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Bianca N M Silva, Policarpo A Sales, Alvaro J Romanha, Silvane M F Murta, Camilo H S Lima, Magaly G Albuquerque, Eliane D'Elia, Jose G de Aquino, Vitor F Ferreira, Fernando C Silva, Angelo C Pinto, Barbara V Silva
BACKGROUND: Chagas disease, also known as American trypanosomiasis, is classified as one of the 17 most important neglected diseases by the World Health Organization. The only drugs with proven efficacy against Chagas disease are benznidazole and nifurtimox, however both show adverse effects, poor clinical efficacy,and the development of resistance. For these reasons, the search for new effective chemical entities is a challenge to research groups and the pharmaceutical industry. OBJECTIVE: Synthesis and antitrypanosomal activities of a series of thiosemicarbazones and semicarbazones containing the 1,2,3-1H triazole isatin scaffold...
September 12, 2018: Medicinal Chemistry
Sumit Dadhwal, Jessica M Fairhall, Shailesh K Goswami, Sarah Hook, Allan Bernard Gamble
An alkene-azide 1,3-dipolar cycloaddition between trans-cyclooctene (TCO) and an azide-capped hydrogel that promotes rapid gel dissolution is reported. Using an ultrashort aryl azide-capped peptide hydrogel (PhePhe), we have demonstrated proof-of-concept where upon reaction with TCO, the hydrogel undergoes a gel-sol transition via 1,2,3-triazoline degradation and 1,6-self-immolation of the generated aniline. The potential application of this as a general trigger in sustained drug delivery is demonstrated through release of encapsulated cargo (doxorubicin)...
October 15, 2018: Chemistry, An Asian Journal
Peng Tan, Hao Tian, Yu Wang, Xiangda Meng, Fei Huang, Xilong Cao, Chengpeng Hu, Li Li, Zhongxiang Zhou
Dipolar clusters are crucial structure factors in electro-optic (EO) effects. Here, the impacts of dipolar clusters on EO effects are investigated in KTa1-x Nbx O3 using electric-field-dependent EO characteristics. The results indicate that the field-driven reorientation of dipolar clusters determines the orientational electric susceptibility, deeply contributing to the excellent quadratic EO effects. The controlled average size of correlated local dipoles and uniform orientation of ferroelectric domains efficiently suppress light scattering, being beneficial for the modulation of incident light...
October 15, 2018: Optics Letters
Mariano Ortega-Muñoz, Fernando Rodríguez-Serrano, Eduardo De Los Reyes-Berbel, Nuria Mut-Salud, Fernando Hernández-Mateo, Andrea Rodríguez-López, José M Garrido, F Javier López-Jaramillo, Francisco Santoyo-González
Saponins are potential wide-spectrum antitumor drugs, and copper(I) catalyzed azide-alkyne 1,3-dipolar cycloaddition is a suitable approach to synthesizing saponin-like compounds by regioselective glycosylation of the C2/C3 hydroxyl and C28 carboxylic groups of triterpene aglycones maslinic acid (MA) and oleanolic acid (OA). Biological studies on the T-84 human colon carcinoma cell line support the role of the hydroxyl groups at C2/C3, the influence of the aglycone, and the bulky nature of the substituents in C28...
September 30, 2018: ACS Omega
J Stigloher, T Taniguchi, H S Körner, M Decker, T Moriyama, T Ono, C H Back
In optics, a light beam experiences a spatial shift in the beam plane upon total internal reflection. This shift is usually referred to as the Goos-Hänchen shift. When dealing with plane waves, it manifests itself as a phase shift between an incoming and reflected wave that depends on the wave vector component along the interface. In the experiments presented here, plane spin waves are excited in a 60-nm-thick Permalloy film and propagate towards the edge of the film. By means of time-resolved scanning Kerr microscopy, we are able to directly detect a phase shift between the incoming and reflected wave...
September 28, 2018: Physical Review Letters
Ming-Da Yang, Chien-Hsin Ho, Sergiu Ruta, Roy Chantrell, Kathryn Krycka, Ondrej Hovorka, Fu-Rong Chen, Ping-Shan Lai, Chih-Huang Lai
The controlled size and surface treatment of magnetic nanoparticles (NPs) make one-stage combination feasible for enhanced magnetic resonance imaging (MRI) contrast and effective hyperthermia. However, superparamagnetic behavior, essential for avoiding the aggregation of magnetic NPs, substantially limits their performance. Here, a superparamagnetic core-shell structure is developed, which promotes the formation of vortex-like intraparticle magnetization structures in the remanent state, leading to reduced dipolar interactions between two neighboring NPs, while during an MRI scan, the presence of a DC magnetic field induces the formation of NP chains, introducing increased local inhomogeneous dipole fields that enhance relaxivity...
