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- Isotope effect (2)
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Articles 1 - 22 of 22
Full-Text Articles in Chemistry
Triple Oxygen Isotope Constraints On Atmospheric O2 And Biological Productivity During The Mid-Proterozoic, Peng Liu, Jingjin Liu, Aoshaung Ji, Christopher T. Reinhard, Noah J. Planavsky, Dmitri Babikov, Raymond G. Najjar, James F. Kasting
Triple Oxygen Isotope Constraints On Atmospheric O2 And Biological Productivity During The Mid-Proterozoic, Peng Liu, Jingjin Liu, Aoshaung Ji, Christopher T. Reinhard, Noah J. Planavsky, Dmitri Babikov, Raymond G. Najjar, James F. Kasting
Chemistry Faculty Research and Publications
Reconstructing the history of biological productivity and atmospheric oxygen partial pressure (pO2) is a fundamental goal of geobiology. Recently, the mass-independent fractionation of oxygen isotopes (O-MIF) has been used as a tool for estimating pO2 and productivity during the Proterozoic. O-MIF, reported as Δ′17O, is produced during the formation of ozone and destroyed by isotopic exchange with water by biological and chemical processes. Atmospheric O-MIF can be preserved in the geologic record when pyrite (FeS2) is oxidized during weathering, and the sulfur is redeposited as sulfate. Here, sedimentary sulfates from …
2d Covalent Organic Frameworks With An Incorporated Manganese Complex For Light Driven Carbon Dioxide Reduction, Denan Wang, Daniel Streater, Yun Peng, Jier Huang
2d Covalent Organic Frameworks With An Incorporated Manganese Complex For Light Driven Carbon Dioxide Reduction, Denan Wang, Daniel Streater, Yun Peng, Jier Huang
Chemistry Faculty Research and Publications
Covalent organic frameworks (COFs) have emerged as a novel class of crystalline porous photocatalytic materials due to their unique properties such as large surface area, tunable porosity, and rigid structure. In this work, we report the direct incorporation of a manganese CO2 molecular catalyst (MC) into COFs (Mn−TTA-COF) and the evaluation of its capability as photocatalyst for visible light driven CO2 reduction to form CO. We found that the photocatalytic activity of Mn−TTA-COF is quite low, which mainly results from the elimination of the CO ligand in the Mn MC upon light illumination, rendering its short duration in …
Spectrumsdt: A Program For Parallel Calculation Of Coupled Rotational-Vibrational Energies And Lifetimes Of Bound States And Scattering Resonances In Triatomic Systems, Igor Gayday, Alexander Teplukhin, Jonathan Moussa, Dmitri Babikov
Spectrumsdt: A Program For Parallel Calculation Of Coupled Rotational-Vibrational Energies And Lifetimes Of Bound States And Scattering Resonances In Triatomic Systems, Igor Gayday, Alexander Teplukhin, Jonathan Moussa, Dmitri Babikov
Chemistry Faculty Research and Publications
We present SpectrumSDT – a program for calculations of energies and lifetimes of bound rotational-vibrational states below and scattering resonances above the dissociation threshold on a global potential energy surface of a triatomic system, which may include stable molecules, weekly-bound van-der-Waals complexes, and unbound atom + diatom scattering systems. Large-amplitude vibrational motion is treated explicitly using hyper-spherical coordinates. Three options for the rotational-vibrational interaction are supported: uncoupled (symmetric top rotor), partially coupled (to include interaction between several nearest states only) and full-coupled (vibrating asymmetric-top rotor). In addition to energies and lifetimes, SpectrumSDT is able to integrate ro-vibrational wave functions over …
Synthesis And Pharmacological Studies Of Ph-Sensitive, Allosteric, And Bivalent Ligands As Modulators Of Gpcrs, Ricardo Rosas Jr.
Synthesis And Pharmacological Studies Of Ph-Sensitive, Allosteric, And Bivalent Ligands As Modulators Of Gpcrs, Ricardo Rosas Jr.
