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Articles 1 - 15 of 15
Full-Text Articles in Physical Sciences and Mathematics
Mechanism For Copper(Ii)-Mediated Disaggregation Of A Porphyrin J-Aggregate, M. Trapani, I. G. Occhiuto, R. Zagami, G. De Luca, M. A. Castriciano, A. Romeo, L. M. Scolaro, Robert F. Pasternack
Mechanism For Copper(Ii)-Mediated Disaggregation Of A Porphyrin J-Aggregate, M. Trapani, I. G. Occhiuto, R. Zagami, G. De Luca, M. A. Castriciano, A. Romeo, L. M. Scolaro, Robert F. Pasternack
Chemistry & Biochemistry Faculty Works
J-aggregates of anionic meso-tetrakis(4-sulfonatophenyl)porphyrin form at intermediate pH (2.3–3.1) in the presence of NiSO₄ or ZnSO₄ (ionic strength, I.S. = 3.2 M). These aggregates convert to monomeric porphyrin units via metallation with copper(II) ions. The kinetics for the disassembly process, as monitored by UV/vis spectroscopy, exhibits zeroth-order behavior. The observed zeroth-order rate constants show a two-term dependence on copper(II) ion concentrations: linear and second order. Also observed is an inverse dependence on hydrogen ion concentration. Activation parameters have been determined for the disassembly process leading to ΔH^≠ = (+163 ± 15) kJ·mol⁻¹ and ΔS^≠ = (+136 ± 11) J·K⁻¹. A …
Lipg A Bifunctional Phospholipase/Thioesterase Involved In Mycobacterial Envelope Remodeling, Christopher Spilling, Pierre Santucci, Vanessa Point, Isabelle Poncin, Alexandre Guy, Celine Crauste, Carole Serveau-Avesque, Jean Galano, Jean-Francois Cavalier, Stephane Canaan
Lipg A Bifunctional Phospholipase/Thioesterase Involved In Mycobacterial Envelope Remodeling, Christopher Spilling, Pierre Santucci, Vanessa Point, Isabelle Poncin, Alexandre Guy, Celine Crauste, Carole Serveau-Avesque, Jean Galano, Jean-Francois Cavalier, Stephane Canaan
Chemistry & Biochemistry Faculty Works
Tuberculosis caused by Mycobacterium tuberculosis is currently one of the leading causes of death from an infectious agent. The main difficulties encountered in eradicating this bacteria are mainly related to (i) a very complex lipid composition of the bacillus cell wall, (ii) its ability to hide from the immune system inside the granulomas, and (iii) the increasing number of resistant strains. In this context, we were interested in the Rv0646c (lipGMTB) gene located upstream to the mmaA cluster which is described as being crucial for the production of cell wall components and required for the bacilli adaptation and survival in …
Generating High-Order Optical And Spin Harmonics From Ferromagnetic Monolayers, G.P. Zhang, M.S. Si, M. Murakami, Y.H. Bai, Thomas George
Generating High-Order Optical And Spin Harmonics From Ferromagnetic Monolayers, G.P. Zhang, M.S. Si, M. Murakami, Y.H. Bai, Thomas George
Chemistry & Biochemistry Faculty Works
High-order harmonic generation (HHG) in solids has entered a new phase of intensive research, with envisioned band-structure mapping on an ultrashort time scale. This partly benefits from a flurry of new HHG materials discovered, but so far has missed an important group. HHG in magnetic materials should have profound impact on future magnetic storage technology advances. Here we introduce and demonstrate HHG in ferromagnetic monolayers. We find that HHG carries spin information and sensitively depends on the relativistic spin–orbit coupling; and if they are dispersed into the crystal momentum k space, harmonics originating from real transitions can be k-resolved and …
Interactions Between Spermine-Derivatized Tentacle Porphyrins And The Human Telomeric Dna G-Quadruplex, Navin C. Sabharwal , '14, Jessica Chen , '17, Joo Hyun Lee , '17, C. M. A. Gangemi, A. D'Urso, Liliya A. Yatsunyk
Interactions Between Spermine-Derivatized Tentacle Porphyrins And The Human Telomeric Dna G-Quadruplex, Navin C. Sabharwal , '14, Jessica Chen , '17, Joo Hyun Lee , '17, C. M. A. Gangemi, A. D'Urso, Liliya A. Yatsunyk
Chemistry & Biochemistry Faculty Works
