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A Redox-Neutral Catechol Synthesis, Q. Wu, D. Yan, Y. Chen, T. Wang, F. Xiong, W. Wei, Y. Lu, W. Sun, Jie Jack Li, J. Zhao
A Redox-Neutral Catechol Synthesis, Q. Wu, D. Yan, Y. Chen, T. Wang, F. Xiong, W. Wei, Y. Lu, W. Sun, Jie Jack Li, J. Zhao
Chemistry Faculty Publications
Ubiquitous tyrosinase catalyses the aerobic oxidation of phenols to catechols through the binuclear copper centres. Here, inspired by the Fischer indole synthesis, we report an iridium-catalysed tyrosinase-like approach to catechols, employing an oxyacetamide-directed C–H hydroxylation on phenols. This method achieves one-step, redox-neutral synthesis of catechols with diverse substituent groups under mild conditions. Mechanistic studies confirm that the directing group (DG) oxyacetamide acts as the oxygen source. This strategy has been applied to the synthesis of different important catechols with fluorescent property and bioactivity from the corresponding phenols. Finally, our method also provides a convenient route to 18O-labelled catechols using …
A Bioinspired And Biocompatible Ortho-Sulfiliminyl Phenol Synthesis, Feng Xiong, Liang Lu, Tian-Yu Sun, Qian Wu, Dingyuan Yan, Ying Chen, Xinhao Zhang, Wei Wei, Yi Lu, Wei-Yin Sun, Jie Jack Li, Jing Zhao
A Bioinspired And Biocompatible Ortho-Sulfiliminyl Phenol Synthesis, Feng Xiong, Liang Lu, Tian-Yu Sun, Qian Wu, Dingyuan Yan, Ying Chen, Xinhao Zhang, Wei Wei, Yi Lu, Wei-Yin Sun, Jie Jack Li, Jing Zhao
Chemistry Faculty Publications
Synthetic methods inspired by Nature often offer unique advantages including mild conditions and biocompatibility with aqueous media. Inspired by an ergothioneine biosynthesis protein EgtB, a mononuclear non-haem iron enzyme capable of catalysing the C–S bond formation and sulfoxidation, herein, we discovered a mild and metal-free C–H sulfenylation/intramolecular rearrangement cascade reaction employing an internally oxidizing O–N bond as a directing group. Our strategy accommodates a variety of oxyamines with good site selectivity and intrinsic oxidative properties. Combining an O–N bond with an X–S bond generates a C–S bond and an S¼N bond rapidly. The newly discovered cascade reaction showed excellent chemoselectivity …
The Contribution Of Methionine To The Stability Of The Escherichia Coli Metniq Abc Transporter-Substrate Binding Protein Complex, P. Nguyen, N. Kadaba, J. Y. Lai, Janet G. Yang, D. C. Rees
The Contribution Of Methionine To The Stability Of The Escherichia Coli Metniq Abc Transporter-Substrate Binding Protein Complex, P. Nguyen, N. Kadaba, J. Y. Lai, Janet G. Yang, D. C. Rees
Chemistry Faculty Publications
Despite the ubiquitous role of ATP-binding cassette (ABC) importers in nutrient uptake, only the Escherichia coli maltose and vitamin B12 ABC transporters have been structurally characterized in multiple conformations relevant to the alternating access transport mechanism. To complement our previous structure determination of the E. coli MetNI methionine importer in the inward facing conformation (Kadaba et al. (2008) Science 321, 250–253), we have explored conditions stabilizing the outward facing conformation. Using two variants, the Walker B E166Q mutation with ATP+EDTA to stabilize MetNI in the ATP-bound conformation and the N229A variant of the binding protein MetQ, shown in …
The Allosteric Regulatory Mechanism Of The Escherichia Coli Metni Methionine Atp Binding Cassette (Abc) Transporter, Janet G. Yang, D. C. Rees
The Allosteric Regulatory Mechanism Of The Escherichia Coli Metni Methionine Atp Binding Cassette (Abc) Transporter, Janet G. Yang, D. C. Rees
Chemistry Faculty Publications
The MetNI methionine importer of Escherichia coli, an ATP binding cassette (ABC) transporter, uses the energy of ATP binding and hydrolysis to catalyze the high affinity uptake of d- and l-methionine. Early in vivo studies showed that the uptake of external methionine is repressed by the level of the internal methionine pool, a phenomenon termed transinhibition. Our understanding of the MetNI mechanism has thus far been limited to a series of crystal structures in an inward-facing conformation. To understand the molecular mechanism of transinhibition, we studied the kinetics of ATP hydrolysis using detergent-solubilized MetNI. We find that transinhibition is …
