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Chemistry

University of Richmond

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Articles 31 - 60 of 104

Full-Text Articles in Physical Sciences and Mathematics

Electrochemical Characterization Of Self-Assembled Monolayers On Gold Substrates Derived From Thermal Decomposition Of Monolayer-Protected Cluster Films, Michael C. Leopold, Tran T. Doan, Melissa J. Mullaney, Andrew F. Loftus, Christopher M. Kidd Aug 2015

Electrochemical Characterization Of Self-Assembled Monolayers On Gold Substrates Derived From Thermal Decomposition Of Monolayer-Protected Cluster Films, Michael C. Leopold, Tran T. Doan, Melissa J. Mullaney, Andrew F. Loftus, Christopher M. Kidd

Chemistry Faculty Publications

Networked films of monolayer-protected clusters (MPCs), alkanethiolate-stabilized gold nanoparticles, can be thermally decomposed to form stable gold on glass substrates that are subsequently modified with self-assembled monolayers (SAMs) for use as modified electrodes. Electrochemical assessment of these SAM-modified gold substrates, including double-layer capacitance measurements, linear sweep desorption of the alkanethiolates, and diffusional redox probing, all show that SAMs formed on gold supports formed from thermolysis of MPC films possess substantially higher defect density compared to SAMs formed on traditional evaporated gold. The density of defects in the SAMs on thermolyzed gold is directly related to the strategies used to assemble …

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Structure-Function Relationships Affecting The Sensing Mechanism Of Monolayer-Protected Cluster Doped Xerogel Amperometric Glucose Biosensors, Luke T. Dipasquale, Nicholas G. Poulos, Jackson R. Hall, Aastha Minocha, Tram Anh Bui, Michael C. Leopold Mar 2015

Structure-Function Relationships Affecting The Sensing Mechanism Of Monolayer-Protected Cluster Doped Xerogel Amperometric Glucose Biosensors, Luke T. Dipasquale, Nicholas G. Poulos, Jackson R. Hall, Aastha Minocha, Tram Anh Bui, Michael C. Leopold

Chemistry Faculty Publications

A systematic study of the structure–function relationships critical to understanding the sensing mechanism of 1st generation amperometric glucose biosensors with an embedded nanoparticle (NP) network is presented. Xerogel-based films featuring embedded glucose oxidase enzyme and doped with alkanethiolate-protected gold NPs, known as monolayer protected clusters (MPCs), exhibit significantly enhanced performance compared to analogous systems without NPs including higher sensitivity, faster response time, and extended linear/dynamic ranges. The proposed mechanism involves diffusion of the glucose to glucose oxidase within the xerogel, enzymatic reaction production of H2O2 with subsequent diffusion to the embedded network of MPCs where it is oxidized, an event …

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Quantitative Analysis Of Heavy Metals In Children’S Toys And Jewelry: A Multi-Instrument, Multi-Technique Exercise In Analytical Chemistry And Public Health, Lauren E. Finch, Margot M. Hillyer, Michael C. Leopold Feb 2015

Quantitative Analysis Of Heavy Metals In Children’S Toys And Jewelry: A Multi-Instrument, Multi-Technique Exercise In Analytical Chemistry And Public Health, Lauren E. Finch, Margot M. Hillyer, Michael C. Leopold

Chemistry Faculty Publications

For most chemistry curricula, laboratory-based activities in quantitative and instrumental analysis continue to be an important aspect of student development/training, one that can be more effective if conceptual understanding is delivered through an inquiry-based process relating the material to relevant issues of public interest and student career trajectories. Laboratory experiences that actively engage students in this manner can be difficult to identify and execute. A special topics, project-based laboratory module is presented here that utilizes multiple techniques and instruments to investigate toxic metal content (lead, cadmium, and arsenic) in children’s toys and toy jewelry. The module effectively illustrates a considerable …

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Functional Layer-By-Layer Design Of Xerogel-Based 1st Generation Amperometric Glucose Biosensors, Nicholas G. Poulos, Jackson R. Hall, Michael C. Leopold Jan 2015

Functional Layer-By-Layer Design Of Xerogel-Based 1st Generation Amperometric Glucose Biosensors, Nicholas G. Poulos, Jackson R. Hall, Michael C. Leopold

