Bioactive PKS–NRPS Alkaloids from the Plant-Derived Endophytic Fungus Xylaria arbuscula

A novel hybrid PKS–NRPS alkaloid, xylarialoid A (1), containing a 13-membered macrocyclic moiety and [5,5,6] fused tricarbocyclic rings, together with ten known cytochalasins (2–11), was isolated from a plant-derived endophytic fungus, Xylaria arbuscula. The chemical structures of all compounds were elucidated using 1D and 2D NMR, HR ESIMS spectroscopic analyses, and electronic circular dichroism (ECD) calculation. Compounds 1–3 and 10 exhibited significant antitumor activities against A549 and Hep G2 cell lines, with IC₅₀ values of 3.6–19.6 μM. In addition, compound 1 showed potent anti-inflammatory activity against LPS-induced nitric oxide (NO) production in macrophage RAW 264.7 cells (IC₅₀, 6.6 μM).     

Determination of L-tryptophan-serum albumin binding by high-performance liquid chromatography

Summary Two high-performance liquid chromatography (HPLC) techniques were developed for the determination of binding constants in the interaction of serum albumin with L-tryptophan: internal calibration and external calibration. The results obtained were compared with those obtained by the classical method of equilibrium dialysis and by gel filtration. While all the methods are equally reliable, the internal and external calibration techniques seem to be superior in their simplicity, speed and convenience.     

白钨酸研究——Ⅶ.K3W2Cl9的制备及反应

用粉状白钨酸作原针,在一般条件下制备K₃W₂Cl₉,产率达53%,证明白钨酸是比黄钨酸优越的钨化学试剂。研究了K₃W₂Cl₉经离子又换转化为酸的形态后与Ndz₂(C0₃)₃的反应。得到了新的化合物NdW₂Cl₉,提出了一条新的制备溶解度大的各种金属离子与W₂Cl₉^3-的化合物的途径。 对K₃W₂Cl₉和NdW₂Cl₉进行了紫外可见尤谱和X针线粉末衍射的测定。     

Potentiometric stripping analysis for tin with a gold film electrode formed in situ on glassy carbon

A gold film electrode formed in situ on glassy carbon is used as the working electrode for the determination of tin over the range 0.1–10 μg ml^?1. Gold(III) added to the solution provides the film and serves as the oxidant for stripping. Two stripping curves corresponding to Sn(Au) → Sn(II) and Sn(II) → Sn(IV) were observed; either can be used for determinations of tin. The equations for the transition time (i.e., stripping signal) and stripping curve derived were verified experimentally.     