October 11, 2018: Advanced Materials
Azzurra Carlon, Enrico Ravera, Giacomo Parigi, Garib N Murshudov, Claudio Luchinat
Data integration in structural biology has become a paradigm for the characterization of biomolecular systems, and it is now accepted that combining different techniques can fill the gaps in each other's blind spots. In this frame, one of the combinations, which we have implemented in REFMAC-NMR, is residual dipolar couplings from NMR together with experimental data from X-ray diffraction. The first are exquisitely sensitive to the local details but does not give any information about overall shape, whereas the latter encodes more the information about the overall shape but at the same time tends to miss the local details even at the highest resolutions...
October 11, 2018: Journal of Biomolecular NMR
Kang-Kuen Ni, Till Rosenband, David D Grimes
We propose a two-qubit gate based on dipolar exchange interactions between individually addressable ultracold polar molecules in an array of optical dipole traps. Our proposal treats the full Hamiltonian of the 1 Σ+ molecule NaCs, utilizing a pair of nuclear spin states as storage qubits. A third rotationally excited state with rotation-hyperfine coupling enables switchable electric dipolar exchange interactions between two molecules to generate an iSWAP gate. All three states are insensitive to external magnetic and electric fields...
September 7, 2018: Chemical Science
G Walters, M Wei, O Voznyy, R Quintero-Bermudez, A Kiani, D-M Smilgies, R Munir, A Amassian, S Hoogland, E Sargent
The quantum-confined Stark effect (QCSE) is an established optical modulation mechanism, yet top-performing modulators harnessing it rely on costly fabrication processes. Here, we present large modulation amplitudes for solution-processed layered hybrid perovskites and a modulation mechanism related to the orientational polarizability of dipolar cations confined within these self-assembled quantum wells. We report an anomalous (blue-shifting) QCSE for layers that contain methylammonium cations, in contrast with cesium-containing layers that show normal (red-shifting) behavior...
October 11, 2018: Nature Communications
Christopher A Rumble, Mark Maroncelli
Time-resolved emission techniques were used to study the excited-state intramolecular electron transfer of 9-(4-biphenyl)-10-methylacridinium (BPAc+ ) in mixtures of 1-butyl-3-methylimidizolium tetrafluoroborate ([Im41 ][BF4 ])+ acetonitrile (ACN), a mixture previously shown to be of nearly constant polarity and nearly ideal mixing behavior. Reaction times ( τ rxn ) track solvation times ( τ solv ) as a function of mixture composition over a range of more than 3 orders of magnitude in τ solv . This same correlation extends to a variety of neat dipolar solvents and ionic liquids...
May 21, 2018: Journal of Chemical Physics
Bryn D Monnery, Valentin V Jerca, Ondrej Sedlacek, Bart Verbraeken, Rachel Cavill, Richard Hoogenboom
Poly(2-alkyl-2-oxazoline)s (PAOx) are regaining interest for biomedical applications, smart materials and recently as dipolar layer in electronic devices. However, their full potential is hampered by the inability to synthesise uniform high-molar mass PAOx, ascribed to intrinsic chain transfer to monomer side reactions. In this work, we proposed alternative intrinsic chain transfer mechanism based on 2-oxazoline and oxazolinium chain end-tautomerisation and derived improved polymerization conditions to suppress chain transfer, allowing for the synthesis of highly defined poly(2-ethyl-2-oxazoline)s up to ca...
October 10, 2018: Angewandte Chemie
Caspar J Schattenberg, Toni M Maier, Martin Kaupp
Hyperfine couplings (HFCs) of open-shell transition-metal centers are known to often depend crucially on core-shell spin polarization (CSSP). The latter is typically underestimated by semi-local density functionals, while admixture of exact exchange (EXX) in (global) hybrid functionals enhances CSSP. Unfortunately, a metal-ligand antibonding character of one or more of the singly occupied molecular orbitals of the complex will cause substantial valence-shell spin polarization (VSSP), which for global hybrids with higher EXX admixtures may lead to substantial spin contamination, thereby deteriorating the overall electronic structure and the dipolar couplings...
October 9, 2018: Journal of Chemical Theory and Computation
Luisa A Ferreira, Alicyia Walczyk Mooradally, Boris Zaslavsky, Vladimir N Uversky, Steffen P Graether
Dehydrins are plant proteins that are able to protect plants from various forms of dehydrative stress such as drought, cold, and high salinity. Dehydrins can prevent enzymes from losing activity after freeze/thaw treatments. Previous studies had suggested that the dehydrins function by a molecular shield effect, essentially preventing a denatured enzyme from aggregating with another enzyme. Therefore, the larger the dehydrin, the larger the shield and theoretically the more effective the protection. Although this relationship holds for smaller dehydrins, it fails to explain why larger dehydrins are less efficient than would be predicted from their size...
