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Chemistry Faculty Publications

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2008

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Articles 1 - 30 of 37

Full-Text Articles in Physical Sciences and Mathematics

Lagrangian Analysis Of Low Altitude Anthropogenic Plume Processing Across The North Atlantic, E. Real, K. S. Law, H. Schlager, A. Roiger, H. Huntrieser, J. Methven, M. Cain, J. Holloway, J. A. Neuman, T. Ryerson, F. Flocke, J. De Gouw, E. Atlas, S. Donnelly, D. Parrish Dec 2008

Lagrangian Analysis Of Low Altitude Anthropogenic Plume Processing Across The North Atlantic, E. Real, K. S. Law, H. Schlager, A. Roiger, H. Huntrieser, J. Methven, M. Cain, J. Holloway, J. A. Neuman, T. Ryerson, F. Flocke, J. De Gouw, E. Atlas, S. Donnelly, D. Parrish

Chemistry Faculty Publications

The photochemical evolution of an anthropogenic plume from the New-York/Boston region during its transport at low altitudes over the North Atlantic to the European west coast has been studied using a Lagrangian framework. This plume, originally strongly polluted, was sampled by research aircraft just off the North American east coast on 3 successive days, and then 3 days downwind off the west coast of Ireland where another aircraft re-sampled a weakly polluted plume. Changes in trace gas concentrations during transport are reproduced using a photochemical trajectory model including deposition and mixing effects. Chemical and wet deposition processing dominated the evolution …

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Patent: Cell-Permeable Miniature Proteins, Alanna S. Schepartz, Douglas S. Daniels, Betsy Smith Nov 2008

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 …

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2d Regional Correlation Analysis Of Single-Molecule Time Trajectories, Xuefei Wang, H. Peter Lu Nov 2008

2d Regional Correlation Analysis Of Single-Molecule Time Trajectories, Xuefei Wang, H. Peter Lu

Chemistry Faculty Publications

We report a new approach of 2D regional correlation analysis capable of analyzing fluctuation dynamics of complex multiple correlated and anticorrelated fluctuations under a noncorrelated noise background. Using this new method, by changing and scanning the start time and end time along a pair of fluctuation trajectories, we are able to map out any defined segments along the fluctuation trajectories and determine whether they are correlated, anticorrelated, or noncorrelated; after which, a cross-correlation analysis can be applied for each specific segment to obtain a detailed fluctuation dynamics analysis. We specifically discuss an application of this approach to analyze single-molecule fluorescence …

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Antibacterial Activity Of Dipeptide Constructions Of Acetylsalicylic Acid And Nicotinic Acid, Ronald Bartzatt, Suat L.G. Cirillo, Jeffrey D. Cirillo Oct 2008

Antibacterial Activity Of Dipeptide Constructions Of Acetylsalicylic Acid And Nicotinic Acid, Ronald Bartzatt, Suat L.G. Cirillo, Jeffrey D. Cirillo

Chemistry Faculty Publications

Two dipeptide drugs are synthesized utilizing an acetylsalicylic acid or nicotinic acid molecule for the framework. A D-alanine-D-alanine dipeptide moiety is attached to the carbonyl carbon of acetylsalicylic acid (I) and nicotinic acid (II). Dipeptide derivatives (I) and (II) showed significant reduction of Escherichia coli (E. coli) bacterial growth and colony-forming units. A mixture of (I) and (II) induced growth inhibition of 8%, 17.5%, 28%, and 42.5% at concentrations of 100, 200, 300, and 400 μg/mL, respectively. Ampicillin demonstrated much less growth inhibition of this penicillin-resistant E. coli bacteria. Derivatives (I) and (II) showed significant reduction of colony-forming units at …

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Fluorescence Sensor Array For Metal Ion Detection Based On Various Coordination Chemistries: General Performance And Potential Application, Zhuo Wang, Manuel A. Palacios, Pavel Anzenbacher Jr. Oct 2008

Fluorescence Sensor Array For Metal Ion Detection Based On Various Coordination Chemistries: General Performance And Potential Application, Zhuo Wang, Manuel A. Palacios, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

A sensor array containing 9 cross-reactive sensing fluorescent elements with different affinity and selectivity to 10 metal cations (Ca2+, Mg2+, Cd2+, Hg2+, Co2+, Zn2+, Cu2+, Ni2+, Al3+, Ga3+) is described. The discriminatory capacity of the array was tested at different ranges of pH and at different cation concentrations using linear discriminant analysis (LDA). Qualitative identification of cations can be determined with over 96% of accuracy in a concentration range covering 3 orders of a magnitude (5-5000 mu M). Quantitative analysis can be achieved with over 90% accuracy in the concentration range between 10 and 5000 mu M. The array performance …

