Open Access. Powered by Scholars. Published by Universities.®

Chemistry Commons™

Open Access. Powered by Scholars. Published by Universities.®

2006

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 571 - 592 of 592

Full-Text Articles in Chemistry

Integrating Micro-Scale Separations To Matrix Assisted Laser Desorption And Ioniation Time Of Flight Mass Spectrometry (Maldi-Tof-Ms) For Protein Analysis, Harrison K. Musyimi Jan 2006

Integrating Micro-Scale Separations To Matrix Assisted Laser Desorption And Ioniation Time Of Flight Mass Spectrometry (Maldi-Tof-Ms) For Protein Analysis, Harrison K. Musyimi

LSU Doctoral Dissertations

This dissertation describes the integration of micro-scale separations to matrix assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI TOF MS) for protein analysis. MALDI MS provides unsurpassed accurate mass measurements of intact bio-molecules, for example peptides and proteins, which in turn generate high molecular specificity enabling the identity, function and structure of these molecules to be characterized. However, in order to realize the full potential of MS in proteomic studies, integrated sample processing on automated and high throughput platforms is required to address the complexity, diversity and the dynamic range of proteomic analysis. The work described here contributes towards …

Go to article

Direct Detection Of Homocysteine And Syntheses Of Lanthanide Complexes As Biosensors, Weihua Wang Jan 2006

Direct Detection Of Homocysteine And Syntheses Of Lanthanide Complexes As Biosensors, Weihua Wang

LSU Doctoral Dissertations

At elevated levels, homocysteine (Hcy) is a risk factor for cardiovascular diseases and Alzheimer’s disease. It’s also implicated in a number of other diseases such as neural tube defects, pregnancy complications, and renal failures. The monitoring of Hcy levels in plasma is of current concern. To date, the biochemical mechanism by which Hcy is involved in disease states is unclear. Herein, we describe highly selective colorimetric methods for the direct determination of Hcy. Inexpensive, commercially available materials are reported. The results show potential application for the detection of Hcy in human blood plasma. Additionally, new HPLC postcolumn detection methods for …

Go to article

Applications Of Titanium-Mediated Reductive Coupling And Cyclocarbonylation Reactions Toward Natural Product Synthesis, Maria A. Appeaning Jan 2006

Applications Of Titanium-Mediated Reductive Coupling And Cyclocarbonylation Reactions Toward Natural Product Synthesis, Maria A. Appeaning

LSU Doctoral Dissertations

Previous work in our laboratory has demonstrated not only a synthetic value of tandem reductive cyclization - carbonylation reactions in the preparation of complex molecules but also the interesting stereoselectivity observed therein. The first part of this work employs the titanium-mediated cyclocarbonylation of tethered dienals for the synthesis of prostaglandin analogues, in particular PGF2α and methyl jasmonate. Based on this hetero Pauson-Khand strategy, we have established an efficient racemic route to both the prostaglandin and the methyl jasmonate core skeletons. Moderate to excellent selectivities with regard to the hetero Pauson-Khand reaction were observed in both cases. The second part …

Go to article

Ab Initio Molecular Dynamics Simulations Of Methylaluminoxane (Mao) Synthesis By Hydrolysis Of Trimethylaluminum, Lacramioara Negureanu Jan 2006

Ab Initio Molecular Dynamics Simulations Of Methylaluminoxane (Mao) Synthesis By Hydrolysis Of Trimethylaluminum, Lacramioara Negureanu

LSU Doctoral Dissertations

MAO is the co-catalyst in the metallocene catalytic systems, which are widely used in single site olefin polymerization due to their high stereoselectivity. To date, the precise structure of MAO, the particular compound or compounds catalytically active in MAO, have eluded researchers. MAO, a white amorphous powder, is not a good sample for a direct spectroscopic characterization, and its NMR spectra are broad and almost featureless. Many structural models have been proposed but none are generally accepted. In the first part of this work the MAO formation mechanism was addressed. Molecular dynamics simulations at MP2 configuration interaction theory level have …

Go to article

Development Of Analytical Techniques For The Analysis Of Submicron Particles And Protein Aggregates, Yohannes H. Rezenom Jan 2006

Development Of Analytical Techniques For The Analysis Of Submicron Particles And Protein Aggregates, Yohannes H. Rezenom