The Dissociation Energy Of The New Diatomic Molecules Sipb And Gepb, A Ciccioli, G Gigli, Giovanni Meloni, E Testani, National Library Of Medicine
The Dissociation Energy Of The New Diatomic Molecules Sipb And Gepb, A Ciccioli, G Gigli, Giovanni Meloni, E Testani, National Library Of Medicine
Chemistry Faculty Publications
The diatomic molecules SiPb and GePb were for the first time identified by producing high temperature vapors of the constituent pure elements in a "double-oven-like" molecular-effusion assembly. The partial pressures of the atomic, heteronuclear, and homonuclear gaseous species observed in the vapor, namely, Si, Ge, Pb, SiPb, GePb, Pb2, Gen, and Sin (n=2-3), were mass-spectrometrically measured in the overall temperature ranges 1753-1961 K (Ge-Pb) and 1992-2314 K (Si-Pb). The dissociation energies of the new species were determined by second- and third-law analyses of both the direct dissociation reactions and isomolecular exchange reactions involving homonuclear molecules. The selected values of the …
The Visual Image Of Chemistry: Perspectives From The History Of Art And Science, Joachim Schummer, Tami I. Spector
The Visual Image Of Chemistry: Perspectives From The History Of Art And Science, Joachim Schummer, Tami I. Spector
Chemistry Faculty Publications
In this paper we investigate the most important visual stereotypes of chemistry as they occur in current portraits of chemists, depictions of chemical plants, and images of chemical glassware and apparatus. By studying the historical origin and development of these stereotypes within the broader context of the history of art and science, and by applying aesthetic and cultural theories, we explore what these images implicitly communicate about the chemical profession to the public. We conclude that chemists, along with commercial artists, have unknowingly created a visual image of chemistry that frequently conveys negative historical associations, ranging from imposture to kitsch. …
Spectroscopic Characterization Of The Ground And Low-Lying Electronic States Of Ga2n Via Anion Photoelectron Spectroscopy., S M. Sheehan, Giovanni Meloni, B F. Parsons, N Wehres, D M. Neumark
Spectroscopic Characterization Of The Ground And Low-Lying Electronic States Of Ga2n Via Anion Photoelectron Spectroscopy., S M. Sheehan, Giovanni Meloni, B F. Parsons, N Wehres, D M. Neumark
Chemistry Faculty Publications
Anion photoelectron spectra of Ga2N− were measured at photodetachment wavelengths of 416nm(2.978eV), 355nm(3.493eV), and 266nm(4.661eV). Both field-free time-of-flight and velocity-map imaging methods were used to collect the data. The field-free time-of-flight data provided better resolution of the features, while the velocity-map-imaging data provided more accurate anisotropy parameters for the peaks. Transitions from the ground electronic state of the anion to two electronic states of the neutral were observed and analyzed with the aid of electronic structure calculations and Franck-Condon simulations. The ground-state band was assigned to a transition between linear ground states of Ga2N−(XΣg+1) and Ga2N(XΣu+2), yielding the electron affinity …
Mass Spectrometric And Computational Study Of Snpb In The Gas Phase, G Gigli, Giovanni Meloni, M Carrozzino
Mass Spectrometric And Computational Study Of Snpb In The Gas Phase, G Gigli, Giovanni Meloni, M Carrozzino
Chemistry Faculty Publications
The SnPb molecule has been identified in a Knudsen effusion mass spectrometry experiment. The direct dissociation reaction and two isomolecular exchange reactions involving the Sn(2) and Pb(2) molecules have been studied, in the 1426-1705 K range of temperatures, using both second and third law procedures. The D(degree)0(SnPb,g) has been derived, for the first time, as (122.6+/-4.0) kJ mol(-1). Density functional and ab initio calculations up to the coupled clusters level of theory were also performed. In addition, the anion dissociation energy D(degree)0(SnPb(-),g) of (179.2+/-4.2) kJ mol(-1) was determined using the D(degree)0(SnPb,g) mass spectrometric value derived in this investigation and literature …
