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Full-Text Articles in Chemistry
High Order Structures Formed By The Natural Aromatic Amino Acids, Gabriel Alexander Kupovics, Zeina Alraawi
High Order Structures Formed By The Natural Aromatic Amino Acids, Gabriel Alexander Kupovics, Zeina Alraawi
Inquiry: The University of Arkansas Undergraduate Research Journal
Excessive concentrations of the natural aromatic amino acids phenylalanine and tyrosine are characteristic of the severe genetic abnormalities known as phenylketonuria (PKU) and tyrosinemia, respectively. Within this context, this feature article authenticates claims that tryptophan can form amyloid-like supramolecular structures in vitro and is the first to propose potential mechanisms of tryptophan self-assembly, including hydrophobic and electrostatic interactions. Thioflavin T (ThT) fluorescence kinetics and transmission electron microscopy (TEM) data suggest the formation of amyloid-like fibrillar structures by natural aromatic amino acids in vitro. Additionally, the propensity of amino acid aggregation increases in the presence of sodium dodecyl sulfate (SDS). The …
A Bond Length – Bond Valence Relationship For Carbon – Nitrogen Bonds, C. Harris, F. D. Hardcastle
A Bond Length – Bond Valence Relationship For Carbon – Nitrogen Bonds, C. Harris, F. D. Hardcastle
Journal of the Arkansas Academy of Science
In a recent study, Pauling’s relationship between bond length and valence was derived along with a definition for his fitting parameter b that incorporates the orbital exponents for each atom contributing to the bond of interest. The values of b for various bonds, including C-N bonds, were calculated using the orbital exponent data. In this study, Pauling’s correlation between bond length and bond valence, as well as his valence sum rule, were used with the recently-derived definition for b in order to produce a relationship specifically applicable to C-N bonds. The resulting equation was checked against published x-ray diffraction data …
A General Valence-Length Correlation For Determining Bond Orders: Application To Carbon-Carbon And Carbon-Hydrogen Chemical Bonds, F. D. Hardcastle
A General Valence-Length Correlation For Determining Bond Orders: Application To Carbon-Carbon And Carbon-Hydrogen Chemical Bonds, F. D. Hardcastle
Journal of the Arkansas Academy of Science
A quantum-mechanical LCAO approach was used to derive Pauling’s popular empirical bond valencelength relationship s = exp((R₀-R)/b), where s is the bond order or bond valence associated with bond length R, and R₀ and b are fitting parameters. An expression for the b “empirical” fitting parameter is derived in terms of atomic orbital exponents. The b parameters calculated from the atomic orbital exponents are consistent with optimized b parameters. In general, atomic orbital exponents may be used to determine bond valence-length relationships for any chemical bond regardless of valence state, oxidation number, physical or chemical environment. In this study, almost …
Wave Profile For Anti-Force Waves With Maximum Possible Currents, M. Hemmati, R. Horn, W. P. Childs, A. K. Meredith
Wave Profile For Anti-Force Waves With Maximum Possible Currents, M. Hemmati, R. Horn, W. P. Childs, A. K. Meredith
Journal of the Arkansas Academy of Science
In the theoretical investigation of the electrical breakdown of a gas, we apply a one-dimensional, steady state, constant velocity, three component fluid model and consider the electrons to be the main element in propagation of the wave. The electron gas temperature, and therefore the electron gas partial pressure, is considered to be large enough to provide the driving force. The wave is considered to have a shock front, followed by a thin dynamical transition region. Our set of electron fluid-dynamical equations consists of the equations of conservation of mass, momentum, and energy, plus the Poisson's equation. The set of equations …
Bond Length - Bond Valence Relationships For Carbon - Carbon And Carbon - Oxygen Bonds, C. Harris, F. D. Hardcastle
