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Articles 601 - 630 of 962

Full-Text Articles in Chemistry

Phosphorylation Of Muc1 By Met Modulates Interaction With P53 And Mmp1 Expression, Pankaj K. Singh, Michelle E. Behrens, John P. Eggers, Ronald Cerny, Jennifer M. Bailey, Kandavel Shanmugam, Sandra J. Gendler, Eric P. Bennett, Michael A. Hollingsworth Jan 2008

Phosphorylation Of Muc1 By Met Modulates Interaction With P53 And Mmp1 Expression, Pankaj K. Singh, Michelle E. Behrens, John P. Eggers, Ronald Cerny, Jennifer M. Bailey, Kandavel Shanmugam, Sandra J. Gendler, Eric P. Bennett, Michael A. Hollingsworth

Ronald Cerny Publications

MUC1, a transmembrane mucin, is a key modulator of several signaling pathways that affect oncogenesis, motility, and cell morphology. The interaction of MUC1 cytoplasmic tail (MUC1CT) with signal transducers and its nuclear translocation and subsequent biological responses are believed to be regulated by phosphorylation status, but the precise mechanisms by which this occurs remain poorly defined. We detected a novel association between the Met receptor tyrosine kinase and the MUC1CT. Met catalyzed phosphorylation of tyrosine at YHPM in the MUC1CT. Stimulation of S2-013.MUC1F pancreatic cancer cells with hepatocyte growth factor facilitated nuclear localization of MUC1CT, as determined by real time …

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Classification Of Chemical Reactions: Stages Of Expertise, Marilyne Stains, Vicente Talanquer Jan 2008

Classification Of Chemical Reactions: Stages Of Expertise, Marilyne Stains, Vicente Talanquer

Department of Chemistry: Faculty Publications

In this study we explore the strategies that undergraduate and graduate chemistry students use when engaged in classification tasks involving symbolic and microscopic (particulate) representations of different chemical reactions. We were specifically interested in characterizing the basic features to which students pay attention when classifying chemical reactions at the symbolic and microscopic levels. We identified the categories that students create when classifying chemical reactions, and compared the performance in simple classification tasks of students with different levels of preparation in the discipline. Our results suggest that advanced levels of expertise in chemical classification do not necessarily evolve in a linear …

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Influence Of Heterocyclic And Oxime-Containing Farnesol Analogs On Quorum Sensing And Pathogenicity In Candida Albicans, Roman Shchepin, Dhammika H.M.L.P. Navarathna, Raluca Dumitru, Shane Lippold, Kenneth W. Nickerson, Patrick Dussault Jan 2008

Influence Of Heterocyclic And Oxime-Containing Farnesol Analogs On Quorum Sensing And Pathogenicity In Candida Albicans, Roman Shchepin, Dhammika H.M.L.P. Navarathna, Raluca Dumitru, Shane Lippold, Kenneth W. Nickerson, Patrick Dussault

Patrick Dussault Publications

A series of synthetic molecules combining a geranyl backbone with a heterocyclic or oxime head group are quorum-sensing molecules that block the yeast to mycelium transition in the dimorphic fungus Candida albicans. A number of the analogs have an IC50 ≤ 10 μM, a level of potency essentially identical to the natural quorum sensing signal, the sesquiterpene farnesol. Two of the most potent analogs, neither toxic toward healthy mice, display remarkably different effects when co-administered with C. albicans. While neither offers protection from candidiasis, one analog mimics farnesol in acting as a virulence factor, whereas the other …

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Fumonisin Level In Corn-Based Food And Feed From Linxian County, A High-Risk Area For Esophageal Cancer In China, Jiansheng Wang, Ying Zhou, Wanbo Liu, Xiangcheng Zhu, Liangcheng Du, Qiaomei Wang Jan 2008

Fumonisin Level In Corn-Based Food And Feed From Linxian County, A High-Risk Area For Esophageal Cancer In China, Jiansheng Wang, Ying Zhou, Wanbo Liu, Xiangcheng Zhu, Liangcheng Du, Qiaomei Wang