Gallium Oxide And Dioxide: Investigation Of The Ground And Low-Lying Electronic States Via Anion Photoelectron Spectroscopy, Giovanni Meloni, S M. Sheehan, D M. Neumark
Gallium Oxide And Dioxide: Investigation Of The Ground And Low-Lying Electronic States Via Anion Photoelectron Spectroscopy, Giovanni Meloni, S M. Sheehan, D M. Neumark
Chemistry Faculty Publications
The GaO and GaO2 molecules were investigated using negative ion photoelectron spectroscopy. All the photoelectron spectra showed vibrationally resolved progressions. With the aid of electronic structure calculations and Franck-Condon spectral simulations, different molecular parameters and energetics of GaO-/GaO and GaO2-/GaO2 were determined, including the electron affinity of GaO, the vibrational frequency of GaO-, and the term energy, spin-orbit splitting, and vibrational frequency for the first excited A 2PiOmega state of GaO. The GaO2- photoelectron spectra comprised three bands assigned as transitions from the linear X 1Sigma(g)+ ground state of GaO2- to three linear neutral states: the A 2Pi(g), B 2Pi(u), …
Response To “Comment On ‘Atomization Energies And Enthalpies Of Formation Of The Snbi[Sub N] (N=1–3) Gaseous Molecules By Knudsen Cell Mass Spectrometry’ ” [J. Chem. Phys. 118, 4766 (2003)], Giovanni Meloni, Karl A. Gingerich
Response To “Comment On ‘Atomization Energies And Enthalpies Of Formation Of The Snbi[Sub N] (N=1–3) Gaseous Molecules By Knudsen Cell Mass Spectrometry’ ” [J. Chem. Phys. 118, 4766 (2003)], Giovanni Meloni, Karl A. Gingerich
Chemistry Faculty Publications
Discusses atomization energies and enthalpies of formation of gaseous molecules of compounds containing tin and bismuth by Knudsen cell mass spectrometry. Procedure followed to evaluate the mass spectrometric equilibrium data regarding these molecules; Statistics of atomization energies and enthalpies calculated; Factors contributing to the necessity of high level of calculations to obtain these figures.
Anion Photoelectron Spectroscopy Of Solvated Transition State Precursors, Harry Gomez, Giovanni Meloni, James Madrid, D M. Neumark
Anion Photoelectron Spectroscopy Of Solvated Transition State Precursors, Harry Gomez, Giovanni Meloni, James Madrid, D M. Neumark
Chemistry Faculty Publications
Photoelectron (PE) spectra have been collected for the clustered bihalide anions XHX−∙(M) (X=Br, I) and BrHI−∙(M), where M=H2O, HBr, and HI, in order to probe the effects of strongly solvating species on the PE spectra of transition state precursor anions. The PE spectra of the XHX−∙(H2O) ions show similar vibrational progressions as the spectra of the bare BrHBr− and IHI− anions, indicating that photodetachment of the bare and hydrated ions accesses similar XHX transition state geometries on the X+HX reactionpotential energy surfaces. These results are consistent with electronic structure calculations that predict a double hydrogen-bonded XHX−∙(H2O) structure in which the …
Atomization Energies And Enthalpies Of Formation Of The Snbin (N=1-3) Gaseous Molecules By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich
Atomization Energies And Enthalpies Of Formation Of The Snbin (N=1-3) Gaseous Molecules By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich
Chemistry Faculty Publications
The equilibria involving the gaseous species SnBi, SnBi2, and SnBi3 above the condensed system Bi–Sn contained in a graphite cell have been investigated by the Knudsen effusion technique combined with mass spectrometry. Third law enthalpies for the reactionsSnBin(g)=Sn(cond)+nBi(g), n=1–3, were evaluated. By combining the experimental reactionenthalpies with the appropriate thermodynamic data taken from literature, the following atomization energies, ΔaHo0, and enthalpies of formation,ΔfHo298.15, in kJ mol−1, have been derived: SnBi, 191.1±12.0 and 317.5±12.0; SnBi2, 415.2±15.0 and 303.0±15.0; SnBi3, 603.4±18.0 and 323.0±18.0.
