PubAg

Main content area

You searched for: Journal Journal of the American Chemical Society Remove constraint Journal: Journal of the American Chemical Society Publication Year 2014 Remove constraint Publication Year: 2014 Source 2014 v.136 no.28 Remove constraint Source: 2014 v.136 no.28
Start Over

Search

58  Search Results

« Previous | 1 - 20 of 58 |
Number of results to display per page

Search Results

1. A Crystalline Phosphaalkene Radical Anion

Author:
Pan, Xiaobo; Wang, Xingyong; Zhao, Yue; Sui, Yunxia; Wang, Xinping
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9834-9837
ISSN:
1520-5126
Subject:
X-ray diffraction; anions; chemical bonding; electron paramagnetic resonance spectroscopy; free radicals; phosphorus; salts; ultraviolet-visible spectroscopy
Abstract:
... Salts containing phosphaalkene radical anions have been isolated and characterized by electron paramagnetic resonance (EPR) spectroscopy, UV–vis absorption spectroscopy, and single-crystal X-ray diffraction. The radical anions feature elongated P–C bonds and an aromatization of fulvene compared to the neutral phosphaalkene. Their EPR spectra and theoretical calculations indicate the spin density o ...
DOI:
10.1021/ja504001x

2. A Gold Exchange: A Mechanistic Study of a Reversible, Formal Ethylene Insertion into a Gold(III)–Oxygen Bond

Author:
Langseth, Eirin; Nova, Ainara; Tråseth, Eline Aa.; Rise, Frode; Øien, Sigurd; Heyn, Richard H.; Tilset, Mats
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 10104-10115
ISSN:
1520-5126
Subject:
X-ray diffraction; ambient temperature; dissociation; ethylene; gold; isomers; ligands; methylene chloride; nuclear magnetic resonance spectroscopy; olefin; thermodynamics
Abstract:
... The Au(III) complex Au(OAcF)₂(tpy) (1, OAcF = OCOCF₃; tpy = 2-p-tolylpyridine) undergoes reversible dissociation of the OAcF ligand trans to C, as seen by ¹⁹F NMR. In dichloromethane or trifluoroacetic acid (TFA), the reaction between 1 and ethylene produces Au(OAcF)(CH₂CH₂OAcF)(tpy) (2). The reaction is a formal insertion of the olefin into the Au–O bond trans to N. In TFA this reaction occurs in ...
DOI:
10.1021/ja504554u

3. A Mechanistic Change Results in 100 Times Faster CH Functionalization for Ethane versus Methane by a Homogeneous Pt Catalyst

Author:
Konnick, Michael M.; Bischof, Steven M.; Yousufuddin, Muhammed; Hashiguchi, Brian G.; Ess, Daniel H.; Periana, Roy A.
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 10085-10094
ISSN:
1520-5126
Subject:
catalysts; energy; ethane; ethanol; ethylene; methane; oxidation; platinum; shale; solvents; sulfuric acid; temperature
Abstract:
... The selective, oxidative functionalization of ethane, a significant component of shale gas, to products such as ethylene or ethanol at low temperatures and pressures remains a significant challenge. Herein we report that ethane is efficiently and selectively functionalized to the ethanol ester of H₂SO₄, ethyl bisulfate (EtOSO₃H) as the initial product, with the Ptᴵᴵ “Periana-Catalytica” catalyst i ...
DOI:
10.1021/ja504368r

4. A Methyltransferase Initiates Terpene Cyclization in Teleocidin B Biosynthesis

Author:
Awakawa, Takayoshi; Zhang, Lihan; Wakimoto, Toshiyuki; Hoshino, Shotaro; Mori, Takahiro; Ito, Takuya; Ishikawa, Jun; Tanner, Martin E.; Abe, Ikuro
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9910-9913
ISSN:
1520-5126
Subject:
Streptomyces; biosynthesis; cations; chemical structure; chromosomes; genes; heterologous gene expression; methylation; methyltransferases; protein kinase C; terpenoids; transcription (genetics)
Abstract:
... Teleocidin B is an indole terpenoid isolated from Streptomyces. Due to its unique chemical structure and ability to activate protein kinase C, it has attracted interest in the areas of organic chemistry and cell biology. Here, we report the identification of genes encoding enzymes for teleocidin B biosynthesis, including nonribosomal peptide synthetase (tleA), P-450 monooxygenase (tleB), prenyltra ...
DOI:
10.1021/ja505224r