Chemistry Faculty Publications

Xerogel-based first-generation amperometric glucose biosensors, constructed through specific layer-by-layer assembly of films featuring glucose oxidase doped xerogel, a diffusion-limiting xerogel layer, and capped with both electropolymerized polyphenol and blended polyurethane semipermeable membranes, are presented. The specific combination of xerogels formed from specific silane precursors, including propyl-trimethoxysilane, isobutyl-trimethoxysilane, octyl-trimethoxysilane, and hydroxymethyl-triethoxysilane, exhibit impressive dynamic and linear ranges of detection (e.g., ≥24–28 mM glucose) and low response times, as well as significant discrimination against common interferent species such as acetaminophen, ascorbic acid, sodium nitrite, oxalic acid, and uric acid as determined by selectivity coefficients. Additionally, systematic electrochemical and contact angle studies of …

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Friedel–Crafts Hydroxyalkylation Of Indoles Mediated By Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Christopher D. Poff, Alissa N. Nizinski Jan 2015

Friedel–Crafts Hydroxyalkylation Of Indoles Mediated By Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Christopher D. Poff, Alissa N. Nizinski

Chemistry Faculty Publications

Indoles and N-alkylindoles undergo Friedel–Crafts addition to aldehydes in the presence of trimethylsilyl trifluoromethanesulfonate and a trialkylamine to produce 3-(1- silyloxyalkyl)indoles. Neutralization of the reaction mixture with pyridine followed by deprotection under basic conditions with tetrabutylammonium fluoride provides the 1:1 adduct as the free alcohol. This method prevents spontaneous conversion of the desired products to the thermodynamically favored bisindolyl(aryl)methanes, a process typically observed when indoles are reacted with aldehydes under acidic conditions.

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First Principles Predictions Of Van Der Waals Bonded Inorganic Crystal Structures: Test Case, Hgcl2, Valentino R. Cooper, Kelling J. Donald Jan 2015

First Principles Predictions Of Van Der Waals Bonded Inorganic Crystal Structures: Test Case, Hgcl2, Valentino R. Cooper, Kelling J. Donald

Chemistry Faculty Publications

We study the crystals structure and stability of four possible polymorphs of HgCl2 using first principles density functional theory. Mercury (II) halides are a unique class of materials which, depending on the halide species, form in a wide range of crystal structures, ranging from densely packed solids to layered materials and molecular solids. Predicting the groundstate structure of any member of this group from first principles, therefore, requires a general purpose functional that treats van der Waals bonding and covalent/ionic bonding adequately. Here, we demonstrate that the non-local van der Waals density functional paired with the C09 exchange functional …

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One-Pot Silyl Ketene Acetal-Formation-Mukaiyama–Mannich Additions To Imines Mediated By Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Jared A. Ingersoll, Hadleigh M. Glist, Carolyn M. Dombrowski, Adam T. Barnett Jan 2015

One-Pot Silyl Ketene Acetal-Formation-Mukaiyama–Mannich Additions To Imines Mediated By Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Jared A. Ingersoll, Hadleigh M. Glist, Carolyn M. Dombrowski, Adam T. Barnett

Chemistry Faculty Publications

In the presence of trimethylsilyl trifluoromethanesulfonate and trialkylamine base, thioesters are readily converted to silyl ketene acetals in situ and undergo Mukaiyama–Mannich addition to N-phenylimines in one pot. The silyl triflates appears to play two roles, activating both the thioester and the imine. This process also works well when thioesters are replaced with amides, esters, or ketones. Products are isolated as desilylated anilines without the necessity of a deprotection step. Yields range from 65-99%.

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Molecular Dynamics Study Of The Opening Mechanism For Dna Polymerase I, Carol A. Parish, Bill R. Miller Iii, Eugene Y. Wu Dec 2014

Molecular Dynamics Study Of The Opening Mechanism For Dna Polymerase I, Carol A. Parish, Bill R. Miller Iii, Eugene Y. Wu

Chemistry Faculty Publications

During DNA replication, DNA polymerases follow an induced fit mechanism in order to rapidly distinguish between correct and incorrect dNTP substrates. The dynamics of this process are crucial to the overall effectiveness of catalysis. Although Xray crystal structures of DNA polymerase I with substrate dNTPs have revealed key structural states along the catalytic pathway, solution fluorescence studies indicate that those key states are populated in the absence of substrate. Herein, we report the first atomistic simulations showing the conformational changes between the closed, open, and ajar conformations of DNA polymerase I in the binary (enzyme:DNA) state to better understand its …