G-rich DNA sequences have the potential to fold into non-canonical G-Quadruplex (GQ) structures implicated in aging and human diseases, notably cancers. Because stabilization of GQs at telomeres and oncogene promoters may prevent cancer, there is an interest in developing small molecules that selectively target GQs. Herein, we investigate the interactions of meso-tetrakis-(4-carboxysperminephenyl)porphyrin (TCPPSpm4) and its Zn(II) derivative (ZnTCPPSpm4) with human telomeric DNA (Tel22) via UV-Vis, circular dichroism (CD), and fluorescence spectroscopies, resonance light scattering (RLS), and fluorescence resonance energy transfer (FRET) assays. UV-Vis titrations reveal binding constants of 4.7 × 10⁶ and 1.4 × 10⁷ M⁻¹ and binding stoichiometry of …
Bis(Triphenylphosphine) Iminium Tetrafluoroborate Chloroform Monosolvate, Rachana Manandhar, Nigam Rath, Myron Jones
Bis(Triphenylphosphine) Iminium Tetrafluoroborate Chloroform Monosolvate, Rachana Manandhar, Nigam Rath, Myron Jones
Chemistry & Biochemistry Faculty Works
In the title compound, C36H30NP2+·BF4−·CHCl3 or [PPN]BF4·CHCl3, where [PPN] = [(Ph3P)2N]+, two triphenylphosphine units are attached to a central N atom. The P—N—P bond angle is 137.69 (11)°. The two P—N bonds are nearly equivalent, with lengths of 1.5834 (18) and 1.5798 (17) Å. Both the BF4− anion and the chloroform solvent molecule are disordered over two positions, with occupancy ratios of 0.872 (3):0.128 (3) and 0.9628 (9):0.0372 (9), respectively. In the crystal, C—H⋯F and C—H⋯Cl hydrogen bonds link the [PPN]+ cations, the BF4− anions, and the chloroform solvent molecules into an array which extends along the b-axis direction.
Crystal Structures Of 2-Bromo-1,1,1,3,3,3-HexaMethyl-2-(TriMethylSilYl)TrisIlane And 2-Bromo-1,1,1,3,3,3-HexaIsopropyl-2-(TriisoPropylSilYl)TriSilane, Eva Gulotty, Richard Staples, Shannon Biros, Peter Gaspar, Nigam Rath, William Winchester
Crystal Structures Of 2-Bromo-1,1,1,3,3,3-HexaMethyl-2-(TriMethylSilYl)TrisIlane And 2-Bromo-1,1,1,3,3,3-HexaIsopropyl-2-(TriisoPropylSilYl)TriSilane, Eva Gulotty, Richard Staples, Shannon Biros, Peter Gaspar, Nigam Rath, William Winchester
Chemistry & Biochemistry Faculty Works
The synthesis and crystal structures of two tris(trialkylsilyl)silyl bromide compounds, C9H27BrSi4 (I, HypSiBr) and C27H63BrSi4 (II, TipSiBr), are described. Compound I was prepared in 85% yield by free-radical bromination of 1,1,1,3,3,3-hexamethyl-2-(trimethylsilyl)trisilane using bromobutane and 2,2′-azobis(2-methylpropionitrile) as a radical initiator at 333 K. The molecule possesses threefold rotational symmetry, with the central Si atom and the Br atom being located on the threefold rotation axis. The Si—Br bond distance is 2.2990 (12) Å and the Si—Si bond lengths are 2.3477 (8) Å. The Br—Si—Si bond angles are 104.83 (3)° and the Si—Si—Si bond angles are 113.69 (2)°, reflecting the steric hindrance …
Conjugation Of Nanomaterials And Nematic Liquid Crystals For Futuristic Applications And Biosensors, Thomas George, Amit Choudhary, Guoqiang Li
Conjugation Of Nanomaterials And Nematic Liquid Crystals For Futuristic Applications And Biosensors, Thomas George, Amit Choudhary, Guoqiang Li
Chemistry & Biochemistry Faculty Works
The established role of nematic liquid crystals (NLCs) in the recent rapid development of displays has motivated researchers to modulate the electro-optical properties of LCs. Furthermore, adding nanomaterials into NLCs has led to enhancements of the properties of NLCs, like reduced threshold of the operating voltage, variation in pretilt angle, reduced switching time, etc. These enhanced properties, due to interfacial dynamics, are enabling wider applications of NLCs and nanomaterials. The recent literature of nanomaterial-doped NLCs is rich with various kinds of nanomaterials in a variety of NLCs. The light has been focused on the most widely used and studied gold …
Quadruplexes In ‘Dicty’: Crystal Structure Of A Four-Quartet G-Quadruplex Formed By G-Rich Motif Found In The Dictyostelium Discoideum Genome, A. Guédin, Linda Yingqi Lin , '20, S. Armane, L. Lacroix, J.-L. Mergny, S. Thore, Liliya A. Yatsunyk
Quadruplexes In ‘Dicty’: Crystal Structure Of A Four-Quartet G-Quadruplex Formed By G-Rich Motif Found In The Dictyostelium Discoideum Genome, A. Guédin, Linda Yingqi Lin , '20, S. Armane, L. Lacroix, J.-L. Mergny, S. Thore, Liliya A. Yatsunyk
Chemistry & Biochemistry Faculty Works
