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Chemistry Faculty Publications

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Articles 1021 - 1050 of 1129

Full-Text Articles in Chemistry

Thermodynamic Stability Of Sn4, Sn5, Sn6, And Sn7 Clusters By Knudsen Cell Mass Spectrometry, Giovanni Meloni, R W. Schmude, J E. Kingcade, Karl A. Gingerich Jan 2000

Thermodynamic Stability Of Sn4, Sn5, Sn6, And Sn7 Clusters By Knudsen Cell Mass Spectrometry, Giovanni Meloni, R W. Schmude, J E. Kingcade, Karl A. Gingerich

Chemistry Faculty Publications

The Knudsen cell mass spectrometric method has been employed to measure the partial pressures of Sn[sub n] (n=1-7) under equilibrium conditions above liquid tin or a tin-gold alloy, contained in a graphite Knudsen cell. From the all-gas analyzed equilibria the following atomization enthalpies Δ[sub a]H[sub 0][sup °](Sn[sub n]), and enthalpies of formation, Δ[sub f]H[sub 298.15][sup °](Sn[sub n]), in kJ mol-1, have been obtained: Sn[sub 4], 750.2±14 and 450.6±14; Sn[sub 5], 990.2±22 and 512.3±22; Sn[sub 6], 1349.7±28 and 452.8±28; Sn[sub 7], 1644.2±37 and 460.0±37. The atomization energies are compared with available …

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Knudsen Cell Mass Spectrometric Investigation Of The B2n Molecule, Giovanni Meloni, M Sai Baba, Karl A. Gingerich Jan 2000

Knudsen Cell Mass Spectrometric Investigation Of The B2n Molecule, Giovanni Meloni, M Sai Baba, Karl A. Gingerich

Chemistry Faculty Publications

High-temperature Knudsen cell mass spectrometry has been used to study the equilibria involving the B2Nmolecule over the Si–BN system. Thermal functions needed in the evaluation of the mass spectrometric equilibrium data have been calculated from available experimental and theoretical molecular parameters. The enthalpy changes for the reactions2B(g)+Si2N(g)=B2N(g)+2Si(g),and BN(s)+B(g)=B2N(g)have been measured. The following atomization enthalpy,ΔaHo0,and enthalpy of formation,ΔfHo298.15,in kJ mol−1, of1045.5±18 and551.3±18 for theB2N molecule have been determined from these reactionenthalpies. Atomization energies of similar molecules have been compared and discussed.

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Thermodynamic Study Of The Gaseous Molecules Al2n, Aln, And Al2n2 By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich Jan 2000

Thermodynamic Study Of The Gaseous Molecules Al2n, Aln, And Al2n2 By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich

Chemistry Faculty Publications

The Knudsen effusion mass spectrometric method has been employed to measure the equilibrium partial pressures of the Al2N molecule over the AlN–Au–graphite system. Theoretical computations were carried out to determine the structure, molecular parameters, and thermodynamic properties of Al2N. The partial pressures have been combined with the calculated thermal functions to determine the atomization enthalpy,ΔaHo0, and enthalpy of formation,ΔfHo298.15, in kJ mol−1, of 783.2±15 and 342.7±15 for Al2N, respectively. Upper values for the dissociation energy of AlN, Do0(AlN,g)⩽368±15 kJ mol−1, and for the atomization enthalpy of Al2N2, ΔaHo0(Al2N2,g)⩽1402 kJ mol−1 have been obtained. These results are discussed and …

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Atomization Enthalpies And Enthalpies Of Formation Of The Germanium Clusters, Ge5, Ge6, Ge7, And Ge8 By Knudsen Effusion Mass Spectrometry, Karl A. Gingerich, R W. Schmude, M Sai Baba, Giovanni Meloni Jan 2000

Atomization Enthalpies And Enthalpies Of Formation Of The Germanium Clusters, Ge5, Ge6, Ge7, And Ge8 By Knudsen Effusion Mass Spectrometry, Karl A. Gingerich, R W. Schmude, M Sai Baba, Giovanni Meloni

Chemistry Faculty Publications

The high-temperature mass spectrometric method was employed to measure the equilibrium partial pressures of small germanium clusters above liquid germanium contained in a graphite Knudsen cell. These data were combined with new thermal functions, calculated from recent theoretical and spectroscopic molecular parameters, to evaluate the atomization enthalpies and enthalpies of formation of Ge[sub 5]-Ge[sub 8]. Mass spectrometric equilibrium data available in literature were also reevaluated. The following atomization enthalpies, Δ[sub a]H[sub 0][sup o](Ge[sub n],g) and enthalpies of formation Δ[sub f]H[sub 298.15][sup o](Ge[sub n],g), in kJ mol-1, have been obtained: Ge[sub 5], 1313±27 and 548±27, Ge[sub 6], 1649±33 and 583±33, Ge[sub …