Liangcheng Du Publications

The level of mycotoxin fumonisins in corn-based food and feed collected from Linxian County, a high-risk area for esophageal cancer in China, has been analyzed using high-performance liquid chromatographic coupled with evaporative laser scattering detector (HPLC-ELSD). A total of 104 corn kernel samples were obtained from local households, granaries, wholesale markets (central markets), and retail markets (stores and supermarkets). Fumonisin B1 (FB1) was detected in the samples from households, granaries, central markets, and stores, with a positive rate of 61.5%, 50%, 33.3%, and 17%, respectively. No fumonisin was detected in samples from the supermarket. The highest FB1 levels (0.30–3.20 μg/ …

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Mechanisms Of Hemoglobin Adaptation To High Altitude Hypoxia, Jay F. Storz, Hideaki Moriyama Jan 2008

Mechanisms Of Hemoglobin Adaptation To High Altitude Hypoxia, Jay F. Storz, Hideaki Moriyama

Hideaki Moriyama Publications

Evidence from a number of vertebrate taxa suggests that modifications of hemoglobin (Hb) function may often play a key role in mediating an adaptive response to high altitude hypoxia. The respiratory functions of Hb are a product of the protein’s intrinsic O2-binding affinity and its interactions with allosteric effectors such as protons, chloride ions, CO2, and organic phosphates. Here we review several case studies involving high altitude vertebrates where it has been possible to identify specific mechanisms of Hb adaptation to hypoxia. In addition to comparative studies of Hbs from diverse animal species, functional studies of …

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Mechanisms Of Hemoglobin Adaptation To High Altitude Hypoxia, Jay F. Storz, Hideaki Moriyama Jan 2008

Mechanisms Of Hemoglobin Adaptation To High Altitude Hypoxia, Jay F. Storz, Hideaki Moriyama

Hideaki Moriyama Publications

Evidence from a number of vertebrate taxa suggests that modifications of hemoglobin (Hb) function may often play a key role in mediating an adaptive response to high altitude hypoxia. The respiratory functions of Hb are a product of the protein’s intrinsic O2-binding affinity and its interactions with allosteric effectors such as protons, chloride ions, CO2, and organic phosphates. Here we review several case studies involving high altitude vertebrates where it has been possible to identify specific mechanisms of Hb adaptation to hypoxia. In addition to comparative studies of Hbs from diverse animal species, functional studies of …

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Preface To Proceedings Of The Fourth San Luis Symposium On Surfaces, Interfaces And Catalysis, Jose Rodriguez, Marjorie Langell Jan 2008

Preface To Proceedings Of The Fourth San Luis Symposium On Surfaces, Interfaces And Catalysis, Jose Rodriguez, Marjorie Langell

Marjorie A. Langell Publications

The following Special Issue of The Journal of Molecular Catalysis A: Chemical consists of the Proceedings of The Fourth San Luis Symposium on Surfaces, Interfaces and Catalysis, a Pan-American Advanced Studies Institute, which took place in Cuernavaca, Mexico, on April 14–23, 2007. This was the fourth in a series of symposia designed to strengthen the links between Latin American and US and European scientists in the areas of surface science and catalysis. The concept was born at a conference in August of 1994 organized to celebrate the 400th anniversary of the founding of the city of San Luis in Argentina. …

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Exploiting Self-Assembly For Ligand-Scaffold Optimization: Substrate-Tailored Ligands For Efficient Catalytic Asymmetric Hydroboration, Shin A. Moteki, James M. Takacs Dec 2007

Exploiting Self-Assembly For Ligand-Scaffold Optimization: Substrate-Tailored Ligands For Efficient Catalytic Asymmetric Hydroboration, Shin A. Moteki, James M. Takacs

James M. Takacs Publications

A self-assembled ligand library (SAL XY) affords a wide range of R/S ratios in Rh-catalyzed asymmetric hydroboration (nbd = 2,5norbornadiene, R* is a chiral substituent). Ligand-scaffold optimization reveals “substrate-tailored” ligands that afford high regio- and enantioselectivity for a variety of ortho-substituted styrene derivatives.

Includes article (4 pp.) and supporting information (106 pp.).