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Silyl Trifluoromethanesulfonate-Activated Para-Methoxybenzyl Methyl Ether As An Alkylating Agent For Thiols And Aryl Ketones, C. Wade Downey, Sarah E. Covington, Derek C. Obenschain, Evan Halliday, James T. Rague, Danielle N. Confair Sep 2014

Silyl Trifluoromethanesulfonate-Activated Para-Methoxybenzyl Methyl Ether As An Alkylating Agent For Thiols And Aryl Ketones, C. Wade Downey, Sarah E. Covington, Derek C. Obenschain, Evan Halliday, James T. Rague, Danielle N. Confair

Chemistry Faculty Publications

para-Methoxybenzyl methyl ether acts as an alkylating agent for thiols in the presence of trimethylsilyl trifluoromethanesulfonate and trialkylamine base in good yields (58-96%). Aryl ketones are alkylated under similar conditions, probably through an enol silane intermediate, also in high yields (67-95%). The active alkylating species is likely a p-methoxybenzyl cation.

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Silyl Triflate-Accelerated Additions Of Catalytically Generated Zinc Acetylides To N-Phenyl Nitrones, C. Wade Downey, Erin N. Maxwell, Danielle N. Confair Aug 2014

Silyl Triflate-Accelerated Additions Of Catalytically Generated Zinc Acetylides To N-Phenyl Nitrones, C. Wade Downey, Erin N. Maxwell, Danielle N. Confair

Chemistry Faculty Publications

Terminal alkynes readily form zinc acetylides in the presence of iPr2NEt and 20 mol% ZnBr2, then attack N-phenyl nitrones activated by trimethylsilyl trifluoromethanesulfonate. Deprotection with aqueous acid yields the N-hydroxyl propargylamine. Yields are generally high for nitrones derived from aromatic aldehydes. Control experiments suggest that the silyl triflate has a significant accelerating effect upon the reaction.

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Multi-Technique Quantitative Analysis And Socioeconomic Considerations Of Lead, Cadmium, And Arsenic In Children's Toys And Toy Jewelry, Margot M. Hillyer, Lauren E. Finch, Alisha S. Cerel, Jonathan D. Dattelbaum, Michael C. Leopold Feb 2014

Multi-Technique Quantitative Analysis And Socioeconomic Considerations Of Lead, Cadmium, And Arsenic In Children's Toys And Toy Jewelry, Margot M. Hillyer, Lauren E. Finch, Alisha S. Cerel, Jonathan D. Dattelbaum, Michael C. Leopold

Chemistry Faculty Publications

A wide spectrum and large number of children’s toys and toy jewelry items were purchased from both bargain and retail vendors and analyzed for arsenic, cadmium, and lead metal content using multiple analytical techniques, including flame and furnace atomic absorption spectroscopy as well as X-ray fluorescence spectroscopy. Particularly dangerous for young children, metal concentrations in toys/toy jewelry were assessed for compliance with current Consumer Safety Product Commission (CPSC) regulations (F963-11). A conservative metric involving multiple analytical techniques was used to categorize compliance: one technique confirmation of metal in excess of CPSC limits indicated a “suspect” item while confirmation on two …

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A Loose Domain Swapping Organization Confers A Remarkable Stability To The Dimeric Structure Of The Arginine Binding Protein From Thermotoga Maritima, Alessia Ruggiero, Jonathan D. Dattelbaum, Maria Staiano, Rita Berisio, Sabato D'Auria, Luigi Vitagliano Jan 2014

A Loose Domain Swapping Organization Confers A Remarkable Stability To The Dimeric Structure Of The Arginine Binding Protein From Thermotoga Maritima, Alessia Ruggiero, Jonathan D. Dattelbaum, Maria Staiano, Rita Berisio, Sabato D'Auria, Luigi Vitagliano

