Chemistry Commons^™

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 M. Galano, Jean-Francois Cavalier, Stephane Canaan

Christopher Spilling

Novel Dna Origami Based Lateral Flow Assay Development, Adrienne Walker

Adrienne Walker

Generating High-Order Optical And Spin Harmonics From Ferromagnetic Monolayers, G.P. Zhang, M.S. Si, M. Murakami, Y.H. Bai, Thomas F. George

Thomas George

Synthesis, Characterization, And Crystal Structure Of The (Η5-C5ph5)Cr(Co)3 Radical, Ray J. Hoobler, Marc A. Hutton, Mills M. Dillard, Michael Castellani, Arnold L. Rheingold, Anne L. Rieger, Philip H. Rieger, Thomas C. Richards, William E. Geiger

Michael P. Castellani

The reaction between Cr(CO)₆ and Na(C₅Ph₅ ) in refluxing diglyme yields [Na(diglyme)_3/2][(C₅Ph₅)Cr(CO)₃], 1. Metathesis of 1 with [Ph₃P=N=PPh₃ ]Cl in CH₂Cl₂ yields [Ph₃P=N=PPh₃][(C₅Ph₅)Cr(CO)₃], 2. Oxidation of 1 by AgBF4 in cold THF under an argon atmosphere produces (C₅Ph₅)Cr(CO)₃, 3. Complexes 2 and 3 form a redox pair connected by a quasireversible one-electron process, E⁰ = -0.69 V vs ferrocene in CH₂Cl₂, …

Synthesis And X-Ray Crystal Structure Of [(C5ph5)Crcl(Μ-Cl)2tl]2: An Example Of The Rare M-X-Tli Linkage (X = Halide), K. Brian Davis, T. David Harris, Michael Castellani, James A. Golen, Arnold L. Rheingold

Michael P. Castellani

Reaction of solid TlCl with [(C5Ph5)CrCl(m-Cl)]2 in CH2Cl2 solvent yields the monomeric complex (C5Ph5)CrCl(m-Cl)2Tl in 80% isolated yield. The C5H5 and C5Me5 analogues do not react with TlCl suggesting a steric basis for the reaction of the C5Ph5 material. An X-ray crystal structure of [(C5Ph5)CrCl(m-Cl)2Tl]2•2CH2Cl2 was obtained.

Substitution Reactions Of (C5ph5)Cr(Co)3: Structural, Electrochemical, And Spectroscopic Characterization Of (C5ph5)Cr(Co)2l, L = Pme3, Pme2ph, P(Ome)3, D. John Hammack, Mills M. Dillard, Michael Castellani, Arnold L. Rheingold, Anne L. Rieger, Philip H. Rieger

Michael P. Castellani

The radical complex (C₅Ph₅)Cr(CO)₃ reacts with small, neutral, monodentate Lewis bases (PMe₃, PMe₂Ph, P(OMe)₃) in THF at −78 °C (PMe₂Ph reacts at ambient temperature) to yield the monomeric substitution products (C₅Ph₅)Cr(CO)₂L·THF as thermally stable solids. Electrochemical and spectroscopic data are provided. An X-ray crystal structure of the hemisolvate (C₅Ph₅)Cr(CO)₂PMe₃·0.5THF was obtained. Frozen-solution ESR spectra of (C₅Ph₅)Cr(CO)₂L in toluene are comparable to those of other low-spin d^{5 …}

1,1´-Diethyl-2,2´,3,3´,4,4´,5,5´-Octamethylferrocenium Tetracyanoethylenide, [Fe(C5etme4)2]+[Tcne]–, A Charge-Transfer Salt Magnetic Solid With A Novel Structural Motif, T. David Harris, Michael Castellani, Arnold L. Rheingold, William M. Reiff, Gordon T. Yee

Michael P. Castellani

1,1′-Diethyl-2,2′,3,3′,4,4′,5,5′-octamethylferrocene has been utilized as a one-electron donor in the synthesis of a tetracyanoethylene charge-transfer salt, [Fe(C₅EtMe₄)₂]⁺[TCNE]⁻. Structural characterization shows that it adopts an arrangement of anions and cations completely different from the usual π stacking seen in analogous decamethylferrocenium compounds. The TCNE radical sits along side of the ferrocene, nearly perpendicular to the planes of the C₅ rings. The nearly square geometry of the TCNE anion creates disorder over two orientations. [Fe(C₅EtMe₄)₂]⁺[TCNE]⁻ is a simple paramagnet exhibiting neither long-range …

Synthesis, Characterization, And Molecular Structure Of Bis(Tetraphenylcyclopentdienyl)Rhodium(Ii)⊗, James E. Collins, Michael Castellani, Arnold L. Rheingold, Edward J. Miller, William E. Geiger, Anne L. Rieger, Philip H. Rieger

