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Investigation Of The Structural, Electronic, And Thermoelectric Properties Of Mono- Chalcogenides, Aida Sheibani

Graduate Theses and Dissertations

The structural, electronic, and thermoelectric properties of GeTe are studied using density functional theory and Boltzmann transport equations. This material has a rhombohedral crystal structure in ambient temperature with a ferroelectric behavior due to lack of inversion symmetry. This study suggests that the presence of asymmetry in GeTe can lead to an improvement in the thermoelectric properties of this material. In addition, studies on introducing Group III, IV, and V dopants to GeSe show that while these impurities can improve the power factor and decrease the lattice thermal conductivity, they cannot enhance the figure of merit.

Ensemble And Single Particle Studies Of Cation Exchange In Cuins2/Zns Qds And Their Application In Super-Resolution Imaging, Anh Tue Nguyen

Graduate Theses and Dissertations

Colloidal quantum dots (QDs) have great potential in many applications such as bioimaging, light emitting diodes, solar cells and lasers. However, a great number of studies have been focused on Cd based (II-VI) and Pb (IV-VI) based materials which are not suitable for mass production. Therefore, alternative types of QD containing less toxic materials have been introduced, including CuInS2 QDs. This I-III-VI semiconductor nanocrystals also attract lots of attention due to their large Stock shift, long fluorescence lifetime and high defect tolerance, making them attractive emitters for applications in bioimaging, photovoltaics and light emitting diodes.

In the first project, we …

Investigation Of Evidence For The Internal Structure Of A Modified Science Motivation Questionnaire Ii (Msmq Ii): A Failed Attempt To Improve Instrument Functioning Across Course, Subject, And Wording Variants, Regis Komperda, Kathryn Hosbein, Michael M. Phillips, Jack Barbera

Chemistry Faculty Publications and Presentations

The Science Motivation Questionnaire II (SMQ II) was developed to measure aspects of student motivation in college-level science courses. Items on the SMQ II are structured such that the word ‘science’ can be replaced with any discipline title (e.g., chemistry) to produce a discipline-specific measure of student motivation. Since its original development as the Science Motivation Questionnaire and subsequent refinement, the SMQ II and its discipline-specific variants have been used in a number of science education studies. However, many studies have failed to produce acceptable validity evidence for their data based on the proposed internal structure of the …

Comparison Of Chemotherapeutic Activities Of Rhodamine-Based Gumbos And Nanogumbos, Nimisha Bhattarai, Mi Chen, Rocío L. Pérez, Sudhir Ravula, Robert Strongin, Karen Mcdonough, Isiah M. Warner

Chemistry Faculty Publications and Presentations

Rhodamine derivatives have been widely investigated for their mitochondrial targeting and chemotherapeutic properties that result from their lipophilic cationic structures. In previous research, we have found that conversion of Rhodamine 6G into nanoGUMBOS, i.e., nanomaterials derived from a group of uniform materials based on organic salts (GUMBOS), led to selective chemotherapeutic toxicity for cancer cells over normal cells. Herein, we investigate the chemotherapeutic activity of GUMBOS derived from four different rhodamine derivatives, two bearing an ester group, i.e., Rhodamine 123 (R123) and SNAFR-5, and two bearing a carboxylic acid group, i.e., rhodamine 110 (R110) and rhodamine B (RB). In this …

Synthesis And Evaluation Of Small Molecule Inhibitors Of Pyruvate Carboxylase, Daniel John Burkett

Master's Theses (2009 -)

Through structure-based drug design (SBDD), a series of small molecules have been synthesized and evaluated for inhibitory activity against the pyruvate carboxylase (PC) enzyme via two biological assays. The -hydroxycinnamic acid scaffold was identified as the most privileged scaffold for inhibition of PC. Analogues of phenylpyruvic acid were generated and evaluated, leading to the discovery of inhibitors with single digit micromolar (M) IC50 values. The most potent inhibitors identified were evaluated for inhibitory activity against other metalloproteins, and 2-hydroxy-3-(quinolone-2-yl)propenoic acid did not significantly inhibit human carbonic anhydrase II, matrix metalloproteinase-2, malate dehydrogenase, or lactate dehydrogenase. The small molecules presented in …

Nitrogen-Doped Graphene-Based Metal Composites For The Non-Enzymatic Detection Of Hydrogen Peroxide, Tajabadi Poor Mohammad Taghi