Dissertations (1934 -)
G protein-coupled receptors (GPCRs) are cell surface receptors that transduce extracellular signals into intracellular effector pathways via heterotrimeric G protein dependent and independent pathways. GPCRs are involved in numerous physiological processes and are implicated in pathological signaling for numerous diseases. Described herein are novel approaches towards the modulation of two specific Class A GPCRs: protease activated receptor 1 (PAR1) and the mu opioid receptor (MOR). Chapter 1 provides a general introduction to GPCRs, which includes structures, signaling, and putative heteromer formation. Chapters 2 and 5 provide background information on PARs and the MOR, respectively. Diverse approaches towards the modulation of …
Dissecting Monomer-Dimer Equilibrium Of An Rnase P Protein Provides Insight Into The Synergistic Flexibility Of 5’ Leader Pre-Trna Recognition, Danyun Zeng, Ainur Abzhanova, Benjamin P. Brown, Nicholas J. Reiter
Dissecting Monomer-Dimer Equilibrium Of An Rnase P Protein Provides Insight Into The Synergistic Flexibility Of 5’ Leader Pre-Trna Recognition, Danyun Zeng, Ainur Abzhanova, Benjamin P. Brown, Nicholas J. Reiter
Chemistry Faculty Research and Publications
Ribonuclease P (RNase P) is a universal RNA-protein endonuclease that catalyzes 5’ precursor-tRNA (ptRNA) processing. The RNase P RNA plays the catalytic role in ptRNA processing; however, the RNase P protein is required for catalysis in vivo and interacts with the 5’ leader sequence. A single P RNA and a P protein form the functional RNase P holoenzyme yet dimeric forms of bacterial RNase P can interact with non-tRNA substrates and influence bacterial cell growth. Oligomeric forms of the P protein can also occur in vitro and occlude the 5’ leader ptRNA binding interface, presenting a challenge in accurately defining …
Electronic Structures And Spectroscopic Signatures Of Diiron Intermediates Generated By O2 Activation Of Nonheme Iron(Ii)–Thiolate Complexes, Danushka M. Ekanayake, Dao Pham, Andrew L. Probst, Joshua R. Miller, Cordina V. Popescu, Adam T. Fiedler
Electronic Structures And Spectroscopic Signatures Of Diiron Intermediates Generated By O2 Activation Of Nonheme Iron(Ii)–Thiolate Complexes, Danushka M. Ekanayake, Dao Pham, Andrew L. Probst, Joshua R. Miller, Cordina V. Popescu, Adam T. Fiedler
Chemistry Faculty Research and Publications
The activation of O2 at thiolate–ligated iron(II) sites is essential to the function of numerous metalloenzymes and synthetic catalysts. Iron–thiolate bonds in the active sites of nonheme iron enzymes arise from either coordination of an endogenous cysteinate residue or binding of a deprotonated thiol-containing substrate. Examples of the latter include sulfoxide synthases, such as EgtB and OvoA, that utilize O2 to catalyze tandem S–C bond formation and S-oxygenation steps in thiohistidine biosyntheses. We recently reported the preparation of two mononuclear nonheme iron–thiolate complexes (1 and 2) that serve as structural active-site models of substrate-bound EgtB …
Covalent Immobilization Of Molecular Complexes On Metal-Organic Frameworks Towards Robust And Highly Efficient Heterogeneous Water Oxidation Catalysts, Xiangming Liang, Sizhou Yang, Junyi Yang, Wanjun Sun, Xiangyang Li, Baochun Ma, Jier Huang, Jiangwei Zhang, Lele Duan, Yong Ding
Covalent Immobilization Of Molecular Complexes On Metal-Organic Frameworks Towards Robust And Highly Efficient Heterogeneous Water Oxidation Catalysts, Xiangming Liang, Sizhou Yang, Junyi Yang, Wanjun Sun, Xiangyang Li, Baochun Ma, Jier Huang, Jiangwei Zhang, Lele Duan, Yong Ding
Chemistry Faculty Research and Publications
