Physical Sciences and Mathematics | Open Access Articles

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

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

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

Chemistry Faculty Publications

The interaction of 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)p (T4MPyP(4+)) with the oligonucleotide DNA duplex [d(GCACGTGC)](2) was studied by two-dimensional (1)H NMR spectroscopy, optical absorbance, circular dichroism, and molecular dynamics simulation employing particle mesh Ewald methods. T4MPyP(4+) 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]. T4MPyP(4+) 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 observed in the complex showed that …

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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

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

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

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

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

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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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

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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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

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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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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Chemistry Faculty Publications

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

Chemistry Faculty Publications

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

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

Chemistry Faculty Publications

[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

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

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

Chemistry Faculty Publications

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

Chemistry Faculty Publications

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

Chemistry Faculty Publications

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

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

Chemistry Faculty Publications

Chemistry Faculty Publications

Chemistry Faculty Publications