Physical Sciences and Mathematics Commons^™

Novel Techniques For Enhancing Sensitivity In Static Headspace, Nicholas Snow, G.P Bullock

Nicholas A Snow

No abstract provided.

Simultaneous Determination Of Pramoxine Hcl And Benzalkonium Chloride In Wound Care Solutions By Hplc, Panagiotis Tavlarakis, Jonine Greyling, Nicholas Snow

Nicholas A Snow

No abstract provided.

Complementary Spectroscopic Assays For Investigating Protein−Ligand Binding Activity: A Project For The Advanced Chemistry Laboratory, David Mascotti, Mark Waner

Mark J. Waner

A protein−ligand binding, guided-inquiry laboratory project with potential application across the advanced undergraduate curriculum is described. At the heart of the project are fluorescence and spectrophotometric assays utilizing biotin-4-fluorescein and streptavidin. The use of the same stock solutions for an assay that may be examined by two distinct spectroscopic techniques offers an opportunity to discuss not only protein−ligand binding but also to compare instrumental techniques and to discuss the underlying physical principles that are the origins of the assays. In addition to critically evaluating analytical techniques, students are pushed to develop quantitative pipetting, estimation, and experimental-design skills to collect and …

A Study Of The Vaporization Enthalpies Of Some 1-Substituted Imidazoles And Pyrazoles By Correlation-Gas Chromatography, Dmitry Lipkind, Chatchawat Plienrasri, James S. Chickos

James Chickos

No abstract provided.

Retinylidene Iminium Salts And Related Systems, Gary Stephen Shaw

Gary M. Shaw

This thesis encompasses some investigations into the structure and chemistry of iminium salts. The interest in this work stems from previous investigations of the visual pigment rhodopsin and a related protein, bacteriorhodopsin. Both of these proteins have been shown to consist of an iminium salt linkage between the chromophore and the protein. Also, these compounds are able to absorb light in the visible region of the spectrum and undergo efficient isomerization processes. A series of iminium salts related to these natural chromophores were prepared and characterized by a variety of spectroscopic methods in both solution and the solid states. In …

Leaching Mechanism Of Semiconducting Minerals, Fathi Habashi

Fathi Habashi

The mechanism of leaching of semiconducting minerals such as PbS, ZnS, UO2, etc., has been the subject of intensive speculation by hydrometallurgists in the early 1950s. The electrochemical mechanism proposed in 1970 by the author in volume 2 of his Principles of Extractive Metallurgy avoids the assumption of forming intermediate complexes that cannot be isolated or identified.

Mechanical Properties Of High Blaine Portland Cement, Masoud Rastegar, Kamran Rahmati Shadbad, Ali Hadidi

Masoud Rastegar

No abstract provided.

(1e,3e)-1,4-Bis(4-Methoxyphenyl)Buta1,3-Diene, Gopinathan Narayan, Nigam P. Rath, Suresh Das

Nigam Rath

Some Features Of The Concentration Oscillations In The Phenylacetylene Oxidative Carbonylation Reaction (In Russian), Sergey N. Gorodsky

Sergey N. Gorodsky

Some modes of concentration oscillations in the homogeneous system KI-PdI2-CO-O2-CH3OH are described in this paper.

2,2′,5,5′-Tetra­Chloro­Benzidine, Onome Ugono, Marcel Douglas, Nigam P. Rath, Alicia M. Beatty

Nigam Rath

2,2′,5,5′-Tetra­Chloro­Benzidine, Onome Ugono, Marcel Douglas, Nigam P. Rath, Alicia M. Beatty

Alicia Beatty

Energetyka Niskoemisyjna, Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.