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Tetrahymena Thermophila And Candida Albicans Group I Intron-Derived Ribozymes Can Catalyze The Trans-Excision-Splicing Reaction, P. Patrick Dotson Ii, Ashley K. Johnson, Stephen M. Testa Sep 2008

Tetrahymena Thermophila And Candida Albicans Group I Intron-Derived Ribozymes Can Catalyze The Trans-Excision-Splicing Reaction, P. Patrick Dotson Ii, Ashley K. Johnson, Stephen M. Testa

Chemistry Faculty Publications

Group I intron-derived ribozymes can catalyze a variety of non-native reactions. For the trans-excision-splicing (TES) reaction, an intron-derived ribozyme from the opportunistic pathogen Pneumocystis carinii catalyzes the excision of a predefined region from within an RNA substrate with subsequent ligation of the flanking regions. To establish TES as a general ribozyme-mediated reaction, intron-derived ribozymes from Tetrahymena thermophila and Candida albicans, which are similar to but not the same as that from Pneumocystis, were investigated for their propensity to catalyze the TES reaction. We now report that the Tetrahymena and Candida ribozymes can catalyze the excision of a …

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Simple Molecule-Based Fluorescent Sensors For Vapor Detection Of Tnt, Grigory V. Zyryanov, Manuel A. Palacios, Pavel Anzenbacher Jr. Sep 2008

Simple Molecule-Based Fluorescent Sensors For Vapor Detection Of Tnt, Grigory V. Zyryanov, Manuel A. Palacios, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

1,4-Diarylpentiptycenes (1a-e) were synthesized from 1,4-dichloro- or 1,4-difluoro-2,5-diarylbenzene derivatives by double base-promoted dehydrohalogenation to give corresponding arynes, which in the presence of anthracene undergo cycloaddition providing 1,4-diarylpentiptycenes in moderate overall yields. The resulting 1,4-diarylpentiptycenes show fluorescence modulated by the 1,4-aryl residues. The fluorescence is quenched in the presence of vapors of nitroaromatic compounds suggesting potential application in sensing of explosives.

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Rational Design Of A Minimal Size Sensor Array For Metal Ion Detection, Manuel A. Palacios, Zhuo Wang, Victor A. Montes, Grigory V. Zyryanov, Pavel Anzenbacher Jr. Aug 2008

Rational Design Of A Minimal Size Sensor Array For Metal Ion Detection, Manuel A. Palacios, Zhuo Wang, Victor A. Montes, Grigory V. Zyryanov, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

The focus of this study was to demonstrate that, in the luminescent sensors, the signal transduction may possibly be the most important part in the sensing process. Rational design of fluorescent sensor arrays for cations utilizing extended conjugated chromophores attached to 8-hydroxyquinoline is reported. All of the optical sensors utilized in the arrays comprise the same 8-hydroxyquinoline (8-HQ) receptor and various conjugated chromophores to yield a different response to various metal cations. This is because the conjugated chromophores attached to the receptor are partially quenched in their resting state, and upon the cation coordination by the 8-HQ, the resulting metalloquinolinolate …

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Role Of Adenine In Thymine-Dimer Repair By Reduced Flavin-Adenine Dinucleotide, Guifeng Li, Vincent Sichula, Ksenija D. Glusac Aug 2008

Role Of Adenine In Thymine-Dimer Repair By Reduced Flavin-Adenine Dinucleotide, Guifeng Li, Vincent Sichula, Ksenija D. Glusac

Chemistry Faculty Publications

We present a study of excited-state behavior of reduced flavin cofactors using femtosecond optical transient absorption spectroscopy. The reduced flavin cofactors studied were in two protonation states: flavin-adenine dinucleotide (FADH(2) and FADH(-)) and flavin-mononucleotide (FMNH2 and FMNH-). We find that FMNH- exhibits multiexponential decay dynamics due to the presence of two bent conformers of the isoalloxazine ring. FMNH2 exhibits an additional fast deactivation component that is assigned to an iminol tautomer. Reduced flavin cofactors also exhibit a long-lived component that is attributed to the semiquinone and the hydrated electron that are produced in photoinduced electron transfer to the solvent. The …

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High-Definition Self-Assemblies Driven By The Hydrophobic Effect: Synthesis And Properties Of A Supramolecular Nanocapsule, Bruce C. Gibb Aug 2008