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Characterization Of Chimeric Lipopolysaccharides From Escherichia Coli Strain Jm109 Transformed With Lipooligosaccharide Synthesis Genes (Lsg) From Haemophilus Influenzae, Nancy J. Phillips, T. J. Miller, J. J. Engstrom, William Melaugh, R. Mclaughlin, M A. Apicella, B W. Gibson Jan 2000

Characterization Of Chimeric Lipopolysaccharides From Escherichia Coli Strain Jm109 Transformed With Lipooligosaccharide Synthesis Genes (Lsg) From Haemophilus Influenzae, Nancy J. Phillips, T. J. Miller, J. J. Engstrom, William Melaugh, R. Mclaughlin, M A. Apicella, B W. Gibson

Chemistry Faculty Publications

Previously, we reported the expression of chimeric lipopolysaccharides (LPS) in Escherichia coli strain JM109 (a K-12 strain) transformed with plasmids containing Haemophilus influenzae lipooligosaccharide synthesis genes (lsg) (Abu Kwaik, Y., McLaughlin, R. E., Apicella, M. A., and Spinola, S. M. (1991) Mol. Microbiol. 5, 2475–2480). In this current study, we have analyzed the O-deacylated LPS and free oligosaccharides from three transformants (designated pGEMLOS-4, pGEMLOS- 5, and pGEMLOS-7) by matrix-assisted laser desorption ionization, electrospray ionization, and tandem mass spectrometry techniques, along with composition and linkage analyses. These data show that the chimeric LPS consist of the complete E. coli LPS core …

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Activation Of P38 Mitogen-Activated Protein Kinase And C-Jun Nh2-Terminal Kinase By Double-Stranded Rna And Encephalomyocarditis Virus: Involvement Of Rnase L, Protein Kinase R, And Alternative Pathways, Mihail S. Iordanov, Jayashree M. Paranjape, Aimin Zhou, John Wong, Bryan R.G. Williams, Eliane F. Meurs, Robert H. Silverman, Bruce E. Magun Jan 2000

Activation Of P38 Mitogen-Activated Protein Kinase And C-Jun Nh2-Terminal Kinase By Double-Stranded Rna And Encephalomyocarditis Virus: Involvement Of Rnase L, Protein Kinase R, And Alternative Pathways, Mihail S. Iordanov, Jayashree M. Paranjape, Aimin Zhou, John Wong, Bryan R.G. Williams, Eliane F. Meurs, Robert H. Silverman, Bruce E. Magun

Chemistry Faculty Publications

Double-stranded RNA (dsRNA) accumulates in virus-infected mammalian cells and signals the activation of host defense pathways of the interferon system. We describe here a novel form of dsRNA-triggered signaling that leads to the stimulation of the p38 mitogen-activated protein kinase (p38 MAPK) and the c-Jun NH2-terminal kinase (JNK) and of their respective activators MKK3/6 and SEK1/MKK4. The dsRNA-dependent signaling to p38 MAPK was largely intact in cells lacking both RNase L and the dsRNA-activated protein kinase (PKR), i.e., the two best-characterized mediators of dsRNA-triggered antiviral responses. In contrast, activation of both MKK4 and JNK by dsRNA was greatly reduced in …

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3-Hydroxykynurenine And 3-Hydroxyanthranilic Acid Generate Hydrogen Peroxide And Promote Α-Crystallin Cross Linking By Metal Ion Reduction, Lee E. Goldstein, Michael C. Leopold, Xudong Huang, Craig S. Atwood, Aleister J. Saunders, Mariana Hartshorn, James T. Lim, Et Al. Jan 2000

3-Hydroxykynurenine And 3-Hydroxyanthranilic Acid Generate Hydrogen Peroxide And Promote Α-Crystallin Cross Linking By Metal Ion Reduction, Lee E. Goldstein, Michael C. Leopold, Xudong Huang, Craig S. Atwood, Aleister J. Saunders, Mariana Hartshorn, James T. Lim, Et Al.

Chemistry Faculty Publications

The kynurenine pathway catabolite 3-hydroxykynurenine (3HK) and redox-active metals such as copper and iron are implicated in cataractogenesis. Here we investigate the reaction of kynurenine pathway catabolites with copper and iron, as well as interactions with the major lenticular structural proteins, the R-crystallins. The o-aminophenol kynurenine catabolites 3HK and 3-hydroxyanthranilic acid (3HAA) reduced Cu(II)>Fe(III) to Cu(I) and Fe(II), respectively, whereas quinolinic acid and the nonphenolic kynurenine catabolites kynurenine and anthranilic acid did not reduce either metal. Both 3HK and 3HAA generated superoxide and hydrogen peroxide in a copper-dependent manner. In addition, 3HK and 3HAA fostered copper-dependent R-crystallin cross-linking. 3HK- …

