Chemistry Commons^™

A Grand Unified Model For Liganded Gold Clusters, Wen Wu Xu, Beien Zhu, Xiao Cheng Zeng, Yi Gao

Xiao Cheng Zeng Publications

A grand unified model (GUM) is developed to achieve fundamental understanding of rich structures of all 71 liganded gold clusters reported to date. Inspired by the quark model by which composite particles (for example, protons and neutrons) are formed by combining three quarks (or flavours), here gold atoms are assigned three ‘flavours’ (namely, bottom, middle and top) to represent three possible valence states. The ‘composite particles’ in GUM are categorized into two groups: variants of triangular elementary block Au₃(2e) and tetrahedral elementary block Au₄(2e), all satisfying the duet rule (2e) of the valence shell, akin to …

Design And Synthesis Of Novel Octacarboxy Porphyrinic Metal-Organic Frameworks, Jacob A. Johnson

Department of Chemistry: Dissertations, Theses, and Student Research

Metal-Organic Frameworks (MOFs) are a class of nanoporous crystalline materials constructed via the interconnection between metal-ions/inorganic clusters and organic ligands. Since the surface area, pore size and distribution, and chemical functionalities of MOFs are highly tunable via the judicious combinations of inorganic clusters and organic ligands, MOFs have attracted intensive interests for a variety of applications including gas adsorption and separation, catalysis, chemical sensing, and drug delivery among others. Porphyrin based ligands are of particular interest for building functional MOFs due to their unique photo-, electro-, and catalytic properties. In addition, the four-fold symmetry of porphyrin ligands offers an effective …

Thermolysis Of Hypervalent Iodine Complexes: Synthesis Of Fluorinated Radiotracers For Positron Emission Tomography And Synthesis Of Quaternary Α-Alkyl Α-Aryl Amino Acids, Jayson J. Kempinger

Department of Chemistry: Dissertations, Theses, and Student Research

Hypervalent iodine complexes can be used to deliver a variety of functional groups to arenes. Delivery of fluorine‑18, in a manner compatible with positron emission tomography (PET), is especially attractive. Vizamyl^TM, an injectable solution of [¹⁸F]Flutemetamol, is currently used to diagnose and monitor the progression of Alzheimer’s Disease (AD), the most common form of dementia. AD affects 47.5 million people across the world as of 2015, and is projected to affect 1 in 85 people by 2050. An improved radiosynthesis of [¹⁸F]Flutemetamol via a diaryliodonium salt is described. The use of nonpolar solvents minimizes …

Chromatographic Studies Of Protein-Based Chiral Separations, Cong Bi, Xiwei Zheng, Shiden Azaria, Sandya Beeram, Zhao Li, David S. Hage

David Hage Publications

The development of separation methods for the analysis and resolution of chiral drugs and solutes has been an area of ongoing interest in pharmaceutical research. The use of proteins as chiral binding agents in high-performance liquid chromatography (HPLC) has been an approach that has received particular attention in such work. This report provides an overview of proteins that have been used as binding agents to create chiral stationary phases (CSPs) and in the use of chromatographic methods to study these materials and protein-based chiral separations. The supports and methods that have been employed to prepare protein-based CSPs will also be …

Selective Iodination Using Diaryliodonium Salts, William H. Miller Iv

Department of Chemistry: Dissertations, Theses, and Student Research

Aryl iodides have become widely recognized as versatile synthetic intermediates, owing to aromatic iodine’s excellent ability to participate in oxidative addition reactions. Iodoarenes readily undergo a variety of synthetic transformations including metal catalyzed cross-coupling reactions, diaryliodonium chemistry, formation of organometallics through reduction or metal-halogen exchange, as well as classical S_N2 type chemistry. Because a wide array of transformations are available for aryl iodides, organic molecules containing this moiety often serve as vital precursors to highly desirable pharmaceuticals.

This thesis describes a simple and selective two-step approach to the formation of aryl iodides. This method proceeds through an easily …

Synthesis And Applications Of Lanthanide Sulfides And Oxides, Christopher Marin

Department of Chemistry: Dissertations, Theses, and Student Research

This dissertation focuses on two of the key fields where lanthanides find ready application: as optically active materials with a focus on the lanthanide sulfides, and as catalytic materials with a focus on cerium oxide.