High-Definition Self-Assemblies Driven By The Hydrophobic Effect: Synthesis And Properties Of A Supramolecular Nanocapsule, Bruce C. Gibb

Chemistry Faculty Publications

High definition self-assemblies, those that possess order at the molecular level, are most commonly made from subunits possessing metals and metal coordination sites, or groups capable of partaking in hydrogen bonding. In other words, enthalpy is the driving force behind the free energy of assembly. The hydrophobic effect engenders the possibility of (nominally) relying not on enthalpy but entropy to drive assembly. Towards this idea, we describe how template molecules can trigger the dimerization of a cavitand in aqueous solution, and in doing so are encapsulated within the resulting capsule. Although not held together by (enthalpically) strong and directional non-covalent …

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An Extended Multireference Study Of The Electronic States Of Para-Benzyne, Carol A. Parish, Evan B. Wang, Hans Lischka Jul 2008

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 …

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Inversion Symmetry And Local Vs. Dispersive Interactions In The Nucleation Of Hydrogen Bonded Cyclic N-Mer And Tape Of Imidazolecarboxamidines, Sihui Long, Venkatraj Muthusamy, Peter G. Willis, Sean Parkin, Arthur Cammers Jul 2008

Inversion Symmetry And Local Vs. Dispersive Interactions In The Nucleation Of Hydrogen Bonded Cyclic N-Mer And Tape Of Imidazolecarboxamidines, Sihui Long, Venkatraj Muthusamy, Peter G. Willis, Sean Parkin, Arthur Cammers

Chemistry Faculty Publications

Substitutional changes to imidazolecarboxamidine that preserved intermolecular hydrogen bonding in the solid state were used to study the relationship between packing and the hydrogen bond motif. Various motifs competed, but the most common imidazolecarboxamidine crystalline phase was a Ci symmetric dimer that established inversion centers by associating enantiomeric tautomers. Counter to intuition, the calculated gas-phase energies per molecule of the solid state atomic coordinates of the Ci dimer motifs were higher than those of the C1 dimer, trimer, tetramer and tape motifs, while the packing densities of Ci dimers were found to be higher. This result …

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The Design And Synthesis Of Novel Goniothalamin Analogues, Mark F. Mechelke, Allissa A. Dillman Jul 2008

The Design And Synthesis Of Novel Goniothalamin Analogues, Mark F. Mechelke, Allissa A. Dillman

Chemistry Faculty Publications

Every two minues a woman in the United States is diagnosed with breast cancer. In recent years, one method to identify potential chemotherapeutic agents has been the mass screening of natural products of cytotoxicity. One compound discovered in this manner was goniothalamin. Gonothalamin was isolated from the dried stem bark of the plant Goniothalamus sesuipedalis and exhibits cell specific anticancer activity against breast cancer. Goniothalamin has been extensively studies and a large number of synthetic analogues have been prepared in an attempt to determine the structural features necessary for bioactivity. These studies have focused primarily on the manipulation of goniothalmin's …

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The Role Of The Tight-Turn, Broken Hydrogen Bonding, Glu222 And Arg96 In The Post-Translational Green Fluorescent Protein Chromophore Formation, Marc Zimmer, Nathan P. Lemay, Alicia L. Morgan, Elizabeth J. Archer, Luisa A. Dickson, Colleen M. Megley Jun 2008

The Role Of The Tight-Turn, Broken Hydrogen Bonding, Glu222 And Arg96 In The Post-Translational Green Fluorescent Protein Chromophore Formation, Marc Zimmer, Nathan P. Lemay, Alicia L. Morgan, Elizabeth J. Archer, Luisa A. Dickson, Colleen M. Megley

Chemistry Faculty Publications

Green fluorescent proteins (GFP) and GFP-like proteins all undergo an autocatalytic post-translational modification to form a centrally located chromophore. Structural analyses of all the GFP and GFP-like proteins in the protein databank were undertaken to determine the role of the tight-turn, broken hydrogen bonding, Gly67, Glu222 and Arg96 in the biosynthesis of the imidazolone group from 65SYG67. The analysis was supplemented by computational generation of the conformation adopted by uncyclized wild-type GFP. The data analysis suggests that Arg96 interacts with the Tyr66 carbonyl, stabilizing the reduced enolate intermediate that is required for cyclization; the carboxylate of Glu222 acts as a …