September 22, 2018: Biophysical Journal
Lokeswara Rao Potnuru, K V Ramanathan
Polarization-inversion (PI) has been applied to proton magic angle spinning (MAS) NMR spectra recorded under fast MAS conditions. The combination of cross-polarization (CP) from carbon to proton and subsequent polarization-inversion produces strong oscillatory behavior in the proton signal intensities at high MAS speeds of 60 kHz. It is observed that by a suitable choice of the polarization-inversion time, a proton spectrum free of methylene and methine protons can be obtained. Such a spectrum, on the one hand, increases the resolution of the crowded proton spectrum and on the other hand provides exclusively chemical shifts of protons such as NH, OH and SH which might otherwise overlap with carbon attached protons...
September 24, 2018: Journal of Magnetic Resonance
Silvia Roscales, Nicole Bechmann, Daniel Holger Weiss, Martin Köckerling, Jens Pietzsch, Torsten Kniess
[This corrects the article DOI: 10.1039/C7MD00575J.].
March 1, 2018: MedChemComm
Fernando Murillo, Jorge Barroso, Maria G de Los Santos, Gustavo Avila, Sudip Pan, Maria Antonieta Fernandez-Herrera, Gabriel Merino
The reaction mechanism for the synthesis of 1,3,4-oxadiazole-2(3H)-ones from hydrazonyl chloride and CO2, in the presence of CsF/18-crown-6 and toluene, is revisited via density functional theory computations. Although this reaction was classified as a 1,3-dipolar cycloaddition earlier, we find some competing pathways involved therein. The mechanisms including the (F-CO2)- anion and the nitrile imine intermediate are some options. The dimerization of nitrile imine is also another competing mechanism in this reaction...
October 4, 2018: Journal of Organic Chemistry
Shuting Pang, Miriam Más-Montoya, Manjun Xiao, Chunhui Duan, Zhenfeng Wang, Xi Liu, Rene Janssen, Gang Yu, Fei Huang, Yong Cao
The packing mode of small molecular semiconductors in thin films is an important factor that controls the performance of their optoelectronic devices. Designing and changing the packing mode via molecular engineering is challenging. Three structurally-related diketopyrrolopyrrole (DPP) based molecules are synthesized to study the effect of replacing C-C bonds by isoelectronic dipolar B←N bonds. By replacing one of the bridging C-C bonds on the peripheral fluorene units of the DPP molecules by a coordinative B←N bond and changing the B←N bond orientation, the optical absorption, fluorescence, and excited state lifetime of the molecules can be tuned...
October 4, 2018: Chemistry: a European Journal
Alejo R Gianotti, Raúl G Ferreyra, Mario R Ermácora
Sterol carrier protein 2 (SCP2) binds lipids with high affinity and broad specificity. The overall hydrophobicity, fluidity, and dipolar dynamics of the binding site of SCP2 from Yarrowia lipolytica were characterized using the environmentally-sensitive fluorescent probe Laurdan. The study revealed a binding site with an overall polarity similar to that of dichloromethane and an internal phase comparable to that of phospholipid membranes with coexisting solid-ordered and liquid-crystalline states. The fluorescence properties of bound Laurdan also revealed that the binding site of SCP2 can accommodate competitively more than one ligand, with micro and nanomolar dissociation constants...
November 2018: Biochimica et biophysica acta. Proteins and proteomics
Ryan T Pekarek, Kara Kearney, Benjamin M Simon, Elif Ertekin, Angus A Rockett, Michael J Rose
The design and fabrication of stable and efficient photoelectrochemical devices requires the use of multifunctional structures with complex heterojunctions composed of semiconducting, protecting, and catalytic layers. Understanding charge transport across such devices is challenging due to the interplay of bulk and interfacial properties. In this work, we analyze hole transfer across n-Si(111)- R|TiO2 photoanodes where - R is a series of mixed aryl/methyl monolayers containing an increasing number of methoxy units (mono, di, and tri)...
October 3, 2018: Journal of the American Chemical Society
Mariusz Tasior, Guillame Clermont, Mireille Blanchard-Desce, Denis Jacquemin, Daniel T Gryko
3,6-Bis(arylethynyl)pyrrolo[3,2-b]pyrroles have been synthesized via a two-step procedure involving double direct alkynylation of the electron-rich core followed by Sonogashira coupling. In comparison with the parent tetraarylo-pyrrolo[3,2-b]pyrroles and benzo-fused pyrrolopyrroles, these new dyes show moderately redshifted absorption. Almost all derivatives show positive fluorescence solvatochromism, and for the first time red-emitting pyrrolopyrroles have been obtained. Computational studies revealed that, in most cases, there is negligible change in the geometry between ground and excited states...
October 1, 2018: Chemistry: a European Journal
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