The lanthanide sulfides have attracted considerable interest for their potential as solar energy conversion materials, pigments, infrared window materials, and phosphor host media. However, applications of these materials remain limited due to their synthetic difficulty along with their not well understood properties compounded by both their difficulty in manufacturing as well as in simulating largely due to the need to take into account f-shell electrons. …

Carbon Nanotubes Affect The Toxicity Of Cuo Nanoparticles To Denitrification In Marine Sediments By Altering Cellular Internalization Of Nanoparticle, Xiong Zheng, Yinglong Su, Yinguang Chen, Rui Wan, Mu Li, Haining Huang, Xu Li

Department of Civil and Environmental Engineering: Faculty Publications

Denitrification is an important pathway for nitrate transformation in marine sediments, and this process has been observed to be negatively affected by engineered nanomaterials. However, previous studies only focused on the potential effect of a certain type of nanomaterial on microbial denitrification. Here we show that the toxicity of CuO nanoparticles (NPs) to denitrification in marine sediments is highly affected by the presence of carbon nanotubes (CNTs). It was found that the removal efficiency of total NO_X⁻-N (NO₃⁻-N and NO₂⁻-N) in the presence of CuO NPs was only 62.3%, but it …

Optimizing Sequence Coverage For A Moderate Mass Protein In Nano-Electrospray Ionization Quadrupole Time-Of-Flight Mass Spectrometry, Ryan E. Matsuda, Venkata Kolli, Megan Woods, Eric D. Dodds, David S. Hage

David Hage Publications

Sample pretreatment was optimized to obtain high sequence coverage for human serum albumin (HSA, 66.5 kDa) when using nano-electrospray ionization quadrupole time-of-flight mass spectrometry (nESI-Q-TOF-MS). Use of the final method with trypsin, Lys-C and Glu-C digests gave a combined coverage of 98.8%. The addition of peptide fractionation resulted in 99.7% coverage. These results were comparable to those obtained previously with matrixassisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The sample pretreatment/nESI-Q-TOF-MS method was also used with collision-induced dissociation to analyze HSA digests and to identify peptides that could be employed as internal mass calibrants in future studies of modifications to HSA.

A Tonb-Dependent Receptor Regulates Antifungal Hsaf Biosynthesis In Lysobacter, Ruping Wang, Huiyong Xu, Liangcheng Du, Shan-Ho Chou, Hongxia Liu, Youzhou Liu, Fengquan Liu, Guoliang Qian

Liangcheng Du Publications

Lysobacter species are Gram-negative bacteria that are emerging as new sources of antibiotics, including HSAF (Heat Stable Antifungal Factor), which was identified from L. enzymogenes with a new mode of action. LesR, a LuxR solo, was recently shown to regulate the HSAF biosynthesis via an unidentified mechanism in L. enzymogenes OH11. Here, we used a comparative proteomic approach to identify the LesR targets and found that LesR influenced the expression of 33 proteins belonging to 10 functional groups, with 9 proteins belonging to the TBDR (TonB-Dependent Receptor) family. The fundamental role of bacterial TBDR in nutrient uptake motivates us to …

Molecular Mechanism For The Biosynthesis And Regulation Of Secondary Metabolites In Lysobacter, Simon Tesfamichael Tombosa

Department of Chemistry: Dissertations, Theses, and Student Research

This thesis presents regulatory and biosynthetic mechanisms by which microorganisms produce secondary metabolites that can potentially be developed into drugs beneficial to humans. The first section shows the role of small signaling molecules in regulating the production of one of the novel antifungal metabolites, heat stable antifungal factor (HSAF), from Lysobacter enzymogenes.

In the second part of the thesis I report our attempts to isolate and characterize the biosynthesis of WBP, a new secondary metabolite from Lysobacter antibioticus OH13. I have included the in-silico analysis of the gene cluster for WBP and the predicted biosynthetic pathway based on analysis …

Studies In Asymmetric Catalysis: Supramolecular Catalysis And Borane-Assisted Hydrogenation, Kazuya Toyama

Department of Chemistry: Dissertations, Theses, and Student Research

Metal-catalyzed catalytic asymmetric reactions have gained enormous attentions and the utilities of such reactions have facilitated natural products syntheses to afford highly bioactive molecules. While these reactions have provided reliable methodologies to transform basic reactants into product(s) with highly enantio- and regioselective manners, the incompatibility with a many functional groups and the associated need to employ protecting groups increases the number of synthetic steps required. Herein, a solution to such an issue has been proposed in catalytic asymmetric hydroboration of styrene derivatives where supramolecular catalysts developed by Takacs et al. were used to achieve highly regio- and stereoselective reaction on …

Binding Of Oxygen To Human Hemoglobin Within The Erythrocyte Using Icam Spectrophotometry, Kyle K. Hill