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Cd2+-Induced Conformational Change Of A Synthetic Metallopeptide: Slow Metal Binding Followed By A Slower Conformational Change, Madhumita Mukherjee, Xianchun Zhu, Michael Y. Ogawa Jun 2008

Cd2+-Induced Conformational Change Of A Synthetic Metallopeptide: Slow Metal Binding Followed By A Slower Conformational Change, Madhumita Mukherjee, Xianchun Zhu, Michael Y. Ogawa

Chemistry Faculty Publications

A two-stranded a-helical coiled coil was prepared having a Cys(4) metal-binding site within its hydrophobic interior. The addition of Cd2+ results in the incorporation of 2 equiv of metal ion, which is accompanied by a conformational change of the peptide, as observed by circular dichroism (CID) spectroscopy. Isothermal titration calorimetry (ITC) shows that the addition of Cd2+ is accompanied by two thermodynamic events. A comparison of the time dependence of the ITC behavior with those of the UV absorption and CID behavior allows the assignment of these events to a preliminary endothermic metal-binding step followed by a slower exothermic conformational …

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Origin Of The Absorption Maxima Of The Photoactive Yellow Protein Resolved Via Ab Initio Multiconfigurational Methods, Pedro B. Coto, Sergio Martí, Monica Oliva, Massimo Olivucci, Manuela Merchan, Juan Andre Jun 2008

Origin Of The Absorption Maxima Of The Photoactive Yellow Protein Resolved Via Ab Initio Multiconfigurational Methods, Pedro B. Coto, Sergio Martí, Monica Oliva, Massimo Olivucci, Manuela Merchan, Juan Andre

Chemistry Faculty Publications

We discuss the role of the protein in controlling the absorption spectra of photoactive yellow protein (PYP), the archetype xanthopsin photoreceptor, using quantum mechanics/molecular mechanics (QM/MM) methods based on ab initio multireference perturbation theory, combined with molecular dynamics (MD) simulations. It is shown that in order to get results in agreement with the experimental data, it is necessary to use a model that allows for a proper relaxation of the whole system and treats the states involved in the electronic spectrum in a balanced way, avoiding biased results due to the effect of nonrepresentative electrostatic interactions on the chromophore.

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Spectroscopy Is Applied Quantum Mechanics. Part 4: Ideal Systems, David W. Ball Jun 2008

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.

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Light-Triggered Proton And Electron Transfer In Flavin Cofactors, Guifeng Li, Ksenija D. Glusac May 2008

Light-Triggered Proton And Electron Transfer In Flavin Cofactors, Guifeng Li, Ksenija D. Glusac

Chemistry Faculty Publications

The pH dependent behavior of two flavin cofactors, flavin-adenine dinucleotide (FAD) and flavin mononucleotide (FMN), has been characterized using femtosecond transient absorption spectroscopy for the first time. The flavin excited state was characterized in three states of protonation (Fl(-), Fl, and FlH(+)). We found that Fl and Fl(-) exhibit the same excited state absorption but that the lifetime of Fl(-) is much shorter than that of Fl. The transient absorption spectrum of FlH(+) is significantly different from Fl and Fl(-), suggesting that the electronic properties of the flavin chromophore become appreciably modified by protonation. We further studied the excited state …

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Preparation Of Halogenated Derivatives Of Thiazolo[5,4-D]Thiazole Via Direct Electrophilic Aromatic Substitution, Vladimir Benin, Alan T. Yeates, Douglas Dudis May 2008

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; …

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One-Pot Enol Silane Formation-Mukaiyama Aldol-Type Addition To Dimethyl Acetals Mediated By Tmsotf, C. Wade Downey, Miles W. Johnson, Kathryn J. Tracy Apr 2008

One-Pot Enol Silane Formation-Mukaiyama Aldol-Type Addition To Dimethyl Acetals Mediated By Tmsotf, C. Wade Downey, Miles W. Johnson, Kathryn J. Tracy

Chemistry Faculty Publications

Various ketones, esters, amides, and thioesters add in high yield to dimethyl acetals in the presence of silyl trifluoromethanesulfonates and an amine base. Acetals derived from aryl, unsaturated, and aliphatic aldehydes are all effective substrates. The reaction proceeds in a single reaction flask, with no purification of the intermediate enol silane necessary.

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Spectroscopy Is Applied Quantum Mechanics. Part 3: Introduction To Quantum Mechanics, David W. Ball Apr 2008

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.

