Physical Sciences and Mathematics Commons^™

Velocity Map Images Of Desorbing Oxygen From Sub-Surface States Of Rh(111), Arved C. Dorst, Friedrich Güthoff, Daniel Schauermann, Alec M. Wodtke, Daniel Killelea, Tim Schäfer

Chemistry: Faculty Publications and Other Works

We combine velocity map imaging (VMI) with temperature-programmed desorption (TPD) experiments to record the angular-resolved velocity distributions of recombinatively-desorbing oxygen from Rh(111). We assign the velocity distributions to desorption from specific surface and sub-surface states by matching the recorded distributions to the desorption temperature. These results provide insight into the recombinative desorption mechanisms and the availability of oxygen for surface-catalyzed reactions.

Synthetic Amphiphiles As Antibiotic Potentiators, Helena Spikes

Dissertations

Antibiotic resistance has become a massive threat to modern medicine. Bacteria acquire resistance either through genetic mutations or mobile genetic elements, such as plasmids. The growing resistance crisis is exacerbated by over-prescription of antibiotics and improper use. As antimicrobial resistance becomes more widespread, superbugs (bacteria resistant to more than one class of drug) have evolved. Since few new drugs reach clinical trials and even fewer are approved by the FDA, we must find a way to make existing drugs more potent. One technique to accomplish this is by using combination therapy. By administering two or more drugs at a time, …

Investigating Small-Group Cognitive Engagement In General Chemistry Learning Activities Using Qualitative Content Analysis And The Icap Framework, Safaa Y. El-Mansy, Jack Barbera, Alissa J. Hartig

Chemistry Faculty Publications and Presentations

The level of students’ engagement during active learning activities conducted in small groups is important to understanding the effectiveness of these activities. The Interactive–Constructive–Active–Passive (ICAP) framework is a way to determine the cognitive engagement of these groups by analyzing the conversations that occur while student groups work on an activity. This study used qualitative content analysis and ICAP to investigate cognitive engagement during group activities in a General Chemistry course at the question level, a finer grain size than previously studied. The analysis determined the expected engagement based on question design and the observed engagement based on group conversations. Comparisons …

Expanding The Scope Of Clickable Azide-Functionalized Nanoclusters To Include Au144, Johanna A. De Jong

Electronic Thesis and Dissertation Repository

Thiolate-protected Au₁₄₄ nanoclusters (NCs) are an intriguing member of the gold NC family. Their geometric structure, distinct electrochemical features, and susceptibility to structural rearrangement under the duress of ligand exchange have been studied. However, there are currently no established protocols for surface modification or tuning of their ligand shells post synthesis. Here, the direct synthesis of three regioisomers of azide-modified Au₁₄₄ NCs with 60 azide moieties, i.e., Au₁₄₄(SC₂H₄C₆H₄-N₃)₆₀, is reported, in which the azide functionality is located at the ortho-, meta-, or …

Helium Nanodroplets As An Efficient Tool To Investigate Hydrogen Attachment To Alkali Cations, Siegfried Kollotzek, José Campos-Martínez, Massimiliano Bartolomei, Fernando Pirani, Lukas Tiefenthaler, Marta I. Hernández, Teresa Lázaro, Eva Zunzunegui-Bru, Tomás González-Lezana, José Bretón, Javier Hernández-Rojas, Olof E. Echt, Paul Scheier

Faculty Publications

We report a novel method to reversibly attach and detach hydrogen molecules to positively charged sodium clusters formed inside a helium nanodroplet host matrix. It is based on the controlled production of multiply charged helium droplets which, after picking up sodium atoms and exposure to H₂ vapor, lead to the formation of Na_m⁺(H₂)_n clusters, whose population was accurately measured using a time-of-flight mass spectrometer. The mass spectra reveal particularly favorable Na⁺(H₂)_n and Na₂⁺(H₂)_n clusters for specific “magic” numbers of attached hydrogen molecules. …