Chemistry Faculty Publications

The arginine binding protein from Thermatoga maritima (TmArgBP), a substrate binding protein (SBP) involved in the ABC system of solute transport, presents a number of remarkable properties. These include an extraordinary stability to temperature and chemical denaturants and the tendency to form multimeric structures, an uncommon feature among SBPs involved in solute transport. Here we report a biophysical and structural characterization of the TmArgBP dimer. Our data indicate that the dimer of the protein is endowed with a remarkable stability since its full dissociation requires high temperature as well as SDS and urea at high concentrations. In order to elucidate …

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Stop Rotating! One Substitution Halts The B19- Motor, Francisco Cervantes-Navarro, Gerarso Martínez-Guajardo, Edison Osorio, Diego Moreno, William Tiznado, Rafael Islas, Kelling J. Donald, Gabriel Merino Jan 2014

Stop Rotating! One Substitution Halts The B19- Motor, Francisco Cervantes-Navarro, Gerarso Martínez-Guajardo, Edison Osorio, Diego Moreno, William Tiznado, Rafael Islas, Kelling J. Donald, Gabriel Merino

Chemistry Faculty Publications

The B19- anion and other boron species have been dubbed ‘Wankel motors’ for the almost barrierless rotation of inner and outer concentric rings relative to each other in these compounds. A single substitution in B19- is shown to shut down the well-established fluxionality in the anion. A carbon atom substituted in the structure to give a neutral CB18 species is shown computationally to enforce bond localization.

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One-Pot Enol Silane Formation-Mukaiyama–Mannich Addition Of Ketones, Amides, And Thioesters To Nitrones In The Presence Of Trialkylsilyl Trifluoromethanesulfonates, C. Wade Downey, Carolyn M. Dombrowski, Erin N. Maxwell, Chelsea L. Safran, Odamea A. Akomah Sep 2013

One-Pot Enol Silane Formation-Mukaiyama–Mannich Addition Of Ketones, Amides, And Thioesters To Nitrones In The Presence Of Trialkylsilyl Trifluoromethanesulfonates, C. Wade Downey, Carolyn M. Dombrowski, Erin N. Maxwell, Chelsea L. Safran, Odamea A. Akomah

Chemistry Faculty Publications

Ketones, amides, and thioesters form enol silanes and add to N-phenylnitrones in one pot in the presence of trimethylsilyl trifluoromethanesulfonate and trialkylamine. The reaction is general to a range of silyl trifluoromethanesulfonates and N-phenylnitrones. The b-(silyloxy)amino carbonyl products are stable to chromatography and can be isolated in 63-99% yield.

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Monolayer-Protected Nanoparticle Doped Xerogels As Functional Components Of Amperometric Glucose Biosensors, Michael Hartley Freeman, Jackson R. Hall, Michael C. Leopold Mar 2013

Monolayer-Protected Nanoparticle Doped Xerogels As Functional Components Of Amperometric Glucose Biosensors, Michael Hartley Freeman, Jackson R. Hall, Michael C. Leopold

Chemistry Faculty Publications

First-generation amperometric glucose biosensors incorporating alkanethiolate-protected gold nanoparticles, monolayer protected clusters (MPCs), within a xerogel matrix are investigated as model systems for nanomaterial-assisted electrochemical sensing strategies. The xerogel biosensors are comprised of platinum electrodes modified with composite films of (3-mercaptopropyl)trimethoxy silane xerogel embedded with glucose oxidase enzyme, doped with Au225(C6)75 MPCs, and coated with an outer polyurethane layer. Electrochemistry and scanning/transmission electron microscopy, including cross-sectional TEM, show sensor construction, humidity effects on xerogel structure, and successful incorporation of MPCs. Analytical performance of the biosensor scheme with and without MPC doping of the xerogel is determined from direct glucose injection during …

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Nanoparticle Film Assemblies As Platforms For Electrochemical Biosensing – Factors Affecting Amperometric Signal Enhancement Of Hydrogen Peroxide, Adrienne R. Schmidt, Natalie D. T. Nguyen, Michael C. Leopold Mar 2013

Nanoparticle Film Assemblies As Platforms For Electrochemical Biosensing – Factors Affecting Amperometric Signal Enhancement Of Hydrogen Peroxide, Adrienne R. Schmidt, Natalie D. T. Nguyen, Michael C. Leopold