Department of Chemistry: Dissertations, Theses, and Student Research

Many of the spectrophotometric techniques used to determine the properties of intracellular human hemoglobin cannot be utilized due to the turbidity of erythrocyte suspensions. An Integrating Cavity Absorption Meter, or ICAM, allows for absorption measurements of strongly scattering samples in the visible-light region of the spectrum. The spectrum of oxygenated hemoglobin within erythrocytes is significantly different from the absorption spectrum of oxygenated hemoglobin in solution. Studies of the oxygen binding to hemoglobin in erythrocytes allowed the four sequential binding constants (Adair constants) to be determined and compared with those of hemoglobin in solution. The Adair constants for hemoglobin in solution …

Optimizing Chemical & Rheological Properties Of Rejuvenated Bitumen, Dominic Nguyen, Hamzeh Haghshenas Fatmehsari, Santosh Kommidi, Yong-Rak Kim

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Bitumen has long been a material used in the construction of roadways, yet new pavement only consists of low fractions of recycled materials due to poor compatibility of aged bitumen and new materials. Thus, rejuvenators, chemical additives, have been used in an attempt to re-balance the chemical composition and restore the physical properties of aged bitumen back to its virgin state. A fundamental understanding of how one particular rejuvenator, soybean oil, revitalizes bitumen was investigated using a multi-scale approach.

Fourier-transform infrared spectroscopy (FTIR) was used to determine the changes in chemical properties of pure and rejuvenated virgin and aged samples. …

Ruthenium-Catalyzed Amination Of Secondary Alcohols Using Borrowing Hydrogen Methodology, Kostiantyn O. Marichev, James M. Takacs

Chemistry Department: Faculty Publications

A new ruthenium complex catalyzes the amination of primary and secondary alcohols and the regioselective mono- and sequential diamination of diols via the borrowing hydrogen pathway. Several variations on new intra- and intermolecular cyclizations of aminoalcohols, diols and diamines lead to heterocyclic ring systems.

A New Ligation System For Protein Conjugation, Alicia J. Curti, Patrick H. Dussault

UCARE Research Products

Click chemistry describes crosslinking reactions in which pairs of functional groups selectively “click” together to form linkages. The idea of our project is to explore the use of cyclobutene-containing fatty acids as a new class of “click” reagents as a tool for protein modification.

There is great interest in performing click reactions under biologically relevant conditions, in the presence of cells, and even within cells. The best known click reaction, the cycloaddition of alkynes and azides, is highly specific, can be conducted in the presence of buffers and proteins, and forms stable cycloadducts. However, use in biological systems is limited …

Alignment For Comprehensive Two-Dimensional Gas Chromatography (Gcxgc) With Global, Low-Order Polynomial Transformations, Davis Rempe, Stephen Reichenbach, Stephen Scott

UCARE Research Products

As columns age and differ between systems, retention times for GC x GC may vary between runs. In order to properly analyze chromatograms, it is often desirable to align chromatographic features between chromatograms. This alignment can be characterized by a mapping of retention times from one chromatogram to the retention times of another chromatogram. Alignment methods can be classified as global or local, i.e., whether the geometric differences between chromatograms are characterized by a single function for the entire chromatogram or by a combination of many functions for different regions of the chromatogram. Previous work has shown that global, low-degree …

Xiao Cheng Zeng Bibliography (April 2016), Xiao Cheng Zeng

Xiao Cheng Zeng Publications

397 articles sorted by topics

Synthesis And Applications Of Cyclobutenes, Benjamin Enns

Department of Chemistry: Dissertations, Theses, and Student Research

Our group is interested in cyclobutene analogs of fatty acids as reactive coatings, potential antibiotics, and as a new class of bioconjugate linkers. A convenient synthesis of this class of molecules was previously reported from our lab. However, ammonia, a key reagent in the earlier route, was recently reclassified as a highly corrosive gas requiring highly specialized equipment for storage and handling. The goal of this research was to find a convenient synthesis for the formation of cyclobutene that did not involve the use of ammonia. The other part of this thesis describes the preparation of a short chain cyclobutene …

Αβ-Peptide Mimics Of Z-Domain Peptides, Samuel H. Gellman, James W. Checco

Chemistry Department: Faculty Publications

Described are αβ-peptide mimics of Z-domain scaffold pep tides, methods of making them, and methods of using them. The αβ-peptide mimics include B-amino acid residues and, optionally, disulfide bonds to stabilize the conformation of the mimics. The compounds may be truncated as compared to conventional Z-domain scaffold peptides and are resistant to proteolytic degradation due to the presence off-amino acid residues. The mimics can be made so as to bind selectively to a desired target.

