具有三维交叉孔道的新型亚磷酸锌的合成与结构

本文报道了一种新型三维亚磷酸锌[HO(CH₂)₂NH₃]₂•[Zn₃(HPO₃)₄]的合成和晶体结构。在它的结构中，ZnO₄和HPO₃严格按照顶点连接的方式交替相连。骨架结构存在两个沿着不同方向无限延伸的由ZnO₄和HPO₃组成的四元环链，在[0 1 0]、[0 4 15]和[0 -4 15]三个方向形成了三个交叉8元环孔道，有机胺阳离子起着平衡电荷和稳定骨架的结构。它的晶体数据为：[HO(CH₂)₂NH₃]₂•[Zn₃(HPO₃)₄],M=640.21, 正交晶系, Fdd2空间群, a=2.8528, b=0.8426, c=1.6159nm, Z=8, V=3.884nm³, R₁=0.0219, wR₂=0.0544。     

Surface chemistry studies of (CdSe)ZnS quantum dots at the air-water interface

Trioctylphosphine oxide- (TOPO-) capped (CdSe)ZnS quantum dots (QDs) were prepared through a stepwise synthesis. The surface chemistry behavior of the QDs at the air-water interface was carefully examined by various physical measurements. The surface pressure-area isotherm of the Langmuir film of the QDs gave an average diameter of 4.4 nm, which matched very well with the value determined by transmission electron microscopy (TEM) measurements if the thickness of the TOPO cap was counted. The stability of the Langmuir film of the QDs was tested by two different methods, compression/decompression cycling and kinetic measurements, both of which indicated that TOPO-capped (CdSe)ZnS QDs can form stable Langmuir films at the air-water interface. Epifluorescence microscopy revealed the two-dimensional aggregation of the QDs in Langmuir films during the early stage of the compression process. However, at high surface pressures, the Langmuir film of QDs was more homogeneous and was capable of being deposited on a hydrophobic quartz slide by the Langmuir-Blodgett (LB) film technique. Photoluminescence (PL) spectroscopy was utilized to characterize the LB films. The PL intensity of the LB film of QDs at the first emission maximum was found to increase linearly with increasing number of layers deposited onto the hydrophobic quartz slide, which implied a homogeneous deposition of the Langmuir film of QDs at surface pressures greater than 20 mN.m(-1).     

DNA electrochemistry through the base pairs not the sugar-phosphate backbone

Using intercalated, covalently bound daunomycin as a redox probe, ground state charge transport in DNA films with a perturbation in base pair stacking was examined in comparison with breaks in the sugar-phosphate backbone. While the introduction of one or even two nicks in the sugar-phosphate backbone yields no detectable effect on electron transfer, a CA mismatch significantly attenuates the electron transfer yield. These results confirm that the base pair stack is the pathway for DNA-mediated charge transfer, not the sugar-phosphate backbone.     

Mechanistic evaluation of arsenite oxidation in TiO2 assisted photocatalysis

We report herein a detailed assessment of the roles of O2, H2O2, *OH, and O2-* in the TiO2 assisted photocatalytic oxidation (PCO) of arsenite. Although both arsenite, As(III), and arsenate, As(V), adsorb extensively onto the surface of TiO2, past studies relied primarily on the analysis of the arsenic species in solution, neglecting those adsorbed onto the surface of TiO2. We used extraction and analyses of the arsenic species adsorbed onto the surface of the TiO2 to illustrate that the oxidation of As(III) to As(V) occurs in an adsorbed state during TiO2 PCO. The TiO2 photocatalytic oxidation (PCO) of surface adsorbed As(III) in deoxygenated solutions with electron scavengers, Cu2+, and polyoxometalates (POM) yields oxidation rates that are comparable to those observed under oxygen saturation, implying the primary role of oxygen is as a scavenger of the conduction band electron. Pulse radiolysis and competition kinetics were employed to determine a rate constant of 3.6 x 10(6) M(-1) s(-1) for the reaction of As(III) with O2-*. Transient absorption studies of adsorbed hydroxyl radicals, generated by subjecting colloidal TiO2 to radiolytic conditions, provide convincing evidence that the adsorbed hydroxyl radical (TiO2+*OH) plays the central role in the oxidation with As(III) during TiO2 assisted photocatalysis. Our results suggest the reaction of superoxide anion radical does not contribute in the conversion of As(III) when compared to the reaction of As(III) with *OH radical during TiO2 PCO.     

