All‐Fullerene Electron Donor–Acceptor Conjugates Izquierdo, Marta; Platzer, Benedikt; Stasyuk, Anton J. ...
Angewandte Chemie International Edition,
May 20, 2019, Letnik:
58, Številka:
21
Journal Article
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The synthesis and characterization of a covalent all‐fullerene C60‐Lu3N@Ih‐C80 electron donor–acceptor conjugate has been realized by sequential 1,3‐dipolar cycloaddition reactions of azomethine ...ylides on Lu3N@Ih‐C80 and C60. To the best of our knowledge, this is the first time that two fullerenes behaving as both electron donor (Lu3N@Ih‐C80) and acceptor (C60) are forming an electroactive dumbbell. DFT calculations reveal up to 16 diastereomeric pairs, that is, 8 with syn and 8 with anti orientation, with the anti‐RSSS isomer being the most stable. Spectroelectrochemical absorption and femtosecond transient absorption experiments support the notion that a C60⋅−‐Lu3N@Ih‐C80⋅+ charge‐separated state is formed. Spin conversion from the charge‐separated singlet state C60⋅−‐Lu3N@Ih‐C80⋅+ into the corresponding triplet state is facilitated by the heavy‐atom effect stemming from the Lu3N‐cluster, which, in turn, slows down the charge recombination by one order of magnitude.
Dumbbell charge transfer: The synthesis of an all‐fullerene electron donor–acceptor conjugate, C60‐Lu3N@Ih‐C80, is reported. In the dumbbell‐like system, one fullerene moiety acts as the donor (Lu3N@Ih‐C80) while the other acts as the acceptor (C60). Spin conversion of the charge‐separated singlet state into the corresponding triplet state slows down the charge recombination by one order of magnitude.
The chemical reduction of a corannulene-based molecular nanographene, C
H
(1), with Na metal in the presence of 18-crown-6 afforded the doubly-reduced state of 1. This reduction provokes a distortion ...of the helicene core and has a significant impact on the aromaticity of the system.
The effect of nonionic cosurfactants on AOT reversed micellar interface and micelle/micelle interactions was studied. The change on the percolating temperature induced by these cosurfactants was ...determined for several water contents, micelle concentration, and cosurfactant type and concentration. Two types of cosurfactants were used, linear chained alkyl alcohols and poly(oxyethylene) alkyl ethers (C i E j ). If an alcohol was added to the microemulsion, a shift in percolation to higher temperature was observed. The opposite was observed for the C i E j . The apparent hydrodynamic radius for the same systems was determined using dynamic light scattering. The apparent hydrodynamic radius of the alcohol-containing microemulsions was only slightly dependent on the concentration and chain size of the alcohol. The C i E j had the opposite effect, the apparent hydrodynamic radius increased for bigger head group sizes and higher concentrations. These results were interpreted in terms of a decrease or an increase of the fluidity of the interface layer. A solubilization site for the cosurfactants is proposed based on this interpretation of the results. Using the experimental results and an association model, the clustering enthalpy and entropy were determined. The clustering process was found to be endothermic and entropically driven.
•We evaluate two installation depths of the dripper for the drip irrigation system.•We evaluate if there was an influence of water quality on the water storage in the soil.•For the experimental area, ...the installation of the drip tube to 0.2m deep presented the best results.•Different layers in the soil profile should be considered for calculating water depth.•The treated sewage effluent did not affect the distribution of water in the soil.
