Label-free fluorescent detection of protein kinase activity based on the aggregation behavior of unmodified quantum dots

Herein, we present a novel label-free fluorescent assay for monitoring the activity and inhibition of protein kinases based on the aggregation behavior of unmodified CdTe quantum dots (QDs). In this assay, cationic substrate peptides induce the selective aggregation of unmodified QDs with anionic surface charge, whereas phosphorylated peptides do not. Phosphorylation by kinase alters the net charge of peptides and subsequently inhibits the aggregation of unmodified QDs, causing an enhanced fluorescence with a 45 nm blue-shift in emission and a yellow-to-green emission color change. Hence the fluorescence response allows this QD-based method to easily probe kinase activity by a spectrometer or even by the naked eye. The feasibility of the method has been demonstrated by sensitive measurement of the activity of cAMP-dependent protein kinase (PKA) with a low detection limit (0.47 mU μL(-1)). On the basis of the fluorescence response of QDs on the concentration of PKA inhibitor H-89, the IC(50) value, the half maximal inhibitory concentration, was estimated, which was in agreement with the literature value. Moreover, the system can be applicable to detect the Forskolin/3-isobutyl-1-methylxantine (IBMX)-stimulated activation of PKA in cell lysate. Unlike the existing QD-based enzyme activity assays in which the modification process of QDs is essential, this method relies on unmodified QDs without the requirement of peptide labeling and QDs' modification, presenting a promising candidate for cost-effective kinase activity and inhibitor screening assays.     

Polymer-functionalized silica nanosphere labels for ultrasensitive detection of tumor necrosis factor-alpha

A signal amplification strategy for sensitive detection of tumor necrosis factor-alpha (TNF-α) using quantum dots (QDs)-polymer-functionalized silica nanosphere as the label was proposed. In this approach, silica nanospheres with good monodispersity and uniform structure were employed as carriers for surface-initiated atom transfer radical polymerization of glycidyl methacrylate, which is readily available functional monomer that possessing easily transformable epoxy groups for subsequent CdTe QDs binding through ring-open reaction. Then, human anti rabbit TNF-α antibody (anti-TNF-α, Ab2, served as a model protein) was bonded to CdTe QDs-modified silica nanospheres coated with polymer to obtain QDs-polymer-functionalized silica nanosphere labels (Si/PGMA/QD/Ab2). The Si/PGMA/QD/Ab2 labels were attached onto a gold electrode surface through a subsequent "sandwich" immunoreaction. This reaction was confirmed by scanning electron microscopy (SEM) and fluorescence microscopic images. Enhanced sensitivity could be achieved by an increase of CdTe QD loading per immunoassay event, because of a large number of surface functional epoxy groups offered by the PGMA. As a result, the electrochemiluminescence (ECL) and square-wave voltammetry (SWV) measurements showed 10.0- and 5.5-fold increases in detection signals, respectively, in comparison with the unamplified method. The detection limits of 7.0 pg mL(-1) and 3.0 pg mL(-1) for TNF-α antibodies by ECL and SWV measurements, respectively, were achieved. The proposed strategy successfully demonstrated a simple, reproducible, specific, and potent method that can be expanded to detect other proteins and DNA.     

MPIC: A High-Throughput Analytical Method for Multiple DNA Targets

We describe the development of a novel combined approach for high-throughput analysis of multiple DNA targets based on multiplex Microdroplet PCR Implemented Capillary gel electrophoresis (MPIC), a two-step PCR amplification strategy. In the first step, the multiple target DNAs are preamplified using bipartite primers attached with universal tail sequences on their 5'-ends. Then, the preamplified templates are compartmentalized individually in the microdroplet of the PCR system, and multiple targets can be amplified in parallel, employing primers targeting their universal sequences. Subsequently, the resulting multiple products are analyzed by capillary gel electrophoresis (CGE). Using genetically modified organism (GMO) analysis as a model, 24 DNA targets can be simultaneously detected with a relative limit of detection of 0.1% (w/w) and absolute limit of detection of 39 target DNA copies. The described system provides a promising alternative for high-throughput analysis of multiple DNA targets.     

Surface-enhanced vibrational spectroscopy of adsorbates on microemulsion synthesized gold nanoparticles

Very small (<10 nm) monodisperse gold nanoparticles (AuNPs) coated with a monolayer of decanethiol were prepared and their surface-enhanced infrared absorption (SEIRA) spectra were measured in the transmission mode. The AuNPs were prepared by the borohydride reduction of HAuCl(4) inside reverse micelles that were made by adding water to a hexane solution of sodium bis(2-ethylhexyl)sulfosuccinate (AOT). The gold nanoparticles were then stabilized by the addition of decanethiol. Subsequent addition of p-nitrothiophenol both facilitated the removal of excess AOT and showed that the gold surface was completely covered by the decanethiol. SEIRA spectra of decanethiol on gold particles prepared in AOT microemulsions were about twelve times more intense than corresponding layers on gold produced by electroless deposition and gave a significantly less noisy spectrum compared to the corresponding surface-enhanced Raman spectrum. The surface-enhanced Raman scattering (SERS) spectra of the same samples showed that the most intense spectrum was obtained from gold nanoparticles with a mean diameter of 2.5 nm. This result is in contrast to previous statements that SERS spectra could only be obtained from particles larger than 10 nm.     

