Life Sciences Commons^™

Synthesis And Characterization Of Polymer (Sulfonated Poly-Ether-Ether-Ketone) Based Nanocomposite (H-Boron Nitride) Membrane For Hydrogen Storage, Naresh Muthu, S. Rajashabala, R. Kannan

Chemistry and Biochemistry Faculty Publications

The development of light weight and compact hydrogen storage materials is still prerequisite to fuel-cell technology to be fully competitive. The present experimental study reports the hydrogen storage capability of sulfonated poly-ether-ether-ketone (SPEEK)-hexagonal boron nitride (h-BN) (SPEEK-h-BN) nanocomposite membranes. The nanocomposite membranes are prepared by considering various amount of h-BN (0, 1, 3 and 5 wt. %) by phase inversion technique. The degree of sulfonation of the PEEK (SPEEK) is found to be 65% by Proton Nuclear Magnetic Resonance (¹H NMR) spectroscopy. Hydrogen adsorption studies have been carried out using a Seiverts-like hydrogenation setup. The membranes are characterized …

Antifungal Amphiphilic Aminoglycoside K20: Bioactivities And Mechanism Of Action, Sanjib K. Shrestha, Cheng-Wei Tom Chang, Nicole Meissner, John Oblad, Jaya P. Shrestha, Kevin N. Sorensen, Michelle M. Grilley, Jon Y. Takemoto

Chemistry and Biochemistry Faculty Publications

K20 is a novel amphiphilic antifungal aminoglycoside that is synthetically derived from the antibiotic kanamycin A. Reported here are investigations of K20′s antimicrobial activities, cytotoxicity, and fungicidal mechanism of action. In vitro growth inhibitory activities against a variety of human and plant pathogenic yeasts, filamentous fungi, and bacteria were determined using microbroth dilution assays and time-kill curve analyses, and hemolytic and animal cell cytotoxic activities were determined. Effects on Cryptococcus neoformans H-99 infectivity were determined with a preventive murine lung infection model. The antifungal mechanism of action was studied using intact fungal cells, yeast lipid mutants, and small unilamellar lipid …

Cloning And Expression For The Future Characterization Of The Air2 Protein, Emily Sue Frampton

Undergraduate Honors Capstone Projects

Air2 is a eukaryotic protein involved in multiple biological processes including protein-protein interactions as well as RNA binding. Air2 plays a critical role in RNA quality control and also helps regulate post-translational modification of various proteins. Although previous studies have revealed information regarding Air2's roles within a cell, the molecular and structural basis for Air2 function is unclear. Using a codon-optimized version of the Air2 gene, various constructs were created that improved the expression and solubility of Air2. Additionally a co-expression complex of Air2 with a PRMTI mutant, K13S, was made to obtain the Air2 protein with a native binding …

Pop2: A Potential Regulator Of Hmt1-Catalyzed Arginine Methylation In Yeast, Celeste Excell

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Protein arginine methylation is an important post-translational modification that is vital in regulating various cellular processes such as gene transcription, cell signaling, and RNA processing. Protein arginine methyltransferases (PRMTs) are responsible for performing this important modification. PRMT1 (protein arginine methyltransferase 1) and Hmt1 (hnRNP methyltransferase 1) are the predominant PRMTs in humans and yeast, respectively. Despite growing momentum in this field, relatively little is understood about PRMT regulation. Further work discovering how PRMTs are regulated will greatly advance our understanding of diseases where PRMTs have been implicated, such as heart disease, viral pathogenesis, and cancer.

It has been discovered that …

Electron Transfer And Substrate Reduction In Nitrogenase, Karamatullah Danyal

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The reduction of nitrogen to ammonia by the industrial Haber-Bosch process is considered one of the major scientific breakthroughs of the last century. It is considered to be responsible for approximately one third of the world's current population. This growth over the past 50 or so years accompanied by the changes in dietary habits due to economic growth have markedly increased the demand for fixed nitrogen in the form of fertilizer. The Haber-Bosch process and biological nitrogen fixation has been able to fulfil this demand. However, this industrial process is costly due to its high temperature and pressure requirements. Every …

Quantum Mechanical Study Of Weak Molecular Interactions, Upendra Adhikari

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Molecular interactions play key role in the existence of biomolecules like proteins and nucleic acids, and various materials. Molecular interactions are weak forces that hold different molecules or different fragments of the same molecule together, and are often referred to as noncovalent interactions. Due to the complexity in biomolecules, these interactions are still poorly understood. This dissertation presents results from quantum mechanical simulations of various types of noncovalent interactions, which are extremely important for the structure and functions of biomolecules and materials.

