Liquefaction of corn stover and preparation of polyester from the liquefied polyol

This research investigated a novel process to prepare polyester from corn stover through liquefaction and crosslinking processes. First, corn stover was liquefied in organic solvents (90 wt% ethylene glycol and 10 wt% ethylene carbonate) with catalysts at moderate temperature under atmospheric pressure. The effect of liquefaction temperature, biomass content, and type of catalyst, such H₂SO₄, HCl, H₃PO₄, and ZnCl₂, was evaluated. Higher liquefaction yield was achieved in 2 wt% sulfuric acid, 1/4 (w/w) stover to liquefying reagent ratio; 160°C temperature, in 2h. The liquefied corn stover was rich in polyols, which can be directly used as feedstock for making polymers without further separation or purification. Second, polyester was made from the liquefied corn stover by crosslinking with multifunctional carboxylic acids and/or cyclic acid anhydrides. The tensile strength of polyester is about 5 MPa and the elongation is around 35%. The polyester is stable in cold water and organic solvents and readily biodegradable as indicated by 82% weight loss when buried in damp soil for 10 mo. The results indicate that this novel polyester could be used for the biodegradable garden mulch film production.     

Structure-Activity Relationship, Cytotoxicity and Mode of Action of 2-Ester-substituted 1,5-Benzothiazepines as Potent Antifungal Agents

Our studies examined the structural features responsible for the antifungal activity of 2-ethoxycarbonyl-1,5- benzothiazepine （7a）. Three series of 1,5-benzothiazepine derivatives were synthesized and screened for their antifungal activity. The results suggested that the ethoxycarbonyl group at the 2 position and the imine moiety on the seven-membered ring are essential for activity. The most potent of the synthesized analogues （7a, 7b） were further studied by evaluating their cytotoxicity and mode of action （for 7a）. The results showed that compounds 7a and 7b were relatively safe for BV2 cells, but compound 7a interfered with Cryptococcus neoformans cell wall integrity by increasing the chitinase activity. Therefore, compound 7a was considered safe as an antifungal agent for animal cells.     

A Near-Infrared-Controllable Artificial Metalloprotease Used for Degrading Amyloid-β Monomers and Aggregates

Proteolysis of amyloid-β (Aβ) is a promising approach against Alzheimer's disease. However, it is not feasible to employ natural hydrolases directly because of their cumbersome preparation and purification, poor stability, and hazardous immunogenicity. Therefore, artificial enzymes have been developed as potential alternatives to natural hydrolases. Since specific cleavage sites of Aβ are usually embedded inside the β-sheet structures that restrict access by artificial enzymes, this strongly hinders their efficiency for practical applications. Herein, we construct a NIR (near-IR) controllable artificial metalloprotease (MoS₂-Co) using a molybdenum disulfide nanosheet (MoS₂) and a cobalt complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (Codota). Evidenced by detailed experimental and theoretical studies, the NIR-enhanced MoS₂-Co can circumvent the restriction by simultaneously inhibition of β-sheet formation and destroying β-sheet structures of the preformed Aβ aggregates in living cell. Furthermore, our designed MoS₂-Co is an easy to graft Aβ-target agent that prevents misdirected or undesirable hydrolysis reactions, and has been demonstrated to cross the blood brain barrier. This method can be adapted for hydrolysis of other kinds of amyloids.     

Isatindolignanoside A,a glucosidic indole-lignan conjugate from an aqueous extract of the Isatis indigotica roots

A glucosidic indole-lignan conjugate with a novel carbon skeleton, named isatindolignanoside A (1), was isolated from an aqueous extract of the Isatis indigotica roots “ban lan gen”. Its structure was determined by comprehensive analysis of spectroscopic data, enzyme hydrolysis, and electronic CD calculations. Compound 1 is active against Coxsackie virus B3 and represents the first example of natural product having a structural feature of conjugation between indole and lignan, and its plausible biosynthetic pathway is postulated.     

EXAFS and DFT studies of microscopic structure with different density upon Zn(II) adsorption on anatase TiO2

Microscopic structures of Zn(II) adsorbed on anatase TiO₂ surface with different densities were studied using extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) calculation. Quantitative analysis of the EXAFS spectra showed that microscopic structures of Zn(II) were fourfold coordinated complexes, and different microscopic structures were present of the solid surface. Three modes of corner–corner/sharing-corner/sharing-edge adsorptions on anatase (101) face cluster were calculated by the DFT method. The results from DFT method were consistent with the EXAFS fittings. The optimized Zn–O average distance of the Zn–O tetrahedron was determined as about 2.00 Å. The Zn–Ti distance was 3.69 Å for the corner–corner adsorption, 3.35 Å for the sharing-corner adsorption, and 3.02 Å for the sharing-edge adsorption. According to the adsorption energies calculated by the DFT method, the microscopic structure of corner–corner adsorption was less stable than those of the other adsorption modes. With the increasing adsorption density, the corner–corner adsorption mode would be enhanced more intensively than the other adsorption modes.     