Chemistry Faculty Publications

Factors affecting the enhanced amperometric signal observed at electrodes modified with polyelectrolyte–gold nanoparticle (Au-NP) composite films, which are potential interfaces for first-generation biosensors, were systematically investigated and optimized for hydrogen peroxide (H2O2) detection. Polyelectrolyte multilayer films embedded with citrate-stabilized gold nanoparticles exhibited high sensitivity toward the oxidation of H2O2. From this Au-NP film assembly, the importance of Au-NP ligand protection, film permeability, the density of Au-NPs within the film, and electronic coupling between Au-NPs (interparticle) and between the film and the electrode (interfacial) were evaluated. Using alternative Au-NPs, including those stabilized with thiols, polymers, and bulky ligands, suggests that the …

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Periplasmic Binding Proteins In Thermophiles: Characterization And Potential Application Of An Arginine-Binding Protein From Thermotoga Maritima: A Brief Thermo-Story, Alessio Ausili, Maria Staiano, Jonathan D. Dattelbaum, Antonio Varriale, Alessandro Capo, Sabato D'Auria Jan 2013

Periplasmic Binding Proteins In Thermophiles: Characterization And Potential Application Of An Arginine-Binding Protein From Thermotoga Maritima: A Brief Thermo-Story, Alessio Ausili, Maria Staiano, Jonathan D. Dattelbaum, Antonio Varriale, Alessandro Capo, Sabato D'Auria

Chemistry Faculty Publications

Arginine-binding protein from the extremophile Thermotoga maritima is a 27.7 kDa protein possessing the typical two-domain structure of the periplasmic binding proteins family. The protein is characterized by a very high specificity and affinity to bind to arginine, also at high temperatures. Due to its features, this protein could be taken into account as a potential candidate for the design of a biosensor for arginine. It is important to investigate the stability of proteins when they are used for biotechnological applications. In this article, we review the structural and functional features of an arginine-binding protein from the extremophile Thermotoga maritima …

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Theoretical Design Of Stable Small Aluminium-Magnesium Binary Clusters, Edison Osorio, Alejandro Vasquez, Elizabeth Florez, Fanor Mondragon, Kelling J. Donald, William Tiznado Jan 2013

Theoretical Design Of Stable Small Aluminium-Magnesium Binary Clusters, Edison Osorio, Alejandro Vasquez, Elizabeth Florez, Fanor Mondragon, Kelling J. Donald, William Tiznado

Chemistry Faculty Publications

We explore in detail the potential energy surfaces of the AlxMgy (x, y = 1–4) systems as case studies to test the utility and limitations of simple rules based on electron counts and the phenomenological shell model (PSM) for bimetallic clusters. We find that it is feasible to design stable structures that are members of this set of small Al–Mg binary clusters, using simple electron count rules, including the classical 4n + 2 Hückel model, and the most recently proposed PSM. The thermodynamic stability of the title compounds has been evaluated using several different descriptors, including …

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Structurally Diverse Hamigerans From The New Zealand Marine Sponge Hamigera Tarangaensis: Nmr-Directed Isolation, Structure Elucidation And Antifungal Activity, A. Jonathan Singh, Jonathan D. Dattelbaum, Jessica J. Field, Zlatka Smart, Ethan F. Woolly, Jacqueline M. Barber, Rosemary Heathcott, John H. Miller, Peter T. Northcote Jan 2013

Structurally Diverse Hamigerans From The New Zealand Marine Sponge Hamigera Tarangaensis: Nmr-Directed Isolation, Structure Elucidation And Antifungal Activity, A. Jonathan Singh, Jonathan D. Dattelbaum, Jessica J. Field, Zlatka Smart, Ethan F. Woolly, Jacqueline M. Barber, Rosemary Heathcott, John H. Miller, Peter T. Northcote

Chemistry Faculty Publications

The NMR-directed investigation of the New Zealand marine sponge Hamigera tarangaensis has afforded ten new compounds of the hamigeran family, and a new 13-epi-verrucosane congener. Notably, hamigeran F (6) possesses an unusual carbon–carbon bond between C-12 and C-13, creating an unprecedented skeleton within this class. In particular, the structural features of 6, hamigeran H (10) and hamigeran J (12) imply a diterpenoid origin, which has allowed the putative biogenesis of three hamigeran carbon skeletons to be proposed based on geranyl geranyl pyrophosphate. All new hamigerans exhibited micromolar activity towards the HL-60 …