Student Works (2020-2029)

Recently, much attention has been devoted to detecting hydrogen peroxide (H2O2) because of its extensive range of applications in chemical synthesis, the textile industry, food production, fuel cell devices, and even in many oxidative biological reactions. Among the various methods of detection of H2O2, electrochemical sensors has many advantages, such as simplicity, high efficiency and sensitivity, as well as good selectivity., To improve the sensitivity of non-enzymatic sensors, noble metal nanoparticles with particular electrocatalytic activities can be utilized. The present research is aimed to design a hybrid approach for the development of novel nanostructures for non-enzymatic detection of H2O2. Herein, …

Synthesis And In Vitro Studies Of Polycaprolactone-Coated Superparamagnetic Iron Oxide Nanoparticles For Magnetic Hyperthermia Therapy, Nasab Ziba Hedayat

Student Works (2020-2029)

Research has garnered a great interest in utilization of superparamagnetic iron oxide nanoparticles (SPIONs) as magnetic nano-heating agents in hyperthermia cancer therapy by profiting from high apoptosis vulnerability of cancer cells at elevated temperatures. However, low oxidation resistance and high agglomeration tendency negatively affect magnetic characteristics of nanoparticles and subsequently their clinical efficiency. Particle surface modifications are potential approaches to endow SPIONs a range of desirable properties including high colloidal dispersity, low aggregation tendency, cytocompatibility, and high oxidation resistance. Currently, polymer coating has led to decrease magnetic hyperthermia efficiency through formation of intermediate layer between nanoheating agents and targeted cells. …

Resonance Raman Spectroscopic Studies Of Peroxo And Hydroperoxo Intermediates In Lauric Acid (La)-Bound Cytochrome P450 119, Remigio Usai, Daniel Kaluka, Piotr J. Mak, Yilin Liu, James R. Kincaid

Chemistry Faculty Research and Publications

Cytochromes P450 bind and cleave dioxygen to generate a potent intermediate compound I, capable of hydroxylating inert hydrocarbon substrates. Cytochrome P450 119, a bacterial cytochrome P450 that serves as a good model system for the study of the intermediate states in the P450 catalytic cycle. CYP119 is found in high temperature and sulfur rich environments. Though the natural substrate and redox partner are still unknown, a potential application of such thermophilic P450s is utilizing them as biocatalysts in biotechnological industry; e.g., the synthesis of organic compounds otherwise requiring hostile environments like extremes of pH or temperature. In the present work …

Hydrogen Peroxide And Antioxidant Enzymes Moderate Interaction Of The Carbon And Oxygen Cycles At The Redoxcline, Fan Wang

Theses and Dissertations

Hydrogen peroxide is a reduced form of dioxygen produced in natural waters from a manifold of abiotic and biological processes. Hydrogen peroxide is highly redox active and it often serves to initiate the formation of reactive oxygen species in the environment. It typically exists in natural waters at concentrations ranging from as low as ~ 1 nanomolar in “blue water” marine environments to as high as 10 micromolar near actively effluxing sediments. It has the potential to cause significant toxicity in aquatic organisms, which have evolved a collection of antioxidant enzymes including peroxidase, catalase, and superoxide dismutase. Work in this …

Protein Co-Assembly And Its Application In Enzyme Engineering, Libo Zhang

Theses and Dissertations

Enzymes, as highly efficient biocatalysts, have been researched extensively in both academia and industry because of their distinct advantages including high substrate specificity, high regio- and stereoselectivity, environmentally benign process, etc. Though enzyme catalysis has been scaled up for commercial processes in the pharmaceutical, food and beverage and detergent industries, technical barriers associated with enzyme implementation persist, i.e., low catalytic efficiency at non-natural environment, exhausting product separations, high cost of certain enzymes, etc. Moreover, currently most industrial enzymes are used in single-step reactions; however, multistep and multienzyme catalysis with optimal efficiency could greatly expand its potential for synthetic applications to …

1. Dft-Guided Discovery Of Hybrid Catalysts For C-C Bond Formation; 2. Synthesis Of A Reported Pdi Inhibitor, Eric Greve

Dissertations (1934 -)