Bond Length - Bond Valence Relationships For Carbon - Carbon And Carbon - Oxygen Bonds, C. Harris, F. D. Hardcastle
Journal of the Arkansas Academy of Science
In the present study, relationships are developed for determining bond orders (also referred to as bond valences or bond numbers) from published bond lengths for carbon-carbon (C-C) and carbon-oxygen (C-O) bonds. The relationships are based on Pauling’s empirical formula s = exp((Ro-R)/b)), where s is the bond order, R is the corresponding bond length, Ro is the unit valence bond length, and b is a fitting parameter. We use a recently derived relationship for the b parameter in terms of the bonding atoms’ published atomic orbital exponents. The resulting equations were checked against published x-ray diffraction (XRD) data for 176 …
Low-Level Mercury Causes Inappropriate Activation In T And B Lymphocytes In The Absence Of Antigen Stimulation, K. L. Weigand, J. L. Reno, B. M. Rowley
Low-Level Mercury Causes Inappropriate Activation In T And B Lymphocytes In The Absence Of Antigen Stimulation, K. L. Weigand, J. L. Reno, B. M. Rowley
Journal of the Arkansas Academy of Science
The immune system primarily utilizes two cell types for adaptive immunity: T lymphocytes and B lymphocytes. T lymphocytes are activated when antigen presenting cells (APCs) present antigen to membrane-bound T cell receptors. B lymphocytes are activated when an antigen binds to receptors embedded in the plasma membrane. In both T and B cells this antigen binding crosslinks the receptor complexes and initiates the signal transduction cascade. These cascades frequently consist of a series of intracellular molecules becoming phosphorylated in a step-wise fashion. Once activated, these cells differentiate into effector cells that clear out the stimulating antigen. Mercury, which is a …
Low Speed Current Bearing Anti-Force Waves, M. Hemmati, W. P. Childs, H. Shojaei, H. Morris
Low Speed Current Bearing Anti-Force Waves, M. Hemmati, W. P. Childs, H. Shojaei, H. Morris
Journal of the Arkansas Academy of Science
For theoretical investigation of electrical breakdown of a gas, we apply a one-dimensional, steady profile, constant velocity, three-component (electrons, ions and neutral particles) fluid model. Our fluid model consists of the equations of conservation of mass, momentum and energy, coupled with the Poison’s equation. The set of equations is referred to as the electron fluid dynamical equations (EFD). This investigation involves breakdown waves with a substantial current behind the wave front, and waves for which the electric field force on electrons is in the opposite direction of the wave propagation (anti-force waves – lightning return stroke). Therefore, the set of …
Wave Profile For Current Bearing Antiforce Waves, H. Morris, W. Childs, P. Pinkston, M. Hemmati, J. Christensen
Wave Profile For Current Bearing Antiforce Waves, H. Morris, W. Childs, P. Pinkston, M. Hemmati, J. Christensen
Journal of the Arkansas Academy of Science
For fluid dynamical analysis of breakdown waves, we employ a one-dimensional, three-component (electrons, ions and neutral particles) fluid model to describe a steady-state, ionizing wave propagating counter to strong electric fields. The electron gas temperature and therefore the electron fluid pressure is assumed to be large enough to sustain the wave motion down the discharge tube. Such waves are referred to as antiforce waves. The complete set of equations describing such waves consists of the equations of conservation of mass, momentum and energy coupled with Poisson’s equation. Inclusion of current behind the wave front alters the set of electron fluid …
Microwave Assisted Synthesis Of Chloropentahaptocyclopentadienediphenylphosphinoethaneruthenium(Ii), S. Muthyala, Mark Draganjac
Microwave Assisted Synthesis Of Chloropentahaptocyclopentadienediphenylphosphinoethaneruthenium(Ii), S. Muthyala, Mark Draganjac
Journal of the Arkansas Academy of Science
No abstract provided.
