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Physical Sciences and Mathematics Commons™

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Chemistry

Utah State University

Chemistry and Biochemistry Faculty Publications

Series

2014

Articles 1 - 16 of 16

Full-Text Articles in Physical Sciences and Mathematics

Chalcogen Bonds In Complexes Of Soxy (X, Y = F, Cl) With Nitrogen Bases, Luis Miguel Azofra, Ibon Alkorta, Steve Scheiner Dec 2014

Chalcogen Bonds In Complexes Of Soxy (X, Y = F, Cl) With Nitrogen Bases, Luis Miguel Azofra, Ibon Alkorta, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

SOF2, SOFCl, and SOCl2 were each paired with a series of N bases. The potential energy surface of the binary complexes were characterized by MP2 calculations with double and triple-ξ basis sets, extrapolated to complete sets. The most stable configurations contained a S···N chalcogen bond with interaction energies as high as 6.8 kcal/mol. These structures are stabilized by a Nlp→σ*(S−Z) electron transfer (Z = O, F, Cl), complemented by Coulombicattraction of N to theσ-hole opposite the Z atom. N···S−F and N···S−Cl chalcogen bonds are stronger than N···S = O interactions.Formation of each chalcogen bond elongates all of the internalcovalent bonds …

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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 Dec 2014

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 …

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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 Dec 2014

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 …

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Designed Supramolecular Filamentous Peptides: Balance Of Nanostructure, Cytotoxicity And Antimicrobial Activity, Dawei Xu, Linhai Jiang, Anju Singh, Derek Dustin, Miao Yang, Ling Liu, Reidar Lund, Timothy J. Sellati, He Dong Nov 2014

Designed Supramolecular Filamentous Peptides: Balance Of Nanostructure, Cytotoxicity And Antimicrobial Activity, Dawei Xu, Linhai Jiang, Anju Singh, Derek Dustin, Miao Yang, Ling Liu, Reidar Lund, Timothy J. Sellati, He Dong

Chemistry and Biochemistry Faculty Publications

This work demonstrates a design strategy to optimize antimicrobial peptides with an ideal balance of minimal cytotoxicity, enhanced stability, potent cell penetration and effective antimicrobial activity, which hold great promise for the treatment of intracellular microbial infections and potentially systemic anti-infective therapy.

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The Interplay Between Charge Transfer, Rehybridization, And Atomic Charges In The Internal Geometry Of Subunits In Noncovalent Interactions, Steve Scheiner Sep 2014

The Interplay Between Charge Transfer, Rehybridization, And Atomic Charges In The Internal Geometry Of Subunits In Noncovalent Interactions, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

When a noncovalent bond is formed, there is frequently some charge transfer from one subunit to the other. The interaction also causes changes in the atomic charges and hybridization patterns of bonding orbitals. The manner in which these various effects combine to cause elongations or contractions of bonds within the individual subunits is examined. In both the cases of CH···O H-bonds and P···N pnicogen bonds, the bond length changes are consistent with the guiding principles generally known as Bent’s rules.

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Less Cookbook And More Research! Synthetic Efforts Toward Jbir-94 And Jbir-125: A Student-Designed Research Project In A Sophomore Organic Chemistry Lab, Mike A. Christiansen, C. L. Crawford, C. D. Mangum Feb 2014

Less Cookbook And More Research! Synthetic Efforts Toward Jbir-94 And Jbir-125: A Student-Designed Research Project In A Sophomore Organic Chemistry Lab, Mike A. Christiansen, C. L. Crawford, C. D. Mangum

Chemistry and Biochemistry Faculty Publications

In light of the meaningful learning gains that can be obtained through a genuine research experience, chemistry educators have had a longstanding interest in making teaching labs less “cookbook-like” and more research-driven [1]. With this mindset, we recently restructured our two-semester sophomore organic chemistry lab course to include a synthesis project that was chosen, designed, and carried out by students. This led to progress toward the syntheses of JBIR-94 and JBIR-125, two antioxidative/anticancer natural products that have yet to be assembled through organic chemistry. The major drawback of our course redesign is that it requires close supervision by an instructor …

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Complexation Of N So2 Molecules (N=1,2,3) With Formaldehyde And Thioformaldehyde, L. M. Azofra, Steve Scheiner Jan 2014

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 …

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Interaction Between Temozolomide And Water: Preferred Binding Sites, O. E. Kasende, A. Matondo, M. Muzomwe, J. T. Muya, Steve Scheiner Jan 2014

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 …

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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 Jan 2014

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 …

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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 Jan 2014

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. …

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Electrodeposited Nickel-Sulfide Films As Competent Hydrogen Evolution Catalysts In Neutral Water, N. Jiang, L. Bogoev, M. Popova, S. Gul, J. Yano, Y. Sun Jan 2014

Electrodeposited Nickel-Sulfide Films As Competent Hydrogen Evolution Catalysts In Neutral Water, N. Jiang, L. Bogoev, M. Popova, S. Gul, J. Yano, Y. Sun

Chemistry and Biochemistry Faculty Publications

The development of low-cost, efficient, and robust electrocatalysts of the hydrogen evolution reaction (HER) is a crucial step toward the conversion and storage of sustainable and carbon-neutral energy resources, such as solar energy. Not only the HER catalysts need to be composed of inexpensive elements, they are also desirable to be prepared at low energy cost. In this work, we report that nickel-sulfide (Ni-S) films prepared by facile potentiodynamic deposition are active HER catalysts in aqueous media. Notably, the Ni-S films showed catalytic activity in water with a wide range of pH values (0 to 14), as well as in …

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Complexes Containing Co2 And So2. Mixed Dimers, Trimers And Tetramers, L. M. Azofra, Steve Scheiner Jan 2014

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 …

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Effects Of Charge And Substituent On The S∙∙∙N Chalcogen Bond, U. Adhikari, Steve Scheiner Jan 2014

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 …

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An Exploration Of The Ozone Dimer Potential Energy Surface, L. M. Azofra, I. Alkorta, Steve Scheiner Jan 2014

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 …

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The Mtr4 Ratchet Helix And Arch Domain Both Function To Promote Rna Unwinding, Lacy L. Taylor, Ryan N. Jackson, Megi Rexhepaj, Alejandra Klauer King, Lindsey K. Lott, Ambro Van Hoof, Sean J. Johnson Jan 2014

The Mtr4 Ratchet Helix And Arch Domain Both Function To Promote Rna Unwinding, Lacy L. Taylor, Ryan N. Jackson, Megi Rexhepaj, Alejandra Klauer King, Lindsey K. Lott, Ambro Van Hoof, Sean J. Johnson

Chemistry and Biochemistry Faculty Publications

Mtr4 is a conserved Ski2-like RNA helicase and a subunit of the TRAMP complex that activates exosomemiated 3-5 turnover in nuclear RNA surveillance and processing pathways. Prominent features of the Mtr4 structure include a four-domain ring-like helicase core and a large arch domain that spans the core. The ‘ratchet helix’ is positioned to interact with RNA substrates as they move through the helicase. However, the contribution of the ratchet helix in Mtr4 activity is poorly understood. Here we show that strict conservation along the ratchet helix is particularly extensive for Ski2-like RNA helicases compared to related helicases. Mutation of residues …

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Strongly Bound Noncovalent (So3)N:H2co Complexes (N = 1, 2), L. M. Azofra, I. Alkorta, Steve Scheiner Jan 2014

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 …

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