NMR spectroscopy
2009-12-01
19F NMR spectroscopy has proved to be a valuable tool to monitor functionally important conformational transitions of nucleic acids. Here, we present a systematic investigation on the application...Full Text Available
2-Acetylpyridine N4-Phenyl- Thiosemicarbazone as a new tool for tumour diagnosis
2009-01-01
The aim of this work was to determine in vivo biodistribution of radiolabelled 2-acetylpyridine N4 phenyl thiosemicarbazone (Ph) and to evaluate its applicability for tumour diagnosis. Ph was labelled with 125I using lactoperoxidase method and radiochemical analysis was performed by chromatography. 125I-Ph production was successful with 86 +- 9.2% of radiochemical purity and high specific activity (17.6 TBq /mmol). 125I-Ph was used for biodistribution and pharmacokinetics studies on Swiss mice bearing Ehrlich solid tumour. 125I-Ph presented a rapid blood clearance (T1/2= 97.2 min.) and the kidneys were the main excretion pathway (CL0.01 mL/min). 125I-Ph uptake was significant in tumour (2.5%ID/g) and tumour-to-normal tissue uptake was more than 20-fold higher depending on ... >>
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