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One-Pot Three-Step Thioconjugate Addition-Oxidation-Diels–Alder Reactions Of Ethyl Propiolate, C. Wade Downey, Smaranda Craciun, Christina A. Vivelo, Ana M. Neferu, Carly J. Mueller, Stephanie Corsi Oct 2012

One-Pot Three-Step Thioconjugate Addition-Oxidation-Diels–Alder Reactions Of Ethyl Propiolate, C. Wade Downey, Smaranda Craciun, Christina A. Vivelo, Ana M. Neferu, Carly J. Mueller, Stephanie Corsi

Chemistry Faculty Publications

Ethyl propiolate undergoes one-pot three-step thioconjugate addition-oxidation-Diels–Alder cycloaddition when treated with a variety of thiols in the presence of catalytic base, meta-chloroperbenzoic acid, lithium perchlorate, and cyclopentadiene. The reaction of S‑aryl thiols is catalyzed by trialkylamines, and the reaction of aliphatic thiols requires catalytic alkoxide base. Yields of the major diastereomer of the conveniently functionalized bicyclic products range from 47 to 81% depending upon the thiol reactant, which compares favorably to yields observed when the entire synthesis is performed step by step.

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One-Pot Synthesis Of (Z)-B-Sulfonyl Enoates From Ethyl Propiolate, C. Wade Downey, Smaranda Craciun, Ana M. Neferu, Christina A. Vivelo, Carly J. Mueller, Brian C. Southall, Stephanie Corsi, Eric W. Etchill, Ryan J. Sault Oct 2012

One-Pot Synthesis Of (Z)-B-Sulfonyl Enoates From Ethyl Propiolate, C. Wade Downey, Smaranda Craciun, Ana M. Neferu, Christina A. Vivelo, Carly J. Mueller, Brian C. Southall, Stephanie Corsi, Eric W. Etchill, Ryan J. Sault

Chemistry Faculty Publications

B-Sulfonyl enoates may be synthesized through a one-pot two-step sequence from ethyl propiolate with good to excellent selectivity for the Z isomer. Trialkylamines catalyze thioconjugate additions of aryl thiols, and alkoxides catalyze the addition of aliphatic thiols. Addition of meta-chloroperbenzoic acid (mCPBA) and LiClO4 to the reaction mixture provides rapid access to the sulfonyl enoates. Yields of the pure Z isomer range from 51 – 90%.

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Challenging Disciplinary Boundaries In The First Year: A New Introductory Integrated Science Course For Stem Majors, Lisa Gentile, Lester Caudill, Mirela Fetea, April L. Hill, Kathy Hoke, Barry Lawson, Ovidiu Z. Lipan, Michael Kerckhove, Carol A. Parish, Krista J. Stenger, Doug Szajda May 2012

Challenging Disciplinary Boundaries In The First Year: A New Introductory Integrated Science Course For Stem Majors, Lisa Gentile, Lester Caudill, Mirela Fetea, April L. Hill, Kathy Hoke, Barry Lawson, Ovidiu Z. Lipan, Michael Kerckhove, Carol A. Parish, Krista J. Stenger, Doug Szajda

Department of Math & Statistics Faculty Publications

To help undergraduates make connections among disciplines so they are able to approach, evaluate, and contribute to the solutions of important global problems, our campus has been focused on interdisciplinary research and education opportunities across the science, technology, engineering, and mathematics (STEM) disciplines. This paper describes the mobilization, planning, and implementation of a first-year interdisciplinary course for STEM majors that integrates key concepts found in traditional first-semester biology, chemistry, computer science, mathematics, and physics courses. This team-taught course, Integrated Quantitative Science (IQS), is half of a first-year student’s schedule in both semesters and is composed of a double lecture and …

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Challenging Disciplinary Boundaries In The First Year: A New Introductory Integrated Science Course For Stem Majors, Lisa Gentile, Lester Caudill, Mirela Fetea, April L. Hill, Kathy Hoke, Barry Lawson, Ovidiu Z. Lipan, Michael Kerckhove, Carol A. Parish, Krista J. Stenger, Doug Szajda May 2012

