Tailoring 3,3′‐Dihydroxyisorenieratene to Hydroxystilbene: Finding a Resveratrol Analogue with Increased Antiproliferation Activity and Cell Selectivity

Four novel compounds were designed by “tailoring” 3,3′‐dihydroxyisorenieratene (a natural carotenoid) based on an isoprene unit retention truncation strategy. Among them, the smallest molecule 1 (2,3,6,2′,3′,6′‐hexamethyl‐4,4′‐dihydroxy‐trans‐stilbene) was concisely synthesized in a one‐pot Stille–Heck tandem sequence, and surfaced as a promising lead molecule in terms of its selective antiproliferative activity mediated by blocking the NCI‐H460 cell cycle in G1 phase. Additionally, theoretical calculations and cell uptake experiments indicate that the unique polymethylation pattern of compound 1 significantly induces a conformational change shift out of planarity and increases its cell uptake and metabolic stability. The observation should be helpful to rationally design resveratrol‐inspired antiproliferative agents.     

Well‐Defined Iron Complexes as Efficient Catalysts for “Green” Atom‐Transfer Radical Polymerization of Styrene,Methyl Methacrylate,and Butyl Acrylate with Low Catalyst Loadings and Catalyst Recycling

Environmentally friendly iron(II) catalysts for atom‐transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N‐trialkylated‐1,4,9‐triazacyclononane (R₃TACN) ligands. Two types of structures were confirmed by crystallography: “[(R₃TACN)FeX₂]” complexes with relatively small R groups have ionic and dinuclear structures including a [(R₃TACN)Fe(μ‐X)₃Fe(R₃TACN)]⁺ moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R₃TACN)FeX₂]_n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl)₃TACN}FeBr₂] ( 4 b ) was the best catalyst for the well‐controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4 b (59 ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4 b (117 ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28 ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined.     

Cellulosic nanocomposite membranes from hydroxypropyl cellulose reinforced by cellulose nanocrystals

Cellulosic nanocomposite membranes were prepared by incorporation of cellulose nanocrystals (CNCs) into a hydroxypropyl cellulose (HPC) matrix using a mixing/evaporation technique. CNCs were obtained from filter paper using the sulfuric acid hydrolysis method with the aid of ultrasonication. The relationship between the microstructure and mechanical properties of the CNCs/HPC nanocomposite membranes was studied. Scanning electron microscopy showed that the CNCs were well dispersed in the HPC matrix, and the fracture surface demonstrated a fibrous characteristic. With increasing CNCs content, the tensile strength and Young’s modulus of the CNCs/HPC nanocomposite membranes gradually increased. At 5 wt% content of CNCs, the strength was increased by 525 % and the Young’s modulus by 124 % compared with pure HPC membrane. Moreover, the effect of the phase change of HPC on the mechanical properties of the CNCs_5wt%/HPC nanocomposite membranes and the corresponding mechanism were also studied.     

Study on the interaction between urea and cellulose by combining solid-state 13C CP/MAS NMR and extended Hückel charges

In this article, solid-state ¹³C CP/MAS NMR combined with extended Hückel charges was applied to investigate the interaction between urea and cellulose in the NaOH/urea aqueous solvent system. Direct experimental evidence was provided to support the interaction between urea and cellulose. The solid-state ¹³C CP/MAS NMR results revealed that complicated complexes are formed by urea, NaOH and cellulose in the solution. Excess urea exists in a free state, which explains why 7 wt% NaOH/12 wt% urea/81 wt% H₂O is the optimal ratio selection to dissolve cellulose. Based on the correlation in which the computed extended Hückel charge on carbon of urea is approximately inversely proportional to its ¹³C chemical shift, a possible interaction model of cellulose, NaOH and urea was proposed. Interactions exist between any two of urea, NaOH and cellulose, which results in the cellulose chain being surrounded by NaOH and urea molecules. NaOH and urea may be in the same surface layer of cellulose chains.     

Novel hydrothermal carbonization of cellulose catalyzed by montmorillonite to produce kerogen-like hydrochar

The conversion of cellulose to petroleum-like fuel is a very challenging yet attractive route to developing biomass-to-fuel technology. Many attempts have been made in liquefaction, pyrolysis and gasification of cellulose to produce fuels or intermediate chemicals. Previous studies indicate that these processes are tough. Hence, the present work is concerned with the development of new technologies for the conversion of cellulose into materials which are analogies to the precursor of petroleum. Montmorillonite-catalyzed hydrothermal carbonization of microcrystalline cellulose for the production of kerogen-like hydrochar under mild conditions was investigated. It was revealed that the hydrothermal carbonization of microcrystalline cellulose alone resulted in hydrochar with type III kerogen-like structure, whereas in the presence of montmorillonite, the hydrothermal carbonization of microcrystalline cellulose yielded a hydrochar-mineral complex, of which the isolated organic fraction was oil-prone type II kerogen-like structure. Results suggested that further improved montmorillonite-aided biomass conversion to more oil-prone kerogen-like solid products could be an alternative efficient route to obtain biofuel and chemicals.     