Technical Note: On Uncertainties In Plant Water Isotopic Composition Following Extraction By Cryogenic Vacuum Distillation, Haoyu Diao, Philipp Schuler, Gregory R. Goldsmith, Rolf T. W. Siegwolf, Matthias Saurer, Marco M. Lehmann

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Recent studies have challenged the interpretation of plant water isotopes obtained through cryogenic vacuum distillation (CVD) based on observations of a large 2H fractionation. These studies have hypothesized the existence of an H-atom exchange between water and organic tissue during CVD extraction with the magnitude of H exchange related to relative water content of the sample; however, clear evidence is lacking. Here, we systematically tested the uncertainties in the isotopic composition of CVD-extracted water by conducting a series of incubation and rehydration experiments using isotopically depleted water, water at natural isotope abundance, woody materials with exchangeable H, and organic materials …

The Synthesis, Lewis Acidity And Catalytic Activity Of Bis(Catecholato)Germanes, Andrew T. Henry

Electronic Thesis and Dissertation Repository

Main group Lewis acids have been shown to be viable alternatives to state-of-theart transition metal catalysts. While extensive research into a variety of p-block Lewis acids have been reported, the field of germanium Lewis acid chemistry has been described as “almost non-existent”. A variety of bis(catecholato)germane derivatives have been synthesized. The Lewis acidity of these compounds was analyzed by the Gutmann-Beckett and fluoride ion affinity methods demonstrating the high Lewis acidity of these complexes. The bis(catecholato)germanes were utilized as Lewis acid catalysts for the hydrosilylation of aldehydes, the hydroboration of alkynes, Friedel-Crafts alkylation of alkenes, and the oligomerization of styrene …

Developing Carbon Quantum Dots As A Luminescent Material And Revisiting Ecl And Led Absolute Measurement Methods, Jonathan Ralph Adsetts

Electronic Thesis and Dissertation Repository

Luminescent materials play increasingly important roles in our lives. Improvements in these materials’ quantum efficiencies (QEs), costs and toxicity can greatly reduce the power consumption, price and environmental damage to the planet, respectively. Carbon quantum dots (CQDs) and luminescent materials exhibiting thermally activated delayed fluorescence (TADF) are two interesting materials in these aspects. Furthermore, measurements on electrochemiluminescence (ECL) and electroluminescence of these luminescent materials can quickly evaluate their performance for many applications. In this thesis, controlled CQD syntheses are revealed beneficial to luminescent materials applications. Their film ECL demonstrated relatively stable anionic and cationic radicals leading to high emission at …

Theoretical Studies Of Molecule-Surface Interactions And Dynamics, Yingqi Wang

Chemistry and Chemical Biology ETDs

Gas-surface scattering involves the conversion of energy in different forms in the impinging molecule, possible bond breaking and forming, and the energy transfer across gas-solid interface. Possible energy dissipation channels include adiabatic energy transfer to the motion of surface phonons and non-adiabatic interactions with surface electron-hole pairs. A complete understanding of the interplay of energy dissipation and physical/chemical changes in the molecule is vital for many important applications such as materials fabrication and heterogenous catalysis.

Gas-surface encounters may occur where non-adiabatic effects are negligible. Two such systems were investigated, both with ample experimental data. One is concerned with the scattering …

Kinetic And Structural Characterization Of A Flavin-Dependent Putrescine N-Hydroxylase From Acinetobacter Baumannii, Noah S. Lyons, Alexandra N. Bogner, John J. Tanner, Pablo Sobrado

Chemistry Faculty Research & Creative Works

Acinetobacter baumannii is a Gram-negative opportunistic pathogen that causes nosocomial infections, especially among immunocompromised individuals. The rise of multidrug resistant strains of A. baumannii has limited the use of standard antibiotics, highlighting a need for new drugs that exploit novel mechanisms of pathogenicity. Disrupting iron acquisition by inhibiting the biosynthesis of iron-chelating molecules (siderophores) secreted by the pathogen is a potential strategy for developing new antibiotics. Here we investigated FbsI, an N-hydroxylating monooxygenase involved in the biosynthesis of fimsbactin A, the major siderophore produced by A. baumannii. FbsI was characterized using steady-state and transient-state kinetics, spectroscopy, X-ray crystallography, and small-angle …

