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Articles 61 - 87 of 87
Full-Text Articles in Physical Chemistry
Highly Nitrated Cyclopropanes As New High Energy Materials: Dft Calculations On The Properties Of C3H6−N(No2)N (N=3–6), Aloysus K. Lawong, David W. Ball
Highly Nitrated Cyclopropanes As New High Energy Materials: Dft Calculations On The Properties Of C3H6−N(No2)N (N=3–6), Aloysus K. Lawong, David W. Ball
Chemistry Faculty Publications
As part of a continuing study of new potential high energy materials, here we present results of calculations on cyclopropane molecules with three or more nitro groups. DFT calculations suggest that all molecules can exist as minimum-energy stationary states. Energy calculations indicate that some nitrocyclopropanes have a specific enthalpy of decomposition in excess of 8kJg−1, suggesting that they be explored as new potential high energy materials.
Beta-Peptides With Improved Affinity For Hdm2 And Hdmx, Elizabeth A. Harker, Douglas S. Daniels, Danielle A. Guarracino, Alanna S. Schepartz
Beta-Peptides With Improved Affinity For Hdm2 And Hdmx, Elizabeth A. Harker, Douglas S. Daniels, Danielle A. Guarracino, Alanna S. Schepartz
Chemistry Faculty Publications
We previously described a series of 314-helical β-peptides that bind the hDM2 protein and inhibit its interaction with a p53-derived peptide in vitro. Here we present a detailed characterization of the interaction of these peptides with hDM2 and report two new β-peptides in which non-natural side chains have been substituted into the hDM2-recognition epitope. These peptides feature both improved affinity and inhibitory potency in fluorescence polarization and ELISA assays. Additionally, one of the new β-peptides also binds the hDM2-related protein, hDMX, which has been identified as another key therapeutic target for activation of the p53 pathway in tumors.
Preparation And Characterization Of Some Substituted Benzyl N-Nitrosocarbamates Containing An N-2-(Methylthio)Ethyl Or A Bis(2-Aminoethyl)Sulfide Functionality, Satya Venkata, Eric Shamo, Vladimir Benin
Preparation And Characterization Of Some Substituted Benzyl N-Nitrosocarbamates Containing An N-2-(Methylthio)Ethyl Or A Bis(2-Aminoethyl)Sulfide Functionality, Satya Venkata, Eric Shamo, Vladimir Benin
Chemistry Faculty Publications
The synthesis and characterization of some substituted benzyl N-nitrosocarbamates with an N-2-(methylthio)ethyl or a bis(2-aminoethyl)sulfide functionality is reported, as a part of a long-term goal to design and prepare novel photolabile structures that could be used as substances for controlled release of alkylating and/or crosslinking agents. The synthesis was accomplished by reaction of benzyl chloroformates with the corresponding amines, resulting in the preparation of carbamates. The latter were subsequently nitrosated, utilizing two different N-nitrosation methods, to yield the target structures.