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Fabrication Of Magnetic Porous Hollow Silica Drug Carriers, Charles J. O'Connor, Gabriel Caruntu Apr 2008

Fabrication Of Magnetic Porous Hollow Silica Drug Carriers, Charles J. O'Connor, Gabriel Caruntu

Chemistry Faculty Publications

Magnetic porous hollow silica nanosphere is a new class of structured nanomaterials for drug delivery. In this paper, we report a synthesis of magnetic porous hollow silica nanospheres MPHSNs using CaCO3 /Fe3O4 composite nanoparticles and cationic surfactant double templates. Fe3O4 nanoparticles were first mixed into CaCO3 using rotating packed bed forming CaCO3 /Fe3O4 composite nanoparticles. Tetraethoxysilane was then added as precursor to form silica layer on the surface of CaCO3 /Fe3O4 composite nanoparticles, while hexadecyltrimethylammonium bromide was used as a second template to direct the formation of porous silica shells. After the calcination of the surfactants and etching away CaCO3, …

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4-Hydroxyphenylretinamide (4hpr) Derivatives Regulate Aromatase Activity And Expression In Breast Cancer Cells, Bin Su, Serena M. Mershon, Laura A. Stonerock, Robert W. Curley Jr., Robert W. Brueggemeier Mar 2008

4-Hydroxyphenylretinamide (4hpr) Derivatives Regulate Aromatase Activity And Expression In Breast Cancer Cells, Bin Su, Serena M. Mershon, Laura A. Stonerock, Robert W. Curley Jr., Robert W. Brueggemeier

Chemistry Faculty Publications

Recent studies exhibit that 4-hydroxyphenylretinamide (4HPR) decreases aromatase activity in breast and placental cells. The effect of synthetic 4HPR analogs on aromatase and expression was examined in three breast cancer cell lines. Most derivatives did not decrease cellular aromatase activity. Two of the analogs even stimulated aromatase activity at the transcriptional level. Only one derivative significantly decreased aromatase in all three breast cancer cell lines and also suppressed CYP19 gene expression in one of the cell line. Placental microsomal aromatase assay rule out the possibility that this compound directly inhibits the aromatase enzyme. A non-genomic mechanism in suppression of cellular …

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A Facile And Efficient Synthesis Of Some (6e)-Hydroximino-4-En-3-One Steroids, Steroidal Oximes From Cinachyrella Spp. Sponges, Jianguo Cui, Liliang Huang, Lei Fan, Aimin Zhou Mar 2008

A Facile And Efficient Synthesis Of Some (6e)-Hydroximino-4-En-3-One Steroids, Steroidal Oximes From Cinachyrella Spp. Sponges, Jianguo Cui, Liliang Huang, Lei Fan, Aimin Zhou

Chemistry Faculty Publications

Using β-sitosterol as a starting material, (6E)-hydroximino-24-ethylcholest-4-en-3-one (1), a natural steroidal oxime from Cinachyrella alloclada and C. apion, was synthesized in four steps with a high overall yield. First, β-sitosterol (5a) is transformed into the corresponding 24-ethylcholest-4-en-3,6-dione (6a) via oxidation with pyridinium chlorochromate (PCC). Selective reduction of 6a by NaBH4 in the presence of CoCl2 gives 24-ethylcholest- 4-en-3β-ol-6-one (7a). The reaction of 7a with hydroxylamine hydrochloride offers the oxime 8a and the oxidation of 8a by Jones reagent gives the target steroid 1. (6E)-Hydroximinocholest-4-en-3-one (2) and (6E)-hydroximino-24-ethylcholest-4,22-dien-3-one (4) were synthesized by a similar method. The cytotoxicity of the synthesized compounds …

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Determination Of Endocannabinoid Receptor Antagonist Sr141716 (Rimonabant) In Plasma By Liquid Chromatograph Tandem Mass Spectrometry, Melissa Mcculloch, Xiang Zhou, Yan Xu, Steve Brunell, Linda Spear Mar 2008

Determination Of Endocannabinoid Receptor Antagonist Sr141716 (Rimonabant) In Plasma By Liquid Chromatograph Tandem Mass Spectrometry, Melissa Mcculloch, Xiang Zhou, Yan Xu, Steve Brunell, Linda Spear

Chemistry Faculty Publications

SR141716 (rimonabant) is an endocannabinoid receptor antagonist. Endocannabinoids are a class of chemicals that affect neurotransmission via G-protein coupled CB1 (brain) and CB2 (peripheral tissue) receptors. Numerous animal studies have shown that SR141716 binds with the CB1 receptor in the brain, resulting in several biological consequences including reduced alcohol intake and reward as well as reduced food consumption. In this work, an analytical method based on liquid chromatography and electrospray ionization tandem mass spectrometry (LC–ESI-MS/MS) has been developed and validated for the quantitative measurement of SR141716 in both human and rat plasma to support the investigation of this compound. A …