Michael P. Castellani

A 5 day diglyme reflux of Rh(acac)3 and K(C5HPh4), followed by treatment with aqueous HPF6, produces orange-yellow [(C5HPh4)2Rh]PF66 in 40 - 50% yield. Reduction of [(C5HPh4)2Rh]PF6 with sodium amalgam in THF yields olive green (C5HPh4)2Rh in 70% yield. (C5HPh4)2Rh crystallizes in the triclinic [Error : unloaded OLE object or mail attachment]space group with unit-cell parameters of a = 8.622 (3) Å, b = 10.778 (4) Å, c = 12.894 (5) Å, a = 65.58 (3)°, b = 72.66 (3)°, g = 83.52 (3)°, and Z = 1. The least squares data refined to RF = 7.63% and …

Halogen Oxidation Reactions Of (C5ph5)Cr(Co)3 And Lewis Base Addition To [(C5ph5)Cr(Μ-X)X]2: Electrochemical, Magnetic, And Raman Spectroscopic Characterization Of [(C5ph5)Crx2]2 And (C5ph5)Crx2(Thf) (X = Cl, Br, I). X-Ray Crystal Structure Of [(C5ph5)Cr(Μ-Cl)Cl]2, Marc A. Hutton, James C. Durham, Robert W. Grady, Brett E. Harris, Carter S. Jarrell, J. Matthew Mooney, Michael Castellani, Arnold L. Rheingold, Ulrich Kölle, Brenda J. Korte, Roger D. Sommer, Gordon T. Yee, J. Matthew Boggess, Roman S. Czernuszewicz

Michael P. Castellani

The 17-electron complex (C5Ph5)Cr(CO)3 reacts with halogens (C6H5I•Cl2, Br2, and I2) in C6H6 to yield the dimeric oxidation products [(C5Ph5)Cr(m-X)X]2 as thermally stable solids. Reactions with other chlorinating agents similarly yield [(C5Ph5)CrCl2]2. An X-ray crystal structure of [(C5Ph5)Cr(m-Cl)Cl]2 was obtained. The magnetic properties of the Cl₂ bridged dimer have been determined and modeled using the usual isotropic hamiltonian which yields J/k = –30 K. Low-temperature (77 K) Raman spectra of solid [(C5Ph5)CrX2]2 (X = Cl, I) allow assignments to be made for the metal-ring and metal halogen stretching modes in the low frequency region (< 600 cm-1). Tetrahydrofuran (THF) cleaves these dimers to yield complexes of the form (C5Ph5)CrX2(THF).

Conjugation Of Nanomaterials And Nematic Liquid Crystals For Futuristic Applications And Biosensors, Thomas F. George, Amit Choudhary, Guoqiang Li

Thomas George

“Fkamathamnareshbabusp18”.Pdf, Nareshbabu Kamatham

Nareshbabu Kamatham

No abstract provided.

Shaping Light In Backward-Wave Nonlinear Hyperbolic Metamaterials, Thomas F. George, Alexander K. Popov, Sergey A. Myslivets, Vitaly V. Slabko, Victor A. Tkachenko

Thomas George

The Subject Librarian Newsletter, Chemistry, Fall 2016, Sandy Avila

Sandy Avila

No abstract provided.

The Subject Librarian Newsletter, Chemistry, Spring 2017, Sandy Avila

Sandy Avila

No abstract provided.

Modification Of Purine And Pyrimidine Nucleosides By Direct C-H Bond Activation, Yong Liang, Stanislaw F. Wnuk

Stanislaw Wnuk

Transition metal-catalyzed modifications of the activated heterocyclic bases of nucleosides as well as DNA or RNA fragments employing traditional cross-coupling methods have been well-established in nucleic acid chemistry. This review covers advances in the area of cross-coupling reactions in which nucleosides are functionalized via direct activation of the C8-H bond in purine and the C5-H or C6-H bond in uracil bases. The review focuses on Pd/Cu-catalyzed couplings between unactivated nucleoside bases with aryl halides. It also discusses cross-dehydrogenative arylations and alkenylations as well as other reactions used for modification of nucleoside bases that avoid the use of organometallic precursors and …

Strain Promoted Click Chemistry Of 2- Or 8-Azidopurine And 5-Azidopyrimidine Nucleosides And 8-Azidoadenosine Triphosphate With Cyclooctynes. Application To Living Cell Fluorescent Imaging, Jessica Zayas, Marie Annoual, Jayanta K. Das, Quentin Felty, Walter Gonzalez, Jaroslava Miksovska, Nima Sharifai, Akira Chiba, Stanislaw F. Wnuk