Patent: Cell-Permeable Miniature Proteins, Alanna S. Schepartz, Douglas S. Daniels, Betsy Smith
Patent: Cell-Permeable Miniature Proteins, Alanna S. Schepartz, Douglas S. Daniels, Betsy Smith
Chemistry Faculty Publications
Abstract: The present invention generally relates to miniature proteins, including miniature proteins that are permeable to cells. Certain aspects of the invention are generally related to miniature proteins, such as avian pancreatic polypeptide (aPP), modified such that the miniature proteins are permeable to cells. For instance, a portion of the aPP, such as the alpha helix region and/or the type II polyproline helix region, may be modified to render the region substantially cationic. As an example, one or more residues may be substituted with cationic amino acid residues such as arginine. The miniature proteins may also have additional functions, such …
An Extended Multireference Study Of The Electronic States Of Para-Benzyne, Carol A. Parish, Evan B. Wang, Hans Lischka
An Extended Multireference Study Of The Electronic States Of Para-Benzyne, Carol A. Parish, Evan B. Wang, Hans Lischka
Chemistry Faculty Publications
A state-averaged, multireference complete active space (CAS) approach was used for the determination of the vertical excitation energies of valence and Rydberg states of para-benzyne. Orbitals were generated with a 10- and 32-state averaged multiconfigurational self-consistent field approach. Electron correlation was included using multireference configuration interaction with singles and doubles, including the Pople correction for size extensivity, multireference averaged quadratic coupled cluster (MR-AQCC) and MR-AQCC based on linear response theory. There is a very high density of electronic states in this diradical system—there are more than 17 states within 7 eV of the ground state including two 3s …
Spectroscopy Is Applied Quantum Mechanics. Part 4: Ideal Systems, David W. Ball
Spectroscopy Is Applied Quantum Mechanics. Part 4: Ideal Systems, David W. Ball
Chemistry Faculty Publications
The article features the last and fourth part of the lecture series about the application of quantum mechanics to spectroscopy. It examines ideal systems with wave functions that can be derived from the Schroedinger equation. It likewise follows discourse for failings of classical mechanics, the quantum hypothesis, and the emergence of a new theory called quantum mechanics.
Preparation Of Halogenated Derivatives Of Thiazolo[5,4-D]Thiazole Via Direct Electrophilic Aromatic Substitution, Vladimir Benin, Alan T. Yeates, Douglas Dudis
Preparation Of Halogenated Derivatives Of Thiazolo[5,4-D]Thiazole Via Direct Electrophilic Aromatic Substitution, Vladimir Benin, Alan T. Yeates, Douglas Dudis
Chemistry Faculty Publications
Chlorination and bromination reactions of thiazolo[5,4-d]thiazole led to the generation of its mono- and dihalogenated derivatives. These are the first instances of successful direct electrophilic aromatic substitution in the thiazolo[5,4-d]thiazole ring system. X-ray analysis demonstrates that both 2-bromothiazolo[5,4-d]-thiazole and 2,5-dibromothiazolo[5,4-d]thiazole are planar structures, with strongly manifested π-stacking in the solid state. Theoretical analysis of the pyridine-catalyzed halogenation (MP2/6-31+G(d) and B3LYP/6-31+G(d)calculations) reveals that introduction of one halogen actually leads to a slightly enhanced reactivity towards further halogenation. Several halogenation mechanisms have been investigated: 1) The direct C-halogenation with N-halopyridine as electrophile; …
Spectroscopy Is Applied Quantum Mechanics. Part 3: Introduction To Quantum Mechanics, David W. Ball
Spectroscopy Is Applied Quantum Mechanics. Part 3: Introduction To Quantum Mechanics, David W. Ball
Chemistry Faculty Publications
The article discusses the pioneering work of Erwin Schrödinger on wave mechanics that forms the basis of modern understanding in subatomic behavior. Schrödinger introduced a second-order differential equation that had to be solved to explain the nature of the hydrogen atom. He also demonstrated that the matrix mechanics of Heisenberg and Born were mathematically equivalent and developed the concept of perturbation theory to explain the Stark effect.
Dirubidium Digallium Oxide Bis(Orthoborate), Robert W. Smith, Chunhua Hu, Christopher D. Despain
Dirubidium Digallium Oxide Bis(Orthoborate), Robert W. Smith, Chunhua Hu, Christopher D. Despain
Chemistry Faculty Publications
The title compound, Rb2Ga2O(BO3)2, is part of the homologous series A2Ga2O(BO3)2 (A = Na, K, Rb and Cs). The structure contains pairs of gallium-centered tetrahedra connected through a shared oxygen vertex. Orthoborate triangles connect the basal vertices of the tetrahedra, forming a three-dimensional network with voids occupied by rubidium ions.