“Zipped Synthesis” By Cross-Metathesis Provides A Cystathionine Β‑Synthase Inhibitor That Attenuates Cellular H2S Levels And Reduces Neuronal Infarction In A Rat Ischemic Stroke Model, Christopher D. Mccune, Su Jing Chan, Matthew L. Beio, Weijun Shen, Woo Jin Chung, Laura M. Szczesniak, Chou Chai, Shu Qing Koh, Peter T.-H. Wong, David B. Berkowitz

David Berkowitz Publications

The gaseous neuromodulator H₂S is associated with neuronal cell death pursuant to cerebral ischemia. As cystathionine β-synthase (CBS) is the primary mediator of H2S biogenesis in the brain, it has emerged as a potential target for the treatment of stroke. Herein, a “zipped” approach by alkene cross-metathesis into CBS inhibitor candidate synthesis is demonstrated. The inhibitors are modeled after the pseudo-C₂-symmetric CBS product (L,L)-cystathionine. The “zipped” concept means only half of the inhibitor needs be constructed; the two halves are then fused by olefin cross-metathesis. Inhibitor design is also mechanism-based, exploiting the favorable kinetics associated with …

Development Of A Direct Activity Probe For Rho-Associated Protein Kinase, Maia Kelly

Department of Chemistry: Dissertations, Theses, and Student Research

Hepatocellular carcinoma (HCC) is an extremely aggressive form of liver cancer with a low survival rate due to high recurrence. Increases in Rho-associated Protein Kinase (ROCK) activity are correlated with a more aggressive, metastatic phenotype associated with advanced HCC. Inhibitors for ROCK have shown potential for the reduction of this metastatic phenotype of HCC. We outline the design and optimization of a direct activity sensor for ROCK that utilizes a phosphorylation-sensitive sulfonamido-oxine fluorophore, termed Sox, and is capable of reporting on the inhibition of ROCK. This CSox-based activity probe utilizes chelation-enhanced fluorescence (ex. = 360 nm and em. = 485 …

Unraveling A Generic Growth Pattern In Structure Evolution Of Thiolate-Protected Gold Nanoclusters, Wen Wu Xu, Yadong Li, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Precise control of the growth of thiolate-protected gold nanoclusters is a prerequisite for their applications in catalysis and bioengineering. Here, we bring to bear a new series of thiolateprotected nanoclusters with a unique growth pattern, i.e., Au₂₀(SR)₁₆, Au₂₈(SR)₂₀, Au₃₆(SR)₂₄, Au₄₄(SR)₂₈, and Au₅₂(SR)₃₂. These nanoclusters can be viewed as resulting from the stepwise addition of a common structural motif [Au₈(SR)₄]. The highly negative values of the nucleus-independent chemical shift (NICS) in the center of the tetrahedral Au4 …

Surprising Impact Of Remote Groups On The Folding–Unfolding And Dimer-Chain Equilibria Of Bifunctional H-Bonding Unimers, Rui Liu, Shuang Cheng, Erin S. Baker, Richard D. Smith, Xiao Cheng Zeng, Bing Gong

Xiao Cheng Zeng Publications

Oligoamide 1, consisting of two H-bonding units linked by a trimethylene linker, was previously found to form a very stable, folded dimer. In this work, replacing the side chains and end groups of 1 led to derivatives that show the surprising impact of end groups on the folding and dimer-chain equilibria of the resultant molecules.

Unraveling A Generic Growth Pattern In Structure Evolution Of Thiolate-Protected Gold Nanoclusters, Wen Wu Xu, Yadong Li, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Precise control of the growth of thiolate-protected gold nanoclusters is a prerequisite for their applications in catalysis and bioengineering. Here, we bring to bear a new series of thiolateprotected nanoclusters with a unique growth pattern, i.e., Au₂₀(SR)₁₆, Au₂₈(SR)₂₀, Au₃₆(SR)₂₄, Au₄₄(SR)₂₈, and Au₅₂(SR)₃₂. These nanoclusters can be viewed as resulting from the stepwise addition of a common structural motif [Au₈(SR)₄]. The highly negative values of the nucleus-independent chemical shift (NICS) in the center of the tetrahedral Au …

Mechanistic Study Of Pressure And Temperature Dependent Structural Changes In Reactive Formation Of Silicon Carbonate, Bingyan Qu, Dongdong Li, Lei Wang, Jili Wu, Rulong Zhou, Bo Zhang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