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Relationship Between The Excited State Relaxation Paths Of Rhodopsin And Isorhodopsin, Angela Strambi, Pedro B. Coto, Luis Manuel Frutos, Nicolas Ferre, Massimo Olivucci Mar 2008

Relationship Between The Excited State Relaxation Paths Of Rhodopsin And Isorhodopsin, Angela Strambi, Pedro B. Coto, Luis Manuel Frutos, Nicolas Ferre, Massimo Olivucci

Chemistry Faculty Publications

The pigment Isorhodopsin, an analogue of the visual pigment Rhodopsin, is investigated via quantum-mechanics/molecular-mechanics computations based on an ab initio multiconfigurational quantum chemical, treatment. The limited <5 kcal mol(-1) error found for the spectral parameters allows for a nearly quantitative analysis of the excited-state structure and reactivity of its 9-cis-retinal chromophore. We demonstrate that, similar to Rhodopsin, Isorhodopsin features a shallow photoisomerization path. However, the structure of the reaction coordinate appears to be reversed. In fact, while the coordinate still corresponds to an asynchronous crankshaft motion, the dominant isomerization component involves a counterclockwise, rather than clockwise, twisting of the 9-cis bond. Similarly, the minor component involves a clockwise, rather than counterclockwise, twisting of the 11-trans bond. Ultimately, these results indicate that Rhodopsin and Isorhodopsin relax along a common excited-state potential energy valley starting from opposite ends. The fact that the central and lowest energy region of such valley runs along a segment of the intersection space between the ground and excited states of the protein explains why the pigments decay at distinctive conical intersection structures.

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C–N Bond Rotation And E–Z Isomerism In Some N-Benzyl-N-Methylcarbamoyl Chlorides: A Dft Study, Michael Horwath, Vladimir Benin Feb 2008

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 …

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Dirubidium Digallium Oxide Bis(Orthoborate), Robert W. Smith, Chunhua Hu, Christopher D. Despain Feb 2008

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.

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Monolayer-Protected Nanoparticle Film Assemblies As Platforms For Controlling Interfacial And Adsorption Properties In Protein Monolayer Electrochemistry, Andrew F. Loftus, Katelyn P. Reighard, Susanna A. Kapourales, Michael C. Leopold Jan 2008

Monolayer-Protected Nanoparticle Film Assemblies As Platforms For Controlling Interfacial And Adsorption Properties In Protein Monolayer Electrochemistry, Andrew F. Loftus, Katelyn P. Reighard, Susanna A. Kapourales, Michael C. Leopold

Chemistry Faculty Publications

Assembled films of nonaqueous nanoparticles, known as monolayer-protected clusters (MPCs), are investigated as adsorption platforms in protein monolayer electrochemistry (PME), a strategy for studying the electron transfer (ET) of redox proteins. Modified electrodes featuring MPC films assembled with various linking methods, including both electrostatic and covalent mechanisms, are employed to immobilize cytochrome c (cyt c) for electrochemical analysis. The background signal (non-Faradaic current) of these systems is directly related to the structure and composition of the MPC films, including nanoparticle core size, protecting ligand properties, as well as the linking mechanism utilized during assembly. Dithiol-linked films of Au225(C6)75 are …

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A Polarizable Force-Field Model For Quantum-Mechanical-Molecular-Mechanical Hamiltonian Using Expansion Of Point Charges Into Orbitals, P. K. Biswas, Valentin Gogonea Jan 2008

A Polarizable Force-Field Model For Quantum-Mechanical-Molecular-Mechanical Hamiltonian Using Expansion Of Point Charges Into Orbitals, P. K. Biswas, Valentin Gogonea

Chemistry Faculty Publications

We present an ab initio polarizable representation of classical molecular mechanics (MM) atoms by employing an angular momentum-based expansion scheme of the point charges into partial wave orbitals. The charge density represented by these orbitals can be fully polarized, and for hybrid quantum-mechanical-molecular-mechanical (QM/MM) calculations, mutual polarization within the QM/MM Hamiltonian can be obtained. We present the mathematical formulation and the analytical expressions for the energy and forces pertaining to the method. We further develop a variational scheme to appropriately determine the expansion coefficients and then validate the method by considering polarizations of ions by the QM system employing the …

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