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Fabrication Of Pillar-Structured Thermal Neutron Detectors, Rebecca J. Nikolić, Adam M. Conway, Catherine E. Reinhardt, Robert T. Graff, Tzu Fang Wang, Nirmalendu Deo, Chin Li Cheung Dec 2007

Fabrication Of Pillar-Structured Thermal Neutron Detectors, Rebecca J. Nikolić, Adam M. Conway, Catherine E. Reinhardt, Robert T. Graff, Tzu Fang Wang, Nirmalendu Deo, Chin Li Cheung

Barry Chin Li Cheung Publications

Pillar detector is an innovative solid state device structure that leverages advanced semiconductor fabrication technology to produce a device for thermal neutron detection. State-of-the-art thermal neutron detectors have shortcomings in achieving simultaneously high efficiency, low operating voltage while maintaining adequate fieldability performance. By using a 3-dimensional silicon PIN diode pillar array filled with isotopic boron 10, (10B) a high efficiency device is theoretically possible. The fabricated pillar structures reported in this work are composed of 2 μm diameter silicon pillars with a 4 μm pitch and pillar heights of 6 and 12 μm. The pillar detector with a …

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Tris(Dialkylamino)Aluminums: Syntheses, Characterization, Volatility Comparison, And Atomic Layer Deposition Of Alumina Thin Films, Casey R. Wade, Carter Silvernail, Chiranjib Banerjee, Axel Soulet, James Mcandrew, John A. Belot Jr. Dec 2007

Tris(Dialkylamino)Aluminums: Syntheses, Characterization, Volatility Comparison, And Atomic Layer Deposition Of Alumina Thin Films, Casey R. Wade, Carter Silvernail, Chiranjib Banerjee, Axel Soulet, James Mcandrew, John A. Belot Jr.

Department of Chemistry: Faculty Publications

The syntheses and characterization of both tris(diethylamino)aluminum and tris(diisopropylamino)aluminum are presented in this letter. Characterization includes vapor pressure measurements and comparison of the two non-pyrophoric precursors showing them to be viable alternatives to trimethylaluminum. Ultimately, tris(diisopropyl)aluminum was successful in the atomic layer deposition of alumina thin films.

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Molecules That Target Beta-Amyloid, Cliff I. Stains, Kalyani Mondal, Indraneel Ghosh Dec 2007

Molecules That Target Beta-Amyloid, Cliff I. Stains, Kalyani Mondal, Indraneel Ghosh

Cliff Stains Publications

The devastating effects of Alzheimer’s and related amyloidogenic diseases have inspired the synthesis and evaluation of numerous ligands to understand the molecular mechanism of the aggregation of the beta-amyloid peptide. Our review focuses on the current knowledge in this field with respect to molecules that have been demonstrated to interact with either oligomeric or fibrillar forms of the beta-amyloid peptide. We describe natural proteins, peptides, peptidomimetics, and small molecules that have been found to interfere with beta-amyloid aggregation. We also detail recent efforts in selecting molecules that target beta-amyloid isolated from antibody, protein, and peptide libraries. These new molecules will …

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A Set Of Phosphatase-Inert “Molecular Rulers” To Probe For Bivalent Mannose 6-Phosphate Ligand-Receptor Interactions, Xiang Fei, Christopher M. Connelly, Richard G. Macdonald, David B. Berkowitz Nov 2007

A Set Of Phosphatase-Inert “Molecular Rulers” To Probe For Bivalent Mannose 6-Phosphate Ligand-Receptor Interactions, Xiang Fei, Christopher M. Connelly, Richard G. Macdonald, David B. Berkowitz

David Berkowitz Publications

A set of bivalent mannose 6-phosphonate “molecular rulers” has been synthesized to examine ligand binding to the M6P/IGF2R. The set is estimated to span a P-P distance range of 16-26 Å (MMFF energy minimization on the hydrated phosphonates). Key synthetic transformations include sugar triflate displacement for phosphonate installation and Grubbs I cross-metathesis to achieve bivalency. Relative binding affinities were tested by radioligand displacement assays versus PMP-BSA (pentamannose phosphate-bovine serum albumin). These compounds exhibit slightly higher binding affinities for the receptor (IC50’s = 3.7-5 &#;M) than the parent, monomeric mannose 6-phosphonate ligand and M6P itself (IC50 = 11.5 …

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Myricetin Inhibits Escherichia Coli Dnab Helicase But Not Primase, Mark A. Griep, Sheldon Blood, Marilynn A. Larson, Scott A. Koepsell, Steven H. Hinrichs Nov 2007

Myricetin Inhibits Escherichia Coli Dnab Helicase But Not Primase, Mark A. Griep, Sheldon Blood, Marilynn A. Larson, Scott A. Koepsell, Steven H. Hinrichs

