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MingBing Zhong, Song Sun, Jiang Cheng, Ying Shao
An iron-catalyzed intermolecular [4+2] cyclization of arylnitrones with geminal-substituted vinyl acetates was developed for the synthesis of 2,4-disubstituted quinolines in moderate to good yields with good functional group compatibilities. Preliminary mechanistic studies suggest a plausible iron-catalyzed C-H activation process under external-oxidant-free conditions.
October 21, 2016: Journal of Organic Chemistry
Pablo Arturo Fernández Garrillo, Lukasz Borowik, Florent Caffy, Renaud Demadrille, Benjamin Grevin
Investigating the photo-carrier dynamics in nanostructured and heterogeneous energy materials is of crucial importance from both fundamental and technological points of view. Here, we demonstrate how non-contact atomic force microscopy combined with Kelvin Probe Force Microscopy under frequency modulated illumination can be used to simultaneously image the surface photo-potential dynamics at different timescales with a sub-10 nm lateral resolution. The basic principle of the method consists in the acquisition of spectroscopic curves of the surface potential as a function of the illumination frequency modulation on a two dimensional grid...
October 20, 2016: ACS Applied Materials & Interfaces
Yujing Zhou, Yan Zhang, Jianbo Wang
A general approach towards diverse fluorinated phosphonates via geminal difunctionalization reactions of α-diazo arylmethylphosphonates is described. The diazo functionality (RR'C[double bond, length as m-dash]N2) is successfully converted to RR'CF2, RR'CHF, RR'CFBr or RR'CFNR''2 groups by employing different fluorination reagents. A variety of fluorinated organophosphorus compounds were readily accessed in good to excellent yields from a common type of precursor.
October 19, 2016: Organic & Biomolecular Chemistry
Hui Yang, Huabo Duan, Xu Wu, Min Wang, Ting Chen, Fanghui Liu, Shizhe Huang, Wei Zhang, Gang Chen, Danfeng Yu, Jinben Wang
The adsorption processes of a geminized amphiphilic polyelectrolyte, comprising double elementary charges and double hydrophobic tails in each repeat unit (denoted as PAGC8), was investigated and characterized by means of quartz crystal microbalance with dissipation (QCM-D), ellipsometry, and atomic force microscopy (AFM). By comparison, the self-assembly behaviors of a traditional polyelectrolyte without hydrophobic chains (denoted as PASC1), and an amphiphilic polyelectrolyte with a single hydrophilic head group and hydrophobic tail in each repeat unit (denoted as PASC8) at the solid/liquid interface, were also investigated in parallel...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Chandresakaran Prathipa, Lakshminarayanan Akilandeswari
There are eight possible pathways for the iron-tricarbonyl-assisted thermal electrocyclic ring opening of fluorocyclobutene due to variations in the orientation of the binding of Fe(CO)3 relative to the fluorine substituent (R1 or R2), stereoselectivity (conrotatory or disrotatory, i.e., C or D), and the torquoselectivity of fluorine (inward-facing or outward-facing, i.e., in or out). A density functional study revealed that the energetically favored pathway is R1 Din. Not only is the D mode favored energetically, but the in configuration was observed to be the lowest-lying mode of R1, despite the general tendency of fluorine substituents to prefer an out configuration...
November 2016: Journal of Molecular Modeling
Benjamin Schumann, Sharavathi G Parameswarappa, Marilda P Lisboa, Naresh Kottari, Fabio Guidetti, Claney L Pereira, Peter H Seeberger
The glycosylation reaction is the key transformation in oligosaccharide synthesis, but it is still difficult to control in many cases. Stereocontrol during cis-glycosidic linkage formation relies almost exclusively on tuning the glycosylating agent or the reaction conditions. Herein, we use nucleophile-directed stereocontrol to manipulate the stereoselectivity of glycosylation reactions. Placing two fluorine atoms in close proximity to the hydroxy group of an aliphatic amino alcohol lowers the oxygen nucleophilicity and reverses the stereoselectivity of glycosylations to preferentially form the desired cis-glycosides with a broad set of substrates...
