Supersaturation-Dependent Formation of Amyloid Fibrils

The supersaturation of a solution refers to a non-equilibrium phase in which the solution is trapped in a soluble state, even though the solute’s concentration is greater than its thermodynamic solubility. Upon breaking supersaturation, crystals form and the concentration of the solute decreases to its thermodynamic solubility. Soon after the discovery of the prion phenomena, it was recognized that prion disease transmission and propagation share some similarities with the process of crystallization. Subsequent studies exploring the structural and functional association between amyloid fibrils and amyloidoses solidified this paradigm. However, recent studies have not necessarily focused on supersaturation, possibly because of marked advancements in structural studies clarifying the atomic structures of amyloid fibrils. On the other hand, there is increasing evidence that supersaturation plays a critical role in the formation of amyloid fibrils and the onset of amyloidosis. Here, we review the recent evidence that supersaturation plays a role in linking unfolding/folding and amyloid fibril formation. We also introduce the HANABI (HANdai Amyloid Burst Inducer) system, which enables high-throughput analysis of amyloid fibril formation by the ultrasonication-triggered breakdown of supersaturation. In addition to structural studies, studies based on solubility and supersaturation are essential both to developing a comprehensive understanding of amyloid fibrils and their roles in amyloidosis, and to developing therapeutic strategies.     

ChemInform Abstract: Ring Structure Formation in Transition-Metal Nitrido Chlorides by Donor—Acceptor Formation.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

均四嗪衍生物结构、生成焓及爆轰性能的理论研究

运用DFT-w B97/6-31+G**方法对23种1,2,4,5-四嗪衍生物的几何结构、自然键轨道(NBO)和生成焓(EOF)进行研究,并在此基础上运用Kamlet-Jacobs方程估算衍生物的爆轰性能,得到其爆速在6.69~9.37 km/s之间;基于统计热力学,求得部分标题化合物在200~800 K温度范围内的热力学性质,随温度T升高,热容Cp、熵Sm及焓Hm逐渐增大。根据最小键级理论,C-R(取代基)键和N-R键可能是1,2,4,5-四嗪衍生物高温裂解的热引发键。综合分析,基团-NO2、-N3和-N=N-有助于提高四嗪衍生物的生成焓和爆轰性能,3,6-二硝基-1,2,4,5-四嗪和3,6-二偶氮基-二硝基-1,2,4,5-四嗪从能量、爆轰性能上可以作为高能量密度材料候选物。     

Co3O4 纳米棒的溶剂热合成及形成机理分析

Co3O4 nanorods have been synthesized at 160℃ for 10 h in the solution of oleic and n-cetane by an emulsion-solvothermal method using Co（NO3）2·6H2O as starting materials. The as-prepared product was characterized by X-ray powder diffraction（XRD）,transmission electron microscope（TEM）,and vibrating sample magnetometer（VSM）. The formation mechanism of the prepared product was analyzed based on formation of rod-like micelles of oleic acid. Cobalt ions can migrate into the micelle core for the nucleation and growth of Co3O4 . The results show that the as-prepared Co3O4 nanorods are with the average size 25×100 nm and in the cubic phase. The magnetic susceptibility meets about linearly with the applied magnetic field at room temperature,and the coercivity （Hc）and remanent magnetization（Ms）values of the product at room temperature are 353 Oe and 0.4 emu/g,respectively. This simple route is also expanded to synthesize other materials with the rod-like morphology.     

Doubling the Carbonate-Binding Capacity of Nanojars by the Formation of Expanded Nanojars

Anion binding and extraction from solutions is currently a dynamic research topic in the field of supramolecular chemistry. A particularly challenging task is the extraction of anions with large hydration energies, such as the carbonate ion. Carbonate-binding complexes are also receiving increased interest due to their relevance to atmospheric CO₂ fixation. Nanojars are a class of self-assembled, supramolecular coordination complexes that have been shown to bind highly hydrophilic anions and to extract even the most hydrophilic ones, including carbonate, from water into aliphatic solvents. Here we present an expanded nanojar that is able to bind two carbonate ions, thus doubling the previously reported carbonate-binding capacity of nanojars. The new nanojar is characterized by detailed single-crystal X-ray crystallographic studies in the solid state and electrospray ionization mass spectrometric (including tandem MS/MS) studies in solution.     