Molecular Structure Of Pentahaptocyclopentadienebis (Tetrahydrothiophene) Triphenylphosphineruthenium(Ii) Triflate, Paul M. Nave, Mark Draganjac, A. W. Cordes
Molecular Structure Of Pentahaptocyclopentadienebis (Tetrahydrothiophene) Triphenylphosphineruthenium(Ii) Triflate, Paul M. Nave, Mark Draganjac, A. W. Cordes
Journal of the Arkansas Academy of Science
No abstract provided.
Synthesis, Characterization, And Properties Of Homometallic Dinuclear Ruthenium Complex Containing Chloro-Phenanthroline And Bipyridine, A. A. Bhuiyan, S. Kudo
Synthesis, Characterization, And Properties Of Homometallic Dinuclear Ruthenium Complex Containing Chloro-Phenanthroline And Bipyridine, A. A. Bhuiyan, S. Kudo
Journal of the Arkansas Academy of Science
This paper deals with the synthesis and spectroscopic investigation of homometallic dinuclear ruthenium(II) complex containing chlorophenanthroline and bipyridine ligands. This bimetallic ruthenium polypyridine complex may be useful for biological electron transfer studies. Heteroleptic ruthenium monomer complex Ru(bpy)2(Cl-phen) (where bpy = 2,2’-bipyridine and Cl-phen = 5-chloro- 1,10-phenanthroline) was prepared in a two step procedure previously developed in our laboratory. This monomer complex was used to prepare the ruthenium dimer complex, (bpy)2Ru(phen-phen)Ru(bpy)2, by utilizing the Ni-catalyzed coupling reaction. Both the complexes were purified by column chromatography. The identity and the integrity of the complexes were confirmed by elemental analysis as well as …
Density Functional Studies Of The Structure And Bonding In Piano Stool Carbene Complexes, John P. Graham, Robbie Davis
Density Functional Studies Of The Structure And Bonding In Piano Stool Carbene Complexes, John P. Graham, Robbie Davis
Journal of the Arkansas Academy of Science
No abstract provided.
Studies Of Zeolite Entrapped Ruthenium Polypyridine Complexes, Anwar A. Bhuiyan
Studies Of Zeolite Entrapped Ruthenium Polypyridine Complexes, Anwar A. Bhuiyan
Journal of the Arkansas Academy of Science
There is an intense interest in designing molecular systems which will absorb visible sunlight, initiate an electron transfer process, and ultimately convert the solar energy to useful chemical energy of fuels such as hydrogen produced from water. The zeolite-entrapped polypyridine complexes of divalent ruthenium hold promise as efficient photocatalysts for net charge separation and such efficiencies are further enhanced by organized incorporation of donor and acceptor components. This paper deals with the synthesis and spectroscopic investigation of zeolite-entrapped ruthenium polypyridine complexes which may be useful in the development of solar energy conversion schemes. The sensitizer molecules, such as Ru(bpy)3 2+ …
Computational Study Of A Novel Dinuclear Metal Complex, Dragos Seghete
Computational Study Of A Novel Dinuclear Metal Complex, Dragos Seghete
Inquiry: The University of Arkansas Undergraduate Research Journal
The first compound containing an M-H-M was recently reported by Vicic et al. With recent availability of large computational resources, molecular modeling has become a reliable tool for confirming experimental results. The novel dinuclear Ni complex [( dippm)2Ni2Br2]( 0 -H) was investigated in this work from a theoretical perspective. Full geometry optimization was carried on the dinuclear Ni complex at the DFT/B3LYP with the 6-31G* basis set. The result verifies the linear Ni-H-Ni bond. Two different starting structures that converged to the same geometry confirm that a global minimum was reached. The computed structure differs from the experimentally determined one …
The Effects Of Multiple Mutations In The Hydrophobic Core Upon The Stability Of Staphylococcal Nuclease, Rebecca L. Danforth
The Effects Of Multiple Mutations In The Hydrophobic Core Upon The Stability Of Staphylococcal Nuclease, Rebecca L. Danforth
Inquiry: The University of Arkansas Undergraduate Research Journal
Previous work in the laboratory of my research advisor, Dr. Wesley Stites, has investigated the core packing of the protein staphylococcal nuclease. The core of a protein is critical in determining a protein's structure and stability. The hydrophobicity of the core has long been thought to be the principal driving force for folding, but recent work in the Stites lab has shown that optimization of van der Waals contacts and minimization of cavities, in our shorthand term, packing, is at least as energetically important. We are building upon this information in our attempt to better pack the protein core. If …