C–N Bond Rotation And E–Z Isomerism In Some N-Benzyl-N-Methylcarbamoyl Chlorides: A Dft Study, Michael Horwath, Vladimir Benin
C–N Bond Rotation And E–Z Isomerism In Some N-Benzyl-N-Methylcarbamoyl Chlorides: A Dft Study, Michael Horwath, Vladimir Benin
Chemistry Faculty Publications
The current report presents the first theoretical study of the restricted CN bond rotation in carbamoyl chlorides. Several N-benzyl-N-methylcarbamoyl chlorides were investigated, with varying pattern of substitution in the aromatic ring. Optimizations and frequency calculations were conducted employing DFT at the B3LYP/6-31+G(d) level of theory. Each of the studied structures exhibits a pair of rotamers (s-Z and s-E), generated upon rotation around the C(O)N bond. The s-E isomer is the global minimum in every case, but the preference for it is usually less than 1 kcal/mol. Two possible transition state structures were identified …
Spectroscopy Is Applied Quantum Mechanics. Part 2: The Quantum Revolution, David W. Ball
Spectroscopy Is Applied Quantum Mechanics. Part 2: The Quantum Revolution, David W. Ball
Chemistry Faculty Publications
The article presents several theories relative to the nature of matter. The quantum theory of German theoretical physicist Max Planck proposes that the energy of a vibrating atom was related to its frequency. Albert Einstein's quantum theory of light hypothesizes that light itself had an energy that was directly proportional to its frequency. Danish physicist Niels Bohr develops an equation that could help explain the lines that appeared in the spectrum of the hydrogen atom.
Biophysical Characterization Of A Beta-Peptide Bundle: Comparison To Natural Proteins, E. James Petersson, Cody J. Craig, Douglas S. Daniels, Jade X. Qiu, Alanna S. Schepartz
Biophysical Characterization Of A Beta-Peptide Bundle: Comparison To Natural Proteins, E. James Petersson, Cody J. Craig, Douglas S. Daniels, Jade X. Qiu, Alanna S. Schepartz
Chemistry Faculty Publications
We recently described the high-resolution X-ray structure of a helical bundle composed of eight copies of the β-peptide Zwit-1F. Like many proteins in Nature, the Zwit-1F octamer contains parallel and antiparallel helices, extensive inter-helical electrostatic interactions, and a solvent-excluded hydrophobic core. Here we explore the stability of the Zwit-1F octamer using circular dichroism (CD) spectroscopy, analytical ultracentrifugation (AU), differential scanning calorimetry (DSC), and NMR. These studies demonstrate that the thermodynamic and kinetic properties of Zwit-1F closely resemble those of α-helical bundle proteins. Together these studies should provide a model for the design of β-peptide proteins with biological functions.
High-Resolution Structure Of A Beta-Peptide Bundle, Douglas S. Daniels, E. James Petersson, Jade X. Qiu, Alanna S. Schepartz
High-Resolution Structure Of A Beta-Peptide Bundle, Douglas S. Daniels, E. James Petersson, Jade X. Qiu, Alanna S. Schepartz
Chemistry Faculty Publications
We recently reported that β-peptides can form discrete hetero-oligomers in aqueous solution. Here we describe the structure of such an oligomer as determined by X-ray crystallography. The structure of Zwit-1F reveals a homo-octamer of two cupped “hands” composed of both parallel and antiparallel 314-helices. The core of the assembly is composed entirely of solvent-excluded β3-homoleucine residues. The Zwit-1F assembly shares many of the physical characteristics of natural proteins.