Theoretical Spectra And Energetics For C-C3hc2h, L-C5h2, And Bipyramidal D3h C5h2, Alexandria G. Watrous, Brent R. Westbrook, Ryan C. Fortenberry

Faculty and Student Publications

The recent astronomical detection of c-C3HC2H and l-C5H2 has led to increased interest in C5H2 isomers and their relative stability. The present work provides the first complete list of anharmonic vibrational spectral data with infrared intensities for three such isomers as well as including the first set of rotational data for the bipyramidal C5H2 isomer allowing for these molecules to serve as potential tracers of interstellar carbon. All three isomers have fundamental vibrational frequencies with at least one notably intense fundamental frequency. The l-C5H2 isomer has, by far, the highest intensities out of the three isomers at 2076.3 cm−1 (738 …

Mechanism Of Magic Number Nacl Cluster Formation From Electrosprayed Water Nanodroplets., Lars Konermann, Yousef Haidar

Chemistry Publications

Events taking place during electrospray ionization (ESI) can trigger the self-assembly of various nanoclusters. These products are often dominated by magic number clusters (MNCs) that have highly symmetrical structures. The literature rationalizes the dominance of MNCs by noting their high stability. However, this argument is not necessarily adequate because thermodynamics cannot predict the outcome of kinetically controlled reactions. Thus, the mechanisms responsible for MNC dominance remain poorly understood. Molecular dynamics (MD) simulations can provide atomistic insights into self-assembly reactions, but even this approach has thus far failed to provide pertinent answers. The current work overcomes this limitation. We focused on …

A Molecular Chemodosimeter To Probe “Closed Shell” Ions In Kidney Cells, Rashid Mia

Faculty Publications

Two quinidine-functionalized coumarin molecular probes have been synthesized and have been found to bind metal cations (Cd2+, Co2+, Cu2+, Fe2+, Hg2+, Ni2+, and Zn2+) with high affinity in organic–aqueous media (DMSO–HEPES). The chemodosimeters coordinate with the Zn2+ ions in a two-to-one ratio (molecular probe : Zn2+) with a log β of 10.0 M−2. Upon the addition of the closed-shell metal ions studied, a fluorescence turn-on via an excimer formation is seen at 542 nm due to the quinaldine moiety adopting a syn arrangement when coordinated to the metal Zn2+ ions. Confocal microscopy monitored free Zn2+ ions in the Human Embryonic …

Biomimetic Modifications Of A Feni Hydrogenase Bridging Cys Residue Ligand, Madeline Kesner, Meghan Mcgreal

Annual Symposium on Biomathematics and Ecology Education and Research

No abstract provided.

Development Of Lipidated Antimicrobial Polycarbonates, Ruixuan Gao

USF Tampa Graduate Theses and Dissertations

Antimicrobial resistance is a global challenge owing to the lack of discovering effective antibiotic agents. Antimicrobial polymers containing the cationic groups and hydrophobic groups which mimic natural host-defense peptides (HDPs) show great promise in combating bacteria. Herein, we report the synthesis of lipidated polycarbonates bearing primary amino groups and hydrophobic moieties (including both the terminal lipid alkyl chain and hydrophobic groups in the sequences) by ring-opening polymerization. The hydrophobic/hydrophilic group ratios were adjusted deliberately and the lengths of the lipid tails at the end of the polymers were modified to achieve the optimized combination for the lead polymers, which exhibited …

Tau Kinetics In Alzheimer's Disease, Daniel B. Hier, Sima Azizi, Matthew S. Thimgan, Donald C. Wunsch

