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Frank Henneberg opublikował 5 miesięcy, 1 tydzień temu
A CoP/graphene composite was synthesized through a coprecipitation and in situ phosphorization protocol using α-Co(OH)2 and graphene oxide as precursors. The similar two-dimensional layered structures ensured evenly attached α-Co(OH)2 nanosheets on the graphene oxide support and the formation of a sandwich-like structure. The sequential in situ phosphorization strategy not only generated a high density of ultrafine CoP nanocrystals but also simultaneously reduced the graphene oxide support. The enough exposed active sites combined with a highly conductive matrix resulted in an excellent electrochemical catalyst for overall water splitting. The overpotential is only 125 mV at 10 mA·cm2 in 0.5 M H2SO4. Good electrocatalytic performance was also exhibited in alkaline conditions for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The overpotential is 119 mV for HER and 374 mV for OER at 10 mA·cm2 in 1 M KOH. More importantly, the composite exhibited much higher exchange current densities during HER processes (1.64 × 10-4 A·cm-2 in 0.5 M H2SO4 and 2.93 × 10-4 A·cm-2 in 1 M KOH) when compared with similar materials reported before. This low-cost, simple, and efficient approach is suitable for mass production and practical applications.Two polymorphic modifications (1-I and 1-II) of the new spin crossover (SCO) complex [FeH2B(pz)(pypz)2] (pz = pyrazole, pypz = pyridylpyrazole; 1) were prepared and investigated by differential scanning calorimetry (DSC), magnetic measurements, Mößbauer, vibrational, and absorption spectroscopy as well as single-crystal and X-ray powder diffraction. DSC measurements reveal that upon heating the thermodynamically metastable form 1-II to ∼178 °C it transforms into 1-I in an exothermic reaction, which proves that these modifications are related by monotropism. Both forms show thermal SCO with T1/2 values of 390 K (1-II) and 270 K (1-I). An analysis of the crystal structures of 1-II and the corresponding Zn(II) (2) and Co(II) (3) complexes that are isotypic with 1-I reveals that form II consists of dimers coupled by strong intramolecular π···π interactions, which is not the case for 1-I. In agreement with these findings, investigations of thin films of 1, where significant π···π interactions should be absent, reveal SCO behavior similar to that of 1-I. These results underscore the importance of cooperativity for the spin-transition behavior of this class of complexes.This paper reports a novel redox-sensitive micellar system for the co-delivery of doxorubicin (Dox) and a chemosensitizer (curcumin, Cur) to overcome the multidrug resistance (MDR) in cancer cells. Dox and Cur were co-conjugated onto a zwitterionic polymer, poly(carboxybetaine) (pCB), to form Cur-pCB-Dox that self-assembled into stable micelles (164.2 ± 4.8 nm). Single-drug conjugates (pCB-Dox and pCB-Cur) were prepared for comparisons. Compared to the high half-maximal inhibitory concentration (IC50) of Dox (437.2 μg/mL), the IC50 value of pCB-Dox (14.1 μg/mL) was only 1/33 that of Dox. Confocal laser scanning microscopy and flow cytometry revealed the greatly enhanced cell uptake of the conjugate due to the enhanced permeability and retention effect of tumor cells on the micellar conjugate. Co-delivery of pCB-Dox with pCB-Cur further reduced the IC50 value by 37% (8.9 μg/mL). More importantly, Cur-pCB-Dox exhibited the strongest cytotoxicity against MCF-7/Adr cells (IC50, 5.87 μg/mL) because the co-delivered Dox and Cur on one carrier specifically transported into the same cells, which inhibited the efflux of Dox by Cur, led to a higher intracellular Dox concentration and made the drugs exert synergistic effects at the targeting regions. The results proved the zwitterionic micelles as promising drug co-delivery vehicles for fighting against MDR.Nonradiative losses in semiconductors are related to defects. At cryogenic temperatures, defect-related photoluminescence (PL) at energies lower than the band-edge PL is observed in methylammonium lead triiodide perovskite. We applied multispectral PL imaging to samples prepared by two different procedures and exhibiting 1 order of magnitude different PL quantum yield (PLQY). The high-PLQY sample showed concentration of the emitting defect sites around 1012-1013 cm-3. No correlation between PLQY and the relative intensity of the defect emission was found when micrometer-sized local regions of the same sample were compared. However, a clear positive correlation between the lower PLQY and higher defect emission was observed when two preparation methods were contrasted. Therefore, although the emissive defects are not connected directly with the nonradiative centers and may be spatially separated at the nano scale, chemical processes during the perovskite synthesis promote/prevent formation of both types of defects at the same time.We present a scheme for transferring conformational degrees of freedom from all-atom (AA) simulations of an intrinsically disordered protein (IDP) to coarse-grained (CG) Monte Carlo (MC) simulations using conformational swap moves. AA simulations of a single histatin 5 peptide in water were used to obtain a structural ensemble, which is reweighted in a CGMC simulation in the presence of a negatively charged surface. For efficient sampling, the AA trajectory was condensed using two approaches RMSD clustering (based on the root-mean-square difference in atom positions) and a „naı̈ve” truncation, where only every 100th frame of the trajectory was included in the library. The results show that even libraries with few structures well reproduce the radius of gyration and interaction free energy as functions of the distance from the surface. We further observe that the surface slightly promotes the secondary structure of histatin 5 and more so if