冬眠哺乳动物氧化应激产生及抗氧化防御机制研究进展

哺乳动物的冬眠是一种季节性异温状态,是对外界恶劣自然环境的一种适应策略。冬眠-阵间觉醒周期中,伴随着生理功能的剧烈变化,从冬眠期间整体代谢的抑制,到阵间觉醒时氧代谢的急剧增加,使动物体内产生了大量的氧自由基。然而,冬眠动物出眠时并未表现出明显的氧化损伤迹象,因此,冬眠哺乳动物被认为是一种天然的抗氧化损伤模型。本文从氧化应激的产生、活性氧的来源、抗氧化防御等方面综述了冬眠哺乳动物对氧化应激的防御,并从其抗氧化的分子调控方面分析了冬眠哺乳动物对氧化应激的适应机制。     

Role of a reaction coordinate in free energy calculations

Abstract

The free energy calculation method emerges as a viable technique for ‘in-silico’ calorimetry. Efficient sampling techniques and the good choice of a reaction path connecting the reactant and the product state enable accurate computations of the free energy differences. We argue that in many cases the thermodynamic integration technique has the lowest variance when the transformation between the reactant and the product state proceeds along the natural path of the studied chemical reaction. We provide examples of free energy calculations for the fragmentation of the charged clusters and the swapping reaction of oligomer formation in proteins that follow a tentative reaction mechanism.     

Enantioseparation of napropamide by supercritical fluid chromatography: Effects of the chromatographic conditions and separation mechanism

Supercritical fluid chromatography (SFC) is already used for enantioseparation in the pharmaceutical industry, but it is rarely used for the separation of chiral pesticides. Comparing with high performence liquid chromatography, SFC uses much more environmnetal friendly and economic mobile phase, supercritical CO₂. In our work, the enantioseparation of an amide herbicide, napropamide, using three different polysaccharide‐type chiral stationary phases (CSPs) in SFC was investigated. By studying the effect of different CSPs, organic modifiers, temperature, back‐pressure regulator pressures, and flow rates for the enantioseparation of napropamide, we established a rapid and green method for enantioseparation that takes less than 2 minutes: The column was CEL2, the mobile phase was CO₂ with 20% 2‐propanol, and the flow rate was 2.0 mL/min. We found that CEL2 demonstrated the strongest resolution capability. Acetonitrile was favored over alcoholic solvents when the CSP was amylose and 2‐propanol was the best choice when using cellulose. When the concentration of the modifiers or the flow rate was decreased, resolutions and analysis times increased concurrently. The temperature and back‐pressure regulator pressure exhibited only minor influences on the resolution and analysis time of the napropamide enantioseparations with these chiral columns. The molecular docking analysis provided a deeper insight into the interactions between the enantiomers and the CSPs at the atomic level and partly explained the reason for the different elution orders using the different chiral columns.     

Kakeromamide A,a new cyclic pentapeptide inducing astrocyte differentiation isolated from the marine cyanobacterium Moorea bouillonii

Kakeromamide A (1), a new cyclic pentapeptide encompassing a thiazole ring moiety and a β-amino acid, was isolated from the marine cyanobacterium Moorea bouillonii. Its structure was elucidated by the spectral analysis and the modified Marfey’s method. Compound 1 induced differentiation of neural stem cells into astrocytes at the concentration of 10?µM.     

Antimicrobial evaluation and action mechanism of pyridinium-decorated 1,4-pentadien-3-one derivatives

A type of pyridinium-decorated 1,4-pentadien-3-one derivatives possessing flexible alkyls were designed and synthesized by integrating the key scaffolds of pyridinium cations and 1,4-pentadien-3-one skeleton in a single molecular architecture. Antimicrobial bioassays indicated that some of the target molecules exerted considerable bioactivities against six phytopathogenic strains, especially for Xanthomonas oryzae pv. oryzae, the minimal EC₅₀ value can reach to 0.504?µg/mL. A plausible action mechanism for this kind of compounds was proposed and confirmed by employing fluorescent spectroscopy, fluorescence microscopy, and scanning electron microscopy. We anticipated that this finding can promote high-efficient lead compounds discovery in the research of antimicrobial chemotherapy.     

sRNA调控细菌耐药相关基因表达研究进展

近年来随着抗菌药物的广泛应用,造成各种耐药菌、多重耐药菌甚至是超级细菌的出现,对抗菌治疗产生严重的威胁。sRNA是一类新发现的基因表达调控因子,通过与靶mRNA或靶蛋白配对,从而调控细胞的生理功能以应对各种环境变化。研究表明,sRNA能够在细菌耐药过程中(如阻碍抗生素进入细胞、将药物外排出菌胞)发挥重要的调控作用。就sRNA参与调控细菌耐药机制相关基因的表达研究展开系统综述,从而为阐明耐药机制及发现新的药物靶点提供有益参考。     

Mechanistic Insights of Zn2+ Storage in Sodium Vanadates

Rechargeable aqueous zinc‐ion batteries (ZIBs) with high safety and low‐cost are highly desirable for grid‐scale energy storage, yet the energy storage mechanisms in the current cathode materials are still complicated and unclear. Hence, several sodium vanadates with NaV₃O₈‐type layered structure (e.g., Na₅V₁₂O₃₂ and HNaV₆O₁₆·4H₂O) and β‐Na_0.33V₂O₅‐type tunneled structure (e.g., Na_0.76V₆O₁₅) are constructed and the storage/release behaviors of Zn²⁺ ions are deeply investigated in these two typical structures. It should be mentioned that the 2D layered Na₅V₁₂O₃₂ and HNaV₆O₁₆·4H₂O with more effective path for Zn²⁺ diffusion exhibit higher ion diffusion coefficients than that of tunneled Na_0.76V₆O₁₅. As a result, Na₅V₁₂O₃₂ delivers higher capacity than that of Na_0.76V₆O₁₅, and a long‐term cyclic performance up to 2000 cycles at 4.0 A g^?1 in spite of its capacity fading. This work provides a new perspective of Zn²⁺ storage mechanism in aqueous ZIB systems.     

Structural Engineering of Multishelled Hollow Carbon Nanostructures for High‐Performance Na‐Ion Battery Anode

Hard carbon has long been considered the leading candidate for anode materials of Na‐ion batteries. Intensive research efforts have been carried out in the search of suitable carbon structure for an improved storage capability. Herein, an anode based on multishelled hollow carbon nanospheres, which are able to deliver an outstanding electrochemical performance with an extraordinary reversible capacity of 360 mAh g^?1 at 30 mA g^?1, is designed. An interesting dependence of the electrochemical properties on the multishelled structural features is identified: with an increase in the shell number of the model carbon materials, the sloping capacity in the charge/discharge curve remains almost unchanged while the plateau capacity continuously increases, suggesting an adsorption‐filling Na‐storage mechanism for the multishelled hollow hard carbon materials. The findings not only provide new perspective in the structural design of high‐performance anode materials, but also shed light on the complicated mechanism behind Na‐storage by hard carbon.