Synthesis and Preliminary Anti‐bacterial Activity of Some 4‐Substituted‐N1‐2‐pyridylsulfanilamide Derivatives

2‐Amino‐4‐ethoxycarbonylpyridine 1 was used as a starting material in the synthesis of some 4‐substituted‐N¹‐2‐pyridylsulfanilamide derivatives to evaluate their antimicrobial activity. The obtained compounds were of no particular effect against the tested organisms except for a noticeable inhibition of B. subtilis, which was of varying extents but remained clearly significant.     

冰晶石-氧化铝熔体结构的计算机模拟研究

用Monte Carlo法对冰晶石-氧化铝系熔体结构作了计算机模拟研究。结果表明: 熔体中既有含“氧桥”和“氟桥”的“多核”离子集团, 如F3Al-O-AlF_3、F_3Al-AlF_3、F_3Al—F—AlF_3—F等; 也有“单核”离子集团如AlF_5~(2-)、AlOF_3~(2-)等。熔体中还存在较松散的xNa~+·yF~-离子集团。熔体中不存在AlO_2~-或AlO_3~(3-)集团。     

CHIP-mediated hyperubiquitylation of tau promotes its self-assembly into the insoluble tau filaments

The tau protein is a highly soluble and natively unfolded protein. Under pathological conditions, tau undergoes multiple post-translational modifications (PTMs) and conformational changes to form insoluble filaments, which are the proteinaceous signatures of tauopathies. To dissect the crosstalk among tau PTMs during the aggregation process, we phosphorylated and ubiquitylated recombinant tau in vitro using GSK3β and CHIP, respectively. The resulting phospho–ub-tau contained conventional polyubiquitin chains with lysine 48 linkages, sufficient for proteasomal degradation, whereas unphosphorylated ub-tau species retained only one–three ubiquitin moieties. Mass-spectrometric analysis of in vitro reconstituted phospho–ub-tau revealed seven additional ubiquitylation sites, some of which are known to stabilize tau protofilament stacking in the human brain with tauopathy. When the ubiquitylation reaction was prolonged, phospho–ub-tau transformed into insoluble hyperubiquitylated tau species featuring fibrillar morphology and in vitro seeding activity. We developed a small-molecule inhibitor of CHIP through biophysical screening; this effectively suppressed tau ubiquitylation in vitro and delayed its aggregation in cultured cells including primary cultured neurons. Our biochemical findings point to a “multiple-hit model,” where sequential events of tau phosphorylation and hyperubiquitylation function as a key driver of the fibrillization process, thus indicating that targeting tau ubiquitylation may be an effective strategy to alleviate the course of tauopathies.

Multiple-hit model for tau aggregation, where sequential events of tau phosphorylation and hyperubiquitylation function as a key driver of the fibrillization process.     

Multifunctional peptide-assembled micelles for simultaneously reducing amyloid-β and reactive oxygen species

The excessive production and deposition of amyloid-β (Aβ) is one of the most important etiologies of Alzheimer''s disease (AD). The interaction between Aβ and metal ions produces aberrant reactive oxygen species (ROS), which induce oxidative stress and accelerate the progression of AD. To reduce Aβ plaques and ROS to maintain their homeostasis is an emerging and ingenious strategy for effective treatment of AD. Herein, we report the rational design of multifunctional micelles (MPGLT) based on a polymer-grafted peptide to simultaneously clear Aβ and ROS for AD therapy. The MPGLT integrating three functional peptides as a ROS scavenger (tk-GSH), β-sheet breaker (LP) and an autophagy activator (TK) respectively, could capture and degrade Aβ. Meanwhile, the tk-GSH on the surface of MPGLT effectively scavenges the intracellular ROS. Consequently, MPGLT reduced the cytotoxicity of Aβ and ROS. In vivo animal studies using an AD mouse model further showed that MPGLT could transport across the blood–brain barrier for decreasing the Aβ plaque and eliminating ROS in vivo. This peptide micelle-based synergistic strategy may provide novel insight for AD therapy.

Multifunctional micelles based on a peptide–polymer for simultaneously targeting Aβ degradation and ROS scavenging for AD therapy.     

Cover Picture: Electrochemical Oxidative Csp3—H/S—H Cross‐Coupling with Hydrogen Evolution for Synthesis of Tetrasubstituted Olefins (Chin. J. Chem. 6/2019)

The inside cover picture shows an electrochemical oxidative Csp³‐H/S‐H activation with hydrogen evolution for the synthesis of tetrasubstituted olefins. This method features very high atom economy, besides hydrogen gas, under the base‐free, transition met‐al‐free, and oxidants‐free conditions, no other by‐products were generated. More details are discussed in the article by Lei et al. on page 547–551.