LSU Doctoral Dissertations

The goal of the research presented in this dissertation is to develop analytical techniques for the analysis of heterogeneous mixtures of submicron particles and protein aggregates. In Chapter 2, a simple and reproducible technique for constructing perfectly aligned gaps in fused-silica capillaries has been developed for postcolumn reagent addition with capillary electrophoresis (CE) to take advantage of laser-induced fluorescence (LIF) detection. This technique uses laser ablation with a Nd:YAG laser to create gaps of 14.0 ¡Ó 2.2 ƒÝm. These structures have been used for reagent addition for postcolumn derivatization with LIF detection and have been tested for the separation of …

Go to article

Synthesis, Characterization And Properties Of Cooper(Ii) Beta-Diketonate Macrocycles, Sylvester Burton Jan 2006

Synthesis, Characterization And Properties Of Cooper(Ii) Beta-Diketonate Macrocycles, Sylvester Burton

LSU Doctoral Dissertations

This dissertation deals with the synthesis and properties of multidentate β-diketone ligands and their transition-metal complexes. (1) We prepared two bis(β-diketones), C1BAH2 and p-XBAH2 (see sketch below), determined their crystal structures, and studied their reactions with copper(II). We envisioned that they would form macrocyclic complexes with 3-6 metal atoms. In both cases, although the initial products are soluble, as expected for the desired molecular products, we were unable to isolate well-behaved molecular solids. In the case of C1BAH2, this may be because the cyclic product requires an unusual combination of conformations of …

Go to article

Infrared Laser Desorption/Ionization Mass Spectrometry: Fundamental And Applications, Mark Little Jan 2006

Infrared Laser Desorption/Ionization Mass Spectrometry: Fundamental And Applications, Mark Little

LSU Doctoral Dissertations

This dissertation on infrared laser desorption/ionization mass spectrometry encompasses fundamental studies of the desorption/ionization process and direct-from-gel laser desorption/ionization applications. Understanding of the fundamentals behind desorption and ionization can lead to improvements in the technique and to new applications. Experiments aimed at advancing this goal are wavelength studies and two-laser infrared/ultraviolet matrix-assisted laser desorption/ionization experiments. The direct-from-gel laser desorption/ionization application in which infrared laser desorption/ionization of analytes directly ionized after gel electrophoretic separation will also be presented. Protein and peptide standards were used as test analytes and the infrared lasers used were a 10.6 micrometers carbon-dioxide laser and a mid-IR …

Go to article

Crystal And Electronic Structures Of Linh₂, Jinbo Yang, X.-D. Zhou, Qingsheng Cai, William Joseph James, William B. Yelon Jan 2006

Crystal And Electronic Structures Of Linh₂, Jinbo Yang, X.-D. Zhou, Qingsheng Cai, William Joseph James, William B. Yelon

Materials Science and Engineering Faculty Research & Creative Works

The crystal structure of LiNH2 was reinvestigated using powder neutron diffraction with high sensitivity. The compound crystallizes in the tetragonal space group I4 with lattice parameters α = b= 5.034 42 (24) Å, c = 10.255 58 (52) Å. It is found that H atoms occupy 8g1(0.2429, 0.1285, 0.1910) and 8g2 (0.3840, 0.3512, 0.1278) sites. The bond lengths between the nearest nitrogen and hydrogen atoms are 0.986 and 0.942 Å, respectively. The bond angle between H-N-H is about 99.97°. These results are significantly different from those of previous experiments. The electronic structure was calculated according to the revised structural …

Go to article

Spirobicyclic Diamines 1: Synthesis Of Proline-Derived Spirolactams Via Thermal Intramolecular Ester Aminolysis, Fintan Kelleher, Sinead Kelly Jan 2006

Spirobicyclic Diamines 1: Synthesis Of Proline-Derived Spirolactams Via Thermal Intramolecular Ester Aminolysis, Fintan Kelleher, Sinead Kelly

Articles

Proline derived [4.4]-spirolactams have been synthesised in good yields by a reductive-amination reaction followed by thermal cyclisation of the resulting amine onto the proline ester group in refluxing toluene. The synthesis of the corresponding [4.5]-spirolactams by the same method gave much reduced yields.