On The Existence And Stability Of Liquid Water On The Martian Surface, Justin Thompson
On The Existence And Stability Of Liquid Water On The Martian Surface, Justin Thompson
Inquiry: The University of Arkansas Undergraduate Research Journal
Present-day Mars is thought to be a frozen desert on which liquid water is not likely to be found. The prevailing assumption has been that due to average temperatures below 273 K and atmospheric pressures at or below water's triple-point vapor pressure of 6.1 mbar, the existence of liquid water as an equilibrium phase at or near the surface is impossible at the present epoch. However, there is substantial evidence that liquid water has existed in the past and may presently still exist on or directly below the Martian surface. I conducted simulation experiments in the Andromeda planetary environmental chamber …
Solid Phase Extraction Of Pesticides With Determination By Gas Chromatography, Anwar A. Bhuiyan, Harry O. Brotherton
Solid Phase Extraction Of Pesticides With Determination By Gas Chromatography, Anwar A. Bhuiyan, Harry O. Brotherton
Journal of the Arkansas Academy of Science
A simple, rapid, and effective method for the extraction of fifteen organochlorine and organophosphorus pesticides based on the use of solid phase Bond Elut C-18 cartridges was studied as an alternative method to those based on extraction with organic solvents. Solid phase extraction is an attractive chromatographic sample preparation technology that reduces analysis time, costs, labor, and solvent consumption relative to traditional liquid/liquid extraction methods. The sample recoveries with the use of solid phase extractions were excellent for most pesticides. Analyte concentration by a factor as great as 1000-fold was achieved readily. The adsorbed pesticides were eluted from the solid …
Synthesis And Chemistry Of Naphthalene Annulated Trienyl Iron Complexes: Potential Anticancer Dna Alkylation Reagents, Traci Means
Synthesis And Chemistry Of Naphthalene Annulated Trienyl Iron Complexes: Potential Anticancer Dna Alkylation Reagents, Traci Means
Inquiry: The University of Arkansas Undergraduate Research Journal
Iron complex chemistry that opens a new door to the medicinal and pharmaceutical worlds is the aim of this research. Specifically, ortho-quinone methide moieties are intermediates in several antitumor drugs and have been identified as bioreductive alkylators of DNA. In our research, a class of iron compounds has been targeted to resemble these quinone methides. It is hoped that these new compounds could be modified to provide a window of opportunity toward the discovery of a selective mode of drug delivery. We have focused our efforts on generating a reactive transition metal complexed 5-membered ring analog of o-quinone methide based …
Chemical Composition Of Particles Of D < 0.20 Mu In The Lower Stratospheric Aerosol, Spring 1993, Joseph D. Scott, David M. Chittenden Ii
Chemical Composition Of Particles Of D < 0.20 Mu In The Lower Stratospheric Aerosol, Spring 1993, Joseph D. Scott, David M. Chittenden Ii
Journal of the Arkansas Academy of Science
The majority of the mass of stratospheric aerosol collected during the spring of 1993 consisted principally of particles of d >0.20 mu containing a mixture of H2SO4 and (NaK)2SO4. However, the composition of the more numerous particles with d< 0.2 mu was very different. X-ray emission spectra (EDS) of individual particles indicated that there were three different chemical populations of small particles. The most numerous population was almost all C with only traces of S and Na. The second population contained metal sulfates and chlorides, possibly accreted to a C-containing matrix. The third population consisted of S- and Cl- containing species and trace amounts of Na and K ions. The number of equivalents of metal ion was much less than that of S and Cl species, indicating that most of the S and Cl was not ionic, but was covalently bonded, perhaps to a C matrix.