气相色谱法分析植物油中的脂肪酸

确定了植物油脂肪酸进行气相色谱分析前合适的样品处理步骤及条件和最佳的气相色谱分析方法,对6种食用植物油进行了处理分析。样品前处理主要步骤及条件:约0.045g样品,先加入萃取剂苯-石油醚(2:1,V/V)2mL;然后用2mL 0.4mol/L KOH-CH3OH溶液作酯化剂,于60℃酯化30 min后,再用1.5mL 15%BF3-CH3OH(w t%)溶液作酯化剂,于50℃酯化40 min。由食用植物油样品甲酯化后进行GC分析可知,各类植物油中的脂肪酸均能得以甲酯化进行准确的定性、定量分析。     

毛细管电泳-电化学发光法测定石蒜鳞茎中的石蒜碱

建立了毛细管电泳-电化学发光(CE-ECL)检测石蒜碱的方法。探讨了检测电位、分离缓冲液pH和浓度、分离电压、进样电压及进样时间等因素对石蒜碱分离检测的影响。在最佳实验条件下,石蒜碱含量在0.03~2μg/mL范围内与其峰面积呈良好的线性关系,相关系数为0.9995,检出限为0.005μg/mL(S/N=3)。对0.8μg/mL石蒜碱进行7次平行实验,其迁移时间、峰高和峰面积的RSD分别为1.7%,5.2%和5.6%。方法应用于石蒜鳞茎中石蒜碱的测定,加标回收率为92.2%~98.6%。     

陕南茶叶稀土元素产地特征研究

为了掌握陕南茶叶中稀土元素含量和分布状况,并利用稀土元素对茶叶产地进行判别,采用ICP-MS法对陕南地区44个茶叶样品中16种稀土元素进行了测定。结果表明:茶叶中不同稀土元素含量差异较大,其中La,Ce,Nd含量较高,平均含量分别为124.81,172.13,87.20μg·kg-1;茶叶样品中稀土氧化物含量范围为200.32~1558.35μg·kg-1,总体上呈东高西低趋势,且均低于国家规定限量;茶叶中稀土元素随地域变化表现出不同分布特征,但具有相似的丰度模式;利用主成分分析将茶叶稀土元素归结为轻稀土组和重稀土组,间接地证明轻稀土元素和重稀土元素在从土壤到茶叶迁移过程中仍存在着差异;聚类分析结果表明,稀土元素可作为陕南茶叶产地判别的重要指标。     

Dynamic and Quantitative Control of the DNA‐Mediated Growth of Gold Plasmonic Nanostructures

Reproducible and controllable growth of nanostructures with well‐defined physical and chemical properties is a longstanding problem in nanoscience. A key step to address this issue is to understand their underlying growth mechanism, which is often entangled in the complexity of growth environments and obscured by rapid reaction speeds. Herein, we demonstrate that the evolution of size, surface morphology, and the optical properties of gold plasmonic nanostructures could be quantitatively intercepted by dynamic and stoichiometric control of the DNA‐mediated growth. By combining synchrotron‐based small‐angle X‐ray scattering (SAXS) with transmission electron microscopy (TEM), we reliably obtained quantitative structural parameters for these fine nanostructures that correlate well with their optical properties as identified by UV/Vis absorption and dark‐field scattering spectroscopy. Through this comprehensive study, we report a growth mechanism for gold plasmonic nanostructures, and the first semiquantitative revelation of the remarkable interplay between their morphology and unique plasmonic properties.     

Asymmetric Cascade Reaction to Allylic Sulfonamides from Allylic Alcohols by Palladium(II)/Base‐Catalyzed Rearrangement of Allylic Carbamates

A regio‐ and enantioselective tandem reaction is reported capable of directly transforming readily accessible achiral allylic alcohols into chiral sulfonyl‐protected allylic amines. The reaction is catalyzed by the cooperative action of a chiral ferrocene palladacycle and a tertiary amine base and combines high step‐economy with operational simplicity (e.g. no need for inert‐gas atmosphere or catalyst activation). Mechanistic studies support a Pd^II‐catalyzed [3,3] rearrangement of allylic carbamates—generated in situ from the allylic alcohol and an isocyanate—as the key step, which is followed by a decarboxylation.