The synthesis and the bulk rheological properties of the highly-branched block polyethers

Several kinds of highly-branched block polyethers were synthesized via anion ring-opening polymerization of propylene oxide (PO) and ethylene oxide (EO), using phenol-amine resin (PA) as the initiator. The rheological properties determined by rotational rheometer all followed the regular rules of polymer systems: under a certain conditions, the bulk polyethers were pseudoplastic and non-Newtonian fluid, and with the increasing of the shear rate and temperature, the apparent viscosity of the block copolymers were reduced. In addition, modulus determination showed that such polyether molecules presented preferable viscosity compared to the elasticity, meanwhile, storage modulus, loss modulus and compound viscosity all decreased with the increasing of temperature. Storage modulus and loss modulus increased along with the scanning frequency increasing. But compared with the same kind of linear polymers, the significant difference was the low melt viscosity, which attributed to the special three-dimension space structure hindering the entanglement of chains. Furthermore, the rheological properties among the several block polyethers showed differences obviously. In other words, the number of block and the content of EO all have a significant effect on the rheological properties, specifically, the modulus will increase with the increasing of the block number and the EO content.     

Synthesis,characterization and properties of novel cellulose derivatives containing phosphorus: cellulose diphenyl phosphate and its mixed esters

Using ionic liquid 1-allyl-3-methylimidazolium chloride as reaction medium, a series of novel cellulose esters containing phosphorus including cellulose diphenyl phosphate (C-Dp) and cellulose acetate (CA)–diphenyl phosphate mixed esters was synthesized homogeneously. The degree of substitution was well controlled by altering reaction conditions, such as the molar ratio of the acylating reagents/anhydroglucose unit and reaction time. The structure and thermal properties of cellulose esters were characterized by FTIR, NMR, wide-angle X-ray powder diffraction and differential scanning calorimetry. All the products possessed excellent solubility in some common organic solvents, and transparent films of cellulose esters were obtained by solution casting. In contrast to C-Dp, CA–diphenyl phosphate mixed esters showed clear glass transitions. More interestingly, these cellulose mixed esters exhibited thermoplastic behavior and could be processed by traditional melt processing methods.     

Tough nanocomposite hydrogels from cellulose nanocrystals/poly(acrylamide) clusters: influence of the charge density,aspect ratio and surface coating with PEG

Cellulose-derived materials are usually characterized by sophisticated structures, leading to unique and multiple functions, which have been a source of inspiration for the fabrication of a wide variety of nanocomposites. Cellulose nanocrystals/poly(acrylamide) (CNCs/PAM) nanocomposite hydrogels were synthesized via in situ polymerization in the CNC suspension. The cellulose from pulp fiber under different sulfuric acid hydrolysis conditions, examined by conductometric titration and transmission electron microscopy, was applied to study how the effects of the surface charge and aspect ratio affect CNCs’ mechanical reinforcement in nanocomposites. The results indicated that the higher surface charge concentration resulted in better dispersibility in aqueous suspension, leading to a more efficient energy dissipation process. The CNC reinforcement behavior followed the percolation model where the greater aspect ratio of CNC contributed to higher mechanical properties. The preferential adsorption of poly(ethylene glycol) (PEG) on the CNC surface was characterized by zeta potential measurements where the fracture strength and fracture elongation of nanocomposites decreased with increasing PEG concentration. The adsorption of PEG on the CNC surface occupied the active sites for polymer chain propagation, which hindered the PAM cross-linking effect on the CNC surface and decreased the cross-linking density of the network.     

液相色谱-电感耦合等离子体质谱联用研究两种铂类化合物的稳定性及分解产物

基于液相色谱-电感耦合等离子体质谱联用方法,研究了低浓度奈达铂在纯水、9 g/L NaCl溶液和人血浆中的稳定性和分解产物。结果表明,72 h内奈达铂在纯水和血浆中稳定,在9 g/L NaCl溶液中易分解为顺铂。基于凝胶色谱-电感耦合等离子质谱联用方法,研究了低浓度顺式-二碘-(1R,2R)-(-)-1,2-环己二胺合铂(II)(DPI)在纯水、9 g/L NaCl溶液和人血浆中的稳定性和分解产物。结果表明,DPI在3种体系中均不稳定,方法检出限为0.4ng/mL(以铂计)。研究了DPI在9 g/L NaCl溶液中的水解过程,通过同时分析铂元素和碘元素形态确定了水解机理。     