Secondary N-Nitrosocarbamate Anions: Structure And Alkylation Reactions. A Dft Study, Vladimir Benin
Secondary N-Nitrosocarbamate Anions: Structure And Alkylation Reactions. A Dft Study, Vladimir Benin
Chemistry Faculty Publications
The current article reports theoretical studies (DFT: B3LYP/6-31+G(d)) on the structure and alkylation reactions of the anions of some secondary N-nitrosocarbamates, a class of ambident nucleophiles whose chemistry has been little explored. Several anions (1–4), with an increasing size of the carbamate alkyl (aryl) group were investigated, in an attempt to establish the influence of the size of that group on the thermal stability and regioselectivity of alkylation of the title anions. The conclusion is that thermal stability and the mode of reaction are affected significantly only in the presence of very large and branched carbamate groups. The thermal …
Orientational Disorder In Sodium Cadmium Trifluoride Trihydrate, Nacdf3·3h2o, Robert W. Smith, Arthur Mar, Jianjun Liu, Stan Schnell, John R. Hardy
Orientational Disorder In Sodium Cadmium Trifluoride Trihydrate, Nacdf3·3h2o, Robert W. Smith, Arthur Mar, Jianjun Liu, Stan Schnell, John R. Hardy
Chemistry Faculty Publications
Attempts to synthesize the hypothetical anhydrous fluoroperovskite NaCdF3, which has been predicted to be stable, resulted instead in a hydrated fluoride of nominal composition NaCdF3·3H2O. It decomposes to sodium fluoride, cadmium fluoride, and water at 60 °C. Its structure has been determined by single-crystal X-ray diffraction. Na0.92(2)Cd1.08F3.08·2.92H2O crystallizes in the cubic space group with a = 8.2369(4) Å and Z = 4. The structure is based on the NaSbF6-type (an ordered variant of the ReO3-type) and features tilted sodium- and cadmium-centred octahedra …
Preparation Of Some Substituted Terephthalic Acids, Susanna Branion, Vladimir Benin
Preparation Of Some Substituted Terephthalic Acids, Susanna Branion, Vladimir Benin
Chemistry Faculty Publications
We report in detail the preparation of two substituted terephthalic acids: 2‐sulfomethylterephthalic acid (1) and 2‐phosphonoterephthalic acid (2). Efficient, short syntheses have been developed for both compounds. They are potentially useful monomers for construction of acid‐pendant polymer chains.
Preparation, Characterization And Dft Studies Of Some New N-Nitrosocarbamates And N-Nitrosoureas, Ragavan Narayanan, Helene Hedian, Eric Shamo, Vladimir Benin
Preparation, Characterization And Dft Studies Of Some New N-Nitrosocarbamates And N-Nitrosoureas, Ragavan Narayanan, Helene Hedian, Eric Shamo, Vladimir Benin
Chemistry Faculty Publications
We are presenting the preparation, characterization and density functional theory (DFT) studies {B3LYP/6-31+G(d)) of several reiated classes of N-nitrosocarbamates and N-nitrosoureas. The iong-range goal is the design and preparation of compounds, which would undergo photochemical or hydrolytic decomposition, to yield stabilized cyclic cations that can serve as alkylating agents at various nucleophilic centers, including DNA bases.
Synthesis, Structural Studies And Desilylation Reactions Of Some N-2-(Trimethylsilyl)Ethyl-N-Nitrosocarbamates, Arpitha Thakkalapally, Vladimir Benin
Synthesis, Structural Studies And Desilylation Reactions Of Some N-2-(Trimethylsilyl)Ethyl-N-Nitrosocarbamates, Arpitha Thakkalapally, Vladimir Benin
Chemistry Faculty Publications
The present report describes the preparation and characterization of several N-2-(trimethylsilyl)ethyl-N-nitrosocarbamates, designed as precursors to thermally unstable secondary N-nitrosocarbamate anions via fluoride-assisted cleavage. X-ray structural studies demonstrate that the core N-nitrosocarbamate moiety has a nearly planar geometry, with an s-E orientation at the N–N bond. DFT calculations (B3LYP/6-31+G(d)) reproduce accurately the structural features of the title compounds and detailed conformational analysis at the same level of theory addresses the long-standing issue of preferred geometries for three classes of related structures: N-nitrosocarbamates, N-nitrosoureas and N-nitrosoamides. Desilylation studies demonstrate that both the …
