The Cytotoxic Effect of α-Synuclein Aggregates

Parkinson's disease is a neurodegenerative disorder involving a functional protein, α-synuclein, whose primary function is related to vesicle trafficking. However, α-synuclein is prone to form aggregates, and these inclusions, known as Lewy bodies, are the hallmark of Parkinson's disease. α-synuclein can alter its conformation and acquire aggregating capacity, forming aggregates containing β-sheets. This protein's pathogenic importance is based on its ability to form oligomers that impair synaptic transmission and neuronal function by increasing membrane permeability and altering homeostasis, generating a deleterious effect over cells. First, we establish that oligomers interfere with the mechanical properties of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) membrane, as demonstrated by nanoindentation curves. In contrast, nanoindentation revealed that the α-synuclein monomer's presence leads to a much more resistant lipid bilayer. Moreover, the oligomers’ interaction with cell membranes can promote lactate dehydrogenase (LDH) release, suggesting the activation of cytotoxic events.     

浓悬浮液中纳米SiO_2团聚体的渗透率

本文基于悬浮液中渗透性颗粒的短时扩散动力学理论,采用低相干光纤动态光散射方法,测量了相同粒径的纳米SiO_2团聚体在不同体积分数时的扩散系数,利用扩散系数随渗透率的变化关系得到纳米SiO_2团聚体的渗透率.结果表明:恒温条件下,具有一定渗透率的团聚体颗粒扩散得比硬球颗粒快.实验测量得到的团聚体渗透率与采用photoshop CS6对团聚体SEM图像进行处理计算得到的渗透率符合较好.     

Assessment of the surfactant-dye binding degree method as an alternative to the methylene blue method for the determination of anionic surfactants in aqueous environmental samples

The surfactant to dye binding degree (SDBD) method is proposed for the routine monitoring of anionic surfactants in aqueous environmental samples and their analytical features compared with those provided by the standard methylene blue (MB) method. This new analytical approach is based on the effect that anionic surfactants exert on the binding degree of the cationic surfactant didodecyldimethylammonium bromide (DDABr) to the anionic dye Coomassie Brilliant Blue G (CBBG). The formation of DDABr-CBBG aggregates is monitored photometrically. The analytical applicability of the proposed method was demonstrated by determining anionic surfactants in tap, river and swamp water, and raw and treated sewage. The mean recoveries obtained ranged between 99 and 101%. The SDBD method offers important advantages over the classical MB method: it is more sensitive, selective, precise, simple and rapid; the analytical response is independent of the molecular structure of the anionic surfactants, and the volume of sample required for analysis and the consumption of organic solvents are significantly reduced.     

基于任意形状颗粒集合二值图像的体积估算模型

基于任意形状颗粒集合的二值图像,提出了估计其体积(或质量)的方法.首先利用发光背景台面获取的颗粒灰度图像变换为相应的二值图像,得到颗粒的边界轮廓.然后再基于其边界信息,定义与颗粒形状特征相关的描述量,并将其无量纲化.将由此定义的无量纲参变量作为回归变量建立一个多元线性回归(multiple linear regression)模型用以估计颗粒集合的扁平度,进而估算颗粒体积.回归变量的系数由随机采样的501个样本颗粒(尺寸范围为4.75～25 mm)用误差最小平方和求得.将模型应用于由具有相似统计分布特征的其他颗粒集合,并将得到的体积估计值与其体积真实值相比较,实验结果显示模型的相对误差在±2%以内.     

Characterization of the light scattering by ensembles of randomly distributed soot aggregates

Soot particles formed in combustion processes commonly exist in the form of ensembles of randomly distributed aggregates of small, nearly spherical monomers. In this paper, these randomly distributed aggregates are numerically generated using a combination of the cluster–cluster aggregation algorithm with the Monte Carlo method. Moreover, an efficient and accurate numerical method is presented for characterizing the light scattering by these complex soot particles illuminated by plane wave and Gaussian beam. This method exploits the unique features of the hybrid finite element-boundary integral method and, more importantly, the unique features of soot aggregates. It is designed in such a manner that it first decomposes the original problem into many sub-regions, where each primary particle is regarded as a sub-region, and then it employs the edge-based finite element method to deal with each sub-region. The sub-regions communicate through the near-field Green’s function. To reduce computational burdens, an iterative domain decomposition method in combination with parallel conjugate gradient method is adopted to solve the coupling system of equations. As an illustration, we present some of our preliminary numerical results. The results are expected to provide useful insights into the optical properties of soot particles formed in combustion processes.     

Indirect magnetic interaction in the “net fractal” systems

A localized spin system of fractal symmetry with indirect exchange between them is considered. We define a specific class of fractals as the “net fractals” which display multidimensional logarithmic periodicity. Basing on this property we model the effective indirect exchange interaction by the conventional RKKY exchange with the logarithmic coordinates playing role of the real space ones. Finally, we discuss the case of non-ideal “net fractals” in which fractional dynamics of the electrons is expected. In this case we show that RKKY exchange integrals are given by the formulas derived under assumption that a system has a fractional spectral dimension.     