Knowledge about soil moisture is essential to maximize irrigation efficiency because it allows the application of water in the proper quantity and at the proper time, thus improving water management. The objective of this study was to evaluate water storage in the soil profile when using a subsurface drip irrigation system at two emitter installation depths (0.20 or 0.40m) and two water qualities (treated sewage effluent (TSE) and freshwater) in two crop cycles of sugarcane (Saccharum officinarum L.) in Campinas—SP (Brazil). The experiment was conducted in the experimental area of FEAGRI-UNICAMP, Campinas—SP, Brazil, adopting a randomized block design (RBD) in a factorial 2×2+1 with 3 replications. The factors studied included the installation of dripper tube at two depths (0.2 and 0.4m) and two qualities of water (TSE and freshwater) plus a non-irrigation control. The TDR (time domain reflectometry) technique was used to evaluate the moisture in the soil profile by installing five probes with rods at 0.2m up to 1.0m depth. Replacement of the calibration equation provided by the TDR reduced the water depth between the first ratoon and the sugarcane plant and reduced the excess humidity from 0.029 and 0.045cm3 to 0.002 and 0.007cm3 when the drippers were installed at 0.2m depth (T2 and T4). The installation of a 0.2m drip tube proved to be an ideal solution for both environmental management and water use efficiency when using treated sewage effluent. No effect on the water distribution in the soil was observed when comparing the water qualities. For management of subsurface drip irrigation by the water balance in the soil, different layers in the soil profile should be considered to calculate the water depth, using the depth of the drip tube installation as a reference.
Breast cancer comprises clinically and molecularly distinct tumor subgroups that differ in cell histology and biology and show divergent clinical phenotypes that impede phase III trials, such as ...those utilizing cathepsin K inhibitors. Here we correlate the epithelial-mesenchymal-like transition breast cancer cells and cathepsin K secretion with activation and aggregation of platelets. Cathepsin K is up-regulated in cancer cells that proteolyze extracellular matrix and contributes to invasiveness. Although proteolytically activated receptors (PARs) are activated by proteases, the direct interaction of cysteine cathepsins with PARs is poorly understood. In human platelets, PAR-1 and -4 are highly expressed, but PAR-3 shows low expression and unclear functions.
Platelet aggregation was monitored by measuring changes in turbidity. Platelets were immunoblotted with anti-phospho and total p38, Src-Tyr-416, FAK-Tyr-397, and TGFβ monoclonal antibody. Activation was measured in a flow cytometer and calcium mobilization in a confocal microscope. Mammary epithelial cells were prepared from the primary breast cancer samples of 15 women with Luminal-B subtype to produce primary cells.
We demonstrate that platelets are aggregated by cathepsin K in a dose-dependent manner, but not by other cysteine cathepsins. PARs-3 and -4 were confirmed as the cathepsin K target by immunodetection and specific antagonists using a fibroblast cell line derived from PARs deficient mice. Moreover, through co-culture experiments, we show that platelets activated by cathepsin K mediated the up-regulation of SHH, PTHrP, OPN, and TGFβ in epithelial-mesenchymal-like cells from patients with Luminal B breast cancer.
Cathepsin K induces platelet dysfunction and affects signaling in breast cancer cells.
The chemical reduction of π‐conjugated bilayer nanographene 1 (C138H120) with K and Rb in the presence of 18‐crown‐6 affords K+(18‐crown‐6)(THF)2{K+(18‐crown‐6)}2(THF)0.5C138H1223− (2) and ...Rb+(18‐crown‐6)2{Rb+(18‐crown‐6)}2(C138H1223−) (3). Whereas K+ cations are fully solvent‐separated from the trianionic core thus affording a “naked” 1.3− anion, Rb+ cations are coordinated to the negatively charged layers of 1.3−. According to DFT calculations, the localization of the first two electrons in the helicene moiety leads to an unprecedented site‐specific hydrogenation process at the carbon atoms located on the edge of the helicene backbone. This uncommon reduction‐induced site‐specific hydrogenation provokes dramatic changes in the (electronic) structure of 1 as the helicene backbone becomes more compressed and twisted upon chemical reduction, which results in a clear slippage of the bilayers.
An unprecedented site‐specific reduction‐induced hydrogenation of a helical bilayer nanographene has been found using K or Rb metals. However, coordination of the metal to the central six‐membered rings of the bilayer helicene in a η3‐mode is only observed for the Rb complex, due to its larger ionic size, thus showing the impact of the cation's size on the reaction product.