Mechanistically Driven Development Of Iridium Catalysts For Asymmetric Allylic Substitution, John F. Hartwig, Levi M. Stanley

Levi M. Stanley

Enantioselective allylic substitution reactions comprise some of the most versatile methods for preparing enantiomerically enriched materials. These reactions form products that contain multiple functionalities by creating carbon−nitrogen, carbon−oxygen, carbon−carbon, and carbon−sulfur bonds. For many years, the development of catalysts for allylic substitution focused on palladium complexes. However, studies of complexes of other metals have revealed selectivities that often complement those of palladium systems. Most striking is the observation that reactions with unsymmetrical allylic electrophiles that typically occur with palladium catalysts at the less hindered site of an allylic electrophile occur at the more hindered site with catalysts based on other …

Bipolar Electrodes: A Useful Tool For Concentration, Separation, And Detection Of Analytes In Microelectrochemical Systems, François Mavré, Robbyn K. Anand, Derek R. Laws, Kwok-Fan Show, Byoung-Yong Chang, John A. Crooks, Richard M. Crooks

Robbyn Anand

Over the past decade, bipolar electrochemistry has emerged from relative obscurity to provide a promising new means for integrating electrochemistry into lab-on-a-chip systems. This article describes the fundamental operating principles of bipolar electrodes, as well as several interesting applications. The graphic, by François Mavré, shows the principle of operation of a bipolar electrode within a microfluidic channel overlaid on a background image of electrogenerated chemiluminescence from an array of 1000 bipolar electrodes.

Particulate Pictures And Kinetic-Molecular Theory Concepts: Seizing An Opportunity, Mark Waner

Mark J. Waner

This work examines commonly used particulate-level pictures meant to illustrate gases. These pictures are found throughout textbooks in the middle grades through the college level, as well as in questions frequently used to assess conceptual learning in students. This work uses the kinetic-molecular theory of gases to demonstrate the inaccuracies often present in these figures, which offers the opportunity to address model limitations to students and to develop better pictures. A basis for using these pictures to discuss models and ideas for ways these pictures can be used for inquiry activities based on analysis of scales is also discussed.

Kinetic And Mechanistic Studies Of The Deuterium Exchange In Classical Keto−Enol Tautomeric Equilibrium Reactions, Michael Nichols, Mark Waner

Mark J. Waner

An extension of the classic keto−enol tautomerization of β-dicarbonyl compounds into a kinetic analysis of deuterium exchange is presented. It is shown that acetylacetone and ethyl acetoacetate undergo nearly complete deuterium exchange of the α-methylene carbon when dissolved in methanol-d4. The extent of deuteration may be monitored via NMR spectroscopy as a function of time. A mechanism for deuterium exchange is presented and shown to be consistent with a consecutive first-order process. The data for acetylacetone are consistent with steady-state kinetics, whereas those of ethyl acetoacetate illustrate nonsteady-state behavior, offering an accessible example where students might collect and analyze real …

Synthesis Of Some Cyclic Indolic Peptoids As Potential Antibacterials, Vicki S. Au, John B. Bremner, Jonathan Coates, Paul A. Keller, Stephen G. Pyne

Paul Keller

The synthesis of cyclic peptoids containing an indole hydrophobic scaffold has been realised through the ring-closing metathesis of diallylated precursors. The precursors and their cyclic counterparts possessed poor antibacterial activity in contrast to previously reported cyclic peptoids containing hydrophobic scaffolds.

[60]Fullerene Amino Acids And Related Derivatives, Glenn A. Burley, Paul A. Keller, Stephen G. Pyne

Paul Keller

This paper is a review of the literature concerning the preparation of [60]fullerene amino acid and peptide derivatives. The structure and applications of these derivatives to the biological and material sciences is also presented.