Electrical Properties And Raman Scattering Study Of Single Crystal Cs2nb4o11, Jianjun Liu, E. P. Kharitonova, Chun-Gang Duan, Wai-Ning Mei, Robert W. Smith, John R. Hardy
Electrical Properties And Raman Scattering Study Of Single Crystal Cs2nb4o11, Jianjun Liu, E. P. Kharitonova, Chun-Gang Duan, Wai-Ning Mei, Robert W. Smith, John R. Hardy
Chemistry Faculty Publications
We studied temperature dependence of complex capacitance, impedance, and polarized Raman spectra of single crystal Cs2Nb4O11. First, we observed a sharp-shaped peak at 165 oC in the complex capacitance, then found drastic changes in the Raman spectra in the same temperature range. Utilizing the pseudosymmetry search of structure space group, we attributed the observed anomalies to a structural change from the room temperature orthorhombic Pnn2 to another or- thorhombic Imm2. We also measured room temperature polarized Raman spectra in different symmetries of normal vibrations and assigned high wavenumber Raman bands to the internal vibrations of NbO6 octahedra and NbO4 …
Rayleigh And Raman Scattering, David W. Ball
Rayleigh And Raman Scattering, David W. Ball
Chemistry Faculty Publications
Details the molecular aspect of Raman spectroscopy. Overview on the molecular absorption process; Information on Rayleigh scattering; Effects of the Raman scattering.
Mea Culpa: Formal Education And The Dis-Integrated World., Brian P. Coppola, Douglas S. Daniels
Mea Culpa: Formal Education And The Dis-Integrated World., Brian P. Coppola, Douglas S. Daniels
Chemistry Faculty Publications
Formal education has removed itself so far from any truly integrated view of the Natural World that fragmentation and certainty are prevailing ethics. Technological progress has resulted in increased specialization within academic disciplines and their concurrent separation from each other. Knowledge is extracted from a fully integrated world, but is examined and defined by the 'dis-integrated' objectives.
The Role Of Written And Verbal Expression In Improving Communication Skills For Students In An Undergraduate Chemistry Program, Brian P. Coppola, Douglas S. Daniels
The Role Of Written And Verbal Expression In Improving Communication Skills For Students In An Undergraduate Chemistry Program, Brian P. Coppola, Douglas S. Daniels
Chemistry Faculty Publications
Proofreading, editing, and critique, the customary assessment tools scientists use to evaluate professional journal articles, grant applications, and any other writing, can be applied equally well in introductory science instruction. Such feedback is, in fact, crucial to growth and development. When learning anything new, students and faculty alike rely heavily on sources other than themselves (‘external editors’) to assess their understanding as they develop self-assessment skills (or ‘internal editors’). Although they rarely describe it in these terms, faculty nonetheless assume that students have developed and refined their internal skills by the time they take examinations and write term papers. Unfortunately, …
Three-Body Analytical Potential For Interacting Helium Atoms, Carol A. Parish, Clifford E. Dykstra
Three-Body Analytical Potential For Interacting Helium Atoms, Carol A. Parish, Clifford E. Dykstra
Chemistry Faculty Publications
Large basis set ab initio calculations have been carried out for a dense grid of points on the He, potential energy surface. Three-body contributions were extracted at every point, and a number of concise functional representations for the three-body potential surface were then examined. Three-body multipolar dispersion terms and other radial and angular terms were used in the representations, and an assessment of relative importance of the different terms is presented. Combined with a two-body He-He potential, the results of this work should offer a high quality interaction potential for simulations of aggregated helium.