October 13, 2016: Angewandte Chemie
Safa Shoaee, Shengqiang Fan, Paul L Burn, Paul E Shaw
Fluorescence-based detection of explosive analytes requires an understanding of the nature of the excited state responsible for the luminescence response of a sensing material. Many measurements are carried out to elucidate the fundamental photophysical properties of an emissive material in solution. However, simple transfer of the understanding gained from the solution measurements to the solid-state can lead to errors. This is in part due to the absence of inter-molecular interactions of the chromophores in solution, which are present in the solid-state...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
Jonathan Coronel-León, Aurora Pinazo, Lourdes Pérez, Mª José Espuny, Ana Mª Marqués, Angeles Manresa
Recently it has been demonstrated that catanionic mixtures of oppositely charged surfactants have improved physicochemical-biological properties compared to the individual components. Isotherms of mixtures of an anionic biosurfactant (lichenysin) and a cationic aminoacid surfactant (C3(LA)2) indicate a strong interaction suggesting the formation of a new "pseudo-surfactant". The antimicrobial properties of the mixture lichenysin and C3(LA)2 M80:20, indicate a synergistic effect of the components. The mechanism of action on the bacterial envelope was assessed by flow cytometry and Transmission Electron Microscopy...
October 4, 2016: Colloids and Surfaces. B, Biointerfaces
Arnau Vilà, Miguel González
The influence of the mass in the photodissociation dynamics of a homonuclear diatomic molecule (X2), embedded in a superfluid helium nanodroplet (T = 0.37 K) of 300 atoms, has been investigated using a hybrid quantum dynamics method recently proposed by us. Several hypothetical isotopic variants of Cl2 have been examined in order to make possible the analysis of a wide diversity of masses (mX: 0.25mCl-1.50mCl). This is probably the first time that this problem has been considered theoretically. The photodissociation mechanism of X2(B) is very similar to that of Cl2(B) and the efficiency of the X2-helium energy exchange mechanism can be so great that it leads to the full and partial (≈86%) geminate recombination for the lower masses explored (mX = 0...
October 5, 2016: Physical Chemistry Chemical Physics: PCCP
Ekaterina A Lukina, Alexander A Popov, Mikhail N Uvarov, Elizaveta A Suturina, Edward J Reijerse, Leonid V Kulik
A composite material of semiconducting polymer P3HT and fullerene derivative PC70BM was studied by means of electron spin echo (ESE) spectroscopy. The out-of-phase ESE signal was observed under laser irradiation of the composite at low temperature. We assume that during the charge separation process firstly the spin-correlated radical pairs in the singlet-polarized spin state are formed, and then the net polarization of radical pairs arises due to spin evolution. Both types of polarizations contribute to the out-of-phase ESE signal in the case of non-ideal microwave pulses...
October 5, 2016: Physical Chemistry Chemical Physics: PCCP
Takuro Matsumoto, Ayaka Ono, Takahiro Ichikawa, Takashi Kato, Hiroyuki Ohno
Gemini amphiphilic zwitterions exhibit thermotropic bicontinuous cubic liquid-crystalline phases having a 3D continuous ionic domain. Incorporation of an acid into the materials led to the creation of novel electrolytes transporting protons efficiently through the 3D continuous domain.
October 6, 2016: Chemical Communications: Chem Comm
Colin R Andrew, Olga N Petrova, Isabelle Lamarre, Jean-Christophe Lambry, Fabrice Rappaport, Michel Negrerie
Nitric oxide (NO) sensors are heme proteins which may also bind CO and O2. Control of heme-gas affinity and their discrimination are achieved by the structural properties and reactivity of the heme and its distal and proximal environments, leading to several energy barriers. In the bacterial NO-sensor cytochrome c' from Alcaligenes xylosoxidans (AXCP), the single Leu16Ala distal mutation boosts the affinity for gas ligands by a remarkable 106-108-fold, transforming AXCP from one of the lowest affinity gas binding proteins to one of the highest...
October 6, 2016: ACS Chemical Biology
Wenchao Huang, Naresh Chandrasekaran, Shyamal K K Prasad, Eliot Gann, Lars Thomsen, Dinesh Kabra, Justin M Hodgkiss, Yi-Bing Cheng, Christopher R McNeill
Here a comprehensive study of the influence of polymer:fullerene mixing behavior on the performance, thin-film microstructure, photophysics and device physics of polymer solar cells is presented. In particular, blends of the donor polymer PBDTTT-EFT with the acceptor PC71BM that exhibit power conversion efficiencies over 9% are investigated. Through tuning of the fullerene concentration in PBDTTT-EFT:PC71BM blends the impact of fullerene mixing behavior is systematically investigated via a combination of synchrotron based X-ray scattering and spectroscopy techniques...