Photoelectron Spectroscopy Of Clh2 - And Cld2 -: A Probe Of The Cl+H2 Van Der Waals Well And Spin-Orbit Excited States, Michael J. Ferguson, Giovanni Meloni, Harry Gomez, D M. Neumark
Photoelectron Spectroscopy Of Clh2 - And Cld2 -: A Probe Of The Cl+H2 Van Der Waals Well And Spin-Orbit Excited States, Michael J. Ferguson, Giovanni Meloni, Harry Gomez, D M. Neumark
Chemistry Faculty Publications
Photoelectron (PE) spectra of ClH−2 and ClD−2 were measured at 299 nm (4.154 eV). Photodetachment of these anions accesses the prereactive van der Waals well on the ground stateCl+H2potential energy surface, as well as the low-lying spin–orbit excited states resulting from the interaction of Cl and Cl* with H2. The PE spectra are dominated by two relatively narrow peaks corresponding to transitions to the neutral Cl⋅H2 and Cl*⋅H2 complexes. The energetics and widths of these features are interpreted in terms of the properties of the anion and neutral potential energy surfaces.
Experimental And Computational Study Of The New Gaseous Molecules Omnf And Omnf[Sub 2], G Balducci, M Campodonico, G Gigli, Giovanni Meloni, S N. Cesaro
Experimental And Computational Study Of The New Gaseous Molecules Omnf And Omnf[Sub 2], G Balducci, M Campodonico, G Gigli, Giovanni Meloni, S N. Cesaro
Chemistry Faculty Publications
The new gaseous species OMnF and OMnF2 were identified and studied by high-temperature Knudsen Cell Mass Spectrometry. Their thermochemical atomization energies were derived through the study of several all-gas equilibria in the temperature range 1735–1913 K. FTIR matrix isolation experiments together with ab initio and density functional calculations were performed to determine the molecular parameters, bond distances, and vibrational frequencies of OMnF(g) and OMnF2(g) . The results allowed us to evaluate a set of thermal functions for the new species that were used in the evaluation of the equilibrium data. The proposed atomization energies and enthalpies of formation are DaH0 …
Thermodynamic Investigation Of The Si7 And Si8 Clusters By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich
Thermodynamic Investigation Of The Si7 And Si8 Clusters By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich
Chemistry Faculty Publications
The Knudsen cell mass spectrometric method has been employed to measure the partial pressures of the Si[sub 7] and Si[sub 8] clusters under equilibrium conditions above liquid silicon, contained in a boron nitride liner inside a graphite Knudsen cell. Gaussian 2 (G2) theory and B3LYP density functional method were employed to determine the geometry, the vibrational frequencies, and the binding energy of the Si[sub 8] cluster. From the all-gas analyzed equilibria the following atomization enthalpies, Δ[sub a]H[sub 0][sup o](Si[sub n]), and enthalpies of formation, Δ[sub f]H[sub 298.15][sup o](Si[sub n]), in kJ mol-1, have been obtained: Si[sub 7], 2381±36 and …
Structure And Thermodynamic Stability Of The Osc And Osc2 Molecules By Theoretical Calculations And By Knudsen Cell Mass Spectrometry, Giovanni Meloni, L M. Thomson, Karl A. Gingerich
Structure And Thermodynamic Stability Of The Osc And Osc2 Molecules By Theoretical Calculations And By Knudsen Cell Mass Spectrometry, Giovanni Meloni, L M. Thomson, Karl A. Gingerich
Chemistry Faculty Publications
Knudsen cell mass spectrometric equilibrium measurements together with theoretical computations have been employed to gain structural and thermodynamic information of the OsC and OsC[sub 2] molecules. Several levels of theory have been applied to determine the structures, molecular parameters, and physico-chemical properties of OsC(g) and OsC[sub 2](g), and their singly charged ions. Complete active space self-consistent field (CASSCF) calculations were performed on the apparent [sup 3]Σ[sup -] ground state and first [sup 3]Δ excited state of OsC. From the analyzed gaseous equilibria and the thermal functions calculated from the computed molecular parameters, the following atomization enthalpies, Δ[sub a]H[sub 0][sup o](OsC,g) …
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
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 …
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
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 …
Knudsen Cell Mass Spectrometric Investigation Of The B2n Molecule, Giovanni Meloni, M Sai Baba, Karl A. Gingerich
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.