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Cu(Ii) Potentiation Of Alzheimer A Neurotoxicity, Xudong Huang, Math P. Cuajungco, Craig S. Atwood, Mariana A. Hartshorn, Joel D. A. Tyndall, Graeme R. Hanson, Karen C. Stokes, Michael C. Leopold, Et Al. Dec 1999

Cu(Ii) Potentiation Of Alzheimer A Neurotoxicity, Xudong Huang, Math P. Cuajungco, Craig S. Atwood, Mariana A. Hartshorn, Joel D. A. Tyndall, Graeme R. Hanson, Karen C. Stokes, Michael C. Leopold, Et Al.

Chemistry Faculty Publications

Oxidative stress markers as well as high concentrations of copper are found in the vicinity of Aβ amyloid deposits in Alzheimer's disease. The neurotoxicity of Aβ in cell culture has been linked to H2O2generation by an unknown mechanism. We now report that Cu(II) markedly potentiates the neurotoxicity exhibited by Aβ in cell culture. The potentiation of toxicity is greatest for Aβ1–42 > Aβ1–40 ≫ mouse/rat Aβ1–40, corresponding to their relative capacities to reduce Cu(II) to Cu(I), form H2O2 in cell-free assays and to exhibit amyloid pathology. The copper complex of Aβ1–42 has a highly positive formal reduction potential (≈+500–550 mV versus …

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Subsidence, Mixing, And Denitrification Of Arctic Polar Vortex Air Measured During Polaris, M. Rex, R. J. Salawitch, G. C. Toon, B. Sen, J. J. Margitan, G. B. Osterman, J. F. Blavier, R. S. Gao, Stephen G. Donnelly Ph.D., E. Keim, J. Neuman, D. W. Fahey, C. R. Webster, D. C. Scott, R. L. Herman, R. D. May, E. J. Moyer, M. R. Gunson, F. W. Irion, A. Y. Chang, C. P. Rinsland, T. P. Bui Nov 1999

Subsidence, Mixing, And Denitrification Of Arctic Polar Vortex Air Measured During Polaris, M. Rex, R. J. Salawitch, G. C. Toon, B. Sen, J. J. Margitan, G. B. Osterman, J. F. Blavier, R. S. Gao, Stephen G. Donnelly Ph.D., E. Keim, J. Neuman, D. W. Fahey, C. R. Webster, D. C. Scott, R. L. Herman, R. D. May, E. J. Moyer, M. R. Gunson, F. W. Irion, A. Y. Chang, C. P. Rinsland, T. P. Bui

Chemistry Faculty Publications

We determine the degree of denitrification that occurred during the 1996-1997 Arctic winter using a technique that is based on balloon and aircraft borne measurements of NOy, N2O, and CH4. The NOy/N2O relation can undergo significant change due to isentropic mixing of subsided vortex air masses with extravortex air due to the high nonlinearity of the relation. These transport related reductions in NOy can be difficult to distinguish from the effects of denitrification caused by sedimentation of condensed HNO3. In this study, high-altitude balloon measurements are used to define the properties of air masses that later descend in the polar …

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Stereoselective Determination Oftrihexyphenidyl In Human Serum By Lc–Esi–Ms, Vladimı́R Čápka, Yan Xu, Yong Hong Chen Nov 1999

Stereoselective Determination Oftrihexyphenidyl In Human Serum By Lc–Esi–Ms, Vladimı́R Čápka, Yan Xu, Yong Hong Chen

Chemistry Faculty Publications

The antiparkinsonian drug trihexyphenidyl (THP) is currently manufactured and administered as a racemate. However, stereochemistry can play significant role in the drug’s pharmacokinetics, biotransformation, metabolism, interaction with cellular and tissue components and overall effect on human body. It is necessary to consider such a drug as a mixture of two compounds (drug enantiomers), with their own effect on the human body. The present paper describes a simple and sensitive LC–MS method for the stereoselective determination of THP in human serum. In this study, the sample was prepared by a solid-phase extraction (SPE) procedure. The enantiomer separation was done using native …

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First Example Of A Double Stranded Helicate With Square-Planar Coordination For The Metal, Marc Zimmer, Derek A. Tocher, Goutam K. Patra, Jnan P. Naskar, Dipankar Datta Nov 1999

First Example Of A Double Stranded Helicate With Square-Planar Coordination For The Metal, Marc Zimmer, Derek A. Tocher, Goutam K. Patra, Jnan P. Naskar, Dipankar Datta

Chemistry Faculty Publications

Reaction of dichlorobis(benzildihydrazone)Ni(II) with biacetylmonoxime in 1:4 molar proportion generates diamagnetic Ni2L2 where LH2 (H = dissociable oximato proton) is HO-N=C(CH3)-C(CH3)=N-N=C(C6H5)-C(C6H5)=N-N=C(CH3)-C(CH3)=N-OH. Our molecular mechanics calculations show that Ni2L2 is an unprecedented double stranded homotopic helicate with the metal ion having a square-planar N4 coordination.