Origins of the Caribbean Rainfall Bimodal Behavior Angeles, Moisés E.; González, Jorge E.; Ramírez-Beltrán, Nazario D. ...
Journal of Geophysical Research. D. Atmospheres,
16 June 2010, Letnik:
115, Številka:
D11
Journal Article
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The annual precipitation pattern in the Caribbean basin shows a distinct bimodal behavior, where the first mode is called the Early Rainfall Season (April–July), and the second mode the Late Rainfall ...Season (August–November). The brief, relatively dry, period in July is usually referred to as the midsummer drought (MSD). It has been hypothesized that the migration through the Caribbean basin of the Intertropical Convergence Zone (ITCZ) and increases in aerosols due to the passing of Saharan Dust across the Caribbean in the summer months may result in the observed precipitation pattern. This paper focuses on determining the origins of the Caribbean MSD. Multiple regression analysis was carried‐out to determine if the ITCZ, the North Atlantic Oscillation (NAO) index, the Vertical Wind Shear (VWS), and different atmospheric particle (AP) concentrations transported from northern Africa correlate with the Caribbean MSD. It is shown that the ITCZ and NAO are weakly correlated with the Caribbean precipitation variability; however, the VWS and aerosol particles revealed an important contribution to rainfall during the summer months. Numerical experiments were then performed to quantify the influence of different VWS scenarios and different AP concentrations on the Caribbean precipitation bimodal behavior. The numerical approach uses the Regional Atmospheric Modeling System coupled with a new cloud microphysics module that allows discrimination between small and giant particles, as well as Cloud Concentration Nuclei (CCN) and Giant CCN activation. These numerical experiments support the statistical result that the VWS and the AP influence the rainfall production and pattern during the MSD. Results indicate that cloud microphysics play an important role in producing the observed climatological bimodal pattern, while variations in large‐scale atmospheric dynamics (like the VWS) help explain variations in the strength and pattern of the bimodal events and behavior.
The thermoelectric properties of molecular junctions consisting of a metal Pt electrode contacting 60fullerene derivatives covalently bound to a graphene electrode have been studied by using a ...conducting-probe atomic force microscope (c-AFM). The 60fullerene derivatives are covalently linked to the graphene via two meta-connected phenyl rings, two para-connected phenyl rings, or a single phenyl ring. We find that the magnitude of the Seebeck coefficient is up to nine times larger than that of Au–C60–Pt molecular junctions. Moreover, the sign of the thermopower can be either positive or negative depending on the details of the binding geometry and on the local value of the Fermi energy. Our results demonstrate the potential of using graphene electrodes for controlling and enhancing the thermoelectric properties of molecular junctions and confirm the outstanding performance of 60fullerene derivatives.
Dengue viruses (DENVs) cause the greatest public health burden globally among the arthropod-borne viruses. DENV transmission risk has also expanded from tropical to subtropical regions due to the ...increasing range of its principal mosquito vector,
. Focal outbreaks of dengue fever (dengue) in the state of Florida (FL) in the USA have increased since 2009. However, little is known about the competence of
populations across different regions of FL to transmit DENVs. To understand the effects of DENV genotype and serotype variations on vector susceptibility and transmission potential in FL, we orally infected a colony of
(Orlando/ORL) with low passage or laboratory DENV-1 through -4. Low passage DENVs were more infectious to and had higher transmission potential by ORL mosquitoes. We used these same DENVs to examine natural
populations to determine whether spatial distributions correlated with differential vector competence. Vector competence across all DENV serotypes was greater for mosquitoes from areas with the highest dengue incidence in south FL compared to north FL. Vector competence for low passage DENVs was significantly higher, revealing that transmission risk is influenced by virus/vector combinations. These data support a targeted mosquito-plus-pathogen screening approach to more accurately estimate DENV transmission risk.
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