5. An Azido-BODIPY Probe for Glycosylation: Initiation of Strong Fluorescence upon Triazole Formation

Author:
Shie, Jiun-Jie; Liu, Ying-Chih; Lee, Yu-Ming; Lim, Carmay; Fang, Jim-Min; Wong, Chi-Huey
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9953-9961
ISSN:
1520-5126
Subject:
alkynes; copper; cycloaddition reactions; fluorescence; gel electrophoresis; glycoproteins; glycosylation; image analysis; triazoles; wavelengths
Abstract:
... We have designed a low fluorescent azido-BODIPY-based probe AzBOCEt (Az10) that undergoes copper(I)-catalyzed 1,3-dipolar cycloadditions with alkynes to yield strongly fluorescent triazole derivatives. The fluorescent quantum yield of a triazole product T10 is enhanced by 52-fold as compared to AzBOCEt upon excitation at a wavelength above 500 nm. Quantum mechanical calculations indicate that the ...
DOI:
10.1021/ja5010174

6. Cell-Permeable Bicyclic Peptide Inhibitors against Intracellular Proteins

Author:
Lian, Wenlong; Jiang, Bisheng; Qian, Ziqing; Pei, Dehua
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9830-9833
ISSN:
1520-5126
Subject:
cell membranes; cyclic peptides; peptidylprolyl isomerase; protein-tyrosine-phosphatase; proteins
Abstract:
... Cyclic peptides have great potential as therapeutic agents and research tools but are generally impermeable to the cell membrane. Fusion of cyclic peptides with a cyclic cell-penetrating peptide produces bicyclic peptides that are cell-permeable and retain the ability to recognize specific intracellular targets. Application of this strategy to protein tyrosine phosphatase 1B and a peptidyl-prolyl ...
DOI:
10.1021/ja503710n
PubMed:
24972263
PubMed Central:
PMC4227718

7. Combining in Situ NEXAFS Spectroscopy and CO2 Methanation Kinetics To Study Pt and Co Nanoparticle Catalysts Reveals Key Insights into the Role of Platinum in Promoted Cobalt Catalysis

Author:
Beaumont, Simon K.; Alayoglu, Selim; Specht, Colin; Michalak, William D.; Pushkarev, Vladimir V.; Guo, Jinghua; Kruse, Norbert; Somorjai, Gabor A.
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9898-9901
ISSN:
1520-5126
Subject:
X-ray absorption spectroscopy; carbon dioxide; catalysts; catalytic activity; cobalt; hydrogen; hydrogenation; nanoparticles; platinum; synthetic fuels; temperature
Abstract:
... The mechanistic role of platinum and precious metals in promoting cobalt hydrogenation catalysts of the type used in reactions such as Fischer–Tropsch synthesis is highly debated. Here we use well-defined monometallic Pt and Co nanoparticles (NPs) and CO₂ methanation as a probe reaction to show that Pt NPs deposited near Co NPs can enhance the CO₂ methanation rate by up to a factor of 6 per Co sur ...
DOI:
10.1021/ja505286j

8. Concerted versus Stepwise Mechanism in Thymidylate Synthase

Author:
Islam, Zahidul; Strutzenberg, Timothy S.; Gurevic, Ilya; Kohen, Amnon
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9850-9853
ISSN:
1520-5126
Subject:
DNA; active sites; antibiotics; arginine; biomimetics; catalysts; catalytic activity; cysteine; drug therapy; drugs; hydrides; isotopes; mutagenesis; thymidylate synthase
Abstract:
... Thymidylate synthase (TSase) catalyzes the intracellular de novo formation of thymidylate (a DNA building block) in most living organisms, making it a common target for chemotherapeutic and antibiotic drugs. Two mechanisms have been proposed for the rate-limiting hydride transfer step in TSase catalysis: a stepwise mechanism in which the hydride transfer precedes the cleavage of the covalent bond ...
DOI:
10.1021/ja504341g
PubMed:
24949852
PubMed Central:
PMC4105062

9. Constructing a Macromolecular K3,3 Graph through Electrostatic Self-Assembly and Covalent Fixation with a Dendritic Polymer Precursor

Author:
Suzuki, Takuya; Yamamoto, Takuya; Tezuka, Yasuyuki
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 10148-10155
ISSN:
1520-5126
Subject:
hydrodynamics; isomers; polymers
Abstract:
... A triply fused tetracyclic macromolecular K₃,₃ graph has been constructed through electrostatic self-assembly of a uniformly sized dendritic polymer precursor having six cyclic ammonium salt end groups carrying two units of a trifunctional carboxylate counteranions, and subsequent covalent conversion by the ring-opening reaction of cyclic ammonium salt groups at an elevated temperature under dilut ...
DOI:
10.1021/ja504891x

10. Copper-Catalyzed Synthesis of Mixed Alkyl Aryl Phosphonates

Author:
Fañanás-Mastral, Martín; Feringa, Ben L.
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9894-9897
ISSN:
1520-5126
Subject:
catalysts; chemical reactions; copper; oxygen; phosphonates; salts
Abstract:
... Copper-catalysis allows the direct oxygen-arylation of dialkyl phosphonates with diaryliodonium salts. This novel methodology proceeds with a wide range of phosphonates and phosphoramidates under mild conditions and gives straightforward access to valuable mixed alkyl aryl phosphonates in very good yields and near perfect selectivity. ...
DOI:
10.1021/ja505281v