Go to article

Spirobicyclic Diamines 2: Synthesis Of Homochiral Diastereoisomeric Proline Derived [4,4]-Spirolactams, Fintan Kelleher, Sinead Kelly Jan 2006

Spirobicyclic Diamines 2: Synthesis Of Homochiral Diastereoisomeric Proline Derived [4,4]-Spirolactams, Fintan Kelleher, Sinead Kelly

Articles

L-Proline derived diastereoisomeric [4.4]-spirolactams have been prepared by a reductive-amination reaction of (R)- or (S)-alanine methyl ester followed by thermal cyclisation of the resulting amine onto the proline ester group in refluxing toluene. Under similar conditions (R)- or (S)-phenylalanine methyl ester gave no cyclisation products, while R- or S-a-methylbenzylamine required treatment with NaNH2 in refluxing toluene to induce cyclisation giving diastereoisomeric [4.4]-spirolactams

Go to article

The Determination Of Probes For The Indirect Detection Of Anions In Capillary Zone Electrophoresis Using Light Emitting Diode Detection, Peter Ashley Balding Jan 2006

The Determination Of Probes For The Indirect Detection Of Anions In Capillary Zone Electrophoresis Using Light Emitting Diode Detection, Peter Ashley Balding

Theses : Honours

This study investigated the potential of a number of compounds to act as probes for the indirect detection of inorganic and organic anions separated by capillary zone electrophoresis and using light emitting diodes (LED) as the light source. Desirable characteristics of the probe anion included: high molar absorptivity, moderate to high electrophoretic mobility, and having a wavelength of maximum absorbance near the maximum emission wavelength of a LED. A preliminary study led to the evaluation of eleven possible compounds. Two of these, p-nitrophenol and 4-hydroxy-3,5-dinitrobenzoic acid were selected for further study as they fulfilled the criteria previously mentioned. The optimised …

Go to article

Growth Of Ge Quantum Dots On Si(100)-(2×1) By Pulsed Laser Deposition, M. S. Hegazy, H. E. Elsayed-Ali Jan 2006

Growth Of Ge Quantum Dots On Si(100)-(2×1) By Pulsed Laser Deposition, M. S. Hegazy, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Self-assembled germanium quantum dots (QDs) were grown on Si(100)-(2×1) by pulsed laser deposition. In situ reflection-high energy electron diffraction (RHEED) and postdeposition atomic force microscopy are used to study the growth of the QDs. Several films of different thicknesses were grown at a substrate temperature of 400 °C using a Q-switched Nd:yttrium aluminum garnet laser (λ= 1064 nm, 40 ns pulse width, 23 J/cm 2 fluence, and 10 Hz repetition rate). At low film thicknesses, hut clusters that are faceted by different planes, depending on their height, are observed after the completion of the wetting layer. With increasing film thickness, …

Go to article

Negative Impact Of Noise On The Principal Component Analysis Of Nmr Data, Steven M. Halouska, Robert Powers Jan 2006

Negative Impact Of Noise On The Principal Component Analysis Of Nmr Data, Steven M. Halouska, Robert Powers

Department of Chemistry: Faculty Publications

Principal component analysis (PCA) is routinely applied to the study of NMR based metabolomic data. PCA is used to simplify the examination of complex metabolite mixtures obtained from biological samples that may be composed of hundreds or thousands of chemical components. PCA is primarily used to identify relative changes in the concentration of metabolites to identify trends or characteristics within the NMR data that permits discrimination between various samples that differ in their source or treatment. A common concern with PCA of NMR data is the potential over emphasis of small changes in high concentration metabolites that would over-shadow signifi …

Go to article

Stability Of Warfarin Solutions For Drug–Protein Binding Measurements: Spectroscopic And Chromatographic Studies, Annette C. Moser, Charles A. Kingsbury, David S. Hage Jan 2006

Stability Of Warfarin Solutions For Drug–Protein Binding Measurements: Spectroscopic And Chromatographic Studies, Annette C. Moser, Charles A. Kingsbury, David S. Hage

Department of Chemistry: Faculty Publications

Warfarin is commonly used in drug–protein binding studies as a displacement marker for Sudlow site I on the protein human serum albumin (HSA). This study examined the stability of aqueous warfarin solutions prepared for such experiments. This was investigated using NMR spectroscopy and affinity chromatography. It was found by 1H NMR that warfarin underwent a slow first-order conversion in aqueous solution. The rate of this reaction increased with temperature, giving rate constants at pH 7.4 of 0.0086 h−1 at 25 °C and 0.041 h−1 at 37 °C. It was concluded from further 1H and 13C NMR studies, along …