Stanislaw Wnuk

Strain-promoted click chemistry of nucleosides and nucleotides with an azido group directly attached to the purine and pyrimidine rings with various cyclooctynes in aqueous solution at ambient temperature resulted in efficient formation (3 min to 3 h) of fluorescent, light-up, triazole products. The 2- and 8-azidoadenine nucleosides reacted with fused cyclopropyl cyclooctyne, dibenzylcyclooctyne, or monofluorocyclooctyne to produce click products functionalized with hydroxyl, amino, N-hydroxysuccinimide, or biotin moieties. The 5-azidouridine and 5-azido-2'-deoxyuridine were similarly converted to the analogous triazole products in quantitative yields in less than 5 min. The 8-azido-ATP quantitatively afforded the triazole product with fused cyclopropyl cyclooctyne in aqueous …

Hyperpolarization Of Silicon Nanoparticles With Tempo Radicals, Jingzhe Hu, Nicholas Whiting, Pratip Bhattacharya

Nicholas Whiting

Recent Approaches In Designing Bioadhesive Materials Inspired By Mussel Adhesive Protein, Pegah Kord Forooshani, Bruce P. Lee

Bruce Lee

Marine mussels secret protein-based adhesives, which enable them to anchor to various surfaces in a saline, intertidal zone. Mussel foot proteins (Mfps) contain a large abundance of a unique, catecholic amino acid, Dopa, in their protein sequences. Catechol offers robust and durable adhe-sion to various substrate surfaces and contributes to the curing of the adhesive plaques. In this article, we review the unique features and the key functionalities of Mfps, catechol chemistry, and strategies for preparing catechol-functionalized poly- mers. Specifically, we reviewed recent findings on the contributions of various features of Mfps on interfacial binding, which include coacervate formation, surface …

Preparation, Modification, Characterization, And Biosensing Application Of Nanoporous Gold Using Electrochemical Techniques, Jay Bhattarai, Dharmendra Neupane, Bishal Nepal, Vasilii Mikhaylov, Alexei Demchenko, Keith Stine

Alexei Demchenko

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

Mark Masthay

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 …

Effects Of Mutations On The Molecular Dynamics Of Oxygen Escape From The Dimeric Hemoglobin Of Scapharca Inaequivalvis, Kevin Trujillo, Tasso Papagiannopoulos, Kenneth W. Olsen

Ken Olsen

Like many hemoglobins, the structure of the dimeric hemoglobin from the clam Scapharca inaequivalvis is a “closed bottle” since there is no direct tunnel from the oxygen binding site on the heme to the solvent. The proximal histidine faces the dimer interface, which consists of the E and F helicies. This is significantly different from tetrameric vertebrate hemoglobins and brings the heme groups near the subunit interface. The subunit interface is also characterized by an immobile, hydrogen-bonded network of water molecules. Although there is data which is consistent with the histidine gate pathway for ligand escape, these aspects of the …

The Dimerization Domain In Dape Enzymes Is Required For Catalysis, Boguslaw Nocek, Anna Starus, Magdalena Makowska-Grzyska, Blanca Gutierrez, Stephen Sanchez, Robert Jedrzejczak, Jamey C. Mack, Kenneth W. Olsen, Andrzej Joachimiak, Richard C. Holz

Ken Olsen

The emergence of antibiotic-resistant bacterial strains underscores the importance of identifying new drug targets and developing new antimicrobial compounds. Lysine and meso-diaminopimelic acid are essential for protein production and bacterial peptidoglycan cell wall remodeling and are synthesized in bacteria by enzymes encoded within dap operon. Thereforedap enzymes may serve as excellent targets for developing a new class of antimicrobial agents. The dapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) convertsN-succinyl-L,L-diaminopimelic acid to L,L-diaminopimelic acid and succinate. The enzyme is composed of catalytic and dimerization domains, and belongs to the M20 peptidase family. To understand the specific role …

The Unsuspected Pathway Of The Allosteric Transition In Hemoglobin, Stefan Fischer, Kenneth W. Olsen, Kwangho Nam, Martin Karplus

Ken Olsen

Large conformational transitions play an essential role in the function of many proteins, but experiments do not provide the atomic details of the path followed in going from one end structure to the other. For the hemoglobin tetramer, the transition path between the unliganded (T) and tetraoxygenated (R) structures is not known, which limits our understanding of the cooperative mechanism in this classic allosteric system, where both tertiary and quaternary changes are involved. The conjugate peak refinement algorithm is used to compute an unbiased minimum energy path at atomic detail between the two end states. Although the results confirm some …

Lysine Biosynthesis In Bacteria: A Metallodesuccinylase As A Potential Antimicrobial Target, Danuta M. Gillner, Daniel P. Becker Ph.D., Richard C. Holz

Richard C. Holz

In this review, we summarize the recent literature on dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) enzymes, with an emphasis on structure–function studies that provide insight into the catalytic mechanism. Crystallographic data have also provided insight into residues that might be involved in substrate and hence inhibitor recognition and binding. These data have led to the design and synthesis of several new DapE inhibitors, which are described along with what is known about how inhibitors interact with the active site of DapE enzymes, including the efficacy of a moderately strong DapE inhibitor.