Concentration controlled multilevel self‐assembly of 3‐armed poly(ethylene glycol)‐b‐poly(ε‐caprolactone) block copolymers investigated by AFM

Concentration dependent morphology of 3‐armed poly(ethylene glycol)‐b‐poly(ε‐caprolactone) copolymer aggregates in aqueous system was investigated by atomic force microscopy (AFM). The AFM results show that, at a low concentration, 4 × 10^?5 g/mL, spherical micelles occur, and unmicellized molecules are not distributed homogeneously in the copolymer aqueous solution. Unequal outspread clusters composed of wormlike aggregates are formed at a moderate copolymer concentration, 4 × 10^?4 g/mL, those wormlike aggregates are orderly packed in the clusters. At a high concentration of 0.05 g/mL, the copolymer aqueous system is indeed a gel at room temperature, outspread clusters of wormlike aggregates join together to forma network structure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1412–1418, 2008     

Catalytic oxidation of soot particulates over MnOx-CeO2 oxides prepared by complexation-combustion method

MnOx-CeO2 oxides prepared by complexation-combustion method were used for soot oxidation. The highest conversion rate of soot was obtained on a MnOx-CeO2 oxide prepared under mild acid condition of pH = 4, where the oxidation temperature corresponding to maximum activity was decreased more than 150℃ compared with that of un-catalytic soot oxidation. The structure and property of the catalysts were investigated by X-ray powder diffraction (XRD) and temperature programmed reduction (TPR). The results indicate...     

A label-free differential proteomic analysis of mouse bronchoalveolar lavage fluid exposed to ultrafine carbon black

Ultrafine carbon black (ufCB) is a potential hazard to the lung. It causes changes in protein expression and it increases alveolar-capillary permeability in the lung. Label-free quantitative proteomic methods allow a sensitive and accurate analytical method for identifying and quantifying proteins in a protein mixture without chemically modifying the proteins. We used a label-free quantitative proteomic approach that combined and aligned LC-MS and LC-MS/MS spectra to analyze mouse bronchoalveolar lavage fluid (BALF) protein changes associated with exposure to ufCB. We developed a simple normalization method for quantification without spiking the internal standard. The intensities of unchanged peptides were used as normalization factors based on a statistical method to avoid the influence of peptides changed because of ufCB. LC-MS/MS spectra and then database searching were used to identify proteins. The relative abundances of the aligned peptides of identified proteins were determined using LC-MS spectra. We identified 132 proteins, of which 77 are reported for the first time. In addition, the expression of 15 inflammatory proteins and surfactant-associated proteins was regulated (i.e., 7 upregulated and 8 downregulated) compared with the controls. Several proteins not previously reported provide complementary information on the proteins present in mouse BALF, and they are potential biomarkers for the understanding of mechanisms involved in ufCB-induced lung disorders hypothesize that using the label-free quantitative proteomic approach introduced here is well suited for more rigorous, large-scale quantitative analysis of biological samples. We hypothesize that this label-free quantitative proteomic approach will be suited for a large-scale quantitative analysis of biological samples.     

Hydrogen‐bonded nucleophile effects in ANS: the reactions of 1‐chloro and 1‐fluoro‐2,4‐dinitrobenzene with 2‐guanidinobenzimidazole, 1‐(2‐aminoethyl)piperidine and N‐(3‐aminopropyl)morpholine in aprotic solvents

The kinetics of the reactions of 2,4‐dinitrofluorobenzene (DNFB) and 2,4‐dinitrochlorobenzene (DNClB) with 2‐guanidinobenzimidazole (2‐GB) at 40 ± 0.2 °C in dimethylsulphoxide (DMSO), toluene, and in toluene–DMSO mixtures, and with 1‐(2‐aminoethyl)piperidine (2‐AEPip) and N‐(3‐aminopropyl)morpholine (3‐APMo) in toluene at 25 ± 0.2 °C were studied under pseudo first‐order conditions. For the reactions of 2‐GB carried out in pure DMSO, the second‐order rate coefficients were independent of the amine concentration. In contrast, the reactions of 2‐GB with DNFB in toluene, showed a kinetic behaviour consistent with a base‐catalysed decomposition of the zwitterionic intermediate. These results suggest an intramolecular H‐bonding of 2‐GB in toluene, which is not present in DMSO. To confirm this interpretation the reactions were studied in DMSO–toluene mixtures. Small amounts of DMSO produce significant increase in rate that is not expected on the basis of the classical effect of a dipolar aprotic medium; the effect is consistent with the formation of a nucleophile/co‐solvent mixed aggregate. For the reactions of 3‐APMo with both substrates in toluene, the second‐order rate coefficients, k_A, show a linear dependence on the [amine]. 3‐APMo is able to form a six‐membered ring by an intramolecular H‐bond which prevents the formation of self‐aggregates. In contrast, a third order was observed in the reactions with 2‐AEPip: these results can be interpreted as a H‐bonded homo‐aggregate of the amine acting as a better nucleophile than the monomer. Most of these results can be well explained within the frame of the ‘dimer nucleophile’ mechanism. Copyright © 2010 John Wiley & Sons, Ltd.