Mark A. Griep Publications

Primase and DnaB helicase play central roles during DNA replication initiation and elongation. Both enzymes are drug targets because they are essential, persistent among bacterial genomes, and have different sequences than their eukaryotic equivalents. Myricetin is a ubiquitous natural product in plants that is known to inhibit a variety of DNA polymerases, RNA polymerases, reverse transcriptases, and telomerases in addition being able to inhibit kinases and helicases. We have shown that myricetin inhibits Escherichia coli DnaB helicase according to a mechanism dominated by noncompetitive behavior with a Ki of 10.0 ± 0.5 μM. At physiological ATP concentration, myricetin inhibits …

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Synthesis And Characterization Of Novel Chiral Conjugated Materials, Andrzej Rajca, Makoto Miyasaka Nov 2007

Synthesis And Characterization Of Novel Chiral Conjugated Materials, Andrzej Rajca, Makoto Miyasaka

Andrzej Rajca Publications

Chirality is increasingly important in the design of organic π-conjugated materials. One of the aspects of the design involves optimization of achiral properties through the introduction of chirality. In this context, the inherent three-dimensional character of chirality and the control of intermolecular interactions associated with diastereomeric recognition provide a versatile handle for the optimization of supramolecular structures, film morphology and liquid crystalline order of π-conjugated polymers and oligomers in three dimensions. These inherently achiral properties have an impact on optoelectronic coupling, which may affect the fabrication of light-emitting diodes, field effect transistors, photodiodes, photovoltaic cells, fluorescent sensors and other devices. …

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Structure And Thermophysical Properties Of Single-Wall Si Nanotubes, Xinwei Wang, Zhen Huang, Tao Wang, Yuk Wai Tang, Xiao Cheng Zeng Nov 2007

Structure And Thermophysical Properties Of Single-Wall Si Nanotubes, Xinwei Wang, Zhen Huang, Tao Wang, Yuk Wai Tang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

In this work, molecular dynamics (MD) simulation based on the environment-dependent interatomic potential is carried out to explore the structure, atomic energy distribution, and thermophysical properties of single-wall Si nanotubes (SWSNTs). The unique structure of SWSNTs leads to a wider range energy distribution than crystal Si (c-Si), and results in a bond order in the range of 4.8~5. The thermal conductivity of SWSNTs is much smaller than that of bulk Si, and shows significantly slower change with their characteristic size than that of Si films. Out of the three types of SWSNTs studied in this work, pentagonal SWSNTs have the …

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A Strategy To Protect And Sensitize Near-Infrared Luminescent Nd3+ And Yb3+: Organic Tropolonate Ligands For The Sensitization Of Ln3+-Doped Nayf4 Nanocrystals, Jian Zhang, Chad M. Shade, Demetra A. Chengelis, Stéphane Petoud Nov 2007

A Strategy To Protect And Sensitize Near-Infrared Luminescent Nd3+ And Yb3+: Organic Tropolonate Ligands For The Sensitization Of Ln3+-Doped Nayf4 Nanocrystals, Jian Zhang, Chad M. Shade, Demetra A. Chengelis, Stéphane Petoud

Department of Chemistry: Faculty Publications

A strategy to sensitize and protect near-infrared (NIR) emitting Nd3+ and Yb3+ is presented. Combining protection provided by the inorganic matrix of NaYF4 nanocrystals and sensitization from tropolonate ligands capped on their surface, the lanthanide cation centered luminescence was observed through the ligand excitation. The extended lanthanide luminescence lifetimes indicate the success of this strategy.

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1,3-Alternate Calix[4]Arene Nitronyl Nitroxide Tetraradical And Diradical: Synthesis, X-Ray Crystallography, Paramagnetic Nmr Spectroscopy, Epr Spectroscopy, And Magnetic Studies, Andrzej Rajca, Maren Pink, Sumit Mukherjee, Suchada Rajca, Kausik Das Oct 2007

1,3-Alternate Calix[4]Arene Nitronyl Nitroxide Tetraradical And Diradical: Synthesis, X-Ray Crystallography, Paramagnetic Nmr Spectroscopy, Epr Spectroscopy, And Magnetic Studies, Andrzej Rajca, Maren Pink, Sumit Mukherjee, Suchada Rajca, Kausik Das

Andrzej Rajca Publications

Calix[4]arenes constrained to 1,3-alternate conformation and functionalized at the upper rim with four and two nitronyl nitroxides have been synthesized, and characterized by X-ray crystallography, magnetic resonance (EPR and 1H NMR) spectroscopy, and magnetic studies. Such calix[4]arene tetraradicals and diradicals provide scaffolds for throughbond and through-space intramolecular exchange couplings.