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Cationic 5,10,15,20-Tetrakis(N-Methylpyridinium-4-Yl)Porphyrin Fully Intercalates At 5‘-Cg-3‘ Steps Of Duplex Dna In Solution, Anton B. Guliaev, Neocles B. Leontis Nov 1999

Cationic 5,10,15,20-Tetrakis(N-Methylpyridinium-4-Yl)Porphyrin Fully Intercalates At 5‘-Cg-3‘ Steps Of Duplex Dna In Solution, Anton B. Guliaev, Neocles B. Leontis

Chemistry Faculty Publications

The interaction of 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)p (T4MPyP4+ with the oligonucleotide DNA duplex [d(GCACGTGC)](2) was studied by two-dimensional 1H NMR spectroscopy, optical absorbance, circular dichroism, and molecular dynamics simulation employing particle mesh Ewald methods. T4MPyP4+ is one of the largest aromatic molecules for which intercalative binding to DNA has been proposed, although this has been called into question by recent X-ray crystallographic work [Lipscomb et al. (1996) Biochemistry 35, 2818-2823]. T4MPyP4+ binding to [d(GCACGTGC)]2 produced a single set of (mostly) upfield-shifted DNA resonances in slow exchange with the resonances of the free DNA. Intra- and intermolecular NOEs …

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Synthesis And Antimalarial Activity Of 11 Dispiro-1,2,4,5-Tetraoxane Analogues Of Wr 148999. 7,8,15,16-Tetraoxadispiro[5.2.5.2]Hexadecanes Substituted At The 1 And 10 Positions With Unsaturated And Polar Functional Groups, Yuxiang Dong, F. Hoffmann-Laroche Ltd., Jacques Chollet, Ronald Kaminsky, James K. Wood, Jonathan L. Vennerstrom Apr 1999

Synthesis And Antimalarial Activity Of 11 Dispiro-1,2,4,5-Tetraoxane Analogues Of Wr 148999. 7,8,15,16-Tetraoxadispiro[5.2.5.2]Hexadecanes Substituted At The 1 And 10 Positions With Unsaturated And Polar Functional Groups, Yuxiang Dong, F. Hoffmann-Laroche Ltd., Jacques Chollet, Ronald Kaminsky, James K. Wood, Jonathan L. Vennerstrom

Chemistry Faculty Publications

Eleven novel dispiro-1,2,4,5-tetraoxanes 3 bearing unsaturated and polar functional groups were designed to enhance the oral antimalarial activity of the prototype tetraoxane 2 (WR 148999). With the exception of 3g and 3h, tetraoxanes 3 were available via the peroxidation of corresponding cyclohexanone derivatives in H2SO4/CH3CN. Tetraoxanes 3g and 3h were prepared by hydrolysis of ester tetraoxanes 3e and 3i, respectively. Five of the 11 tetraoxanes were inactive, but six tetraoxanes had IC50 values of 6-26 nM against the K1 and NF54 strains of Plasmodium falciparum compared to corresponding IC50 values of 28 and 39 nM for …

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[2,3:5,6]Dibenzo[2.2.2]Octa-2,5,7-Triene (C2/C) And [2,3:5,6]Dibenzo[2.2.2]Octa-2,5-Diene, Lary Burrows, John M. Masnovi, Ronald J. Baker Feb 1999

[2,3:5,6]Dibenzo[2.2.2]Octa-2,5,7-Triene (C2/C) And [2,3:5,6]Dibenzo[2.2.2]Octa-2,5-Diene, Lary Burrows, John M. Masnovi, Ronald J. Baker

Chemistry Faculty Publications

Two barrelene homologs are reported. Strain in the bicyclic framework of [2,3:5,6]dibenzo[2.2.2]octa-2,5,7- triene, (I) (C16H12), which is manifest in the deviations from ideality of the bond angles in the central bicyclic ringoSyStem and compression of the double bond [1.312 (3)A], is reduced in the more saturated derivative, [2,3:5,6]dibenzo[2.2.2]octa-2,5-diene, (II) (CI6H14), with the corresponding single bond being 1.5380 (19)A. The formation of isomorphs of (I) in both chiral (C2) and achiral (C2/c) space groups has implications for asymmetric syntheses involving solid (I) which rely on a non-centrosymmetric space group.