using explicit surface charges rather than smeared charges.The structures of the sponge-derived dibrominated bis-indole alkaloids, namely, echinosulfone A (2) and the echinosulfonic acids A to D (9-12), have been revised based upon reanalysis of their NMR spectroscopic and MS spectrometric data, comparison of this data with those reported for structurally related compounds, and based on their common biogenesis. The reinterpreted spectroscopic evidence has been corroborated by the total synthesis of the revised structure of echinosulfone A (2). This was achieved by bis-carbonylation at C-3 of the magnesium salt of 6-bromoindole with triphosgene to afford the new dibrominated bis-indole ketone, bis(6-bromo-1H-indol-3-yl)methanone (3), followed by N-sulfonation of one indole moiety to furnish 6-bromo-3-(6-bromo-1H-indole-3-carbonyl)-1H-indole-1-sulfonate (2). The five marine alkaloids corrected herein each contain an indole sulfamate and are all carbon-bridged dibrominated bis-indoles echinosulfone A (2) is a di(1H-indol-3-yl)methanone, while the echinosulfonic acids A to D (9-12) are methyl 2,2-bis(1H-indol-3-yl) acetates.Polycyclic aromatic hydrocarbons (PAHs) present in crude oil are known to impair visual development in fish. However, the underlying mechanism of PAH-induced toxicity to the visual system of fish is not understood. Embryonic zebrafish (Danio rerio) at 4 h post fertilization were exposed to weathered crude oil and assessed for visual function using an optokinetic response, with subsequent samples taken for immunohistochemistry and gene expression analysis. Cardiotoxicity was also assessed by measuring the heart rate, stroke volume, and cardiac output, as cardiac performance has been proposed to be a contributing factor to eye-associated malformations following oil exposure. Larvae exposed to the highest concentrations of crude oil (89.8 μg/L) exhibited an increased occurrence of bradycardia, though no changes in stroke volume or cardiac output were observed. However, genes important in eye development and phototransduction were downregulated in oil-exposed larvae, with an increased occurrence of cellular apoptosis, reduced neuronal connection, and reduced optokinetic behavioral response in zebrafish larvae.We report herein a sustainable method for the preparation of 2-arylpyridines through C-H arylation of pyridines using in situ formed diazonium salts (from commercially available aromatic amines) in the presence of a photoredox catalyst under blue light-emitting diode (LED) irradiation. The reaction is tolerant to a wide range of functional groups (e.g., halogen, nitrile, formyl, acetyl, ester). Applications to the C-H bond arylation of bipyridine ligands is also presented.An enantioselective total synthesis of (-)-batrachotoxinin A is accomplished based on a key photoredox coupling reaction and the subsequent local-desymmetrization operation. After the expedient assembly of the highly oxidized steroid skeleton, a delicate sequence of redox manipulations was carried out to deliver a late-stage intermediate on gram scale-and ultimately (-)-batrachotoxinin A in an efficient manner.The development of environmentally friendly and long-term marine antifouling coating remains a huge challenge in the maritime industry. For this purpose, we developed a novel and efficient antifouling coating based on a synergistic strategy, incorporating contact inhibition, fouling repelling, and antifouling properties. Results demonstrated that the coating could efficiently resist the adhesion of protein, bacteria, and Navicula diatoms. More importantly, marine field tests showed the coating could efficiently inhibit biofouling for at least 8 months. This approach paves a new way for the development of environmentally friendly and long-term antifouling coating.Conventionally, z-direction modulation of two-dimensional covalent organic frameworks (2D-COFs) is difficult to achieve because they rely on spontaneous π-π interactions to form 3D architectures. Herein, we report a facile construction of a novel intercalated covalent organic framework (Intercalated-COF) by synchronizing operations of supramolecular donor-acceptor (D-A) interactions (A unit 2,5,8,11-tetra(p-formylphenyl)-perylene diimide (PDI) 1; D unit perylene 3, as intercalator) in the vertical directions, with polymerizations (by only reacting 1 with p-phenylenediamine 2) in the lateral directions. In this Intercalated-COF, the PDI-based covalent 2D layers are uniformly separated by perylene guest layers. This supramolecular strategy opens the possibility for z-direction modulation of 2D-COFs through „intercalating” various guest molecules and thus may contribute to the exploration of advanced applications of these porous and crystalline frameworks.Very-short, short-, medium-, and long-chain chlorinated paraffins (vSCCPs, SCCPs, MCCPs, and LCCPs, respectively) were analyzed in different tissues of the terrestrial short-tailed mamushi (Gloydius brevicaudus) and the semi-aquatic red-backed rat snake (Elaphe rufodorsata) from the Yangtze River Delta, China. The total CP concentrations in liver, muscle, and adipose tissues in the two snake species were in the range of 2500-24 000, 4900-48 000, and 12-630 ng/g lw, respectively. Tissue burdens indicated that vSCCPs (C6-9) and SCCPs (C10-13) preferentially distributed to snake liver, while adipose was an important storage site and sink of MCCPs (C14-17) and LCCPs (C>18). On a lipid weight basis, vSCCPs and SCCPs were found in highest concentrations in red-backed rat snake liver and MCCPs and LCCPs in muscle, whereas for short-tailed mamushi, all CP groups were predominant in muscle, probably reflecting ecosystem/food web differences. Moreover, vSCCPs, SCCPs, MCCPs, and LCCPs were found to be biomagnified from black-spotted frogs to red-backed rat snakes with mean (maximum) biomagnification factors of 2.