The major challenges to practical implementation of efficient noble metal based molecular water oxidation catalysts are their stability and recycle ability. Herein, noble metal Ru based molecular water oxidation catalysts were covalently anchored in MOFs through “amide bond” as bridges, which leads to the formation of high-efficiency and robust heterogeneous catalysts for water oxidation reaction. We show that the efficiency for CeIV-driven water oxidation was significantly enhanced by 120 times when the Ru molecules were immobilized on the frameworks of MIL-101(Cr). The relationship between recycle stability and the structure of the Ru complexes covalently anchored in MOFs was …
Catalytic Transfer Deuteration And Hydrodeuteration: Emerging Techniques To Selectively Transform Alkenes And Alkynes To Deuterated Alkanes, Zoua Pa Vang, Samuel J. Hintzsche, Joseph R. Clark
Catalytic Transfer Deuteration And Hydrodeuteration: Emerging Techniques To Selectively Transform Alkenes And Alkynes To Deuterated Alkanes, Zoua Pa Vang, Samuel J. Hintzsche, Joseph R. Clark
Chemistry Faculty Research and Publications
Increasing demand for deuterium-labeled organic molecules has spurred a renewed interest in selective methods for deuterium installation. Catalytic transfer deuteration and transfer hydrodeuteration are emerging as powerful techniques for the selective incorporation of deuterium into small molecules. These reactions not only obviate the use of D2 gas and pressurized reaction setups but provide new opportunities for selectively installing deuterium into small molecules. Commercial or readily synthesized deuterium donors are typically employed as easy-to-handle reagents for transfer deuteration and hydrodeuteration reactions. In this minireview, recent advances in the catalytic transfer deuteration and hydrodeuteration of alkenes and alkynes for the selective …
Copper-Catalyzed Transfer Hydrogenation, Deuteration, And Selective Transfer Hydrodeuteration Of Aryl Alkynes, Kiera Behlow
Copper-Catalyzed Transfer Hydrogenation, Deuteration, And Selective Transfer Hydrodeuteration Of Aryl Alkynes, Kiera Behlow
Master's Theses (2009 -)
Transfer hydrogenation utilizes a non-H2 source of hydrogen to reduce double and triple bonds, utilizing transition metal catalysts in addition to some organocatalysts. The use of earth-abundant first row transition metals with ligands that fine tune the reactivity of the catalyst allows for the selective reduction of unsaturated functionalities by utilizing cheap and ubiquitous hydrogen sources such as water and various alcohols. This precludes the need for highly flammable H2 gas, which is often used with heterogeneous catalysts that offer limited selectivity and functional group tolerability. Catalysts optimized for the transfer hydrogenation of the desired functionality can be implemented to …
Efficient Method For An Approximate Treatment Of The Coriolis Effect In Calculations Of Quantum Dynamics And Spectroscopy, With Application To Scattering Resonances In Ozone, Igor Gayday, Dmitri Babikov
Efficient Method For An Approximate Treatment Of The Coriolis Effect In Calculations Of Quantum Dynamics And Spectroscopy, With Application To Scattering Resonances In Ozone, Igor Gayday, Dmitri Babikov
Chemistry Faculty Research and Publications
A numerical approach is developed to capture the effect of rotation–vibration coupling in a practically affordable way. In this approach only a limited number of adjacent rotational components are considered to be coupled, while the couplings to other rotational components are neglected. This partially coupled (PC) approach permits to reduce the size of Hamiltonian matrix significantly, which enables the calculations of ro-vibrational states above dissociation threshold (scattering resonances) for large values of total angular momentum. This method is employed here to reveal the role of the Coriolis effect in the ozone formation reaction at room temperature, dominated by large values …
In Situ Activated Co3–XNiXO4 As A Highly Active And Ultrastable Electrocatalyst For Hydrogen Generation, Kailu Guo, Yantao Wang, Junfeng Huang, Min Lu, Hua Li, Yong Peng, Pinxian Xi, Haoli Zhang, Jier Huang, Siyu Lu, Cailing Xu