1. Dual amine/pi Lewis acid catalyst systems have been reported for intramolecular direct additions of aldehydes/ketones to unactivated alkynes and occasionally alkenes, but related intermolecular reactions are rare. We reasoned that bulky metal ligands and bulky amine catalysts could minimize catalyst poisoning and could facilitate certain examples of direct intermolecular additions of unactivated aldehydes/ketones to alkenes/alkynes. Density Functional Theory (DFT) ground state calculations on putative catalytic intermediates for alkyne versus organocatalyst complexation to the -acid, and also the key carbon-carbon bond formation were used to prioritize ligand/organocatalyst combinations. Our calculations suggested that PyBOX-Pt(II) catalysts for alkene/alkyne activation could be combined …

An Angelman Syndrome Substitution In The Hect E3 Ubiquitin Ligase C-Terminal Lobe Of E6ap Affects Protein Stability And Activity, Steven A. Beasley, Chloe E. Kellum, Rachel J. Orlomoski, Feston Idrizi, Donald E. Spratt

Chemistry

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by speech impairment, intellectual disability, ataxia, and epilepsy. AS is caused by mutations in the maternal copy of UBE3A located on chromosome 15q11-13. UBE3A codes for E6AP (E6 Associated Protein), a prominent member of the HECT (Homologous to E6AP C-Terminus) E3 ubiquitin ligase family. E6AP catalyzes the posttranslational attachment of ubiquitin via its HECT domain onto various intracellular target proteins to regulate DNA repair and cell cycle progression. The HECT domain consists of an N-lobe, required for E2~ubiquitin recruitment, while the C-lobe contains the conserved catalytic cysteine required for ubiquitin transfer. …

Identification Of Peptide Sequence To Block Dengue Virus Transmission Into Cells Via In Silico And In Vitro Assays, Arumugam Aathe Cangaree

Student Works (2020-2029)

Dengue virus (DV) infection has become main public wellbeing concerns, affecting approximately 390 million people worldwide. This fact was reported by the World Health Organization. Yet, there is no commercial antiviral treatment for DV infection. Therefore, the development of potent and non-toxic anti-DV, as a complement for the existing treatment strategies, are urgently needed. Herein, we investigate a series of low molecular weight peptides inhibitors by aiming the cellular entry process as the promising approach to block DV infection. The peptides were designed based on previously reported peptide sequence, DN58opt (TWWCFYFCRRHHPFWFFYRHN), to identify minimal effective inhibitory sequence via molecular docking …

Features Of Heart Activity Of Cattle In The Conditions Of Southern Aral Sea Region, Svetlana Mambetullaeva, Khayratdin Seytkamalov

Karakalpak Scientific Journal

In this article, the results of comparative analysis of electrocardiogram are shown for the cows of different breeds in the Aral Sea region. It is set that the high temperature of the environment and sunny insolation render a negative influence on the functional parameters of the cardiac vascular system of animals. There are facts about the cows of different breeds at the influence of different temperatures that have unidirectional functional changes in the operation of the heart. At the same time, we will mark that these changes are less expressed for the cows of the improved zebu visible cattle, what …

Photoelectric Injection Amplification Of Al–Al2o3–P-Cdte–Mo Structures At Low Bias Voltages, A K. Uteniyazov

Karakalpak Scientific Journal

The results of studies of photoelectric injection enhancement of the Al–Al₂O₃–p-CdTe –Mo structure upon application of low bias voltages. It has been shown that the studied Al-Al₂O₃–p-CdTe-Mo structure under can be represented as a n⁺-p-R_ом structure with a long base. Conducted researches show that Al-Al₂O₃–p-CdTe-Mo structure has unique properties. It has very high photocurrent and photosensitivity at both direct and reverse dias voltage under even small bias voltage (up to 500mV).