Chemistry Faculty Research & Creative Works

The Cytoskeletal Protein Tau is Implicated in the Pathogenesis of Alzheimer's Disease Which is Characterized by Intra-Neuronal Neurofibrillary Tangles Containing Abnormally Phosphorylated Insoluble Tau. Levels of Soluble Tau Are Elevated in the Brain, the CSF, and the Plasma of Patients with Alzheimer's Disease. to Better Understand the Causes of These Elevated Levels of Tau, We Propose a Three-Compartment Kinetic Model (Brain, CSF, and Plasma). the Model Assumes that the Synthesis of Tau Follows Zero-Order Kinetics (Uncorrelated with Compartmental Tau Levels) and that the Release, Absorption, and Clearance of Tau is Governed by First-Order Kinetics (Linearly Related to Compartmental Tau Levels). …

Structural Dynamics Of A Thermally Stressed Monoclonal Antibody Characterized By Temperature-Dependent H/D Exchange Mass Spectrometry., Nastaran N Tajoddin, Lars Konermann

Chemistry Publications

Differential scanning calorimetry (DSC) is a standard tool for probing the resilience of monoclonal antibodies (mAbs) and other protein therapeutics against thermal degradation. Unfortunately, DSC usually only provides insights into global unfolding, although sequential steps are sometimes discernible for multidomain proteins. Temperature-dependent hydrogen/deuterium exchange (HDX) mass spectrometry (MS) has the potential to probe heat-induced events at a much greater level of detail. We recently proposed a strategy to deconvolute temperature-dependent HDX data into contributions from local dynamics, global unfolding/refolding, as well as chemical labeling. However, that strategy was validated only for a small protein (Tajoddin, N. N.; Konermann, L.

Chelation Equilibria And Π-Electron Delocalization In Neutral Hypercoordinate Organosilicon Complexes Of Pyrithione, Erin R. Tiede, Matthew T. Heckman, William W. Brennessel, Bradley M. Kraft

Chemistry Faculty/Staff Publications

A series of neutral pyrithionato (OPTO) organosilicon compounds, R3Si(OPTO) [R = Me (1), Ph (2)], cis-R2Si(OPTO)2 [R = Me (3), Et (4), iPr (5), tBu (6), mesityl (10), allyl (11), p-tolyl (13); R2 = (CH2)3 (7), (CH2)4 (8), (CH2)5 (9), Me, allyl (12)], and cis-R2Si(OPTO)Cl [R = Me (14), iPr (15), allyl (16), p-tolyl (17), mesityl (18), Ph (19)], have been prepared and characterized by 1H, 13C, and 29Si NMR spectroscopy. X-ray crystallographic analysis reveals four-coordinate silicon atoms in 1, 2, 6, and 10, five-coordinate in 3, 9, 11, 12, and 14–19, six-coordinate …

Exploring The Biomedical Applications Of Polyurethane-Based Foams, Films, And Hydrogels, Anand Utpal Vakil

Dissertations - ALL

Shape memory polymers (SMPs) are a class of smart materials that can be temporarily stored in a deformed shape and can actively recover their original shape upon exposure to an external stimulus, such as heat, magnetic field, moisture, pH, light, or electric field. The ability of SMPs to change shape when required can be used for a wide range of applications, especially in the case of minimally invasive biomedical applications. In this work, polyurethane-based SMPs were explored for their use in tissue engineering, drug delivery, and wound healing applications.

In the second chapter, low density porous foams with tunable degradability …

Spectroscopic Study Of The Br−+Ch3i→I−+Ch3br Sn2 Reaction, Hayden T. Robinson, Timothy R. Corkish, Christian T. Haakansson, Peter D. Watson, Allan J. Mckinley, Duncan A. Wild

Research outputs 2022 to 2026

Mass spectrometry and anion photoelectron spectroscopy have been used to study the gas-phase S_N2 reaction involving Br^- and CH₃I. The anion photoelectron spectra associated with the reaction intermediates of this S_N2 reaction are presented. High-level CCSD(T) calculations have been utilised to investigate the reaction intermediates that may form as a result of the S_N2 reaction along various different reaction pathways, including back-side attack and front-side attack. In addition, simulated vertical detachment energies of each reaction intermediate have been calculated to rationalise the photoelectron spectra.