纳米激光粒度仪在生物药品团聚物测试中的应用

探讨了纳米激光粒度仪测定生物药品团聚物质量浓度的方法。以SALD–7500nano颗粒测试仪为例,介绍其在测量纳米级颗粒物粒度范围方面的应用。通过进一步分析颗粒浓度与光强度成正比的关系获得以质量浓度形式给出的粒度分布数据。通过牛血清蛋白(BSA)团聚物测量的实例,验证了颗粒物质量浓度的测试方法。该方法可用于生物制药领域对团聚物的监控测量以及评价药品药效、安全性能等。     

A Rapidly Reversible Chemical Dimerizer System to Study Lipid Signaling in Living Cells

Chemical dimerizers are powerful tools for non‐invasive manipulation of enzyme activities in intact cells. Here we introduce the first rapidly reversible small‐molecule‐based dimerization system and demonstrate a sufficiently fast switch‐off to determine kinetics of lipid metabolizing enzymes in living cells. We applied this new method to induce and stop phosphatidylinositol 3‐kinase (PI3K) activity, allowing us to quantitatively measure the turnover of phosphatidylinositol 3,4,5‐trisphosphate (PIP₃) and its downstream effectors by confocal fluorescence microscopy as well as standard biochemical methods.     

Silver‐Catalyzed Decarboxylative Trifluoromethylthiolation of Aliphatic Carboxylic Acids in Aqueous Emulsion

A silver‐catalyzed decarboxylative trifluoromethylthiolation of secondary and tertiary carboxylic acids under mild conditions tolerates a wide range of functional groups. The reaction was dramatically accelerated by its performance in an aqueous emulsion, which was formed by the addition of sodium dodecyl sulfate to water. It was proposed that the radical, which was generated from the silver‐catalyzed decarboxylation in the “oil‐in‐water” droplets, could easily react with the trifluoromethylthiolating reagent to form the product.     

Redox Chemistry of a Hydroxyphenyl‐Substituted Borane

Chemical reduction of a hydroxyphenyl‐substituted borane triggers a sequential electron‐ and intramolecular hydrogen‐atom‐transfer process to afford a hydridoborate phenoxide dianion. On the other hand, hydrogen‐atom abstraction of the borane leads to the isolation of a neutral borylated phenoxyl radical, which can be transformed to the corresponding benzoquinone borataalkene derivative by reduction with cobaltocene.     

Control of Three‐Dimensional Cell Adhesion by the Chirality of Nanofibers in Hydrogels

In the three‐dimensional (3D) extracellular matrix (ECM), the influence of nanofiber chirality on cell behavior is very important; the helical nanofibrous structure is closely related to the relevant biological events. Herein, we describe the use of the two enantiomers of a 1,4‐benzenedicarboxamide phenylalanine derivative as supramolecular gelators to investigate the influence of the chirality of nanofibers on cell adhesion and proliferation in three dimensions. It was found that left‐handed helical nanofibers can increase cell adhesion and proliferation, whereas right‐handed nanofibers have the opposite effect. These effects are ascribed to the mediation of the stereospecific interaction between chiral nanofibers and fibronectin. The results stress the crucial role of the chirality of nanofibers on cell‐adhesion and cell‐proliferation behavior in 3D environments.     

X‐Ray Emission Spectroscopy: A Spectroscopic Measure for the Determination of NO Oxidation States in Fe–NO Complexes

Extensive study of the electronic structure of Fe‐NO complexes using a variety of spectroscopic methods was attempted to understand how iron controls the binding and release of nitric oxide. The comparable energy levels of NO π* orbitals and Fe 3d orbitals complicate the bonding interaction within Fe? NO complexes and puzzle the quantitative assignment of NO oxidation state. Enemark–Feltham notation, {Fe(NO)_x}ⁿ, was devised to circumvent this puzzle. This 40‐year puzzle is revisited using valence‐to‐core X‐ray emission spectroscopy (V2C XES) in combination with computational study. DFT calculation establishes a linear relationship between ΔE_σ2s*‐σ2p of NO and its oxidation state. V2C Fe XES study of Fe? NO complexes reveals the ΔE_σ2s*‐σ2p of NO derived from NO σ_2s*/σ_2p→Fe_1s transitions and determines NO oxidation state in Fe? NO complexes. Quantitative assignment of NO oxidation state will correlate the feasible redox process of nitric oxide and Fe‐nitrosylation biology.