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Relationship Between Udp-Glucose 4-Epimerase Activity And Oligoglucose Glycoforms In Two Strains Of Neisseria Meningitidis, F K. Lee, B W. Gibson, William Melaugh, A Zaleski, M A. Apicella Jan 1999

Relationship Between Udp-Glucose 4-Epimerase Activity And Oligoglucose Glycoforms In Two Strains Of Neisseria Meningitidis, F K. Lee, B W. Gibson, William Melaugh, A Zaleski, M A. Apicella

Chemistry Faculty Publications

Sodium dodecyl sulfate-polyacrylamide gel analysis of lipooligosaccharide (LOS) from Neisseria meningitidis has demonstrated considerable microheterogeneity in the variable region of LOS due to the presence of novel glycoforms. As a step toward understanding the basis for the expression of these novel glycoforms, we have examined the LOS structures and UDP-glucose 4-epimerase (epimerase) activity levels in two strains (NMB and MA-1) and their respective galE mutants. Strain NMB was found to have low epimerase activity and to contain multiple glycoforms, some of which appear to contain only glucose sugars. The galE mutant had only the oligoglucose glycoforms. Strain MA-1 had higher …

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Experimental And Theoretical Investigations Of The Structure And The Stability Of The Bnsi Molecule, Giovanni Meloni, R Viswanathan Jan 1999

Experimental And Theoretical Investigations Of The Structure And The Stability Of The Bnsi Molecule, Giovanni Meloni, R Viswanathan

Chemistry Faculty Publications

Theoretical computations were carried out to determine the structure and molecular parameters of the BNSi molecule. The most stable isomer is found to have a BNSi linear geometry. Thermal functions as derived from the theoretical computed molecular parameters were used in the evaluation of the thermodynamic properties of BNSi from high-temperature Knudsen effusion mass spectrometric equilibrium data. From the reactions analyzed by the second-law and third-law methods, the enthalpy of formation,ΔfHo0, and of atomization, ΔaHo0, in kJ mol−1, for BNSi, were obtained as 398±16 and 1078±17, respectively.

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Thermodynamic Investigation Of The Ainc And Aicn Isomers By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich Jan 1999

Thermodynamic Investigation Of The Ainc And Aicn Isomers By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich

Chemistry Faculty Publications

Equilibria involving the isomers AlNC and AlCN above a mixture of aluminum nitride, graphite, and gold contained in a graphite Knudsen cell were investigated with a mass spectrometer. The enthalpies of formation,ΔfHo0, and of atomization, ΔaHo0, in kJ mol−1, for AlNC and AlCN, were derived as 281.3±14 and 303.8±14, and as 1228.1±15 and 1205.6±15, respectively.

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No(Y) Partitioning From Measurements Of Nitrogen And Hydrogen Radicals In The Upper Troposphere, E. R. Keim, S. A. Mckeen, R. S. Gao, Stephen G. Donnelly Ph.D., R. C. Wamsley, L. A. Del Negro, D. W. Fahey, T. F. Hanisco, E. J. Lanzendorf, M. H. Proffitt, J. J. Margitan, E. J. Hintsa, L. Jaeglé, C. R. Webster, R. D. May, D. C. Scott, R. J. Salawitch, J. C. Wilson, C. T. Mcelroy, E. L. Atlas, F. Flocke, T. P. Bui Jan 1999

No(Y) Partitioning From Measurements Of Nitrogen And Hydrogen Radicals In The Upper Troposphere, E. R. Keim, S. A. Mckeen, R. S. Gao, Stephen G. Donnelly Ph.D., R. C. Wamsley, L. A. Del Negro, D. W. Fahey, T. F. Hanisco, E. J. Lanzendorf, M. H. Proffitt, J. J. Margitan, E. J. Hintsa, L. Jaeglé, C. R. Webster, R. D. May, D. C. Scott, R. J. Salawitch, J. C. Wilson, C. T. Mcelroy, E. L. Atlas, F. Flocke, T. P. Bui

Chemistry Faculty Publications

Recent studies using NO, NO(y), OH and HO2 (HO(X)) observations have postulated acetone and convection of peroxides as significant sources of HO(X) in the upper troposphere (UT). This work focuses on the effect these additional HO(X) sources have on the modeled NO(y) partitioning and comparisons of the modeled NO(x)/NO(y) ratio to observations. The measured NO(x)/NO(y) ratio is usually much higher than predicted regardless of the presence of acetone in the model. The exception occurs for air parcels having low NO(y) and O3 values. For these air parcels the measured NO(x)/NO(y) ratio is much lower than the calculated ratio unless acetone …

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Observation And Application Of Optical Interference And Diffraction Effects In Reflection From Photochemically Fabricated Gaussian Interfaces, Lynne Koker, Kurt W. Kolasinski Jan 1999

Observation And Application Of Optical Interference And Diffraction Effects In Reflection From Photochemically Fabricated Gaussian Interfaces, Lynne Koker, Kurt W. Kolasinski

Chemistry Faculty Publications

No abstract provided.