Synthesis Of A Ruthenium-Tetra(Tht)Dichloride Compound And The Molecular Structure Of The Partially Oxidized Compound Rucl2(Tht)2.2(Tht-O)1.8, L. A. Thornton, Mark Draganjac, Andres Meza, A. W. Cordes
Synthesis Of A Ruthenium-Tetra(Tht)Dichloride Compound And The Molecular Structure Of The Partially Oxidized Compound Rucl2(Tht)2.2(Tht-O)1.8, L. A. Thornton, Mark Draganjac, Andres Meza, A. W. Cordes
Journal of the Arkansas Academy of Science
No abstract provided.
Non-Commercial Software For The Analysis And Interpretation Of High Resolution Molecular Spectra, A. R. Ford, Scott W. Reeve
Non-Commercial Software For The Analysis And Interpretation Of High Resolution Molecular Spectra, A. R. Ford, Scott W. Reeve
Journal of the Arkansas Academy of Science
No abstract provided.
Synthesis And Characterization Of A Ruthenium-Thioxane Complex, Amanda Wroble, Scotty Sproles, Mark Draganjac, Paul M. Nave
Synthesis And Characterization Of A Ruthenium-Thioxane Complex, Amanda Wroble, Scotty Sproles, Mark Draganjac, Paul M. Nave
Journal of the Arkansas Academy of Science
No abstract provided.
Hammett Correlations Of The Amide Proton Chemical Shift In A Series Of 1-Tosyl-3-(4-Substituted Phenyl)Ureas, Frank L. Setliff, Melody K. Harrison
Hammett Correlations Of The Amide Proton Chemical Shift In A Series Of 1-Tosyl-3-(4-Substituted Phenyl)Ureas, Frank L. Setliff, Melody K. Harrison
Journal of the Arkansas Academy of Science
No abstract provided.
Double Cysteine Mutations In Staphylococcal Nuclease: The Effect Of Artificially Introduced Disulfide Bonds On Protein Structure And Stability, Anna Terry
Inquiry: The University of Arkansas Undergraduate Research Journal
Since a protein's function depends on its structure, basic research in protein structure facilitates the solution of many practical problems, such as the synthesis of more effective medicines. With this larger goal in sight, the purpose of this research project is to understand better the chemical principles that underlie protein structure and stability. Disulfide bonds are a potentially stabilizing feature of many proteins. They may form between cysteine residues in close proximity to one another if the orientation is favorable. Often found in proteins produced by organisms that grow at high temperatures, disulfide bonds may anchor side chains together, making …
Preparation Of An Electrophilic 3-Methylindole Derivative: Difficulties In Forming A Stable, Suitable Material For The Preparation Of Tryptophan, Jason Boggs, Mariah Mcmasters, Robert W. Curley Jr., Michael J. Panigot
Preparation Of An Electrophilic 3-Methylindole Derivative: Difficulties In Forming A Stable, Suitable Material For The Preparation Of Tryptophan, Jason Boggs, Mariah Mcmasters, Robert W. Curley Jr., Michael J. Panigot
Journal of the Arkansas Academy of Science
In an attempt to prepare stereoselectively beta-deuterated tryptophan, N-protected indole-3-methanol compounds were prepared with model studies being done on undeuterated material. Conversion of these compounds to electrophilic species proved exceptionally difficult and resulted in very low yields or recovered starting material only. A summary of the current results utilizing N-tosyl indole-3-methanol will be presented as well as efforts using N-Boc indole-3-methanol.