Synthesis Of Supramolecular Complex L– (-) – Menthol, Ziyada Djumanova Dr, Lolaxan Ettibaeva, Ugilay Abduraxmonova, Zulfiya Khalmuratova

Karakalpak Scientific Journal

In this article glycyrrhizic acid content with menthol in several various proportions (2:1; 4:1; 9:1), information was given on synthesis and physical and chemical properties of new supermolecular complexes. Received supramolecular complexes concerning 4:1 it was chemically defined and also studied the structure of supramolecular complexes by physical methods on the basis of interaction of organic molecules with electromagnetic radiation, in particular their range IR – of spectroscopy. Our work of the near future will be turned to check its recent supramolecular complexes on the basis of GA: Menthol for growth of a plant and biotic elasticity of tension …

Spectrophotometric Characterization Of The Complexation Of Gossypol Acetic Acid With Cobalt Ion, Ugilay Abdurahmanova, Habibjon Kushiev, Maral Askarova, Dilafruz Allanazarova

Karakalpak Scientific Journal

The authors of the article suggest simple and express method of spectrophotometric determination of cobalt with the help of derivatives of gossypol. Optimal conditions of determining cobalt are found. Under optimal conditions there was created a graded graph, which is more linear in the range for cobalt concentration of 10.0 – 50.0 microgram/25 ml, contents and constants of cobalt complex with gossypol vinegar acid.

Stabilizing Capability Of Gum Arabic On The Synthesis Of Poly(Styrene-Methylmethacrylate-Acrylic Acid) Latex For The Generation Of Colloidal Crystal Films, Ikhazuagbe Ifijen, Stanley Omorogbe, Muniratu Maliki, Ifeanyi Odiachi, Aireguamen Aigbodion, Esther Ikhuoria

Tanzania Journal of Science

This article describes the generation and characterization of colloidal crystals from particles of gum arabic (GA) and sodium dodecylbenzene sulfate (SDBS) emulsified poly(styrene methylmethacrylate-acrylic acid) (P(St-MMA-AA) latex. The colloidal latex was synthesized using GA and SDBS as the emulsifying agents and then used to generate colloidal crystal films via the vertical deposition technique. Dynamic light scattering analysis placed the average particle diameter, polydispersity and Zeta potential at about 122 nm, 0.014 and –36.20 mV for the as-synthesized GA emulsified terpolymer latex and 213 nm, 0.006, –35.60 mV for the SDBS emulsified terpolymer latex, respectively. Thermo-gravimetric analysis and differential scanning calorimetry …

Construction Of Giant 2d And 3d Metallo-Supramolecules Based On Pyrylium Salts Chemistry, Yiming Li

USF Tampa Graduate Theses and Dissertations

Pyrylium salts are a type of six-membered cationic heterocycles with one positively charged oxygen atom. Since the discovery of pyrylium salts in 1911, such salts have been underappreciated for a long time. Until 1960s, the importance of pyrylium salts has been realized as versatile precursors in a variety of organic syntheses. Due to their high reactivity towards various nucleophiles, pyrylium salts were widely used for the convenient synthesis of diverse heterocyclic compounds. Starting from 1980s, the high reactive feature of pyrylium salts were further utilized to synthesize viologen polymers with pyridinium salts in the backbones. During the past two decades, …

Geochemical Characteristics Of Soil In Relation To Occurrence Of Entomopathogenic Nematodes (Epns) In Osogbo, Osun State, Nigeria, Mohammed Rufai, Abidat Shittu, Monsuru Adeleke

Tanzania Journal of Science

The occurrence and abundance of entomopathogenic nematodes (EPNs) vary across locations, and this has been attributed to many factors including soil physico-chemical properties. This study examined the influence of selected soil chemicals on the occurrence of EPNs under different cultivated lands in Osun state, Southwestern Nigeria. EPNs were isolated from 23.33% of the soil samples in selected sites using decantation and centrifugation method and nematodes observed under standard microscopy were identified based on morphological analysis of infective juveniles (IJs). This study has revealed the presence of nematodes of the families Steinernema and Heterorhabditis in the sampled soils. Soil chemical properties, …

Leaf Traits Can Be Used To Predict Rates Of Litter Decomposition, Marc Rosenfield, Jennifer L. Funk, Jason K. Keller, Catrina Clausen, Kimberlee Cyphers

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Strong relationships exist between litter chemistry traits and rates of litter decomposition. However, leaf traits are more commonly found in online trait databases than litter traits and fewer studies have examined how well leaf traits predict litter decomposition rates. Furthermore, while bulk leaf nitrogen (N) content is known to regulate litter decomposition, few studies have explored the importance of N biochemistry fractions, such as protein and amino acid concentration. Here, we decomposed green leaves and naturally senesced leaf litter of nine species representing a wide range of leaf functional traits. We evaluated the ability of traits associated with leaf and …