Challenging Disciplinary Boundaries In The First Year: A New Introductory Integrated Science Course For Stem Majors, Lisa Gentile, Lester Caudill, Mirela Fetea, April L. Hill, Kathy Hoke, Barry Lawson, Ovidiu Z. Lipan, Michael Kerckhove, Carol A. Parish, Krista J. Stenger, Doug Szajda

Biology Faculty Publications

To help undergraduates make connections among disciplines so they are able to approach, evaluate, and contribute to the solutions of important global problems, our campus has been focused on interdisciplinary research and education opportunities across the science, technology, engineering, and mathematics (STEM) disciplines. This paper describes the mobilization, planning, and implementation of a first-year interdisciplinary course for STEM majors that integrates key concepts found in traditional first-semester biology, chemistry, computer science, mathematics, and physics courses. This team-taught course, Integrated Quantitative Science (IQS), is half of a first-year student’s schedule in both semesters and is composed of a double lecture and …

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Cbe5e− (E = Al, Ga, In, Tl): Planar Pentacoordinate Carbon In Heptaatomic Clusters, Abril C. Castro, Gerarso Martinez-Guajardo, Thomas Johnson, Jesus M. Ugalde, Yan-Bo Wu, Jose M. Mercero, Thomas Heine, Kelling J. Donald, Gabriel Merino Jan 2012

Cbe5e− (E = Al, Ga, In, Tl): Planar Pentacoordinate Carbon In Heptaatomic Clusters, Abril C. Castro, Gerarso Martinez-Guajardo, Thomas Johnson, Jesus M. Ugalde, Yan-Bo Wu, Jose M. Mercero, Thomas Heine, Kelling J. Donald, Gabriel Merino

Chemistry Faculty Publications

A series of clusters with the general formula CBe5E- (E = Al, Ga, In, Tl) are theoretically shown to have a planar pentacoordinate carbon atom. The structures show a simple and rigid topological framework—a planar EBe4 ring surrounding a C center, with one of the ring Be–Be bonds capped in-plane by a fifth Be atom. The system is stabilized by a network of multicenter σ bonds in which the central C atom is the acceptor, and π systems as well by which the C atom donates charge to the Be and E atoms that encircle it.

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Plane And Simple: Planar Tetracoordinate Carbon Centers In Small Moleculesw, Chad Crigger, Bernard K. Wittmaack, Marina Tawfik, Gabriel Merino, Kelling J. Donald Jan 2012

Plane And Simple: Planar Tetracoordinate Carbon Centers In Small Moleculesw, Chad Crigger, Bernard K. Wittmaack, Marina Tawfik, Gabriel Merino, Kelling J. Donald

Chemistry Faculty Publications

A class of neutral 18-electron molecules with planar tetracoordinate carbon (ptC) centers is introduced. We show computationally that when n = 3 the neutral singlet molecule C(BeH)n(BH2)4-n and other isoelectronic (18-valence electron) molecules of main group elements collapse from locally tetrahedral arrangements at the C-center to (near) planar tetracoordinate structures. For C(BeH)3BH2 and C(CH3)(BH2)Li2, for example, the tetrahedral type conformation is not even a minimum on the potential energy surface at the B3PW91, MP2(full), or CCSD levels of theory. The Mg analogue C(MgH)3BH2 …

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Sweep, Step, Pulse, And Frequency-Based Techniques Applied To Protein Monolayer Electrochemistry At Nanoparticle Interfaces, Debbie S. Campbell-Rance, Tran T. Doan, Michael C. Leopold Nov 2011

Sweep, Step, Pulse, And Frequency-Based Techniques Applied To Protein Monolayer Electrochemistry At Nanoparticle Interfaces, Debbie S. Campbell-Rance, Tran T. Doan, Michael C. Leopold

Chemistry Faculty Publications

Protein monolayer electrochemistry (PME), a strategy using synthetic platforms to study the electron transfer (ET) properties of adsorbed proteins, has been successfully applied to proteins adsorbed at monolayer-protected gold cluster (MPCs) assembled films, an adsorption interface shown to be an effective alternative, compared to traditional self-assembled monolayer (SAM) films, for the immobilization and study of ET proteins. Within PME studies, cyclic voltammetry (CV) remains the most commonly applied electrochemical technique in spite of several limitations that occur when the sweep technique is used at either platform. In particular, CV for PME at MPC films results in analysis complications stemming from …