11. Design and Synthesis of Bipyridine Platinum(II) Bisalkynyl Fullerene Donor–Chromophore–Acceptor Triads with Ultrafast Charge Separation

Author:
Lee, Sai-Ho; Chan, Chris Tsz-Leung; Wong, Keith Man-Chung; Lam, Wai Han; Kwok, Wai-Ming; Yam, Vivian Wing-Wah
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 10041-10052
ISSN:
1520-5126
Subject:
absorption; electrochemistry; electron transfer; energy transfer; fullerene; methylene chloride; models; platinum; spectroscopy
Abstract:
... Donor–chromophore–acceptor triads, (PTZ)₂-Pt(bpy)-C₆₀ and (ᵗBuPTZ)₂-Pt(bpy)-C₆₀, along with their model compound, (Ph)₂-Pt(bpy)-C₆₀, have been synthesized and characterized; their photophysical and electrochemical properties have been studied, and the origin of the absorption and emission properties has been supported by computational studies. The photoinduced electron transfer reactions have been ...
DOI:
10.1021/ja5040073

12. Design, Development, Mechanistic Elucidation, and Rational Optimization of a Tandem Ireland Claisen/Cope Rearrangement Reaction for Rapid Access to the (Iso)Cyclocitrinol Core

Author:
Plummer, Christopher W.; Wei, Carolyn S.; Yozwiak, Carrie E.; Soheili, Arash; Smithback, Sara O.; Leighton, James L.
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9878-9881
ISSN:
1520-5126
Subject:
biosynthesis; chemical reactions; chemical structure; fungal proteins; temperature
Abstract:
... An approach to the synthesis of the (iso)cyclocitrinol core structure is described. The key step is a tandem Ireland Claisen/Cope rearrangement sequence, wherein the Ireland Claisen rearrangement effects ring contraction to a strained 10-membered ring, and that strain in turn drives the Cope rearrangement under unusually mild thermal conditions. A major side product was identified as resulting fro ...
DOI:
10.1021/ja505131v

13. Design of Asymmetric Particles Containing a Charged Interior and a Neutral Surface Charge: Comparative Study on in Vivo Circulation of Polyelectrolyte Microgels

Author:
Chen, Kai; Xu, Jing; Luft, J. Christopher; Tian, Shaomin; Raval, Jay S.; DeSimone, Joseph M.
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9947-9952
ISSN:
1520-5126
Subject:
amines; crosslinking; electrolytes; hydrogels; nucleic acids; oxygen; polymers
Abstract:
... Lowering the modulus of hydrogel particles could enable them to bypass in vivo physical barriers that would otherwise filter particles with similar size but higher modulus. Incorporation of electrolyte moieties into the polymer network of hydrogel particles to increase the swelling ratio is a straightforward and quite efficient way to decrease the modulus. In addition, charged groups in hydrogel p ...
DOI:
10.1021/ja503939n
PubMed:
24941029
PubMed Central:
PMC4227716

14. Direct Band Gap Silicon Allotropes

Author:
Wang, Qianqian; Xu, Bo; Sun, Jian; Liu, Hanyu; Zhao, Zhisheng; Yu, Dongli; Fan, Changzeng; He, Julong
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9826-9829
ISSN:
1520-5126
Subject:
clean energy; electric power; optical properties; photovoltaic cells; silicon; solar collectors; solar energy
Abstract:
... Elemental silicon has a large impact on the economy of the modern world and is of fundamental importance in the technological field, particularly in solar cell industry. The great demand of society for new clean energy and the shortcomings of the current silicon solar cells are calling for new materials that can make full use of the solar power. In this paper, six metastable allotropes of silicon ...
DOI:
10.1021/ja5035792

15. Disruption of Allosteric Response as an Unprecedented Mechanism of Resistance to Antibiotics

Author:
Fishovitz, Jennifer; Rojas-Altuve, Alzoray; Otero, Lisandro H.; Dawley, Matthew; Carrasco-López, Cesar; Chang, Mayland; Hermoso, Juan A.; Mobashery, Shahriar
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9814-9817
ISSN:
1520-5126
Subject:
X-radiation; active sites; antibiotic resistance; biosynthesis; death; methicillin; methicillin-resistant Staphylococcus aureus; mutants
Abstract:
... Ceftaroline, a recently approved β-lactam antibiotic for treatment of infections by methicillin-resistant Staphylococcus aureus (MRSA), is able to inhibit penicillin-binding protein 2a (PBP2a) by triggering an allosteric conformational change that leads to the opening of the active site. The opened active site is now vulnerable to inhibition by a second molecule of ceftaroline, an event that impai ...
DOI:
10.1021/ja5030657