A new sort of noncovalent interaction is identified. This new sort of interaction originates from a direct interaction …

Complexation Of N So2 Molecules (N=1,2,3) With Formaldehyde And Thioformaldehyde, L. M. Azofra, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Ab initio and density functional theory calculations are used to examine complexes formed between H2CO and H2CS with 1, 2, and 3 molecules of SO2. The nature of the interactions is probed by a variety of means, including electrostatic potentials, natural bond orbital, atoms in molecules, energy decomposition, and electron density redistribution maps. The dimers are relatively strongly bound, with interaction energies exceeding 5 kcal/mol. The structures are cyclic, containing both a O/S⋯S chalcogen bond and a CH⋯O H-bond. Addition of a second SO2 molecule leads to a variety of heterotrimer structures, most of which resemble the original dimer, where …

Interaction Between Temozolomide And Water: Preferred Binding Sites, O. E. Kasende, A. Matondo, M. Muzomwe, J. T. Muya, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Computational methods are used to predict the most favorable site of temozolomide towards attack by a water molecule. The energetics of the various complexes are presented as well as their geometries, including perturbations of each subunit caused by the presence of the other. Molecular electrostatic potential and Natural Bond Orbital (NBO) data are used to understand the interactions which conclude the terminal amide group is the preferred attack site where water can act as simultaneous proton donor and acceptor. Other potential proton acceptor N atoms within the aromatic ring structure represent weaker binding sites. Some of the less strongly bound …

Strongly Bound Noncovalent (So3)N:H2co Complexes (N = 1, 2), L. M. Azofra, I. Alkorta, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The potential energy surfaces (PES) for the SO3:H2CO and (SO3)2:H2CO complexes were thoroughly examined at the MP2/aug-cc-pVDZ computational level. Heterodimers and trimers are held together primarily by SO chalcogen bonds, supplemented by weaker CHO and/or OC bonds. The nature of the interactions is probed by a variety of means, including electrostatic potentials, AIM, NBO, energy decomposition, and electron density redistribution maps. The most stable dimer is strongly bound, with an interaction energy exceeding 10 kcal mol(-1). Trimers adopt the geometry of the most stable dimer, with an added SO3 molecule situated so as to interact with both of the original …

Substituent Effects In The Noncovalent Bonding Of So2 To Molecules Containing A Carbonyl Group. The Dominating Role Of The Chalcogen Bond, L. M. Azofra, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The SO2 molecule is paired with a number of carbonyl-containing molecules, and the properties of the resulting complexes are calculated by high-level ab initio theory. The global minimum of each pair is held together primarily by a S···O chalcogen bond wherein the lone pairs of the carbonyl O transfer charge to the π* antibonding SO orbital, supplemented by smaller contributions from weak CH···O H-bonds. The binding energies vary between 4.2 and 8.6 kcal/mol, competitive with even some of the stronger noncovalent forces such as H-bonds and halogen bonds. The geometrical arrangement places the carbonyl O atom above the plane of …

Competition Between Lone Pair-Π, Halogen Bond, And Hydrogen Bond In Adducts Of Water With Perhalogenated Alkenes C2clnf4-N (N = 0-4), U. Adhikari, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

A thorough search of the potential energy surface is carried out for heterodimers of water with C2ClnF4−n. Three different types of interactions are observed. Structures dominated by a lone pair–π interaction have the highest binding energies, and are stabilized by charge transfer from O lone pairs of H2O to the Csingle bondC π* antibonding orbital of the alkene. Halogen-bonded O⋯Cl complexes are slightly less strongly bound, followed by OH⋯X hydrogen bonds. The replacements of Cl by F atoms have only small effects upon binding energies. Inclusion of vibrational and entropic effects removes the clear energetic superiority of lp–π binding energies. …

Complexes Containing Co2 And So2. Mixed Dimers, Trimers And Tetramers, L. M. Azofra, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Mixed dimers, trimers and tetramers composed of SO2 and CO2 molecules are examined by ab initio calculations to identify all minimum energy structures. While AIM formalism leads to the idea of a pair of C···O bonds in the most stable heterodimer, bound by some 2 kcal mol(-1), NBO analysis describes the bonding in terms of charge transfer from O lone pairs of SO2 to the CO π* antibonding orbitals. The second minimum on the surface, just slightly less stable, is described by AIM as containing a single O···O chalcogen bond. The NBO picture is that of two transfers in opposite …

Effects Of Charge And Substituent On The S∙∙∙N Chalcogen Bond, U. Adhikari, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Neutral complexes containing a S···N chalcogen bond are compared with similar systems in which a positive charge has been added to the S-containing electron acceptor, using high-level ab initio calculations. The effects on both XS···N and XS+···N bonds are evaluated for a range of different substituents X = CH3, CF3, NH2, NO2, OH, Cl, and F, using NH3 as the common electron donor. The binding energy of XMeS···NH3 varies between 2.3 and 4.3 kcal/mol, with the strongest interaction occurring for X = F. The binding is strengthened by a factor of 2–10 in charged XH2S+···NH3 complexes, reaching a maximum of …

An Exploration Of The Ozone Dimer Potential Energy Surface, L. M. Azofra, I. Alkorta, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The (O3)2 dimer potential energy surface is thoroughly explored at the ab initio CCSD(T) computational level. Five minima are characterized with binding energies between 0.35 and 2.24 kcal/mol. The most stable may be characterized as slipped parallel, with the two O3 monomers situated in parallel planes. Partitioning of the interaction energy points to dispersion and exchange as the prime contributors to the stability, with varying contributions from electrostatic energy, which is repulsive in one case. Atoms in Molecules analysis of the wavefunction presents specific O⋯O bonding interactions, whose number is related to the overall stability of each dimer. All internal …