Guanine-rich DNA has the potential to fold into non-canonical G-quadruplex (G4) structures. Analysis of the genome of the social amoeba Dictyostelium discoideum indicates a low number of sequences with G4-forming potential (249–1055). Therefore, D. discoideum is a perfect model organism to investigate the relationship between the presence of G4s and their biological functions. As a first step in this investigation, we crystallized the dGGGGGAGGGGTACAGGGGTACAGGGG sequence from the putative promoter region of two divergent genes in D. discoideum. According to the crystal structure, this sequence folds into a four-quartet intramolecular antiparallel G4 with two lateral and one diagonal loops. The G-quadruplex …
Synthesis And Characterization Of (Pyno−)2gacl: A Redox-Active Gallium Complex, Jacob M. Kirsh , '17, Audra J. Woodside , '19, B. C. Manor, P. J. Carroll, Paul R. Rablen, Christopher R. Graves
Synthesis And Characterization Of (Pyno−)2gacl: A Redox-Active Gallium Complex, Jacob M. Kirsh , '17, Audra J. Woodside , '19, B. C. Manor, P. J. Carroll, Paul R. Rablen, Christopher R. Graves
Chemistry & Biochemistry Faculty Works
We report the synthesis of a gallium complex incorporating redox-active pyridyl nitroxide ligands. The (pyNO−)2GaCl complex was prepared in 85% yield via a salt metathesis route and was characterized by 1H and 13C NMR spectroscopies, X-ray diffraction, and theory. UV–Vis absorption spectroscopy and electrochemistry were used to access the optical and electrochemical properties of the complex, respectively. Our discussion focuses primarily on a comparison of the gallium complex to the corresponding aluminum derivative and shows that although the complexes are very similar, small differences in the electronic structure of the complexes can be correlated to the identity of the metal.
The Spin-Forbidden A^4z-—X^2n(1/2) Transition Of Geh Detected In Absorption Using Intracavity Laser Spectroscopy, James O'Brien, L. O'Brien, L. Harms
The Spin-Forbidden A^4z-—X^2n(1/2) Transition Of Geh Detected In Absorption Using Intracavity Laser Spectroscopy, James O'Brien, L. O'Brien, L. Harms
Chemistry & Biochemistry Faculty Works
The a 4Σ--X 2Π1/2 transition of GeH has been recorded in absorption for the first time using Intracavity Laser Spectroscopy (ILS). The GeH molecules were produced in a 0.40-0.60 A DC plasma discharge inside an aluminum hollow cathode, using 500 mTorr of Ar, 100 mTorr of H2, and 200 mTorr of GeH4. This cathode is located within the resonator cavity of a Coherent Verdi™ V-10 pumped dye laser. Effective path lengths for this series of measurements using the ILS method ranged from 2 to 7 km. Spectra were calibrated using the absorption spectrum of I2 collected from an extracavity cell, …
Shaping Light In Backward-Wave Nonlinear Hyperbolic Metamaterials, Thomas George, Alexander Popov, Sergey Myslivets, Vitaly Slabko, Victor Tkachenko
Shaping Light In Backward-Wave Nonlinear Hyperbolic Metamaterials, Thomas George, Alexander Popov, Sergey Myslivets, Vitaly Slabko, Victor Tkachenko
Chemistry & Biochemistry Faculty Works
Backward electromagnetic waves are extraordinary waves with contra-directed phase velocity and energy flux. Unusual properties of the coherent nonlinear optical coupling of the phase-matched ordinary and backward electromagnetic waves with contra-directed energy fluxes are described that enable greatly-enhanced frequency and propagation direction conversion, parametrical amplification, as well as control of shape of the light pulses. Extraordinary transient processes that emerge in such metamaterials in pulsed regimes are described. The results of the numerical simulation of particular plasmonic metamaterials with hyperbolic dispersion are presented, which prove the possibility to match phases of such coupled guided ordinary and backward electromagnetic waves. Particular …
Preparation, Modification, Characterization, And Biosensing Application Of Nanoporous Gold Using Electrochemical Techniques, Jay Bhattarai, Dharmendra Neupane, Bishal Nepal, Vasilii Mikhaylov, Alexei Demchenko, Keith Stine
Preparation, Modification, Characterization, And Biosensing Application Of Nanoporous Gold Using Electrochemical Techniques, Jay Bhattarai, Dharmendra Neupane, Bishal Nepal, Vasilii Mikhaylov, Alexei Demchenko, Keith Stine