October 5, 2016: ACS Applied Materials & Interfaces
Joshua C Byers, Thomas Heiser, Maksim Skorobogatiy, Oleg A Semenikhin
A series of encapsulated and non-encapsulated bulk heterojunction photovoltaic devices containing poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) with different P3HT:PCBM ratios were investigated using traditional steady state as well as non-steady state intensity modulated photocurrent spectroscopy (IMPS) techniques. The steady state J-V measurements showed that PCBM content did not have a significant effect on the efficiency for freshly prepared devices, whereas aged non-encapsulated devices exhibited a strong dependence on PCBM content...
October 5, 2016: ACS Applied Materials & Interfaces
Andrea Pietropolli Charmet, Paolo Stoppa, Nicola Tasinato, Santi Giorgianni, Alberto Gambi
The gas-phase infrared spectra of 1-chloro-1-fluoroethene (geminal chloro-fluoroethene, ClFC=CH2, 1,1-C2H2ClF) were recorded at medium resolution in the range 400 - 6400 cm(-1) and the vibrational analysis led to revise the previous assignments for the ν11 (A'' symmetry), ν2 (A' symmetry) and ν1 (A' symmetry) bands. Besides the fundamentals, all the most relevant spectral features were interpreted in terms of overtone and combination bands, thus obtaining an accurate description of the vibrational structure of ClFC=CH2...
October 3, 2016: Journal of Physical Chemistry. A
Wolfgang Tress, Beatrice Beyer, Negar Ashari Astani, Feng Gao, Simone Meloni, Ursula Rothlisberger
Efficient organic solar cells are based on (electron) donor-acceptor heterojunctions. An optically generated excited molecular state (exciton) is dissociated at this junction, forming a charge-transfer (CT) state in an intermediate step before the electron and hole are completely separated. The observed highly efficient dissociation of this Coulombically bound state raises the question on the dissociation mechanism. Here, we show that the observed high quantum yields of charge carrier generation and CT state dissociation are due to extended (and consequently weakly bound) CT states visible in absorption and emission spectra and first-principles calculations...
October 6, 2016: Journal of Physical Chemistry Letters
Latifa Bouzhir-Sima, Roberto Motterlini, Julia Gross, Marten H Vos, Ursula Liebl
The aerobic Gram-negative bacterium Burkholderia xenovorans expresses two highly homologous carbon monoxide (CO)-responsive transcriptional regulators, RcoM-1 and RcoM-2, which display extraordinarily high CO affinities, even under oxygenic conditions. To gain insight into the origin and perspectives of this feature, we characterized the ligand-binding properties of the N-terminal, heme-binding Per/Arnt/Sim sensor domain of RcoM-2 by time-resolved spectroscopy. We show that upon photodissociation of the heme-ligand bond, CO geminately rebinds to the heme with picosecond time constants and more than 99% rebinding yield, an unprecedented property of native heme proteins...
October 6, 2016: Journal of Physical Chemistry. B
Amanda C Raimer, Kelsey M Gray, A Gregory Matera
Survival Motor Neuron (SMN) protein localizes to both the nucleus and the cytoplasm. Cytoplasmic SMN is diffusely localized in large oligomeric complexes with core member proteins, called Gemins. Biochemical and cell biological studies have demonstrated that the SMN complex is required for the cytoplasmic assembly and nuclear transport of Sm-class ribonucleoproteins (RNPs). Nuclear SMN accumulates with spliceosomal small nuclear (sn)RNPs in Cajal bodies, sub-domains involved in multiple facets of snRNP maturation...
September 20, 2016: RNA Biology
Gregory D Mc Cluskey, Samy Mohamady, Scott D Taylor, Stephen L Bearne
CTP synthase (CTPS) catalyzes the conversion of UTP to CTP and is a target for the development of antiviral, anticancer, antiprotozoal, and immunosuppressive agents.Inhibition by the antineoplastic cytidine analogue gemcitabine causes depletion of intracellular CTP levels, but the direct inhibition of CTPS by its metabolite gemcitabine-5'-triphosphate (dF-dCTP) has not been demonstrated.We show that dF-dCTP is a potent competitive inhibitor of Escherichia coli CTPS with respect to UTP (Ki = 3.0 ± 0.1 µM), and its binding affinity exceeds that of CTP by ~75-fold...
September 19, 2016: Chembiochem: a European Journal of Chemical Biology
Thibaut Courant, Rahul Kumar, Serge Turcaud, Laurent Micouin
α-Alkynyl-α'-trimethylsilylhydrazones are used as novel Rh(II)-carbenoids precursors. These new carbenoids have shown very good reactivity in Si-H insertion reactions, leading to original propargylic geminal-bis(silanes) in a two-step sequential process.
October 7, 2016: Organic Letters
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