Study On New Strategy Toward Gold(I/Iii) Redox Catalysis, Shuyao Zhang

USF Tampa Graduate Theses and Dissertations

This dissertation mainly contains three parts: 1) the study of ligand assisted gold oxidative addition toward aryl iodide to achieve the alkene difunctionalization. 2) The selective arylation reaction via electrochemical anode oxidation promoted gold redox chemistry. 3) The π acid reactivity of gold redox chemistry under electrochemistry conditions.

In the first part, the gold-catalyzed intermolecular oxyarylation of alkene is reported. This work employed the oxidative addition of aryl iodide to Me-DalphosAu+ for the formation of Au(III)-Ar intermediate. The better binding ability of alkene over O nucleophiles ensured the success of intermolecular oxyarylation, giving desired products with broad substrate scope and …

Ferrocenium Salt Aided Substitution Reactions And Synthesis Of Glycosylated Curcumin Derivatives, Deva Saroja Talasila

Dissertations

Organic synthesis has been significantly advanced with the employment of transition metal complexes. The discovery of transition metal catalysts provided the synthetic community with powerful tools for accelerating reactions and making them more selective and efficient. Many chemical reactions do not happen without a catalyst.

Iron-based catalysts have several advantages for the chemical industry because it is a non-toxic and ecologically friendly metal. Our group previously found that ferrocenium cations with a 3+ oxidation state of iron-catalyzed propargylic substitution reactions at low temperatures. The sandwich structure of ferrocenes allows substituents to be introduced on the cyclopentadienyl rings, which allows for …

Threonine Phosphorylation Of An Electrochemical Peptide-Based Sensor To Achieve Improved Uranyl Ion Binding Affinity, Channing C. Thompson, Rebecca Lai

Chemistry Department: Faculty Publications

We have successfully designed a uranyl ion (U(VI)-specific peptide and used it in the fabrication of an electrochemical sensor. The 12-amino acid peptide sequence, (n) DKDGDGYIpTAAE (c), originates from calmodulin, a Ca(II)-binding protein, and contains a phosphothreonine that enhances the sequence’s affinity for U(VI) over Ca(II). The sensing mechanism of this U(VI) sensor is similar to other electrochemical peptide-based sensors, which relies on the change in the flexibility of the peptide probe upon interacting with the target. The sensor was systematically characterized using alternating current voltammetry (ACV) and cyclic voltammetry. Its limit of detection was 50 nM, which is lower …

Synthesis, Characterization And Cell Viability Of Novel Tripodal Amines, Kinsley Lupton

Honors College Theses

Cancer, over the years, has become a much more prevalent focus for the scientific community. Organizations and laboratories all over the world have spent countless hours searching for a cure, trying to learn more about what makes cancer so powerful and what is the best way to stop its growth. Iron-chelation drugs were already on the market, and it was shown that they did have the ability to act as both iron-chelators and anticancer drugs. Most of these iron-chelating drugs are not as effective at killing cancer cells as the medical field desires. Novel iron-chelating tris-indolyl derivatives, GSO2, GSO4 and …

Agricultural Aerosols: The Impact Of Farming Activity On Ice Nucleating Particles, Joseph Robinson

The Journal of Purdue Undergraduate Research

Farming activities cause particles such as soil dust and plant material to be emitted into the air. Some of these aerosols can become ice nucleating particles (INPs), serving as seeds for ice and mixed-phase clouds. While there have been ground-based studies of these particles in the western Great Plains and a single air-based study in Indiana, there is a distinct lack of ground-based studies in the Midwest. In Indiana, over two-thirds of the state is farmland, with over 75% of land in Tippecanoe County used for agriculture. Despite farming being such an essential part of life in Indiana, the connection …