The discovery of the silicon carbonate through chemical reaction between porous SiO₂ and gaseous CO₂ addressed a long-standing question regarding whether the reaction between CO₂ and SiO₂ is possible. However, the detailed atomic structure of silicon carbonate and associated reaction mechanism are still largely unknown. We explore structure changes of silicon carbonate with pressure and temperature based on systematic ab initio molecular dynamics simulations. Our simulations suggest that the reaction proceeds at the surface of the porous SiO₂. Increasing number of CO₂ molecules can take part in the reaction by increasing either the …

Near-Barrierless Ammonium Bisulfate Formation Via A Loop-Structure Promoted Proton-Transfer Mechanism On The Surface Of Water, Lei Li, Manoj Kumar, Chongqin Zhu, Jie Zhong, Joseph S. Francisco, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

In the atmosphere, a well-known and conventional pathway toward the formation of ammonium sulfate is through the neutralization of sulfuric acid with ammonia (NH₃) in water droplets. Here, we present direct ab initio molecular dynamics simulation evidence of the formation of ammonium bisulfate (NH₄HSO₄) from the hydrated NH₃ and SO₃ molecules in a water trimer as well as on the surface of a water droplet. This reaction suggests a new mechanism for the formation of ammonium sulfate in the atmosphere, especially when the concentration of NH₃ is high (e.g., ∼10 μg …

Probing The Structures Of Gold–Aluminum Alloy Clusters AuXAlY−: A Joint Experimental And Theoretical Study, Navneet S. Khetrapal, Tian Jian, Rhitankar Pal, Gary V. Lopez, Seema Pande, Lai-Sheng Wang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Besides the size and structure, compositions can also dramatically affect the properties of alloy nanoclusters. Due to the added degrees of freedom, determination of the global minimum structures for multi-component nanoclusters poses even greater challenges, both experimentally and theoretically. Here we report a systematic and joint experimental/theoretical study of a series of gold–aluminum alloy clusters, Au_xAl_y⁻(x + y = 7,8), with various compositions (x = 1–3; y = 4–7). Well-resolved photoelectron spectra have been obtained for these clusters at different photon energies. Basin-hopping global searches, coupled with density functional theory calculations, are used …

Engineering Escherichia Coli For High‑Yield Geraniol Production With Biotransformation Of Geranyl Acetate To Geraniol Under Fed‑Batch Culture, Wei Liu, Xin Xu, Rubing Zhang, Tao Cheng, Yujin Cao, Xiaoxiao Li, Jiantao Guo, Huizhou Liu, Mo Xian

Chemistry Department: Faculty Publications

Background: Geraniol is an acyclic monoterpene alcohol, which exhibits good prospect as a gasoline alternative. Geraniol is naturally encountered in plants at low concentrations and an attractive target for microbial engineering. Geraniol has been heterologously produced in Escherichia coli, but the low titer hinders its industrial applications. Moreover, bioconversion of geraniol by E. coli remains largely unknown.

Results: Recombinant overexpression of Ocimum basilicum geraniol synthase, Abies grandis geranyl diphosphate synthase, and a heterotic mevalonate pathway in E. coli BL21 (DE3) enabled the production of up to 68.6 ± 3 mg/L geraniol in shake flasks. Initial fed-batch fermentation only increased geraniol …

Ring Closures And The Hammond Postulate, Charles A. Kingsbury

Chemistry Department: Faculty Publications

This work reports an investigation of ring closure processes in relation to the Hammond postulate. Calculations favor the importance of thermodynamics, not kinetics, as the basis for the Hammond postulate. A kinetically rapid, but thermodynamically unfavorable reaction is shown to resemble product. The ease of ring closure to three-membered rings, compared to four-membered rings, is thought to be associated with conformational mobility and perhaps vibrations coupled to the reaction coordinate motion in the case of four-membered rings.

Highly Porous Zirconium Metal−Organic Frameworks With Β‑Uh3‑Like Topology Based On Elongated Tetrahedral Linkers, Xin Zhang, Xu Zhang, Jacob A. Johnson, Yu-Sheng Chen, Jian Zhang

Chemistry Department: Faculty Publications

Two non-interpenetrated zirconium metal−organic frameworks (Zr-MOFs), NPF-200 and NPF-201, were synthesized via the assembly of elongated tetrahedral linkers with Zr₆ and Zr₈ clusters. They represent the first examples of MOFs to have the β-UH₃-like, 4,12,12T1 topology. Upon activation, NPF-200 exhibits the largest BET surface area (5463 m²g⁻¹) and void volume (81.6%) among all MOFs formed from tetrahedral ligands. Composed of negative-charged boron-centered tetrahedral linkers, NPF-201 is an anionic Zr-MOF which selectively uptakes photoactive [Ru(bpy)₃]²⁺for heterogeneous photo-oxidation of thioanisole.

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