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Articles 31 - 60 of 95
Full-Text Articles in Physical Sciences and Mathematics
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
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%.
First Principles Predictions Of Van Der Waals Bonded Inorganic Crystal Structures: Test Case, Hgcl2, Valentino R. Cooper, Kelling J. Donald
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 …
Molecular Dynamics Study Of The Opening Mechanism For Dna Polymerase I, Carol A. Parish, Bill R. Miller Iii, Eugene Y. Wu
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 …
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
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.
Silyl Triflate-Accelerated Additions Of Catalytically Generated Zinc Acetylides To N-Phenyl Nitrones, C. Wade Downey, Erin N. Maxwell, Danielle N. Confair
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.
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
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 …
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
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 …
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
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.
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
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.
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
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 …
Monolayer-Protected Nanoparticle Doped Xerogels As Functional Components Of Amperometric Glucose Biosensors, Michael Hartley Freeman, Jackson R. Hall, Michael C. Leopold
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 …
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
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 …
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
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 …
Theoretical Design Of Stable Small Aluminium-Magnesium Binary Clusters, Edison Osorio, Alejandro Vasquez, Elizabeth Florez, Fanor Mondragon, Kelling J. Donald, William Tiznado
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 …
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
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%.
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
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.
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
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.
Plane And Simple: Planar Tetracoordinate Carbon Centers In Small Moleculesw, Chad Crigger, Bernard K. Wittmaack, Marina Tawfik, Gabriel Merino, Kelling J. Donald
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 …
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
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 …
Optical And Electrochemical Properties Of Multi-Layer Polyelectrolyte Thin Films Incorporating Spherical, Gold Colloid Nanomaterials, Tran T. Doan, Robert W. Day, Michael C. Leopold
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 …
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
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.
Charge Saturation And Neutral Substitutions In Halomethanes And Their Group 14 Analogues, Bernard K. Wittmaack, Chad Crigger, Matthew Guarino, Kelling J. Donald
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 …
Crystallization And Preliminary X-Ray Crystallographic Analysis Of Ligand-Free And Arginine-Bound Forms Of Thermotoga Maritima Arginine-Binding Protein, Alessia Ruggiero, Jonathan D. Dattelbaum, Anna Pennacchio, Luisa Iozzion, Maria Staiano, Matthew S. Luchansky, Bryan S. Der, Rita Berisio, Sabato D'Auria, Luigi Vitagliano
Crystallization And Preliminary X-Ray Crystallographic Analysis Of Ligand-Free And Arginine-Bound Forms Of Thermotoga Maritima Arginine-Binding Protein, Alessia Ruggiero, Jonathan D. Dattelbaum, Anna Pennacchio, Luisa Iozzion, Maria Staiano, Matthew S. Luchansky, Bryan S. Der, Rita Berisio, Sabato D'Auria, Luigi Vitagliano
Chemistry Faculty Publications
The arginine-binding protein from Thermotoga maritima (TmArgBP) is an arginine-binding component of the ATP-binding cassette (ABC) transport system in this hyperthermophilic bacterium. This protein is endowed with an extraordinary stability towards thermal and chemical denaturation. Its structural characterization may provide useful insights for the clarification of structure– stability relationships and for the design of new biosensors. Crystallization trials were set up for both arginine-bound and ligand-free forms of TmArgBP and crystals suitable for crystallographic investigations were obtained for both forms. Ordered crystals of the arginine adduct of TmArgBP could only be obtained by using the detergent LDAO as an additive …
Stabilizing Carbon-Lithium Stars, Nancy Perez-Peralta, Maryel Contreras, William Tiznado, John Stewart, Kelling J. Donald, Gabriel Merino
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 …
Electrochemical Investigation Of Azurin Thermodynamic And Adsorption Properties At Monolayer-Protected Cluster Film Assemblies – Evidence For A More Homogeneous Adsorption Interface, Tran Doan, Morgan Lynn Vargo, John K. Gerig, Chris P. Gulka, Matthew L. Trawick, Jonathan D. Dattelbaum, Michael C. Leopold
Electrochemical Investigation Of Azurin Thermodynamic And Adsorption Properties At Monolayer-Protected Cluster Film Assemblies – Evidence For A More Homogeneous Adsorption Interface, Tran Doan, Morgan Lynn Vargo, John K. Gerig, Chris P. Gulka, Matthew L. Trawick, Jonathan D. Dattelbaum, Michael C. Leopold
Chemistry Faculty Publications
Thermodynamic and adsorption properties of protein monolayer electrochemistry (PME) are examined for Pseudomonas aeruginosa azurin (AZ) immobilized at an electrode modified with a networked film of monolayer-protected clusters (MPCs) to assess if nanoparticle films of this nature offer a more homogeneous adsorption interface compared to traditional self-assembled monolayer (SAM) modified electrodes. Specifically, electrochemistry is used to assess properties of surface coverage, formal potential, peak broadening, and electron transfer (ET) kinetics as a function of film thickness. The modification of a surface with dithiol-linked films of MPCs (Au225C675) provides a more uniform binding interface for AZ that results in voltammetry with …