In Situ Activated Co3–XNiXO4 As A Highly Active And Ultrastable Electrocatalyst For Hydrogen Generation, Kailu Guo, Yantao Wang, Junfeng Huang, Min Lu, Hua Li, Yong Peng, Pinxian Xi, Haoli Zhang, Jier Huang, Siyu Lu, Cailing Xu
Chemistry Faculty Research and Publications
The spinel Co3O4 has emerged as a promising alternative to noble-metal-based electrocatalysts for electrochemical water electrolysis in alkaline medium. However, pure Co3O4, despite having high activity in anodic water oxidation, remains inactive toward the hydrogen evolution reaction (HER). Here, a Ni-doped Co3O4(Co3–xNixO4) prepared by a simple method exhibits favorable HER activity and stability (>300 h, whether in 1 M KOH or the realistic 30 wt % KOH solution) after in situ electrochemical activation, outperforming almost all of the oxide-based electrocatalysts. More …
Resonant Two-Photon Ionization And Velocity Mapped Ion Imaging Studies Of Aromatic Van Der Waals Complexes, James T. Makuvaza
Resonant Two-Photon Ionization And Velocity Mapped Ion Imaging Studies Of Aromatic Van Der Waals Complexes, James T. Makuvaza
Dissertations (1934 -)
The study of van der Waals complexes provides a means for understanding the nature and strength of non-covalent interactions. Non-covalent interactions including C-H/, C-H/O, C-H/N, C-H/F, halogen and chalcogen bonding are found in important intermediates that regulate chemical and biological processes in many forefront areas of science including molecular self-assembly, drug substrate interactions, supramolecular chemistry, crystal engineering and biochemistry. To better understand these interactions, laser spectroscopic techniques that include mass selected two color resonant two photon ionization (2CR2PI) and velocity mapped ion imaging spectroscopy in combination with complementary ab initio calculations were used to probe the electronic structure, geometries, and …
Hydrogen-Bonded Clusters: A Study Of The Elusive Anisole-Ammonia And Anisole-Water 1:1 Complexes, John Lawrence Loman
Hydrogen-Bonded Clusters: A Study Of The Elusive Anisole-Ammonia And Anisole-Water 1:1 Complexes, John Lawrence Loman
Master's Theses (2009 -)
The hydrogen bond is one of the most important and versatile interactions found in most subsets of chemistry and biology. This interaction is responsible for reactions and characteristic properties of the systems in thereof. This interaction is just one of several available non-covalent interactions that can occur and over the past several decades of molecular spectroscopy studies, the definition of the hydrogen bond has become broader compared to the “classic” definition. To accurately study the hydrogen-bonding in these systems can be quite challenging due to the size and complexity of the molecules involved, as well as the other interactions that …
Synthesis Of Composites From Cellulose, Chitosan, And Ciprofloxacin Hci Encapsulated In Sporopollenin Capsules, Mark Mitmoen
Synthesis Of Composites From Cellulose, Chitosan, And Ciprofloxacin Hci Encapsulated In Sporopollenin Capsules, Mark Mitmoen
Master's Theses (2009 -)
In order to be effective dressings for the treatment of infected wounds in the battlefield, it is essential that composite materials made from the biopolymers Cellulose and Chitosan contain broad-spectrum antibiotic drugs. These drugs must first be encapsulated into microcapsules in order to protect them from the manufacturing process, ensuring that they remain in a usable form in the final product. Here we demonstrate the successful encapsulation of Ciprofloxacin HCl into Sporopollenin Exine Capsules (SEC) to produce Cipro@SEC, followed by incorporation of Cipro@SEC into a polymer composite consisting of a mixture of Cellulose and Chitosan dissolved in 1-butylmethylimidazolium chloride, an …
Biochemical Analysis Of Dual T-Loop Rna Motifs That Perform Shape Recognition Of The Trna Elbow, John Aparicio Aguirre