Does temperature enhance acute mortality effects of ambient particle pollution in Tianjin City, China

Only a few epidemiological studies have explored whether there were interactive effects between temperature and particulate matter < 10 μm in aerodynamic diameter (PM₁₀) on mortality, especially in Asian countries. The present study used time-series analysis to explore the modification effects of temperature on the association between PM₁₀ and the cause-specific mortality for cardiovascular, respiratory, cardiopulmonary, stroke and ischemic heart diseases (IHD), as well as non-accidental mortality in Tianjin between 2007 and 2009. Results showed that the PM₁₀ effects were stronger on high temperature level days than that on low temperature level days. The interactions between PM₁₀ and temperature were statistically significant on cardiovascular, cardiopulmonary, and IHD mortalities. The effect estimates per 10-μg/m³ increase in PM₁₀ concentrations at the moving average of lags 0 and 1 day in high temperature level were 0.62% (95% confidence interval (CI): 0.27, 0.97) for non-accidental, 0.92% (0.47, 1.36) for cardiovascular, 0.74% (− 0.33, 1.82) for respiratory, 0.89% (0.47, 1.32) for cardiopulmonary, 0.65% (0.00, 1.31) for stroke and 1.20% (0.63, 1.78) for IHD mortalities. In addition, the PM₁₀ effects on high temperature level days were stronger on older (≥ 65 years) compared with younger subjects (< 65 years). This suggests that the modifying effects of the temperature should be considered when analyzing health impacts of ambient PM₁₀.     

Sub-micrometer particulate air pollution and cardiovascular mortality in Beijing, China

Background

While the link between particulate matter and cardiovascular mortality is well established, it is not fully investigated and understood which properties of the aerosol might be responsible for the health effects, especially in polluted mega-city areas.

Objectives

Our goal was to explore the association between daily cardiovascular mortality and different particle metrics in the sub-micrometer range in Beijing, China.

Methods

We obtained daily counts of cause-specific cardiovascular deaths in the Beijing urban area for the period March 2004 to August 2005. Concurrently, continuous measurements of particle number size distributions were performed. Particle number concentrations (NC) between 0.003 μm and 0.8 μm were converted to particle mass and surface area concentrations assuming spherical particles. Semi-parametric Poisson regression models adjusting for trend, seasonality, day of the week, and meteorology were used to estimate immediate, delayed and cumulative particle effects. Additionally, effect modification by air mass origin was investigated.

Results

We observed associations between daily cardiovascular mortality and particle NC for a 2-days delay. Moreover, nearly all particle metrics showed 2-days delayed associations with ischemic heart disease mortality. The strongest association was found for particle NC in the size range 0.03-0.1 μm (7.1% increase in daily mortality with a 95%-confidence interval of 2.9%-11.5%, per an increase of 6250 particles/cm³). Results for surface and mass concentrations with a lag of two days indicated effect modification by air mass origin, whereas effects of particle NC were not modified.

Conclusions

Results show an elevated risk of cardiovascular mortality in Beijing from short-term exposure to particulate air pollution in the sub-micrometer range. Results also indicate that locally produced smaller particles and regionally transported particles may exhibit different effects in Beijing.     

New Latency Model for Dynamic Frequency Scaling on Network-on-Chip

Modulating both the clock frequency and supply voltage of the network-on-chip （NoC） during runtime can reduce the power consumption and heat flux, but will lead to the increase of the latency of NoC. It is necessary to find a tradeoff between power consumption and communication latency. So we propose an analytical latency model which can show us the relationship of them. The proposed model to analyze latency is based on the M/G/1 queuing model, which is suitable for dynamic frequency scaling. The experiment results show that the accuracy of this model is more than 90%.     

酸性天然气与水体系内超临界-气-液-水合物多相平衡模型

针对酸性天然气与水体系内超临界-气-液-水合物多相平衡,构建了基于Gibbs自由能最小化原理的多组分流体多相平衡模型。为了提高其鲁棒性和计算精度,提出了相态稳定性判别的热力学判据和相组成分析的约束优化模型;考虑分子间非对称相互作用,建立了改进的Peng-Robinson状态方程,提出了统一的气体多参数平衡常数关系式,构建了不同相态中的逸度模型;建立了CH₄+CO₂+H₂S+H₂O体系的相平衡实验数据库,提出了对相平衡模型参数进行同步确定的多参数非线性拟合算法。与传统模型对比结果表明,新模型的收敛性更好、计算误差更小。     

APAM在水/高岭石界面吸附行为的试验和分子模拟研究

微细高岭石对煤泥浮选与煤泥水处理会产生不利影响,为深入了解水溶液中阴离子聚丙烯酰胺（APAM）与高岭石的作用机理,通过APAM在高岭石颗粒上的吸附量及残留量、絮凝沉降后上清液的浊度、絮团的Zeta电位和尺寸分布等分析了APAM对微细高岭石悬浮液的吸附现象和沉降规律,借用数量密度分布、水密度分布和自扩散系数等分子动力学参数计算研究其中的吸附作用和桥连机制．结果表明：除浊效果与APAM的吸附性能和残留量相关,絮团尺寸主要与残留量相关．随着APAM质量浓度的增加,APAM与高岭石表面的吸附能力和非键作用增-强,其以水分子为“纽带”间接吸附在高岭石（001）面,通过氢键直接吸附在高岭石（001）面．APAM与高岭石表面的吸附是形成桥连机制的前提,APAM的扩散范围和扩散速度共同决定桥连机制的强弱,扩散范围对桥连机制的影响效果更大．APAM分子链越多,扩散范围越大,桥连性能越强,有利于絮团的生长变大;APAM过量导致溶液黏度增大,扩散速度降低,桥连机制减弱,阻碍颗粒的沉降．大量水分子与APAM在高岭石表面存在强烈地竞争吸附,阻碍了氢键作用的形成．     

活性氢物质存在时丁硫醚在HZSM催化剂上的催化脱硫转化反应研究

1. Introduction The negative effects, which accompanied with the high-speed development of the petroleum and automobile industries in the last century, show that the sulfur compounds are usually the harmful component in oil products, and affect the proper…