Rapid Vertical Flow Assay On Aunp Plasmonic Paper For Sers-Based Point Of Need Diagnostics, Richard Frimpong

Theses and Dissertations

SERS based immunoassays for point-of-care diagnostics is a promising tool to facilitate biomarker detection for early disease diagnosis and control. The technique is based on a sandwiched system in which antigen is first captured by a selective substrate and then labeled by an extrinsic Raman label (ERL). Here, we report on the use of gold nanoparticle modified filter paper as a novel capture membrane in a vertical flow format. This vertical flow configuration affords reproducible flow of sample and label through the capture substrate to overcome diffusion limited kinetics and significantly reduced assay time. The filter paper was selected due …

Recent Advancement In Pseudo-Random Binary Sequence Signals-Based Fast Reconstruction Of Impedance Spectrum And Its Applications In Electrochemical Energy Sources, Wei-Heng Li, Qiu-An Huang, Wei-Ming Yang, Chang-Ping Yang, Jiu-Jun Zhang

Journal of Electrochemistry

With the extensive application of impedance spectroscopy, the time-consuming issue of its traditional testing methods has become more and more serious, which limits its application range. In the study of accelerating impedance measurement or reconstruction, the synthesis of wideband excitation signals and the design of high efficiency estimation algorithms have been identified as important ways. In view of the purpose of rapid impedance reconstruction, Pseudo-Random Binary Sequence (PRBS) has the advantages of flat power spectrum and easy generation, and has a good application prospect. This paper reviews three core issues in rapid reconstruction of impedance spectrum: PRBS signal types, different …

A Simple And Sensitive Aptamer-Based Electrochmical Sensor For Determination Of Aflatoxin B1, Bing Liu, Yao-Shuai Zhao, Yue Qin, Yi Wang, Yan-Jie Zhu, Shuo Wang

Journal of Electrochemistry

Aflatoxin B1 has attracted much attention because of its high toxicity and carcinogenicity, which has become a great concern in food safety. Based on the principle of specific binding between Aflatoxin B1 and its aptamer, an aptamer-based electrochemical sensor had been designed and developed for the determination of minor Aflatoxin B1 contained in grain. The mesoporous carbons were first modified on the surface of the working electrode, and then the gold nanoparticles were on-site electrodeposited at a constant potential. Each modified electrode was characteritised by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). As a result, the surface area …

Antimicrobial Strategies For Topical Applications, Kelsey Marie Lopez

LSU Doctoral Dissertations

Bacteria can thrive in diverse environments and are often harmless or beneficial. Bacteria in digestive tracts is one example of beneficial bacteria; however, bacteria can be harmful and when this type proliferates, it can cause infections within hosts. Bacterial infections are easily treated with antibiotics in most cases. However, bacteria are also capable of developing mutations which could cause them to become multi-drug resistant and eventually, “superbugs.” Therefore, the development of novel antimicrobial agents and materials capable of combating drug-resistant bacteria is necessary. Research presented in this dissertation focuses on different strategies for minimizing and preventing topical bacterial infections using …

Adsorption Behavior Of Chemically / Charged Modified Antibodies On Gold Nanoparticles, Samuel Okyem

Theses and Dissertations

Gold nanoparticles (AuNPs) have been exploited in the various domains of science such as drug delivery, bio-sensing, immunoassays and environmental sensors, due to their optical properties and intriguing surface chemistry. Different scientific procedures have been used to effectively immobilize antibodies onto AuNPs. Although acceptable outcomes have been achieved in the immobilization of antibodies onto AuNPs, the sensitivity of these immobilized antibodies to target antigen or binding sites is limited due to improper orientation of the antibodies. Also, the possibility of nanoparticle aggregation when exposed to proteins limits its biomedical applicability.