Biochemical Analysis Of Dual T-Loop Rna Motifs That Perform Shape Recognition Of The Trna Elbow, John Aparicio Aguirre
Master's Theses (2009 -)
T-loops are highly abundant, structurally conserved five nucleotide motifs that facilitate long range intra- and intermolecular interactions and function to stabilize the tertiary fold of RNA. Interlocked or dual T-loop motifs provide additional thermodynamic stability and perform long-range docking of other RNA molecules. Dual T-loop RNA structures are present within the multi-turnover ribonuclease P-based ribozyme, the ribosome, and the bacterial tRNA-sensing riboswitch genetic element. In all three systems, a dual T-loop structure recognizes TYC/D-loop region of tRNA. Interestingly, sequence conservation at specific positions in the T-loops suggest a conserved interlocked RNA architecture. While X-ray crystallography provides insight into the putative …
Development Of Mqct Method For Calculations Of Collisional Energy Transfer For Astrochemistry And Planetary Atmospheres, Bikramaditya Mandal
Development Of Mqct Method For Calculations Of Collisional Energy Transfer For Astrochemistry And Planetary Atmospheres, Bikramaditya Mandal
Dissertations (1934 -)
A mixed quantum/classical methodology and an efficient computer code, named MQCT, were developed to model molecular energy transfer processes relevant to astrochemical environments and planetary atmospheres and applied to several real systems. In particular, the rotational energy transfer in N2 + Na collisions was studied with the focus on quantum phase, differential cross-sections, and scattering resonances, and excellent agreement with full quantum results was found. For H2O + H2, detailed calculations were carried out with the focus on allowed vs. forbidden transitions between the ortho/para states of both collision partners. Again, excellent agreement with full quantum calculations was achieved. Calculations …
Toward Understanding The Origin Of Mass-Independent Fractionation In Sulfur Allotropes And In Ozone, Igor Gayday
Toward Understanding The Origin Of Mass-Independent Fractionation In Sulfur Allotropes And In Ozone, Igor Gayday
Dissertations (1934 -)
Mysterious isotope effects, found in atmospheric ozone, cannot be explained by the standard mass-dependent statistical model. Similar mass-dependent isotope effects were also uncovered in sulfur deposits older than 2 billion years. In an effort to pinpoint possible reasons of these isotope effects, we build a theoretical description of the recombination reactions in sulfur allotropes and in ozone. No potential energy surface exists for the sulfur allotropes, so electronic structure calculations are also required. Ab initio calculation of two dimensionally reduced (2D and 3D) models of the potential energy surface for the tetrasulfur molecule at CCSD(T)-F12 and MRCI levels of theory …
Design And Synthesis Of Selective Estrogen Receptor Agonists, Edward Edward Wetzel
Design And Synthesis Of Selective Estrogen Receptor Agonists, Edward Edward Wetzel
Dissertations (1934 -)
Estrogens are hormones that regulates many different physiological functions. A decline in estrogen leads to significant issues that decrease the quality of life. Past treatments of menopausal symptoms included the administration of estrogen. However, side effects such as an increased risk of breast cancer, made this an unattractive therapeutic option. When a new estrogen receptor (ERβ) was discovered, it provided new hope for hormone replacement therapy (HRT). ERβ was shown to inhibit tumor growth, whereas ERα regulates breast cancer proliferation in certain types of breast cancer. The therapeutic benefits of targeting ERβ are vast; herein we focus on the benefits …
Synthetic And Mechanistic Studies Of Ruthenium Catalyzed C-C, C-H And C-N Bond Activation Reactions, Nuwan Asanka Pannilawithana
Synthetic And Mechanistic Studies Of Ruthenium Catalyzed C-C, C-H And C-N Bond Activation Reactions, Nuwan Asanka Pannilawithana