Reaction Of Alpine-Borane With Aldehydes: Reactivity Rate Assessment By Observation Of The Disappearance Of The Carbonyl N - Pi* Peak By Uv-Visible Spectroscopy, Layla Bland, Michael J. Panigot
Reaction Of Alpine-Borane With Aldehydes: Reactivity Rate Assessment By Observation Of The Disappearance Of The Carbonyl N - Pi* Peak By Uv-Visible Spectroscopy, Layla Bland, Michael J. Panigot
Journal of the Arkansas Academy of Science
Due to an unexpectedly difficult reduction of indole-3-carbaldehyde and of isobutyraldehyde using the chiral reducing agent Alpine-Borane, the reactivity of several aliphatic, aromatic, and unsaturated aldehydes was investigated. This was done in order to determine whether there was a relationship between aldehyde structure and reduction rate. It was found that aliphatic aldehydes and aromatic aldehydes with no strongly electron-donating groups on the arene ring reduced faster than unsaturated aldehydes.
Hammett Correlations Of The Sulfonamide Proton Chemical Shift In A Series Of N-(Substituted Aryl)-P-Toluenesulfonamides, Frank L. Setliff, Tyson K. Spradlin
Hammett Correlations Of The Sulfonamide Proton Chemical Shift In A Series Of N-(Substituted Aryl)-P-Toluenesulfonamides, Frank L. Setliff, Tyson K. Spradlin
Journal of the Arkansas Academy of Science
No abstract provided.
Studies Of Tryptophans In Membrane- Spanning "Walp" Peptides By Deuterium Nmr Spectroscopy, Nichole Reed
Studies Of Tryptophans In Membrane- Spanning "Walp" Peptides By Deuterium Nmr Spectroscopy, Nichole Reed
Inquiry: The University of Arkansas Undergraduate Research Journal
WALP pep tides of sequence acetyl-Gly-Trp-Trp-(Leu-Ala)-Trp-Trp-Ala-ethanolamine insert into lipid bilayers as membrane-spanning a-helices and modulate the lipid phase behavior as functions of n and the lipid acyl chain length. A key feature of the WALP peptides is the positioning of tryptophan (Trp) indole rings at the membrane/water interface. For the examples WALP19 with n = 6.5 and WALP23 with n = 8.5, we have labeled individual indoles with deuterium and incorporated the labeled peptides in oriented, hydrated bilayers of Dimyristoyl-phosphatidylcholine (DMPC). Deuterium NMR spectra from these samples show sharp resonances when the membrane normal is aligned either parallel (Beta = …
Preparation Of Methyl 5-Chloro-6-Fluoronicotinate By Fluoride-Chloride Exchange, Frank L. Setliff, Leslie B. Coop
Preparation Of Methyl 5-Chloro-6-Fluoronicotinate By Fluoride-Chloride Exchange, Frank L. Setliff, Leslie B. Coop
Journal of the Arkansas Academy of Science
No abstract provided.
Analysis Of A Mixture Of Several Dihalonicotinic Acids By Gas Chromotography And Gas Chromotography-Mass Spectrometry, Cheryl L. Fossler, Frank L. Setliff, Ali U. Shaikh
Analysis Of A Mixture Of Several Dihalonicotinic Acids By Gas Chromotography And Gas Chromotography-Mass Spectrometry, Cheryl L. Fossler, Frank L. Setliff, Ali U. Shaikh
Journal of the Arkansas Academy of Science
Six 2,5- and 5,6- dihalonicotinic acids in a mixture were converted to their corresponding methyl esters and then analyzed by gas chromatography and gas chromatography-mass spectrometry. Four methods of conversion were compared for their GC sensitivity, efficiency and analysis time. In Method #1, using HC1 and methanol as the reagents, the displacement of the halogens by chlorine (from HC1) at 2- and 6-positions was a common occurrence, rendering the method inefficient. In Method #2 (BF3/methanol), the displacement of halogens by methoxide was evident. Method #3 (dicyclohexylcarbodiimide/methanol) produced a mixture of derivatives with a poor yield. Method #4 (diazomethane) gave a …