固载化烷基咪唑离子液体对盐酸体系中Fe(Ⅲ)的吸附性能研究

分别将N-甲基咪唑和N-丁基咪唑通过共价键固定于树脂载体上,制备了固载化甲基咪唑离子液体(MCl)和固载化丁基咪唑离子液体(BCl),MCl和BCl可作为一种新型的强碱型阴离子交换树脂。研究了MCl和BCl对盐酸体系中Fe(III)的吸附性能,其吸附平衡时间为6h,拟二级动力学模型能更好地描述MCl和BCl对Fe(III)的吸附动力学过程;随着温度的升高,MCl和BCl对Fe(III)的吸附量增大,表明该过程是一个吸热反应,在298K时,MCl和BCl对Fe(III)的最大吸附量分别为24.9mg/g和71.1mg/g;随着盐酸浓度的增加,MCl和BCl对Fe(III)的吸附量增大,而且溶液中Cl-浓度的增加,也会提高MCl和BCl对Fe(III)的吸附量。MCl和BCl可从盐酸体系中回收Fe(III),而且BCl的效果要优于MCl。     

三元层状MAX相固溶体研究进展

MAX相是一类具有层状结构的三元碳化物或(和)氮化物,M是过渡金属元素,A主要是ⅢA~ⅤA族元素,X是C或N元素。这类化合物兼具陶瓷材料和金属材料的特点,具有优异的导电、导热、耐腐蚀以及抗氧化等性能,在诸多领域具有潜在应用价值。近年来,新元素、新结构和固溶体MAX相的不断出现,进一步扩展了MAX相家族。固溶体MAX相是将合适的元素固溶到已知MAX相中而得到的新MAX相。本文分四类总结了127种MAX相固溶体,对其结构改变和性能调控进行了概括,并指出目前研究存在的理论问题和亟须解决的关键技术,最后对MAX相固溶体的发展进行了预测和展望。     

Prediction of interaction between small molecule and enzyme using AdaBoost

The knowledge of whether one enzyme can interact with a small molecule is essential for understanding the molecular and cellular functions of organisms. In this paper, we introduce a classifier to predict the small molecule– enzyme interaction, i.e., whether they can interact with each other. Small molecules are represented by their chemical functional groups, and enzymes are represented by their biochemical and physicochemical properties, resulting in a total of 160 features. These features are input into the AdaBoost classifier, which is known to have good generalization ability to predict interaction. As a result, the overall prediction accuracy, tested by tenfold cross-validation and independent sets, is 81.76% and 83.35%, respectively, suggesting that this strategy is effective. In this research, we typically choose interactions between small molecules and enzymes involved in metabolism to ultimately improve further understanding of metabolic pathways. An online predictor developed by this research is available at . Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Reaction kinetics of stover liquefaction in recycled stover polyol

The purpose of this research was to study the kinetics of liquefaction of crop residues. The liquefaction of corn stover in the presence of ethylene glycol and ethylene carbonate using sulfuric acid as a catalyst was studied. It was found that the liquefaction yield was a function of ratio of solvent to corn stover, temperature, residence time, and amount of catalyst. Liquefaction of corn stover was conducted over a range of conditions encompassing residence times of 0–2.5 h, temperatures of 150–170°C, sulfuric acid concentrations of 2–4% (w/w), and liquefaction reagent/corn stover ratio of 1–3. The liquefaction rate constants for individual sets of conditions were examined using a first-order reaction model. Rate constant increased with the increasing of liquefaction temperature, catalyst content, and liquefaction reagent/corn stover ratio. Reuse of liquefied biomass as liquefying agent was also evaluated. When using recycled liquefied biomass instead of fresh liquefaction reagent, the conversion is reduced. It appeared that 82% of liquefaction yield was achieved after two times of reuse.     

中国沿海地质环境与区域持续发展的若干问题探讨

本文分析了中国沿海岩石圈动力学的基础特征, 指出中国东部沿海地质环境与灾害存在南北分异的格局, 阐述了沿海区域工程地质环境的基本规律, 并通过全球及中国近百年海平面变化, 以及人类工程活动对河口海岸地质环境影响的分析, 对沿海地区未来的地质环境与灾害趋向做了初步评估, 并认为中国沿海21世纪的环境与发展将面临严峻的挑战, 特别是环渤海地区。最后, 对影响沿海区域发展的若干问题进行了初步探讨并提出了几点建议。