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A Comparison Of Observations And Model Simulations Of NoX/NoY In The Lower Stratosphere, R. S. Gao, D. W. Fahey, L. A. Del Negro, Stephen G. Donnelly Ph.D., E. R. Keim, J. A. Neuman, E. Teverovskaia, P. O. Wennberg, T. F. Hanisco, E. J. Lanzendorf, M. H. Proffitt, J. J. Margitan, J. C. Wilson, J. W. Elkins, R. M. Stimpfle, R. C. Cohen, C. T. Mcelroy, T. P. Bui, R. J. Salawitch, S. S. Brown, A. R. Ravishankara, R. W. Portmann, M. K.W. Ko, D. K. Weisenstein, P. A. Newman Jan 1999

A Comparison Of Observations And Model Simulations Of NoX/NoY In The Lower Stratosphere, R. S. Gao, D. W. Fahey, L. A. Del Negro, Stephen G. Donnelly Ph.D., E. R. Keim, J. A. Neuman, E. Teverovskaia, P. O. Wennberg, T. F. Hanisco, E. J. Lanzendorf, M. H. Proffitt, J. J. Margitan, J. C. Wilson, J. W. Elkins, R. M. Stimpfle, R. C. Cohen, C. T. Mcelroy, T. P. Bui, R. J. Salawitch, S. S. Brown, A. R. Ravishankara, R. W. Portmann, M. K.W. Ko, D. K. Weisenstein, P. A. Newman

Chemistry Faculty Publications

Extensive airborne measurements of the reactive nitrogen reservoir (NOy) and its component nitric oxide (NO) have been made in the lower stratosphere. Box model simulations that are constrained by observations of radical and long-lived species and which include heterogeneous chemistry systematically underpredict the NOx (= NO + NO2) to NOy ratio. The model agreement is substantially improved if newly measured rate coefficients for the OH + NO2 and OH + HNO3 reactions are used. When included in 2-D models, the new rate coefficients significantly increase the calculated ozone loss due to NOx and modestly change the calculated ozone abundances in …

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Two-Photon Excitation Of Rhenium Metal-Ligand Complexes, Joseph R. Lakowicz, Felix N. Castellano, Ignacy Gryczynski, Zygmunt Gryczynski, Jonathan D. Dattelbaum Jan 1999

Two-Photon Excitation Of Rhenium Metal-Ligand Complexes, Joseph R. Lakowicz, Felix N. Castellano, Ignacy Gryczynski, Zygmunt Gryczynski, Jonathan D. Dattelbaum

Chemistry Faculty Publications

We describe the emission spectral properties of two rhenium metal-ligand complexes with one and two-photon excitation, Re(bpy)2(CO)3Cl and [Re(bpy)(CO)3CH3CN]+, where bpy is 2,2’-bipyridyl and CH3CN is acetonitrile. Similar emission spectra and intensity decay times characteristic of the metal-to-ligand charge transfer state were observed for one- and two-photon excitation. The lifetime and quantum yield of the acetonitrile complex are approximately 14-fold higher than that of the chloride complex. Both complexes display high anisotropies near 0.33 in frozen solution with one-photon excitation. Two-photon excitation results in anisotropies about 40% larger, …

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The Cytotoxicity And Mode Of Action Of 2,3,4-Trisubstituted Pyrroles And Related Derivatives In Human Tmolt4 Leukemia Cells, John T. Gupton, B. S. Burham, B. D. Byrd, K. E. Krumpe, C. Stokes, J. Shuford, S. Winkle, T. Webb, A. E. Warren, C. R. Barnes, J. Henry, I. H. Hall Jan 1999

The Cytotoxicity And Mode Of Action Of 2,3,4-Trisubstituted Pyrroles And Related Derivatives In Human Tmolt4 Leukemia Cells, John T. Gupton, B. S. Burham, B. D. Byrd, K. E. Krumpe, C. Stokes, J. Shuford, S. Winkle, T. Webb, A. E. Warren, C. R. Barnes, J. Henry, I. H. Hall

Chemistry Faculty Publications

4-Carbechoxy-l-methyl-2-phenacyl-3-phenylpyrrole (9), 4-carbethoxy-2-(4-methoxybcnzoyl)-3-(4-methoxyphcnyl)pyrrole (10) and 2-(4-methoxybenzoyl)-3,4-bis-(4-methoxyphenyl)pyrrole (11) proved to be potent cytotoxic agents against the growth of murine and human leukemias and lymphomas. Selective toxicity was demonstrated against the growth of solid tumors, e.g. human adenocarcinoma of the colon SW480 and ileum HCT-8, glioma U-87-MG, and rat UMR-106 osteosarcoma. A mode of action study in Tmolt4 leukemia cells demonstrated that the agents inhibited de novo purine synthesis at the regulatory sites PRPP-amido transferase, IMP dehydrogenase as well as dihydrofolate reductase resulting in significant inhibition of DNA synthesis in 60 min. Other biochemical sites …