Reactions Of Iminoglycines With C60 Fullerene And Their Unambiguous Characterisation Using Nmr Spectroscopy, Paul A. Keller, Stephen G. Pyne, Bill C. Hawkins

Paul Keller

This review examines the addition of iminoglycine derivatives to C60, yielding protected fullerenyl pyrroline derivatives. Subsequent reduction with sodium cyanoborohydride produces ring-opening adducts which are protected fullerenyl α-amino acids. Pyrroline bisadducts can be produced using tethers to link two iminoglycine units together, and variations include combining with malonate reactive groups this giving rise to interesting observations as to the regioselectivity of such reactions. All derivatives are fully characterised by NMR spectroscopy, and in the case of bis-adducts, the regioselectivity is determined from 1H/13C and 13C/13C connectivity patterns using HMBC and INADEQUATE experiments, respectively, thus eliminating the need for comparative techniques …

New Cyclic Peptides Via Ring-Closing Metathesis Reactions And Their Anti-Bacterial Activities, Timothy P. Boyle, John B. Bremner, Jonathan Coates, John Deadman, Paul A. Keller, Stephen G. Pyne, David I. Rhodes

Paul Keller

As part of a program investigating cyclic peptides with an internal aromatic hydrophobic scaffold as potential novel anti-bacterial agents, we explored the synthesis of simple tyrosine-based systems. These were prepared via key intermediates containing internal allylglycine and allyltyrosine residues for subsequent ring closing metathesis reactions. Although the resulting anti-bacterial activity against Staphylococcus aureus was modest, this represents a novel and simple route to this class of compounds. One intermediate acyclic dipeptide precursor showed good activity against S. aureus with an MIC of 7.8 µg/mL.

Regioselective Synthesis Of Novel E-Edge-[60]Fullerenylmethanodihydropyrroles And 1,2-Dihydromethano[60]Fullerenes, Leila Chaker, Graham E. Ball, James R. Williams, Glenn A. Burley, Bill C. Hawkins, Paul A. Keller, Stephen G. Pyne

Paul Keller

Treatment of a tethered N-(diphenylmethylene)glycinate-malonate derivative with [60]fullerene under Bingel conditions yielded an e-edge-[60]fullerenylmethanodihydropyrrole adduct in a regioselective manner. The regiochemical outcome was independent of the order of addition of either the N-(diphenylmethylene)glycinate or the malonate moieties. This new bis-adduct was also prepared in 13C enriched form allowing for its unequivocal structural characterization by 2D INADEQUATE NMR experiments. Ring-opening of the dihydropyrrole functionality of the bisadducts under reductive conditions gave exclusively novel dihydromethano[60]fullerene derivatives.

A Convenient And Efficient Synthesis Of (S)-Lysine And (S)-Arginine Homologues Via Olefin Cross-Metathesis, Timothy P. Boyle, John B. Bremner, Jonathan A. Coates, Paul A. Keller, Stephen G. Pyne

Paul Keller

A convenient five step synthesis of (S)-homolysine, incorporating a key olefin cross-metathesis step in the chain extension methodology, has been developed, together with a six step related synthesis of a new homologue of arginine, (S)-bishomoarginine.

Antimalarial Activity Of 2,4-Diaminopyrimidines, J. Morgan, R. Haritakul, Paul A. Keller

Paul Keller

A series of 2,4- and 4,6-diaminopyrimidines were prepared and evaluated for their in vitro antimalarial activity. Of the 12 compounds tested 7 showed reasonable activity with 1 having a sub-micromolar IC50.

Aryl Nitro Reduction With Iron Powder Or Stannous Chloride Under Ultrasonic Irradiation, A. B. Gamble, James A. Garner, Christopher Gordon, S. M. J. O'Conner, Paul A. Keller

Paul Keller

The selective reduction of aryl nitro compounds in the presence of sensitive functionalities, including halide, carbonyl, nitrile and ester substituents under ultrasonic irradiation at 35 kHz is reported in yields of 39-98%. Iron powder proved superior to stannous chloride with high tolerance of sensitive functional groups and high yields of the desired aryl amines in relatively short reaction times. Simple experimental procedure and purification also make the iron reduction of aryl nitro compounds advantageous over other methods of reduction.