Includes Supplemental Data (27 pages).

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Quantum Confinement Of Crystalline Silicon Nanotubes With Nonuniform Wall Thickness: Implication To Modulation Doping, Binghai Yan, Xiao Cheng Zeng, Jian Wu, Bing-Lin Gu, Wenghui Duan Sep 2007

Quantum Confinement Of Crystalline Silicon Nanotubes With Nonuniform Wall Thickness: Implication To Modulation Doping, Binghai Yan, Xiao Cheng Zeng, Jian Wu, Bing-Lin Gu, Wenghui Duan

Xiao Cheng Zeng Publications

First-principles calculations of crystalline silicon nanotubes (SiNTs) show that nonuniformity in wall thickness can cause sizable variation in the band gap as well as notable shift in the optical absorption spectrum. A unique quantum confinement behavior is observed: the electronic wave functions of the valence band maximum and conduction band minimum are due mainly to atoms located in the thicker side of the tube wall. This is advantageous to spatially separate the doping impurities from the conducting channel in doped SiNTs. Practically, the performance of the SiNT-based transistors may be substantially improved by selective p/n doping in the thinner side …

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Thermal Stability Of Nanostructurally Stabilized Zirconium Oxide, Fereydoon Namavar, Gonghua Wang, Chin Li Cheung, Renat F. Sabirianov, Xiao Cheng Zeng, Wai Ning Mei, Jaeil Bai, Joseph R. Brewer, Hani Haider, Kevin L. Garvin Sep 2007

Thermal Stability Of Nanostructurally Stabilized Zirconium Oxide, Fereydoon Namavar, Gonghua Wang, Chin Li Cheung, Renat F. Sabirianov, Xiao Cheng Zeng, Wai Ning Mei, Jaeil Bai, Joseph R. Brewer, Hani Haider, Kevin L. Garvin

Xiao Cheng Zeng Publications

Nanostructurally stabilized zirconium oxide (NSZ) hard transparent films were produced without chemical stabilizers by the ion beam assisted deposition technique (IBAD). A transmission electron microscopy study of the samples produced below 150 °C revealed that these films are composed of zirconium oxide (ZrO2) nanocrystallites of diameters 7.5 ± 2.3 nm. X-ray and selected-area electron diffraction studies suggested that the as-deposited films are consistent with cubic phase ZrO2. Rutherford backscattering spectroscopy (RBS) indicated the formation of stoichiometric ZrO2. The phase identity of these optically transparent NSZ films was in agreement with cubic ZrO2, …

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Ab Initio Study Of Hydrogen Adsorption On Benzenoid Linkers In Metal–Organic Framework Materials, Yi Gao, Xiao Cheng Zeng Aug 2007

Ab Initio Study Of Hydrogen Adsorption On Benzenoid Linkers In Metal–Organic Framework Materials, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

We have computed the energies of adsorption of molecular hydrogen on a number of molecular linkers in metal–organic framework solid materials using density functional theory (DFT) and ab initio molecular orbital methods. We find that the hybrid B3LYP (Becke three-parameter Lee–Yang–Parr) DFT method gives a qualitatively incorrect prediction of the hydrogen binding with benzenoid molecular linkers. Both local-density approximation (LDA) and generalized gradient approximation (GGA) DFT methods are inaccurate in predicting the values of hydrogen binding energies, but can give a qualitatively correct prediction of the hydrogen binding. When compared to the more accurate binding- energy results based on the …

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The 14N Quadrupole Coupling In Hexamethylene Triperoxide Diamine (Hmtd), John Persons, Gerard S. Harbison Aug 2007

The 14N Quadrupole Coupling In Hexamethylene Triperoxide Diamine (Hmtd), John Persons, Gerard S. Harbison

Gerard S. Harbison Publications

Using high-field NMR, we have determined the magnitude of the nuclear quadrupole interaction in hexamethylene triperoxide diamine (HMTD), the explosive allegedly used in the London bombings of July 2005. The experimental quadrupolar coupling constant, 5.334 MHz, is in good agreement with quantum chemical calculations. The predicted single zero-field transition frequency should lie in a relatively empty part of the 14N nuclear quadrupole resonance (NQR) spectrum; the spin relaxation rate is reasonably fast.