Thermodynamic Study Of The Gaseous Molecules Al2n, Aln, And Al2n2 By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich
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 …
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
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 …
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
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 …
Experimental And Theoretical Investigations Of The Structure And The Stability Of The Bnsi Molecule, Giovanni Meloni, R Viswanathan
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.
Thermodynamic Investigation Of The Ainc And Aicn Isomers By Knudsen Cell Mass Spectrometry, Giovanni Meloni, Karl A. Gingerich
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.
Dissociation Energies Of The Ga2, In2, And Gain Molecules, G Balducci, G Gigli, Giovanni Meloni
Dissociation Energies Of The Ga2, In2, And Gain Molecules, G Balducci, G Gigli, Giovanni Meloni
Chemistry Faculty Publications
The group III metal dimers Ga2 and In2 and the newly identified intermetallic molecule GaIn were investigated in a Knudsen cell-mass spectrometric study of the vapors over gallium–indium alloys. From the all-gas equilibria analyzed by the second-law and third-law methods the following dissociation energies were derived; D00 (Ga2)=110.8±4.9 kJ mol−1, D00 (In2)=74.4±5.7 kJ mol−1, D00 (GaIn)=90.7±3.7 kJ mol−1. The value here measured for the dissociation energy of In2 is discussed and compared with a previous experimental determination and with the results of more recent theoretical investigations.
Identification Of The Adp-L-Glycero-D-Manno-Heptose-6-Epimerase (Rfad) And Heptosyltransferase Ii (Rfaf) Biosynthesis Genes From Nontypeable Haemophilus Influenzae 2019, W A. Nichols, B W. Gibson, William Melaugh, N G. Lee, M Sunshine, M A. Apicella
Identification Of The Adp-L-Glycero-D-Manno-Heptose-6-Epimerase (Rfad) And Heptosyltransferase Ii (Rfaf) Biosynthesis Genes From Nontypeable Haemophilus Influenzae 2019, W A. Nichols, B W. Gibson, William Melaugh, N G. Lee, M Sunshine, M A. Apicella
Chemistry Faculty Publications
Haemophilus influenzae is an important human pathogen. The lipooligosaccharide (LOS) of H. influenzae has been implicated as a virulence determinant. To better understand the assembly of LOS in nontypeable H. influenzae (NtHi), we have cloned and characterized the rfaD and rfaF genes of NtHi 2019, which encode the ADP-L-glycero-D-manno-heptose-6-epimerase and heptosyltransferase II enzymes, respectively. This cloning was accomplished by the complementation of Salmonella typhimurium lipopolysaccharide (LPS) biosynthesis gene mutants. These deep rough mutants are novobiocin susceptible until complemented with the appropriate gene. In this manner, we are able to use novobiocin resistance to select for specific NtHi LOS inner core …
Characterization Of A Transposon Tn916-Generated Mutant Of Haemophilus Ducreyi 35000 Defective In Lipooligosaccharide Biosynthesis, B W. Gibson, A A. Campagnari, William Melaugh, M A. Apicella, S Grass, Jing Wang, Katherine L. Palmer, R S. Munson
Characterization Of A Transposon Tn916-Generated Mutant Of Haemophilus Ducreyi 35000 Defective In Lipooligosaccharide Biosynthesis, B W. Gibson, A A. Campagnari, William Melaugh, M A. Apicella, S Grass, Jing Wang, Katherine L. Palmer, R S. Munson
Chemistry Faculty Publications