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Phorbol 12-Myristate 13-Acetate Stimulates Lysophosphatidic Acid Secretion From Ovarian And Cervical Cancer Cells But Not From Breast Or Leukemia Cells, Zhongzhou Shen, Jerome Belinson, Richard E. Morton, Yan Xu Dec 1998

Phorbol 12-Myristate 13-Acetate Stimulates Lysophosphatidic Acid Secretion From Ovarian And Cervical Cancer Cells But Not From Breast Or Leukemia Cells, Zhongzhou Shen, Jerome Belinson, Richard E. Morton, Yan Xu

Chemistry Faculty Publications

Lysophosphatidic acid (LPA) is present in ascites from patients with ovarian cancer. It stimulates calcium release and growth of ovarian cancer cells bothin vitroandin vivo.Recently, we found that LPA levels were significantly elevated in plasma from patients with ovarian cancer and other gynecological cancers. In contrast, LPA levels were not elevated in patients with breast cancer and leukemias. In view of this, we investigated whether gynecological cancer cells could produce LPA. LPA was extracted from the supernatant of cells culturedin vitroand purified by thin layer chromatography. After hydrolysis and transmethylation, the fatty acid derivatives were analyzed by gas chromatography. We …

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Multi-Site Proton Interactions With Natural Organic Matter, D. Scott Smith, James R. Kramer Nov 1998

Multi-Site Proton Interactions With Natural Organic Matter, D. Scott Smith, James R. Kramer

Chemistry Faculty Publications

Water samples from various locations in Norway were used to isolate natural organic matter (NOM). The NOM was isolated using both reverse osmosis and low-pressure low-temperature evaporation for each sample site. These samples were titrated from -log[H+] 3 to 11 at 0.1 unit intervals. The data were analyzed using the Discrete Site Analysis (DISI) technique for pKa intervals of 0.2. The acidity constants are grouped into four classes: strong (pKa < 5), intermediate strong (5.1< pKa < 7.5), intermediate weak (7.6 < pKa < 9.2), and weak (pKa > 9.3). All samples, regardless of isolation method, were found to contain strong and weak ligands, along with some intermediate ligands. For the same …

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Fluorescence Analysis For Multi-Site Aluminum Binding To Natural Organic Matter, D. Scott Smith, James R. Kramer Nov 1998

Fluorescence Analysis For Multi-Site Aluminum Binding To Natural Organic Matter, D. Scott Smith, James R. Kramer

Chemistry Faculty Publications

Natural organic matter (NOM) samples isolated from different water sources in Norway were compared using their fluorescence properties. Fluorescence surfaces were observed at pH 4.36 and deconvoluted using SIMPLISMA (Windig and Guilment 1991). There were a total of seven different fluorophores observed for these samples and each sampling site had between four and six ofthe fluorescent components. These components were observed to bind Al during titrations at the same pH. Multiresponse titration curves were fit using the method of Smith and Kramer (1998) and most of the binding strengths are similar to values for Suwannee River fulvic acid (1ogK’ between …

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Conserved Geometrical Base-Pairing Patterns In Rna, Neocles B. Leontis, Eric Westhof Nov 1998

Conserved Geometrical Base-Pairing Patterns In Rna, Neocles B. Leontis, Eric Westhof

Chemistry Faculty Publications

RNA molecules fold into a bewildering variety of complex 3D structures. Almost every new RNA structure obtained at high resolution reveals new, unanticipated structural motifs, which we are rarely able to predict at the current stage of our theoretical understanding. Even at the most basic level of specific RNA interactions – base-to-base pairing – new interactions continue to be uncovered as new structures appear. Compilations of possible non-canonical base-pairing geometries have been presented in previous reviews and monographs (Saenger, 1984; Tinoco, 1993). In these compilations, the guiding principle applied was the optimization of hydrogen-bonding. All possible pairs with two standard …

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Comparison Between Dc-8 And Er-2 Species Measurements In The Tropical Middle Troposphere: No, NoY, O3, Co2, Ch4, And N2O, A. J. Weinheimer, D. D. Montzka, T. L. Campos, J. G. Walega, B. A. Ridley, Stephen G. Donnelly Ph.D., E. R. Keim, L. A. Del Negro, M. H. Proffitt, J. J. Margitan, K. A. Boering, A. E. Andrews, B. C. Daube, S. C. Wofsy, B. E. Anderson, J. E. Collins, G. W. Sachse, S. A. Vay, J. W. Elkins, P. R. Wamsley, E. L. Atlas, F. Flocke, S. Schauffler, C. R. Webster, R. D. May, M. Loewenstein, J. R. Podolske, T. P. Bui, K. R. Chan, S. W. Bowen, M. R. Schoeberl, L. R. Lait Sep 1998