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Synthesis And Structural Characterization Of Two Five Coordinate Aluminum Alkyl And Bis(Trimethylsilyl)Amino Complexes Bearing Acyclic Tetradentate Schiff Bases, C. R. Wade, B. J. Lamprecht, V. W. Day, John A. Belot Aug 2007

Synthesis And Structural Characterization Of Two Five Coordinate Aluminum Alkyl And Bis(Trimethylsilyl)Amino Complexes Bearing Acyclic Tetradentate Schiff Bases, C. R. Wade, B. J. Lamprecht, V. W. Day, John A. Belot

Department of Chemistry: Faculty Publications

Two acyclic Schiff-base ligands, bis-5,5′-(1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-one and bis-5,5′-(1,3-ethanediyldiimino)- 2,2-dimethyl-4-hexene-3-one, were used to complex homoleptic triethylaluminum and tris[bis(trimethylsilyl)amino]alu minum, respectively. The acid–base reactions proceeded in excellent yields with elimination of ethane or bis(trimethylsilyl)amine during in situ deprotonation of the protio Schiff-base. The colorless aluminum complexes crystallized from n-pentane and were characterized by standard methods including single crystal X-ray diffraction. Polymerization of racemic lactide, with addition of alcohol, yielded PLA with narrow polydispersities but low molecular weights.

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Exohedral Silicon Fullerenes: SiNPtN/2 (20≤N≤60), Yong Pei, Yi Gao, Xiao Cheng Zeng Jul 2007

Exohedral Silicon Fullerenes: SiNPtN/2 (20≤N≤60), Yong Pei, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Using density functional theory method we show that hollow silicon fullerene cages, SiN(20≤N≤60), can be fully stabilized by exohedrally coated platinum atoms (PtN/2), denoted as SiNPtN/2. The exohedral coating PtN/2 passivates the dangling bonds of the silicon cages, thereby making the silicon cages SiN to retain the symmetry and structure of homologous carbon fullerenes CN. In particular, the Ih symmetrical, 60-atom silicon buckminsterfullerene cage (Si60) can be fully stabilized by exohedrally coated 30 Pt atoms. Properties of SiNPtN/2 …

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Topoisomerase Ii-Drug Interaction Domains: Identification Of Substituents On Etoposide That Interact With The Enzyme, Amy M. Wilstermann, Ryan P. Bender, Murrell Godfrey, Sungjo Choi, Clemens Anklin, David B. Berkowitz, Neil Osheroff, David E. Graves Jul 2007

Topoisomerase Ii-Drug Interaction Domains: Identification Of Substituents On Etoposide That Interact With The Enzyme, Amy M. Wilstermann, Ryan P. Bender, Murrell Godfrey, Sungjo Choi, Clemens Anklin, David B. Berkowitz, Neil Osheroff, David E. Graves

David Berkowitz Publications

Etoposide is one of the most successful chemotherapeutic agents used for the treatment of human cancers. The drug kills cells by inhibiting the ability of topoisomerase II to ligate nucleic acids that it cleaves during the double-stranded DNA passage reaction. Etoposide is composed of a polycyclic ring system (rings A–D), a glycosidic moiety at the C4 position, and a pendant ring (E–ring) at the C1 position. Although drug-enzyme contacts, as opposed to drug-DNA interactions, mediate the entry of etoposide into the topoisomerase II-drug-DNA complex, the substituents on etoposide that interact with the enzyme have not been identified. Therefore, saturation transfer …

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Linear, Redox Modified Dna Probes As Electrochemical Dna Sensors, Francesco Ricci, Rebecca Lai, Kevin W. Plaxco Jul 2007

Linear, Redox Modified Dna Probes As Electrochemical Dna Sensors, Francesco Ricci, Rebecca Lai, Kevin W. Plaxco

Rebecca Lai Publications

We show here that hybridization-linked changes in the dynamics of a redox-modified, electrode-bound linear (as opposed to stem-loop) probe DNA produce large changes in Faradaic current, allowing for the ready detection of target oligonucleotides.