16. DNA-Modified Polymer Pores Allow pH- and Voltage-Gated Control of Channel Flux

Author:
Buchsbaum, Steven F.; Nguyen, Gael; Howorka, Stefan; Siwy, Zuzanna S.
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9902-9905
ISSN:
1520-5126
Subject:
DNA; cell membranes; drugs; membrane potential; nanopores; pH; polymers
Abstract:
... Biological channels embedded in cell membranes regulate ionic transport by responding to external stimuli such as pH, voltage, and molecular binding. Mimicking the gating properties of these biological structures would be instrumental in the preparation of smart membranes used in biosensing, drug delivery, and ionic circuit construction. Here we present a new concept for building synthetic nanopor ...
DOI:
10.1021/ja505302q

17. Enzyme Architecture: Deconstruction of the Enzyme-Activating Phosphodianion Interactions of Orotidine 5′-Monophosphate Decarboxylase

Author:
Goldman, Lawrence M.; Amyes, Tina L.; Goryanova, Bogdana; Gerlt, John A.; Richard, John P.
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 10156-10165
ISSN:
1520-5126
Subject:
amides; catalysts; decarboxylation; energy; hydrogen bonding; mutants; mutation; orotic acid; thermodynamics
Abstract:
... The mechanism for activation of orotidine 5′-monophosphate decarboxylase (OMPDC) by interactions of side chains from Gln215 and Try217 at a gripper loop and R235, adjacent to this loop, with the phosphodianion of OMP was probed by determining the kinetic parameters kcₐₜ and Kₘ for all combinations of single, double, and triple Q215A, Y217F, and R235A mutations. The 12 kcal/mol intrinsic binding en ...
DOI:
10.1021/ja505037v
PubMed:
24958125
PubMed Central:
PMC4227808

18. Fine-Tuning the Energy Barrier for Metal-Mediated Dinitrogen NN Bond Cleavage

Author:
Keane, Andrew J.; Yonke, Brendan L.; Hirotsu, Masakazu; Zavalij, Peter Y.; Sita, Lawrence R.
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9906-9909
ISSN:
1520-5126
Subject:
Gibbs free energy; energy; isomerization; nitrogen
Abstract:
... Experimental data support a mechanism for NN bond cleavage within a series of group 5 bimetallic dinitrogen complexes of general formula, {Cp*M[N(ⁱPr)C(R)N(ⁱPr)]}₂(μ-N₂) (Cp* = η⁵-C₅Me₅) (M = Nb, Ta), that proceeds in solution through an intramolecular “end-on-bridged” (μ-η¹:η¹-N₂) to “side-on-bridged” (μ-η²:η²-N₂) isomerization process to quantitatively provide the corresponding bimetallic bis(μ ...
DOI:
10.1021/ja505309j

19. Formation of Oligonucleotide-Gated Silica Shell-Coated Fe3O4-Au Core–Shell Nanotrisoctahedra for Magnetically Targeted and Near-Infrared Light-Responsive Theranostic Platform

Author:
Li, Wei-Peng; Liao, Pei-Yi; Su, Chia-Hao; Yeh, Chen-Sheng
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 10062-10075
ISSN:
1520-5126
Subject:
drug therapy; drugs; gold; iron oxides; magnetic materials; magnetic resonance imaging; magnetism; nanocarriers; nanogold; nanoparticles; neoplasms; oligonucleotides; porous media; silica
Abstract:
... A new multifunctional nanoparticle to perform a near-infrared (NIR)-responsive remote control drug release behavior was designed for applications in the biomedical field. Different from the previous studies in formation of Fe₃O₄-Au core–shell nanoparticles resulting in a spherical morphology, the heterostructure with polyhedral core and shell was presented with the truncated octahedral Fe₃O₄ nanop ...
DOI:
10.1021/ja504118q

20. Gold-Catalyzed 1,3-Transposition of Ynones

Author:
Kazem Shiroodi, Roohollah; Soltani, Mohammad; Gevorgyan, Vladimir
Source:
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9882-9885
ISSN:
1520-5126
Subject:
chemical bonding; electronics; gold; stereochemistry; thermodynamics
Abstract:
... An efficient, regioselective gold-catalyzed 1,3-transposition reaction of ynones and diynones has been developed. It was found that stereoelectronic (interrupted conjugation) and electronic (extended conjugation) factors could efficiently govern the regioselectivity of this thermodynamically controlled transformation. The produced conjugated diynones were efficiently transformed into diverse alkyn ...
DOI:
10.1021/ja504892c
PubMed:
24971528
PubMed Central:
PMC4206192