Dissertations (1934 -)
Transition metal-catalyzed selective CH, CC and CN bond activation reactions represent a challenging and synthetically important field in organic chemistry. In particular, transition-metal catalytic unreactive bond activation protocols are applicable in various stereoselective and atom economical complex organic molecule synthesis. Recently, significant research efforts have been made for utilizing catalytic CH and CC bond cleavage methods in the further development of commercially valuable pharmaceuticals and agrochemicals. The well-defined cationic Ru–H complex was found to be an effective catalyst for mediating the coupling reaction of 1,2-disubstituted indoles with α,β-unsaturated aldehydes and ketones, in which the regioselective Cα–Cβ activation of the carbonyl …
Scope And Mechanistic Studies Of Ruthenium Catalyzed C-N Bond Activation Reactions, Pandula Taepith Kirinde Arachchige
Scope And Mechanistic Studies Of Ruthenium Catalyzed C-N Bond Activation Reactions, Pandula Taepith Kirinde Arachchige
Dissertations (1934 -)
Primary aliphatic amines which are ubiquitous in natural products, traditionally considered as inert to substitution reactions. Recent studies clearly demonstrated that the aliphatic deaminative coupling chemistry can be used to make valuable scaffolds through C–N bond activation on transition metal complexes. The catalytic system generated in situ from the tetranuclear Ru–H complex with a catechol ligand (2-9/2-16) and independently synthesized ruthenium catecholate complex 2-11 was found to be effective for the direct deaminative coupling of primary amines. The catalytic system formed in-situ from the reaction of cationic Ru–H complex 2-10 with 3,4,5,6-tetrachloro-1,2-benzoquinone 2-12 was found to mediate a regioselective deaminative …
Four Isotope-Labeled Recombination Pathways Of Ozone Formation, Dmitri Babikov, Elizaveta Grushnikova, Igor Gayday, Alexander Teplukhin
Four Isotope-Labeled Recombination Pathways Of Ozone Formation, Dmitri Babikov, Elizaveta Grushnikova, Igor Gayday, Alexander Teplukhin
Chemistry Faculty Research and Publications
A theoretical approach is developed for the description of all possible recombination pathways in the ozone forming reaction, without neglecting any process a priori, and without decoupling the individual pathways one from another. These pathways become physically distinct when a rare isotope of oxygen is introduced, such as 18O, which represents a sensitive probe of the ozone forming reaction. Each isotopologue of O3 contains two types of physically distinct entrance channels and two types of physically distinct product wells, creating four recombination pathways. Calculations are done for singly and doubly substituted isotopologues of ozone, eight rate coefficients …
Unraveling A Trifecta Of Weak Non-Covalent Interactions: The Dissociation Energy Of The Anisole-Ammonia 1:1 Complex, John L. Loman, James T. Makuvaza, Damian L. Kokkin, Scott A. Reid
Unraveling A Trifecta Of Weak Non-Covalent Interactions: The Dissociation Energy Of The Anisole-Ammonia 1:1 Complex, John L. Loman, James T. Makuvaza, Damian L. Kokkin, Scott A. Reid
Chemistry Faculty Research and Publications
The anisole-ammonia 1:1 complex is a challenge for both experiment and theory. Early studies supported a non-planar structure, involving a trifecta of weak non-covalent interactions: N-H/O, N-H/π, and C-H/N. The calculated structure and binding energy of the complex proved remarkably sensitive to the level of theory employed. Here, we report the first experimental measurement of the ground state dissociation energy of the complex, and derive an excited (S1) state dissociation energy that is in excellent agreement with the cutoff observed in the experimental excitation spectrum. Results are compared with previous predictions and new calculations based on benchmarked Density …