There is some evidence that the surface charge of antibodies …

Ordered Mesoporous Carbon/Graphene/Nickel Foam For Flexible Dopamine Detection With Ultrahigh Sensitivity And Selectivity, Lai-Yu Wang, Xin Xi, Dong-Qing Wu, Xiong-Yu Liu, Wei Ji, Rui-Li Liu

Journal of Electrochemistry

Electro-catalytic reduction is an efficient way to achieve resourcable transformation of CO₂, which is one of the important techniques to solve the global environmental problems originated from excessive CO₂ emission. In this study, a membrane electrode assembly(MEA) type CO₂ electro-reduction electrolytic cell was constucted, which enables CO₂ feeding and real-time KHCO₃ aqueous updating on both sides of the cathode gas diffusion electrode (GDE). By means of the electrolytic cell, effects of KHCO₃ concentration and updating inside the liquid electrolytic chamber on CO₂ electro-reduction activity, production distribution and stability were investigated. The experimental …

Heterometallic Multinuclear Nodes Directing Mof Electronic Behavior, Otega A. Ejegbavwo, Anna A. Berseneva, Corey R. Martin, Gabrielle A. Leith, Shubham Pandey, Amy J. Brandt, Kyoung Chul Park, Abhijai Mathur, Sharfa Farzandh, Vladislav V. Klepov, Brittany J. Heiser, Mvs Chandrashekhar, Stavros G. Karakalos, Mark D. Smith, Simon R. Phillpot, Sophya Garashchuk, Donna A. Chen, Natalia B. Shustova Prof. Dr.

Faculty Publications

Metal node engineering in combination with modularity, topological diversity, and porosity of metal–organic frameworks (MOFs) could advance energy and optoelectronic sectors. In this study, we focus on MOFs with multinuclear heterometallic nodes for establishing metal−property trends, i.e., connecting atomic scale changes with macroscopic material properties by utilization of inductively coupled plasma mass spectrometry, conductivity measurements, X-ray photoelectron and diffuse reflectance spectroscopies, and density functional theory calculations. The results of Bader charge analysis and studies employing the Voronoi–Dirichlet partition of crystal structures are also presented. As an example of frameworks with different nodal arrangements, we have chosen MOFs with mononuclear, …

Investigating The Reversibility Of Protein Adsorption On Gold Nanoparticles And The Role Of Free Thiol, Awosiji Olatunde Awotunde

Theses and Dissertations

Protein-gold nanoparticle (AuNP) bioconjugates have many potential applications in nanomedicine. A thorough understanding of the interaction between the protein and AuNP is critical to engineering these functional bioconjugates with desirable properties. In this work, we investigate the role of free thiols presented by the protein on the stability of the protein-AuNP conjugate. Human serum albumin (HSA) was modified with 2-iminothiolane (Traut’s reagent) to introduce additional thiols on the protein surface, and three variants of HSA were synthesized to present 1, 5, and 20 free thiols by controlling the molar excess of the chemical modifier. Protein exchange studies on AuNPs were …

Structural Basis For The Hydrolytic Dehalogenation Of The Fungicide Chlorothalonil, Daniel S. Catlin, Xinhang Yang, Brian Bennett, Richard C. Holz, Dali Liu

Chemistry: Faculty Publications and Other Works

Cleavage of aromatic carbon–chlorine bonds is critical for the degradation of toxic industrial compounds. Here, we solved the X-ray crystal structure of chlorothalonil dehalogenase (Chd) from Pseudomonas sp. CTN-3, with 15 of its N-terminal residues truncated (ChdT), using single-wavelength anomalous dispersion refined to 1.96 Å resolution. Chd has low sequence identity (<15%) compared with all other proteins whose structures are currently available, and to the best of our knowledge, we present the first structure of a Zn(II)-dependent aromatic dehalogenase that does not require a coenzyme. ChdT forms a “head-to-tail” homodimer, formed between two α-helices from each monomer, with three Zn(II)-binding sites, two of which occupy the active sites, whereas the third anchors a structural site at the homodimer interface. The catalytic Zn(II) ions are solvent-accessible via a large hydrophobic (8.5 × 17.8 Å) opening to bulk solvent and two hydrophilic branched channels. Each active-site Zn(II) ion resides in a distorted trigonal bipyramid geometry with His117, His257, Asp116, Asn216, and a water/hydroxide as ligands. A conserved His residue, His114, is hydrogen-bonded to the Zn(II)-bound water/hydroxide and likely functions as the general acid-base. We examined substrate binding by docking chlorothalonil (2,4,5,6-tetrachloroisophtalonitrile, TPN) into the hydrophobic channel and observed that the most energetically favorable pose includes a TPN orientation that coordinates to the active-site Zn(II) ions via a CN and that maximizes a π–π interaction with Trp227. On the basis of these results, along with previously reported kinetics data, we propose a refined catalytic mechanism for Chd-mediated TPN dehalogenation.