Go to article

A Minimum-Impact Method For Measuring Corrosion Rate Of Steel-Hulled Shipwrecks In Seawater, Matthew A. Russell, David L. Conlin, Larry E. Murphy, Donald L. Johnson, Brent M. Wilson, James D. Carr Jan 2006

A Minimum-Impact Method For Measuring Corrosion Rate Of Steel-Hulled Shipwrecks In Seawater, Matthew A. Russell, David L. Conlin, Larry E. Murphy, Donald L. Johnson, Brent M. Wilson, James D. Carr

Department of Chemistry: Faculty Publications

Current research on USS Arizona is focused on a minimum-impact technique for calculating corrosion rate of the battleship’s steel hull by analysing physical and chemical properties of marine encrustation covering the exposed hull. An equation is derived that allows concretion thickness, density, and total iron content to be used to calculate corrosion rate of steel hull plate.

Go to article

Janus Scorpionates:  Supramolecular Tectons For The Directed Assembly Of Hard−Soft Alkali Metallopolymer Chains, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier Jan 2006

Janus Scorpionates:  Supramolecular Tectons For The Directed Assembly Of Hard−Soft Alkali Metallopolymer Chains, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier

Chemistry Faculty Research and Publications

A new scorpionate ligand [HB(mtda)3-] containing mercaptothiadiazolyl (mtda) heterocyclic rings with both hard nitrogen donors and soft sulfur donors has been prepared. This new ligand, the Janus scorpionate, is a hybrid of a tris(pyrazolyl)borate and a tris(mercaptoimidazolyl)borate. The differential hard/soft character of the dissimilar donor groups in this bridging ligand was exploited for the controlled solid-state organization of homometallic and heterometallic alkali metal coordination polymers. Remarkably, in the case of sodium, coordination polymers with both acentric (with NaS3N3H kernels) and centric (with alternating NaN6 and NaS6H2 kernels) chains are …

Go to article

Exchange Coupling And Contribution Of Induced Orbital Angular Momentum Of Low-Spin Fe^3+ Ions To Magnetic Anisotropy In Cyanide-Bridged Fe2m2 Molecular Magnets: Spin-Polarized Density-Functional Calculations, Stephen Holmes, Kyungwha Park Jan 2006

Exchange Coupling And Contribution Of Induced Orbital Angular Momentum Of Low-Spin Fe^3+ Ions To Magnetic Anisotropy In Cyanide-Bridged Fe2m2 Molecular Magnets: Spin-Polarized Density-Functional Calculations, Stephen Holmes, Kyungwha Park

Chemistry & Biochemistry Faculty Works

Electronic structure and intramolecular exchange constants are calculated for three cyanide-bridged molecular magnets, [Tp⋆FeIII(CN)3MII(DMF)4]2(OTf)2∙2DMF (MII=Mn,Co,Ni) (abbreviated as Fe2Mn2, Fe2Co2, and Fe2Ni2) that have been recently synthesized, within a generalized-gradient approximation in spin-polarized density-functional theory (DFT). Here Tp⋆=[C3(CH3)2HN2]3BH, OTf=O3SCF3, and DMF=HCON(CH3)2. Due to strong ligand fields present in the [Tp⋆FeIII(CN)3]− units, the Fe3+ ions exhibit a low ground-state spin of S=1/2. Our calculations show that the metal ions in the Fe2Mn2 molecule interact antiferromagnetically via cyanide ligands, while those in the Fe2Co2 and Fe2Ni2 molecule interact ferromagnetically. The calculations also suggest that the smallest gaps between the highest occupied molecular orbital …

Go to article

Residual Stress Distribution, Intermolecular Force, And Frictional Coefficient Maps In Diamond Films: Processing-Structure-Mechanical Property Relationship, Sanju Gupta, Oliver Williams, R. J. Patel, Eric W. Bohannan, P. W. May Jan 2006

Residual Stress Distribution, Intermolecular Force, And Frictional Coefficient Maps In Diamond Films: Processing-Structure-Mechanical Property Relationship, Sanju Gupta, Oliver Williams, R. J. Patel, Eric W. Bohannan, P. W. May

Chemistry Faculty Research & Creative Works

Carbon in its various forms, specifically nanocrystalline diamond, may become a key material for the manufacturing of micro- and nano-electromechanical (M/NEMS) devices in the 21st Century. in order to utilize effectively these materials for M/NEMS applications, understanding of their microscopic structure and physical properties (mechanical, in particular) become indispensable. the micro- and nanocrystalline diamond films were grown using hot-filament and microwave chemical vapor deposition techniques involving novel CH4 / [TMB for boron doping and H2S for sulfur incorporation] in high hydrogen dilution chemistry. to investigate residual stress distribution and intermolecular forces at the nanoscale, the films were characterized using Raman …