Enhanced Electrochemistry Of Nanoparticle-Embedded Polyelectrolyte Films: Interfacial Electronic Coupling And Distance Dependence, Callie E. Dowdy, Michael C. Leopold
Enhanced Electrochemistry Of Nanoparticle-Embedded Polyelectrolyte Films: Interfacial Electronic Coupling And Distance Dependence, Callie E. Dowdy, Michael C. Leopold
Chemistry Faculty Publications
Factors affecting the electronic communication believed to be responsible for the enhanced solution electrochemistry observed at electrodes modified with hybrid polyelectrolyte–nanoparticle (PE–NP) film assemblies were systematically investigated. Specifically, the faradaic current and voltammetric peak splitting recorded for cyclic voltammetry of ferricyanide redox species (Fe(CN)63−/4−) at films constructed with various architectures of citrate-stabilized gold NPs embedded in polyelectrolyte films composed of poly-l-lysine and poly-S-styrene were used to establish the relative importance of both distance and electronic coupling. Layer-by-layer construction of PE–NP films allowed for the position and density of NPs to be varied within the film to assess electronic coupling between …
Acetic Acid Aldol Reactions In The Presence Of Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Miles W. Johnson, Daniel H. Lawrence, Alan S. Fleisher, Kathryn J. Tracy
Acetic Acid Aldol Reactions In The Presence Of Trimethylsilyl Trifluoromethanesulfonate, C. Wade Downey, Miles W. Johnson, Daniel H. Lawrence, Alan S. Fleisher, Kathryn J. Tracy
Chemistry Faculty Publications
In the presence of TMSOTf and a trialkylamine base, acetic acid undergoes aldol addition to non-enolizable aldehydes under exceptionally mild conditions. Acidic workup yields the β-hydroxy carboxylic acid. The reaction appears to proceed via a three-step, one-pot process, including in situ trimethylsilyl ester formation, bis-silyl ketene acetal formation, and TMSOTf-catalyzed Mukaiyama aldol addition. Independently synthesized TMSOAc also undergoes aldol additions under similar conditions.
Amino Acid Transport In Thermophiles: Characterization Of An Arginine-Binding Protein In Thermotoga Maritima. 2. Molecular Organization And Structural Stability, Andrea Scirè, Anna Marabotti, Maria Staiano, Luisa Iozzion, Matthew S. Luchansky, Bryan S. Der, Jonathan D. Dattelbaum, Fabio Tanfani, Sabato D'Auria
Amino Acid Transport In Thermophiles: Characterization Of An Arginine-Binding Protein In Thermotoga Maritima. 2. Molecular Organization And Structural Stability, Andrea Scirè, Anna Marabotti, Maria Staiano, Luisa Iozzion, Matthew S. Luchansky, Bryan S. Der, Jonathan D. Dattelbaum, Fabio Tanfani, Sabato D'Auria
Chemistry Faculty Publications
ABC transport systems provide selective passage of metabolites across cell membranes and typically require the presence of a soluble binding protein with high specificity to a specific ligand. In addition to their primary role in nutrient gathering, the binding proteins associated with bacterial transport systems have been studied for their potential to serve as design scaffolds for the development of fluorescent protein biosensors. In this work, we used Fourier transform infrared spectroscopy and molecular dynamics simulations to investigate the physicochemical properties of a hyperthermophilic binding protein from Thermotoga maritima. We demonstrated preferential binding for the polar amino acid arginine …
Amino Acid Transport In Thermophiles: Characterization Of An Arginine-Binding Protein In Thermotoga Maritima, Matthew S. Luchansky, Bryan S. Der, Sabato D'Auria, Gabriella Pocsfalvi, Luisa Iozzion, Daniela Marasco, Jonathan D. Dattelbaum
Amino Acid Transport In Thermophiles: Characterization Of An Arginine-Binding Protein In Thermotoga Maritima, Matthew S. Luchansky, Bryan S. Der, Sabato D'Auria, Gabriella Pocsfalvi, Luisa Iozzion, Daniela Marasco, Jonathan D. Dattelbaum
Chemistry Faculty Publications
Members of the periplasmic binding protein superfamily are involved in the selective passage of ligands through bacterial cell membranes. The hyperthermophilic eubacterium Thermotoga maritima was found to encode a highly stable and specific periplasmic arginine-binding protein (TM0593). Following signal sequence removal and overexpression in Escherichia coli, TM0593 was purified by thermoprecipitation and affinity chromatography. The ultra-stable protein with a monomeric molecular weight of 27.7 kDa was found to exist as both a homodimer and homotrimer at appreciable concentrations even under strongly denaturing conditions, with an estimated transition temperature of 116 °C. Its multimeric structure may provide further evidence of …
Tuning Σ-Holes: Charge Redistribution In The Heavy (Group 14) Analogues Of Simple And Mixed Halomethanes Can Impose Strong Propensities For Halogen Bonding, Kelling J. Donald, Bernard K. Wittmaack, Chad Crigger
Tuning Σ-Holes: Charge Redistribution In The Heavy (Group 14) Analogues Of Simple And Mixed Halomethanes Can Impose Strong Propensities For Halogen Bonding, Kelling J. Donald, Bernard K. Wittmaack, Chad Crigger
Chemistry Faculty Publications
Halogen bonding between halide sites (in substituted organic molecules or inorganic halides) and Lewis bases is a rapidly progressing area of exploration. Investigations of this phenomenon have improved our understanding of weak intermolecular interactions and suggested new possibilities in supramolecular chemistry and crystal engineering. The capacity for halogen bonding is investigated at the MP2(full) level of theory for 100 compounds, including all 80 MH4-nXn systems (M = C, Si, Ge, Sn, and Pb; X = F, Cl, Br, and I). The charge redistribution in these molecules and the (in)stability of the σ-hole at X as …