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Slow Turning Reveals Enormous Quadrupolar Interactions (Streaqi), John Persons, Gerard S. Harbison Apr 2007

Slow Turning Reveals Enormous Quadrupolar Interactions (Streaqi), John Persons, Gerard S. Harbison

Gerard S. Harbison Publications

We introduce a new solid-state NMR method, which uses very slow sample rotation to visualize NMR spectra whose width exceeds feasible spectrometer bandwidths. It is based on the idea that if we reorient a tensor by a known angle about a known axis, the shifts in the NMR frequencies observed across the spectral width allow us to reconstruct the entire tensor. Called STREAQI (Slow Turning Reveals Enormous Anisotropic Quadrupolar Interactions), this method allows us to probe NMR nuclei that are intractable to current methods. To prove the concept and demonstrate its promise we have implemented the method for several 79Br …

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Classification Of Chemical Substances Using Particulate Representations Of Matter: An Analysis Of Student Thinking, Marilyne Stains, Vicente Talanquer Apr 2007

Classification Of Chemical Substances Using Particulate Representations Of Matter: An Analysis Of Student Thinking, Marilyne Stains, Vicente Talanquer

Department of Chemistry: Faculty Publications

We applied a mixed-method research design to investigate the patterns of reasoning used by novice undergraduate chemistry students to classify chemical substances as elements, compounds, or mixtures based on their particulate representations. We were interested in the identification of the representational features that students use to build a classification system, and in the characterization of the thinking processes that they follow to group substances in different classes. Students in our study used structural and chemical composition features to classify chemical substances into elements, compounds, and mixtures. Many of the students’ classification errors resulted from strong mental associations between concepts (e.g., …

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Doping Golden Buckyballs: Cu@Au16- And Cu@Au17- Cluster Anions, Lei-Ming Wang, Satya S. Bulusu, Hua-Jin Zhai, Xiao Cheng Zeng, Wang Mar 2007

Doping Golden Buckyballs: Cu@Au16- And Cu@Au17- Cluster Anions, Lei-Ming Wang, Satya S. Bulusu, Hua-Jin Zhai, Xiao Cheng Zeng, Wang

Xiao Cheng Zeng Publications

The discovery of the unique catalytic effects of gold nanoparticles on oxide substrates[1] has stimulated a flurry of research into the structures and properties of free gold nanoclusters, which may hold the key to elucidating the catalytic mechanisms of supported gold clusters. One of the most remarkable results has been the discovery of planar gold cluster anions (Aun-) of up to twelve gold atoms and the 2D to 3D transition for clusters with n larger than 12.[2]– [4] Among larger gold clusters, Au20 has been found to be a perfect tetrahedron.[5] A more recent study of …

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Molecular Dynamics Of Homogeneous Nucleation In The Vapor Phase Of Lennard-Jones. Iii. Effect Of Carrier Gas Pressure, Kenji Yasuoka, Xiao Cheng Zeng Mar 2007

Molecular Dynamics Of Homogeneous Nucleation In The Vapor Phase Of Lennard-Jones. Iii. Effect Of Carrier Gas Pressure, Kenji Yasuoka, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

A molecular dynamics simulation of vapor phase nucleation has been performed with 40 000 Lennard-Jones particles for the target gas and 0–160 000 particles for the carrier gas. Three carrier gas models are adopted, including a soft-core model, a Lennard-Jones model, and a modified Lennard-Jones model in which the attractive interaction can be adjusted. The effect of the carrier-gas pressure is assessed through computing and comparing the rate of nucleation and cluster size distribution. It is found that the effect of the carrier-gas pressure can be strongly dependent on the carrier-gas model. A positive effect _enhancement of the nucleation rate_ …

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Hydrogen Storage In Pillared Li-Dispersed Boron Carbide Nanotubes, Xiaojun Wu, Yi Gao, Xiao Cheng Zeng Mar 2007

Hydrogen Storage In Pillared Li-Dispersed Boron Carbide Nanotubes, Xiaojun Wu, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Ab initio density-functional theory study suggests that pillared Li-dispersed boron carbide nanotubes is capable of storing hydrogen with a mass density higher than 6.0 weight% and a volumetric density higher than 45 g/L. The boron substitution in carbon nanotube greatly enhances the binding energy of Li atom to the nanotube, and this binding energy (~ 2.7 eV) is greater than the cohesive energy of lithium metal (~1.7 eV), preventing lithium from aggregation (or segregation) at high lithium doping concentration. The adsorption energy of hydrogen on the Li-dispersed boron carbide nanotube is in the range of 10 – 24 kJ/mol, suitable …

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