Combining Structure-Based Drug Design And Pharmacophores, Renate Griffith, T. T. T. Luu, James A. Garner, Paul A. Keller

Paul Keller

Development towards integrated computer-aided drug design methodologies is presented by utilising crystal structure complexes to produce structure-based pharmacophores. These novel pharmacophores represent the ligand features that are involved in interactions with the target protein, as well as the space around the ligand occupied by the protein. The protein-ligand complexes can also yield information about all interactions that ligands could potentially form with the binding site, as well as about the size of the binding cavity. Together, these describe a 'superligand', which can also be viewed as a pharmacophore. Various types of novel pharmacophores are discussed and compared, using HIV-1 Reverse …

Discovery Of A Strongly Apoptotic Ruthenium Complex Through Combinatorial Coordination Chemistry, Seann P. Mulcahy

Seann P. Mulcahy

A strategy for combinatorial parallel coordination chemistry is introduced that provides access to libraries of tris-heteroleptic ruthenium complexes in an economical fashion. Using this method, a library of 560 constitutionally unique, monocationic ruthenium complexes was synthesized, followed by a screening for anticancer activity and resulting in the identification of three hits with promising cytotoxic properties in HeLa cancer cells. A subsequent structure–activity relationship led to the discovery of the surprisingly simple anticancer complex [Ru(tBu2bpy)2(phox)]PF6 (complex 1), with tBu2bpy = 4,4′-di-tert-buty-2,2′-bipyridine and Hphox = 2-(2′-hydroxyphenyl)oxazoline, displaying an LC50 value in HeLa cells of 1.3 μM and 0.3 μM after incubation for …

Absolute Ground-State Nitrogen Atom Density In A N2/Ch4 Late Afterglow: Talif Experiments And Modelling Studies, Et. Es-Sebbar, M.-C. Gazeau, Y. Benilan, A. Jolly, C D. Pintassilgo

Dr. Et-touhami Es-sebbar

Following a first study on a late afterglow in flowing pure nitrogen post discharge, we report new two-photon absorption laser-induced fluorescence (TALIF) measurements of the absolute ground-state atomic nitrogen density N(4S) and investigate the influence of methane introduced downstream from the discharge by varying the CH4 mixing ratio from 0% up to 50%. The N (4S) maximum density is about 2.2 × 1015 cm−3 in pure N2 for a residence time of 22 ms and does not change significantly for methane mixing ratio up to ~15%, while above, a drastic decrease is observed. The influence of the residence time has …

Cation-Specific And Anion-Specific Abraham Model Correlations For Solute Transfer Into Ionic Liquid Solvents, Laura M. Grubbs, Mariam Saifullah, Nohelli E. De La Rosa, William E. Acree Jr., Michael H. Abraham, Qichao Zhao, Jared L. Anderson

Jared L. Anderson

Data have been assembled from the published literature on the infinite dilution activity coefficients and gas solubilities of solutes dissolved in ionic liquid (IL) solvents. In total data for more than 1790 solute-IL pairs were compiled. The published experimental data were converted to gas-to-IL and water-to-IL partition coefficients, and correlated with the ion-specific equation coefficient version of the Abraham general solvation model. Ion-specific equation coefficients were calculated for 19 different cations and 12 different anions. The calculated ion-specific equation coefficients describe the experimental gas-to-IL and water-to-IL partition coefficient data to within 0.114 and 0.139 log units, respectively. Reported for the …

Photoreactive Crystalline Quasiracemates, Rebecca C. Grove, Steven H. Malehorn, Meghan E. Breen, Kraig A. Wheeler

Kraig A. Wheeler

Rationally designed racemic and quasiracemic sulfonamidecinnamic acids assemble to give hydrogen-bonded dimers with coplanar alignment of neighboring olefins. The quasiracemate phase contains near inversion-related motifs with chemically distinct components forming supramolecular heterodimers that undergo asymmetric photodimerization.

Experimental And Theoretical Studies On Nitrogen Plasma And Methane Photolysis: Implications For Laboratory Simulations Of Titan’S Atmosphere, M-C. Gazeau, Y. Benilan, E. Arzoumanian, Et. Es-Sebbar, A. Jolly

Dr. Et-touhami Es-sebbar

No abstract provided.