To define the role of the surface lipooligosaccharide (LOS) of Haemophilus ducreyi in the pathogenesis of chancroid, Tn916 mutants of H. ducreyi 35000 defective in expression of the murine monoclonal antibody (MAb) 3F11 epitope on H. ducreyi LOS were identified by immunologic screening. One mutant, designated 1381, has an LOS which lacks the MAb 3F11 epitope and migrates with an increased mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The gene disrupted by the Tn916 element in strain 1381 was identified by cloning the sequences flanking the Tn916 element. The sequences were then used to probe a lambda DASHII genomic library. …
The Lipooligosaccharides Of Haemophilus Ducreyi Are Highly Sialylated, William Melaugh, A A. Campagnari, B W. Gibson
The Lipooligosaccharides Of Haemophilus Ducreyi Are Highly Sialylated, William Melaugh, A A. Campagnari, B W. Gibson
Chemistry Faculty Publications
The major lipooligosaccharides of the sexually transmitted pathogen Haemophilus ducreyi 35000 have been previously found to terminate in N-acetyllactosamine and sialyl-N-acetyllactosamine, Neu5Ac alpha 2-->3Gal beta 1-->4GlcNAc (W. Melaugh, N. J. Phillips, A. A. Campagnari, M. V. Tullius, and B. W. Gibson, Biochemistry 33: 13070-13078, 1994). In this study, mass spectrometry and composition analyses have shown that the lipooligosaccharides from three other H. ducreyi strains also contain N-acetyllactosamine and are highly sialylated (approximately 30 to 50%), although one African strain was found to contain neither of these structural features.
Use Of Pyocin To Select A Haemophilus Ducreyi Variant Defective In Lipooligosaccharide Biosynthesis, A A. Campagnari, R Karalus, M A. Apicella, William Melaugh, A J. Lesse, B W. Gibson
Use Of Pyocin To Select A Haemophilus Ducreyi Variant Defective In Lipooligosaccharide Biosynthesis, A A. Campagnari, R Karalus, M A. Apicella, William Melaugh, A J. Lesse, B W. Gibson
Chemistry Faculty Publications
Haemophilus ducreyi, a cause of genital ulcer disease in developing countries, appears to facilitate the heterosexual transmission of the human immunodeficiency virus in Africa. Despite an increase in studies of this gram-negative human pathogen, little is known about the pathogenesis of chancroid. Our studies have shown that the lipooligosaccharides (LOS) of H. ducreyi may play an important role in ulcer formation. Monoclonal antibody and mass spectrometric analyses identified a terminal trisaccharide present on H. ducreyi LOS that is immunochemically similar to human paragloboside. This epitope is present on the LOS of Neisseria gonorrhoeae, and it may be the site of …
Investigation Of The Structural Heterogeneity Of Lipooligosaccharides From Pathogenic Haemophilus And Neisseria Species And Of R-Type Lipopolysaccharides From Salmonella Typhimurium By Electrospray Mass Spectrometry, B W. Gibson, William Melaugh, Nancy J. Phillips, M A. Apicella, A A. Campagnari, J M. Griffiss
Investigation Of The Structural Heterogeneity Of Lipooligosaccharides From Pathogenic Haemophilus And Neisseria Species And Of R-Type Lipopolysaccharides From Salmonella Typhimurium By Electrospray Mass Spectrometry, B W. Gibson, William Melaugh, Nancy J. Phillips, M A. Apicella, A A. Campagnari, J M. Griffiss
Chemistry Faculty Publications
Heterogeneity in the lipooligosaccharides (LOS) of pathogenic Haemophilus and Neisseria species is evident from the multiplicity of components observed with electrophoretic analyses. Knowledge of the precise structures that make up these diverse LOS molecules is clearly the key to reaching an understanding of pathogenic processes such as phase variation and molecular mimicry. Except for a few cases, little is known about the specific structural features of LOS that underlie phase variation and molecular mimicry, partly because of the inherent difficulties in the structural elucidation of these complex glycolipids. In the lipopolysaccharides (LPS) from Salmonella typhimurium and Escherichia coli, rough, or …