Formation of antiferromagnetic thiolate-bridged and sulfide-bridged complexes

Reactions of Cp₂Cr₂(SCMe₃)₂S (1) with rhenium complexes (CO)(NO)Re(PR₃)₂X₂ [R=Et, X=Cl (7a); R=Et, X=O₃SCF₃ (7b); R=OMe, X=O₃SCF₃ (7c)] containing strongly bound phosphine ligands and with Pd(PPrⁱ ₃)₂Cl₂ (8) containing bulky P donors were studied. The reaction between compounds1 and7a does not occur in various solvents within a temperature range of 22–80 °C. Interaction of1 with triflat derivatives7b and7c yields the paramagnetic tetrahedral homonuclear cationic cluster Cp₄Cr₄S₄ ⁺O₃SCF₃ ⁻ (10) and the binuclear methylated complex Cp₂Cr₂(SCMe₃)₂(SMe)⁺O₃SCF₃ ⁻ (11), respectively. The reaction of compound1 with8 affords the antiferromagnetic heteronuclear cluster Cp₂Cr₂(SCMe₃)S₂PdCl(PPrⁱ ₃) (12). The structure of the core of12 is analogous to the structures of the rhodium-containing complexes Cp₂Cr₂(μ-SCMe₃)(μ₃-S)₂RhL₂. Although compound8 reacts with Fe₃S₂(CO)₉ (5), the major products are the homometallic trinuclear clusters Fe₃S₂(CO)₈(PPrⁱ ₃) (14) (as a mixture of isomers) and Fe₃S₂(CO)₇(PPrⁱ ₃)₂ (15), whereas the heteronuclear complex (CO)₆Fe₂S₂Pd(PPrⁱ ₃)₂ (16) was found only in trace amounts. The reasons for the difference in the reactivities of the rhenium and palladium derivatives toward compounds1 and5 are discussed. The structures of complexes10 (two crystal modifications),11, 12, 15, and16 were established by X-ray structural analysis of the single crystals. For Part 4, see I. L. Eremenko, S. E. Nefedov, H. Berke, B. I. Kolobkov, and V. M. Novotortsev,Organometallics, 1995,14, 1132. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 141–152, January, 1997.     

Effect of Natural Deep Eutectic Solvents on trans-Resveratrol Photo-Chemical Induced Isomerization and 2,4,6-Trihydroxyphenanthrene Electro-Cyclic Formation

trans-Resveratrol is a natural bioactive compound with well-recognized health promoting effects. When exposed to UV light, this compound can undergo a photochemically induced trans/cis isomerization and a 6π electrochemical cyclization with the subsequent formation of 2,4,6-trihydroxyphenanthrene (THP). THP is a potentially harmful compound which can exert genotoxic effects. In this work we improved the chromatographic separation and determination of the two resveratrol isomers and of THP by using a non-commercial pentafluorophenyl stationary phase. We assessed the effect of natural deep eutectic solvents (NaDES) as possible photo-protective agents by evaluating cis-resveratrol isomer and THP formation under different UV-light exposure conditions with the aim of enhancing resveratrol photostability and inhibiting THP production. Our results demonstrate a marked photoprotective effect exerted by glycerol-containing NaDES, and in particular by proline/glycerol NaDES, which exerts a strong inhibitory effect on the photochemical isomerization of resveratrol and significantly limits the formation of the toxic derivative THP. Considering the presence of resveratrol in various commercial products, these results are of note in view of the potential genotoxic risk associated with its photochemical degradation products and in view of the need for the development of green, eco-sustainable and biocompatible resveratrol photo-stable formulations.     

Synthesis and Metal Complex Formation of Nitrogen-Oxygen Donor Macrocyclic Ligands

Reduction of 2,3:9,10-dibenzo-5,12-diaza-1,8-dioxacylotetradecane-5,11-diene( 1 ) with sodium borohydride in ethanol generates 2,3:9,10-dibenzo-5,12-diaza-1,8-dioxacyclotetradecane( 2 ) in high yield. The macrocyclic ligand 2,3:9,10-dibenzo-5,12-diaza-1,8-dioxacyclotetradecane-N,N′-diacetic acid ( 3 ) has been synthesized and characterized. In addition, reaction of ( 2 ) with an excess of acrylonitrile gives 2,3:9,10-dibenzo-5,12-diaza-1,8-dioxacyclotetradecane-N,N′-di(2-cyanoethyl) ( 4 ). Several new complexes of these ligands with nickel(II), copper(II) and cobalt(II) have been prepared and identified. The structures of these complexes are proposed on the basis of elemental analysis, ¹H, ¹³C-NMR, IR, UV-VIS spectra, magnetic susceptibility and conductivity data.     