Chemistry & Biochemistry Faculty Works
Nanoporous gold (np-Au), because of its high surface area-to-volume ratio, excellent conductivity, chemical inertness, physical stability, biocompatibility, easily tunable pores, and plasmonic properties, has attracted much interested in the field of nanotechnology. It has promising applications in the fields of catalysis, bio/chemical sensing, drug delivery, biomolecules separation and purification, fuel cell development, surface-chemistry-driven actuation, and supercapacitor design. Many chemical and electrochemical procedures are known for the preparation of np-Au. Recently, researchers are focusing on easier and controlled ways to tune the pores and ligaments size of np-Au for its use in different applications. Electrochemical methods have good control over fine-tuning …
Amide Neighbouring Group Effects In Peptides: Phenylalanine As Relay Amino Acid In Long‐Distance Electron Transfer, U. Wille, J. Nathanael, L. Gamon, M. Cordes, Paul R. Rablen, T. Bally, K. Fromm, B. Giese
Amide Neighbouring Group Effects In Peptides: Phenylalanine As Relay Amino Acid In Long‐Distance Electron Transfer, U. Wille, J. Nathanael, L. Gamon, M. Cordes, Paul R. Rablen, T. Bally, K. Fromm, B. Giese
Chemistry & Biochemistry Faculty Works
Nature uses proteins as medium for long‐distance electron transfer (ET) to carry out redox reactions in distant compartments. This ET occurs either by a single‐step superexchange or through a multi‐step charge hopping process, which uses side chains of amino acids as stepping stones. In this study we demonstrate that Phe can act as a relay amino acid for long‐distance electron hole transfer through peptides. The considerably increased susceptibility of the aromatic ring to oxidation is caused by the lone pairs of neighbouring amide carbonyl groups, which stabilize the Phe radical cation. This neighbouring amide group effect helps to better understand …
Ruthenium Complexes Of The General Formula [Rucl 2 (Phox) 2 ] As Precatalysts In Propargylic Substitution Reactions, Negar Jourabchian, Kellsie Jurkowski, Eike Bauer
Ruthenium Complexes Of The General Formula [Rucl 2 (Phox) 2 ] As Precatalysts In Propargylic Substitution Reactions, Negar Jourabchian, Kellsie Jurkowski, Eike Bauer
Chemistry & Biochemistry Faculty Works
After activation by chloride abstraction utilizing NaBArF as an activator (BArF = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate), a complex of the general formula [RuCl2 (PHOX)2 ] was utilized as a catalyst in propargylic substitution reactions, where PHOX is a phosphinooxazoline ligand. Oxygen and nitrogen-centered nucleophiles could be employed in the substitution of a propargylic acetate to obtain the corresponding propargylic substitution products in 87% to 9% isolated yields (45 °C, 16 h reaction time, toluene solvent, 1-2 mol% catalyst loading, 1-2 mol% activator).
Identification Of 4-Isopropyl–Thiotropolone As A Novel Anti-Microbial: Regioselective Synthesis, Nmr Characterization, And Biological Evaluation, Mohamed Elagawany, Mohamed Elagawany, Lamees Hegazy, Feng Cao, Maureen Donlin, Nigam Rath, John Tavis, Bahaa Elgendy, Bahaa Elgendy
Identification Of 4-Isopropyl–Thiotropolone As A Novel Anti-Microbial: Regioselective Synthesis, Nmr Characterization, And Biological Evaluation, Mohamed Elagawany, Mohamed Elagawany, Lamees Hegazy, Feng Cao, Maureen Donlin, Nigam Rath, John Tavis, Bahaa Elgendy, Bahaa Elgendy
Chemistry & Biochemistry Faculty Works
We have synthesized and separated tosylated thujaplicin isomers for the first time, and elucidated their structures using 1D, 2D-NMR techniques and X-ray crystallography. The tosylated isomers were used to synthesize 4-isopropyl–thiotropolone and 6-isopropyl–thiotropolone in a regioselective manner. 1H and 13C Chemical shifts of synthesized isomers were fully assigned using several NMR experiments, and their isotropic magnetic shielding was calculated using the GIAO (Gauge Including Atomic Orbitals) method and the B3LYP def2-TZVPP level of theory. The calculated chemical shift values were in a good agreement with the experimental results. The biological activity of all synthesized compounds was evaluated against the fungal …