Processing Of Plastic Film From Potato Starch: Effect Of Drying Methods, Kourtney Collier, Samantha Goins, Austin Chirgwin, Isabelle Stanfield

The Journal of Purdue Undergraduate Research

Starch-based plastics are biodegradable, compostable compounds made of starch and plasticizers from natural sources. Their fabrication involves the starch-plasticizer reaction at 70–100°C followed by cooling and drying. Th e most common drying method is air drying (natural convection), which is effective but slow. Th e objective of this work is to study the effect of fast drying (forced convection) on the quality of the plastic film. Th is work compares the effects of drying conditions and drying rate on warpage, shrinkage rate, and presence of bubbles. Five drying methods are studied: (1) natural convection with uncovered petri dish, (2) natural …

Vitamin E Does Not Disturb Polyunsaturated Fatty Acid Lipid Domains, Mitchell Dipasquale, Michael H.L. Nguyen, Stuart R. Castillo, Isabelle J. Dib, Elizabeth G. Kelley, Drew Marquardt

Chemistry and Biochemistry Publications

The function of vitamin E in biomembranes remains a prominent topic of discussion. As its limitations as an antioxidant persist and novel functions are discovered, our understanding of the role of vitamin E becomes increasingly enigmatic. As a group of lipophilic molecules (tocopherols and tocotrienols), vitamin E has been shown to influence the properties of its host membrane, and a wealth of research has connected vitamin E to polyunsaturated fatty acid (PUFA) lipids. Here, we use contrast-matched small-angle neutron scattering and differential scanning calorimetry to integrate these fields by examining the influence of vitamin E on lipid domain stability in …

Synthesis And Characterization Of Nanocomposites For Environmental Remediation, Nethaji S

Technical Collection

My current work deals with the preparation and characterization of nanocomposites for effluent treatment applications. The expertise lies on the preparation of carbonaceous nanocomposites including graphitic materials. The prepared materials are characterized thoroughly by different methods like FE-SEM, TEM, FT-IR, XRD, VSM, surface area and porosity. The composite materials are used for the removal of conventional and emerging contaminants like antibiotics, pesticide residues, endocrine disruptors etc. In addition to the batch studies, fabrication of microcolumns to aid the scale-up of the process is also carried out. I have published 14 research publications with around 1000 citations and h-index of 11. …

College Of Natural Sciences Newsletter, September & October 2022, College Of Natural Sciences

College of Natural Sciences Newsletters and Reports

Volume 3, Issue 6

Page 1 Dean's Message
Page 2 Awards & Recognition
Page 3 Midwest Regional ACS Meeting
Page 4 North Central ASM Meeting
Page 5 Geography Department Travel
Page 6-7 Media Coverage of CNS
Page 7 REMAST Program at SDState receives national spotlight
Page 8 Celebrating the lives of those who touched the College
Page 9 Innovative Learning Spaces
Page 10 Open PRAIRIE Data
Page 11 2022 CNS Scholarship Brunch
Page 12-14 Fall 2022 Outreach Events

Nucleobase-Modified Nucleosides And Nucleotides: Applications In Biochemistry, Synthetic Biology, And Drug Discovery, Anthony J. Berdis

Chemistry Faculty Publications

DNA is often referred to as the "molecule of life " since it contains the genetic blueprint for all forms of life on this planet. The core building blocks composing DNA are deoxynucleotides. While the deoxyribose sugar and phosphate group are ubiquitous, it is the composition and spatial arrangement of the four natural nucleobases, adenine (A), cytosine (C), guanine (G), and thymine (T), that provide diversity in the coding information present in DNA. The ability of DNA to function as the genetic blueprint has historically been attributed to the formation of proper hydrogen bonding interactions made between complementary nucleobases. However, …