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Optical And Electrochemical Properties Of Multi-Layer Polyelectrolyte Thin Films Incorporating Spherical, Gold Colloid Nanomaterials, Tran T. Doan, Robert W. Day, Michael C. Leopold Sep 2011

Optical And Electrochemical Properties Of Multi-Layer Polyelectrolyte Thin Films Incorporating Spherical, Gold Colloid Nanomaterials, Tran T. Doan, Robert W. Day, Michael C. Leopold

Chemistry Faculty Publications

Polyelectrolyte multilayer (PEM) films incorporating various types of spherical, gold nanomaterials (NMs) were investigated to assess the existence of electrochemical and/or optical signal enhancement effects directly attributable to embedded NMs and the relationship of these effects to film structure and composition. Specifically, electrostatically assembled films of cationic poly-L-lysine (PLL) and anionic poly(4-styrene sulfonate) (PSS) incorporating one of four types of spherical, gold colloid NMs were constructed on 3-(aminopropyl)trimethoxysilane (3-APTMS)-modified glass substrates for optical studies or 11-mercaptoundecanoic (MUA)-modified gold electrodes for electrochemical studies. The NMs inserted into the PEM films include citrate-stabilized gold nanoparticles, thioctic acid-stabilized gold nanoparticles (TAS-NPs), MUA-modified monolayer …

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Synthesis Of N-Acyl-N,O-Acetals From N-Aryl Amides And Acetals In The Presence Of Tmsotf, C. Wade Downey, Alan S. Fleisher, James T. Rague, Chelsea L. Safran, Megan E. Venable, Robert D. Pike Sep 2011

Synthesis Of N-Acyl-N,O-Acetals From N-Aryl Amides And Acetals In The Presence Of Tmsotf, C. Wade Downey, Alan S. Fleisher, James T. Rague, Chelsea L. Safran, Megan E. Venable, Robert D. Pike

Chemistry Faculty Publications

Secondary amides undergo in situ silyl imidate formation mediated by TMSOTf and an amine base, followed by addition to acetal acceptors to provide N-acyl-N,O-acetals in good yields. An analogous, high-yielding reaction is observed with 2-mercaptothiazoline as the silyl imidate precursor. Competing reduction of the acetal to the corresponding methyl ether via transfer hydrogenation can be circumvented by the replacement of i-Pr2NEt with 2,6-lutidine under otherwise identical reaction conditions.

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Charge Saturation And Neutral Substitutions In Halomethanes And Their Group 14 Analogues, Bernard K. Wittmaack, Chad Crigger, Matthew Guarino, Kelling J. Donald Jan 2011

Charge Saturation And Neutral Substitutions In Halomethanes And Their Group 14 Analogues, Bernard K. Wittmaack, Chad Crigger, Matthew Guarino, Kelling J. Donald

Chemistry Faculty Publications

A computational analysis of the charge distribution in halomethanes and their heavy analogues (MH4-nXn: M= C, Si, Ge, Sn, Pb; X = F, Cl, Br, I) as a function of n uncovers a previously unidentified saturation limit for fluorides when M ≠ C. We examine the electron densities obtained at the CCSD, MP2(full), B3PW91, and HF levels of theory for 80 molecules for four different basis sets. A previously observed substituent independent charge at F in fluoromethanes is shown to be a move toward saturation that is restricted by the low polarizability of C. This limitation …

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Stabilizing Carbon-Lithium Stars, Nancy Perez-Peralta, Maryel Contreras, William Tiznado, John Stewart, Kelling J. Donald, Gabriel Merino Jan 2011

Stabilizing Carbon-Lithium Stars, Nancy Perez-Peralta, Maryel Contreras, William Tiznado, John Stewart, Kelling J. Donald, Gabriel Merino

Chemistry Faculty Publications

We have explored in silico the potential energy surfaces of the C5Linn-6 (n = 5, 6, and 7) clusters using the Gradient Embedded Genetic Algorithm (GEGA) and other computational strategies. The most stable forms of C5Li5-- and C5Li6 are two carbon chains linked by two lithium atoms in a persistent seven membered ring capped by two Li atoms. The other Li atoms are arrayed on the edge of the seven membered ring. In contrast, the global minimum structure for C5Li7+ is a bicapped star …

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