Comparison Between Dc-8 And Er-2 Species Measurements In The Tropical Middle Troposphere: No, NoY, O3, Co2, Ch4, And N2O, A. J. Weinheimer, D. D. Montzka, T. L. Campos, J. G. Walega, B. A. Ridley, Stephen G. Donnelly Ph.D., E. R. Keim, L. A. Del Negro, M. H. Proffitt, J. J. Margitan, K. A. Boering, A. E. Andrews, B. C. Daube, S. C. Wofsy, B. E. Anderson, J. E. Collins, G. W. Sachse, S. A. Vay, J. W. Elkins, P. R. Wamsley, E. L. Atlas, F. Flocke, S. Schauffler, C. R. Webster, R. D. May, M. Loewenstein, J. R. Podolske, T. P. Bui, K. R. Chan, S. W. Bowen, M. R. Schoeberl, L. R. Lait

Chemistry Faculty Publications

We compare measurements of six species taken aboard NASA DC-8 and ER-2 aircraft during two flight legs in the tropical middle troposphere near Hawaii. NO, NOy, O3, CH4, and N2O measurements agree to within the limits set by the known systematic errors. For CO2, which can be measured with better relative precision than the other five species, differences in measured values from the two platforms are slightly larger than expected if the air masses sampled by the two aircraft were indeed similar in CO2 composition to better than 0.08%. Copyright 1998 by the American Geophysical Union.

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Simultaneous Formation Of Functional Leading And Lagging Strand Holoenzyme Complexes On A Small, Defined Dna Substrate, Anthony J. Berdis, Stephen J. Benkovic Sep 1998

Simultaneous Formation Of Functional Leading And Lagging Strand Holoenzyme Complexes On A Small, Defined Dna Substrate, Anthony J. Berdis, Stephen J. Benkovic

Chemistry Faculty Publications

The biochemical characterization of leading and lagging strand DNA synthesis by bacteriophage T4 replication proteins has been addressed utilizing a small, defined primer/template. The ATP hydrolysis activity of 44/62, the clamp loading complex responsible for holoenzyme assembly, was monitored during assembly of both the leading and lagging strand holoenzyme complex. The ATPase activity of 44/62 diminishes once a functional holoenzyme is assembled on both the leading and lagging strand. The assembly of the lagging strand holoenzyme is facilitated by several factors including biotinylated streptavidin blocks at the end of the fork strands, preassembly of the leading strand holoenzyme, and by …

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Electron Transfer Catalysis Of The Hydrogenolysis Of Acyl Dicarbonyl Cyclopentadienyliron Complexes By Tributyltin Hydride, Christian Amatore, Mekki Bayachou, Olivier Buriez, Jean Noel Verpeaux Sep 1998

Electron Transfer Catalysis Of The Hydrogenolysis Of Acyl Dicarbonyl Cyclopentadienyliron Complexes By Tributyltin Hydride, Christian Amatore, Mekki Bayachou, Olivier Buriez, Jean Noel Verpeaux

Chemistry Faculty Publications

The conversion of acyl dicarbonyl cyclopentadienyliron compounds Cp(CO)2Fe(COR) into aldehydes is not straightforward. It is shown here, mainly from electrochemical results, that the hydrogenolysis of the metal acyl bond can be efficiently achieved by trialkytin hydrides under very mild conditions, according to a chain reaction process initiated by an electron transfer to the acyl complex. The expected aldehyde is formed together with the heterobinuclear iron-tin complex.

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Sequence-Specific Photomodification Of Dna By An Oligonucleotide-Phenanthrodihydrodioxin Conjugate, Kestutis G. Bendinskas, Andreas Harsch, R. Marshall Wilson, W. Robert Midden Sep 1998

Sequence-Specific Photomodification Of Dna By An Oligonucleotide-Phenanthrodihydrodioxin Conjugate, Kestutis G. Bendinskas, Andreas Harsch, R. Marshall Wilson, W. Robert Midden

Chemistry Faculty Publications

We introduce a new member of a family of photochemically active oligonucleotide conjugates. A Phenanthrodihydrodioxin (PDHD)-based agent was synthesized and covalently linked to a 5'-end of the 9-mer oligonucleotide via a hexamethylene linker. The conjugate hybridized to a complementary 30-nucleotide-long target and efficiently cleaved it in a sequence specific manner. Up to 67% of target was specifically damaged (51% cross-links and 16% direct cleavage). While the photosensitizer alone nonspecifically damaged only Gs in a single-stranded target, its conjugate cross-linked to and damaged also A, T, and C sites in a target in agreement with duplex and tripler formation.

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