Identification Of A Histidine Metal Ligand In The Arge-Encoded N-Acetyl-L-Ornithine Deacetylase From Escherichia Coli, Wade C. Mcgregor, Danuta M. Gillner, Sabina I. Swierczek, Dali Liu, Richard C. Holz

Richard C. Holz

The H355A, H355K, H80A, and H80K mutant enzymes of the argE-encoded N-acetyl-L-ornithine deacetylase (ArgE) from Escherichia coli were prepared, however, only the H355A enzyme was found to be soluble. Kinetic analysis of the Co(II)-loaded H355A exhibited activity levels that were 380-fold less than Co(II)-loaded WT ArgE. Electronic absorption spectra of Co(II)-loaded H355A-ArgE indicate that the bound Co(II) ion resides in a distorted, five-coordinate environment and Isothermal Titration Calorimetry (ITC) data for Zn(II) binding to the H355A enzyme provided a dissociation constant (Kd) of 39 μM. A three-dimensional homology model of ArgE was generated using the X-ray crystal structure of the …

The Dimerization Domain In Dape Enzymes Is Required For Catalysis, Boguslaw Nocek, Anna Starus, Magdalena Makowska-Grzyska, Blanca Gutierrez, Stephen Sanchez, Robert Jedrzejczak, Jamey C. Mack, Kenneth W. Olsen, Andrzej Joachimiak, Richard C. Holz

Richard C. Holz

The emergence of antibiotic-resistant bacterial strains underscores the importance of identifying new drug targets and developing new antimicrobial compounds. Lysine and meso-diaminopimelic acid are essential for protein production and bacterial peptidoglycan cell wall remodeling and are synthesized in bacteria by enzymes encoded within dap operon. Thereforedap enzymes may serve as excellent targets for developing a new class of antimicrobial agents. The dapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) convertsN-succinyl-L,L-diaminopimelic acid to L,L-diaminopimelic acid and succinate. The enzyme is composed of catalytic and dimerization domains, and belongs to the M20 peptidase family. To understand the specific role …

Inhibitors Of Bacterial N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase (Dape) And Demonstration Of In Vitro Antimicrobial Activity, Danuta Gillner, Nicola Armoush, Richard C. Holz, Daniel P. Becker

Richard C. Holz

The dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) is a critical bacterial enzyme for the construction of the bacterial cell wall. A screen biased toward compounds containing zinc-binding groups (ZBG’s) including thiols, carboxylic acids, boronic acids, phosphonates and hydroxamates has delivered a number of micromolar inhibitors of DapE from Haemophilus influenzae, including the low micromolar inhibitor l-captopril (IC50 = 3.3 μM, Ki = 1.8 μM). In vitro antimicrobial activity was demonstrated for l-captopril against Escherichia coli.

Direct Patterning Of A Cyclotriveratrylene Derivative For Directed Self-Assembly Of C60, Zachary R. Osner, Dorjderem Nyamjav, Richard C. Holz, Daniel P. Becker

Richard C. Holz

A novel apex-modified cyclotriveratrylene (CTV) derivative with an attached thiolane-containing lipoic acid linker was directly patterned onto gold substrates via dip-pen nanolithography (DPN). The addition of a dithiolane-containing linker to the apex of CTV provides a molecule that can adhere to a gold surface with its bowl-shaped cavity directed away from the surface, thereby providing a surface-bound CTV host that can be used for the directed assembly of guest molecules. Subsequent exposure of these CTV microarrays to C60 in toluene resulted in the directed assembly of predesigned, spatially controlled, high-density microarrays of C60. The molecular recognition capabilities of this CTV …

Crystal Structure And Hirshfeld Analysis Of 2-(5-Bromo­Thio­Phen-2-Yl)Aceto­Nitrile, Ted M. Pappenfus, Tiana L. Wood, Joseph L. Morey, Wyatt D. Wilcox, Daron E. Janzen

Daron E Janzen, Ph.D.

No abstract provided.

Pyridinium-Functionalized Pyromellitic Diimides With Stabilized Radical Anion States, Andrew J. Greenlee, Charles K. Ofosu, Qifan Xiao, Mohammed M. Modan, Daron E. Janzen, Dennis D. Cao

Daron E Janzen, Ph.D.

No abstract provided.