Go to article

Segmental Dynamics Of Poly(Isopropyl Acrylate)-D7 On Silica, Piyawan Krisanangkura, Frank D. Blum Jan 2006

Segmental Dynamics Of Poly(Isopropyl Acrylate)-D7 On Silica, Piyawan Krisanangkura, Frank D. Blum

Chemistry Faculty Research & Creative Works

For a polymer film deposited on a surface, the strength of the surfacesegment interaction affects the mobility of polymer-chain segments. The selfconsistent field lattice model of Scheutjens and Fleer,1 based on mean-field lattice models of polymer at interfaces,2 has been used to describe the distribution of conformations of polymers on surfaces. Adsorbed-polymer segments may be classified as belonging to loops, trains or tails. There are different techniques used to study the molecular motion of the polymer including modulated differential scanning calorimetry (MDSC)3 and nuclear magnetic resonance (NMR).4,5 in this work, solid-state deuterium (2H) NMR was used to characterize the polymer …

Go to article

Separation And Quantification Of N-Acetylcysteine-Amide (Naca) By Hplc With Fluorescence Detection, Wei Wu, Glenn Goldstein, Craig D. Adams, Richard H. Matthews, Nuran Ercal Jan 2006

Separation And Quantification Of N-Acetylcysteine-Amide (Naca) By Hplc With Fluorescence Detection, Wei Wu, Glenn Goldstein, Craig D. Adams, Richard H. Matthews, Nuran Ercal

Chemistry Faculty Research & Creative Works

N-acetyl-l-cysteine (NAC) is a well-known antioxidant that is capable of facilitating glutathione (GSH) biosynthesis and replenishing intracellular GSH under oxidatively challenging circumstances. N-acetyl-cysteine-amide (NACA), the amide form of NAC, is a newly designed and synthesized thiol-containing compound which is believed to be more lipophilic and permeable through cell membranes than NAC. The metabolic and antioxidant effects of these compounds in vitro and in vivo are under investigation. However, an analytical method that can separate and quantify both compounds simultaneously is not yet available, to the best of our knowledge. Because of their structural similarities, the two compounds are difficult to …

Go to article

Enhancing The Third-Order Nonlinear Optical Properties Of Porphyrins And Molecular Wires, Jonathan L. Humphrey Jan 2006

Enhancing The Third-Order Nonlinear Optical Properties Of Porphyrins And Molecular Wires, Jonathan L. Humphrey

Theses and Dissertations

The third-order nonlinear optical (NLO) properties of indium tin oxide (ITO) thin films, Fe3+, Mn3+, Co2+ 5,10,15,20-tetrakis-4hydroxytetraphenyl)porphyrin (TPP) films, and a series of ethynyl-linked azobenzene oligomers were investigated using degenerate four wave mixing (DFWM) with 100 fs laser pulses. To measure the NLO of ITO thin films, A DFWM method for measuring thin films on thick substrates was refined for the characterization of films less than 100 nm thick and applied to ITO films ~25 nm thick. It was found that the third-order nonlinear susceptibility of ITO, χ(3)ITO, is purely electronic at 900 - 1300 nm (11000 - 7700 cm-1) …

Go to article

Photochemical Applications To The Study Of Complexity Phospholipid Bilayer Environments, Christopher John Wohl Jr. Jan 2006

Photochemical Applications To The Study Of Complexity Phospholipid Bilayer Environments, Christopher John Wohl Jr.

Theses and Dissertations

The physical and biophysical properties of a biological membrane model, phosphatidylcholine bilayers, were investigated using novel spiropyran/merocyanine molecular probes. The femtosecond to second dynamics of this system's photochemistry enabled bilayer viscosity and free volume to be studied over a broad time scale. Spiropyrans/merocyanines with different polarity were synthesized by changing the substitution of the indole moiety enabling determination of the trans-membrane properties of the bilayer. In addition, transient grating spectroscopy was used to study thermal energy transfer in phospholipid bilayers on a picosecond time scale.Femtosecond transient absorption spectroscopy was used to study the photo-induced spiropyran ring-opening and isomerization reactions that …

Go to article

First Prev