CeO2担载Cu纳米粒子电催化CO2还原产乙烯：CeO2不同暴露晶面对催化性能的影响

Fossil fuels are expected to be the major source of energy for the next few decades. However, combustion of nonrenewable resources leads to the release of large quantities of CO₂, the primary greenhouse gas. Notably, the concentration of CO₂ in the atmosphere is increasing annually at an astounding rate. Electrochemical CO₂ reduction (ECR) to value-added fuels and chemicals using electricity from intermittent renewable energy sources is a carbon-neutral method to alleviate anthropogenic CO₂ emissions. Despite the steady progress in the selective generation of C₁ products (CO and formic acid), the production of multi-carbon species still suffers from low selectivity and efficiency. As an ECR product, ethylene (C₂H₄) has a higher energy density than do C₁ species and is an important industrial feedstock in high demand. However, the conversion of CO₂ to C₂H₄ is plagued by low productivity and large overpotential, in addition to the severe competing hydrogen evolution reaction (HER) during the ECR. To address these issues, the design and development of advanced electrocatalysts are critical. Here, we demonstrate fine-tuning of ECR to C₂H₄ by taking advantage of the prominent interaction of Cu with shape-controlled CeO₂ nanocrystals, that is, cubes, rods, and octahedra predominantly covered with (100), (110), and (111) surfaces, respectively. We found that the selectivity and activity of the ECR depended strongly on the exposed crystal facets of CeO₂. The overall ECR Faradaic efficiency (FE) over Cu/CeO₂(110) (FE ≈ 56.7%) surpassed that of both Cu/CeO₂(100) (FE ≈ 51.5%) and Cu/CeO₂(111) (FE ≈ 48.4%) in 0.1 mol·L^-1 KHCO₃ solutions with an H-type cell. This was in stark contrast to the exclusive occurrence of the HER over pure carbon paper, CeO₂(100), CeO₂(110), and CeO₂(111). In particular, the FE toward C₂H₄ formation and the partial current density increased in the sequence Cu/CeO₂(111) < Cu/CeO₂(100) < Cu/CeO₂(110) within applied bias potentials from -1.00 to -1.15 V (vs. the reversible hydrogen electrode), reaching 39.1% over Cu/CeO₂(110) at a mild overpotential (1.13 V). The corresponding values for Cu/CeO₂(100) and Cu/CeO₂(111) were FE_C2H4 ≈ 31.8% and FE_C2H4 ≈ 29.6%, respectively. The C₂H₄ selectivity was comparable to that of many reported Cu-based electrocatalysts at similar overpotentials. Furthermore, the FE for C₂H₄ remained stable even after 6 h of continuous electrolysis. The superior ECR activity of Cu/CeO₂(110) to yield C₂H₄ was attributed to the metastable (110) surface, which not only promoted the effective adsorption of CO₂ but also remarkably stabilized Cu⁺, thereby boosting the ECR to produce C₂H₄. This work offers an alternative strategy to enhance the ECR efficiency by crystal facet engineering.     

RADIATION CROSSLINKING OF BRANCHED POLY (VINYL ACETATE)

In the present work, radiation crosslinking of different branched poly (vinyl acetate) have beemstudied and the validity of the relationship between sol fraction and radiation dose: R(S+S~(1/2)=1/U_(1qo)+p′_o/q_oR~βto branched poly(vinyl acetate) have been assured.     

ATISINE型二萜生物碱的圆二色谱(CD)

C_(20)-二萜生物碱结构复杂,环上大多有含氧的基团。利用NMR、MS等确定羟基、羰基在分子中的位置往往不够有力。特別是对于C_1~3或C_(11)位上羰基,没有可靠而简便的光谱鉴別方法。我们通过对几个Atisine型含羰基化合物的圆二色谱研究发现,由CD谱确定羰基在C_6位、C_(11)位及C_(13)位是一种简便有效的方法。     

CoFe-LDH nanowire arrays on graphite felt: A high-performance oxygen evolution electrocatalyst in alkaline media

Developing non-noble-metal oxygen evolution reaction(OER) electrocatalysts with high performance is critical to electrocatalytic water splitting. In this work, we fabricated Co Fe-layered double hydroxide(LDH) nanowire arrays on graphite felt(Co Fe-LDH/GF) via a hydrothermal method. The Co Fe-LDH/GF, as a robust integrated 3 D OER anode, exhibits excellent catalytic activity with the need of low overpotential of 252 and 285 m V to drive current densities of 10 and 100 m A/cm2 in 1.0 mol/L KOH, r...     

质子交换膜燃料电池铂基催化剂研究进展北大核心CSCD

燃料电池是一种将化学能直接转化为电能的能量转换装置,具有能量密度高、利用率高、清洁安静等优点。在不同类型的燃料电池中,质子交换膜燃料电池(PEMFC)不仅能量密度高,而且具有在近常温条件下工作的特点,因此受到广泛关注。目前,商业化PEMFC仍采用铂基纳米材料作为催化剂,其中缺乏低成本、高效的阴极催化剂是限制PEMFC性能提升和成本降低的关键因素之一。本文综述PEMFC催化剂的结构可控制备及其对阴极氧还原反应和膜电极性能的影响,阐述调控催化剂结构提高PEMFC性能的方法,特别是提高贵金属催化剂的利用率,降低膜电极中贵金属用量的研究进展。