Pairwise And Many-Body Contributions To Interaction Potentials In He(N) Clusters, Carol A. Parish, Clifford E. Dykstra
Pairwise And Many-Body Contributions To Interaction Potentials In He(N) Clusters, Carol A. Parish, Clifford E. Dykstra
Chemistry Faculty Publications
High level ab initio calculations have been carried out to assess the pairwise additivity of potentials in the attractive or well regions of the potential surfaces of clusters of helium atoms. A large basis set was employed and calculations were done at the Brueckner orbital coupled cluster level. Differences between calculated potentials for several interacting atoms and the corresponding summed pair potentials reveal the three‐body and certain higher order contributions to the interaction strengths. Attraction between rare gas atoms develops from dispersion, and so helium clusters provide the most workable systems for analyzing nonadditivity of dispersion. The results indicate that …
Nonlinear Optical Properties Of Bacteriorhodopsin: Assignment Of The Third-Order Polarizability Based On Two-Photon Absorption Spectroscopy, Robert R. Birge, Mark Masthay, Jeffery A. Stuart, Jack R. Tallent, Chian-Fan Zhang
Nonlinear Optical Properties Of Bacteriorhodopsin: Assignment Of The Third-Order Polarizability Based On Two-Photon Absorption Spectroscopy, Robert R. Birge, Mark Masthay, Jeffery A. Stuart, Jack R. Tallent, Chian-Fan Zhang
Chemistry Faculty Publications
The third-order (pi) -electron polarizability, (gamma) (pi), of bacteriorhodopsin in the 0.0 - 1.2 eV optical region is assigned based on an analysis of the experimental two-photon properties of the low-lying singlet state manifold. The following selected values of (gamma) (pi) (units of 10-36 esu) are observed: (gamma) (0;0,0,0) equals 2482 +/- 327; (gamma) (-3(omega) ;(omega) ,(omega) ,(omega) ) equals 2976 +/- 385 ((omega) equals 0.25 eV), 5867 +/- 704 ((omega) = 0.5 eV), 14863 +/- 1614 ((omega) = 0.66 eV), 15817 +/- 2314 ((omega) equals 1.0 eV), 10755 +/- 1733 ((omega) equals 1.17 eV). The third-order polarizability of this …
Origins Of The Quantum Efficiency Duality In The Primary Photochemical Event Of Bacteriorhodopsin, Robert R. Birge, Leonore A. Findsen, Albert F. Lawrence, Mark Masthay, Chian-Fan Zhang
Origins Of The Quantum Efficiency Duality In The Primary Photochemical Event Of Bacteriorhodopsin, Robert R. Birge, Leonore A. Findsen, Albert F. Lawrence, Mark Masthay, Chian-Fan Zhang
Chemistry Faculty Publications
Experimental and theoretical evidence is presented which suggests that two distinct forms of light-adapted bacteriorhodopsin may exist. We propose that these two forms have characteristic photocycles with significantly different primary quantum yields. INDO-PSDCI molecular orbital procedures and semiempirical molecular dynamics simulations predict that one ground state geometry of bR undergoes photochemistry with a primary quantum yield, Φ1, of ~ 0.27, and that a second ground state geometry, with a slightly displaced counterion, yields Φ1 ~ 0.74. This theoretical model is supported by the observation that literature measurements of Φ1 tend to fall into one of two categories- those that observe …
A Theoretical Investigation Of The One– And Two–Photon Properties Of Porphyrins, Mark Masthay, Leonore A. Findsen, Brian M. Pierce, David F. Bocian, James S. Lindsey, Robert R. Birge
A Theoretical Investigation Of The One– And Two–Photon Properties Of Porphyrins, Mark Masthay, Leonore A. Findsen, Brian M. Pierce, David F. Bocian, James S. Lindsey, Robert R. Birge
Chemistry Faculty Publications
The one‐ and two‐photon properties of free base porphin, free base porphin dianion, and the 2,4‐substituted diformyl and divinyl analogs of these molecules are studied using a semiempirical SCF‐MO formalism (CNDO‐π‐SCF‐MO‐PSDCI) including extensive single and double configuration interaction. Strongly two‐photon allowed states are predicted to lie in the Soret region as well as in the region between the Soret and visible bands. A number of the two‐photon allowed states in the Soret region are predicted to have two‐photon absorptivities exceeding 100×10−50 cm4 s molecule−1 photon−1. The calculations indicate that the visible (Q) states are well characterized by the …