β-酪蛋白淀粉样纤维沉淀的形成及影响因素

利用硫磺素T(ThT)荧光分析法和透射电子显微镜检测β-酪蛋白形成淀粉样纤维沉淀(Fibril)的动力学过程, 研究了磷脂和硫酸肝素对其Fibril形成的影响. 实验结果表明, β-酪蛋白在65 ℃下, pH值为5.4~9.0的范围内, 加热252 h以上, 并未形成Fibril, 说明β-酪蛋白是一种很好的分子伴侣, 在高温、 弱酸和弱碱条件下均不形成淀粉样纤维沉淀. 甘油磷酸胆碱D6PC和D9PC可以显著地促进β-酪蛋白的Fibril的形成, 说明一定条件下蛋白质可能与细胞膜之间存在相互作用而导致其二级构象的转变. 硫酸肝素对β-酪蛋白形成Fibril具有促进作用, 在炎症组织中, 硫酸肝素表达量的增加有可能促进β-酪蛋白形成Fibril, 说明乳腺炎与乳腺中的Corpora Amylacea的形成存在一定的联系.     

Formation of Lutein, β-Carotene and Astaxanthin in a Coelastrella sp. Isolate

In this study, the effect of media composition, N/P ratio and cultivation strategy on the formation of carotenoids in a Coelastrella sp. isolate was investigated. A two-stage process utilizing different media in the vegetative stage, with subsequent re-suspension in medium without nitrate, was employed to enhance the formation of carotenoids. The optimal growth and carotenoid content (β-carotene and lutein) in the vegetative phase were obtained by cultivation in M-8 and BG11 media. Use of a N/P ratio of 37.5 and low light intensity of 40 μmol m⁻² s⁻¹ (control conditions) led to optimal biomass production of up to 1.31 g L⁻¹. Low concentrations of astaxanthin (maximum of 0.31 wt. %) were accumulated under stress conditions (nitrogen-deficient medium containing 1.5 % of NaCl and light intensity of 500 μmol m⁻² s⁻¹), while β-carotene and lutein (combined maximum of 2.12 wt. %) were produced under non-stress conditions. Lipid analysis revealed that palmitic (C16:0) and oleic (C18:1) constituted the main algal fatty acid chains (50.2 ± 2.1% of the total fatty acids), while esterifiable lipids constituted 17.2 ± 0.5% of the biomass by weight. These results suggest that Coelastrella sp. could also be a promising feedstock for biodiesel production.     

Base-catalyzed Formation of Enamines from β,β-Dicyanostyrene Derivatives with N-Bromosaccharin

A new method for the synthesis of functional enamines from β,β-dicyanostyrene derivatives and N-bromosaccharin(NBSA) was developed. In the presence of Na₂CO₃, the the reaction of β,β-dicyanostyrene derivatives with NBSA can generate the corresponding enamines smoothly in a mixed solvent of dichloromethane and N,N-dimethylformamide (DMF)(volume ratio 1:1) at 50℃. The reaction of 14 kinds of β,β-dicyanostyrene derivatives with NBSA was investigated. Screened olefins afforded the corresponding enamines in good to excellent yields(up to 94%), indicating that the method has a wide adaptability for the substrate. The catalyst used is inexpensive and stable for storage. The amino groups of all products in their structures are on the α-position of products, revealing the reaction has an excellent regioselectivity. The possible pathway involving aminobromination of β,β-dicyanostyrene derivative with NBSA first and then elimination of HBr process in one pot has been proposed. The structures of all products were confirmed by ¹H NMR, ¹³C NMR and HRMS analysis.     

ChemInform Abstract: Gaseous Fluorodiazonium Ions. Experimental and Theoretical Study on Formation and Structure of FN+ 2.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Formation and characterization of PEDOT-modified Nafion 117 membranes

Nafion 117 membranes were modified with a thin film of poly(3,4-ethylenedioxythiophene) (PEDOT) by a diffusion-controlled polymerization process using a two-compartment cell with the monomer EDOT on one side of the membrane and the oxidizing agent FeCl₃ on the other side. The methanol permeability and ion conductivity of the composite PEDOT/Nafion membranes were measured as a function of temperature and polymerization time by DC and AC polarization measurements in four-electrode technique and permeation experiments in a diaphragm cell. These modified membranes have lower methanol permeability while maintaining adequate conductivity.     

液态金属Al快速凝固过程中团簇结构的形成特性

A simulation study on the formation characteristics of clusters in a large-scale liquid Al system consisting of 105 atoms has been performed by the molecular dynamics method. And a cluster-type index method（CTIM）has been used to describe the structural configurations of various clusters. The results demonstrate that the icosahedron clusters（12 0 12 0）and their combinations play the most important role in the microstructure transition. The nanoclusters（containing up to 104 atoms）have been formed by combining some middle clusters which have been formed by combining smaller basic clusters. The structures of these nano-clusters are very different from those of nano-clusters obtained by evaporation,ionic spray methods,and so on. The latter is formed by the multi-shell crystals accumulated with an atom as the center and the surrounding atoms arranged according to octahedron configuration. The center atoms of these basic clusters are bond-connected each other with the linear or twisting mode. The corners of the nano-cluster just could become the starting points of the dendrite growth in the solidification processes of liquid metals.