Detection of immunoglobulin E using an aptamer based dot-blot assay

A novel aptamer based dot-blot assay for the detection of immunoglobulin E (IgE) was developed. A biotinylated aptamer was employed as the bio-recognition element to specifically interact with the target protein immobilized onto a nitrocellulose membrane substrate. Avidin conjugated horseradish peroxidase was introduced onto the membrane through the biotin-avidin system to catalyze the hydrogen peroxide mediated oxidation of 3,3’,5,5’-tetramethylbenzidine, thereby producing the blue-colored insoluble product. The intensity of the dots increased as the concentration of IgE increased. The spot intensity was quantified using a simple portable instrument. A linear response relationship between the spot intensity and the concentration of IgE over the range of 50 nmol/L to 1 μmol/L was obtained. The detection limit for IgE using the aptamer-based assay was 2.89 nmol/L. This assay was found to discriminate IgE from non-target proteins such as thrombin, bovine serum albumin and immunoglobulin G.     

Electrochemical biosensors and logic devices based on aptamers

Aptamers are molecular recognition elements with high specificity that are selected from deoxyribonucleic acid/ribonucleic acid (DNA/RNA) library. Compared with the traditional protein recognition elements,aptamers have excellent properties such as cost-effective,stable,easy for synthesis and modification. In recent years,electrochemistry plays an important role in biosensor field because of its high sensitivity,high stability, fast response and easy miniaturization. Through the combination of these two technologies and our rational design,we constructed a series of biosensors and biochips that are simple,fast,cheap and miniaturized. Firstly,we designed an adenosine triphosphate (ATP) electrochemical biosensor based on the strand displacement strategy. We can detect as low as 10 nmol/L of ATP both in pure solution and complicated cell lysates. Secondly,we creatively split the aptamers into two fragments and constructed the sandwich assay platform only based on single aptamer sequence. We successfully transferred this design on biochips with multiple micro electrodes (6×6) and accomplished multiplex detection. In the fields of biochips and biocomputers,we designed several DNA logic gates with electric (electrochemical) signal as output which paves a new way for the development of DNA computer.     

Microplate chemiluminescence enzyme immunoassay for the quantitative evaluation of carbohydrate antigen 72-4 in human serum

A highly sensitive and specific microplate chemiluminescence enzyme immunoassay （CLEIA） was developed for the quantitative evaluation of carbohydrate antigen 72-4 （CA72-4） in human serum, using luminol-H2O2 catalyzed by horseradish peroxidase （HRP） as the chemiluminescence system. The simple and quick determination was accomplished through a sandwich reaction mode. Several physicochemical parameters of the immunoreaction, including incubation conditions, antibody coating conditions, dilution ratio of anti-CA72-4-HRP conjugate, and chemiluminescence reaction time, were studied and optimized. The proposed method exhibited a linear range of 0-200 U/mL with correlation coefficient and detection limit of 0.9995 and 0.18 U/mL, respectively. The inter-assay and intra-assay coefficients of variation （CV） were both less than 10%. The average recovery of two clinical sera with low and high concentration CA72-4 was 99.3% and 98.7%, respectively. Normal tumor markers, including AFP, CEA, CA24-2, CA19-9 and CA15-3, did not cross-react with each other. The method＇s stability was evaluated by assessing its analytical performance after storing the immunoreagents at 4℃ and 37℃ for 7 days. Little difference was found, indicating satisfactory stability of the method. The present method has been successfully applied to the detection of CA72-4 human serum, and showed a good correlation with the commercially available ELISA kit （r^2=0.9383）. This method showed great potential in the fabrication of diagnostic kit for CA72-4, and could be well used in diagnosis of cancer in clinical practice.     

Effect of Thrombin on the Apoptosis of Hippocampal Neurons in vitro

Hippocampal neurons were treated by thrombin and thrombin receptor activating peptides (TRAP). Cell survival rate was decreased in a dose-dependent manner by MTT assay. The numbers of apoptotic cell and apoptotic rate of hippocampal neurons treated by different concentrations of thrombin were increased in a dose-dependent manner by terminal deoxynucleotidyl transferase (TdT) mediated dUTP-biotin nick end-labeling (TUNEL) method and Flow Cytometry. When the concentration of thrombin is 40 U/mL, TUNEL positive cells and apoptotic rate of hippocampal neurons reached peak value, were 27. 3 4.0 and (29.333 4.633 ) %, respectively. Immunocytochemistry assay show that Bcl-2 protein expression was down- regulated and Bax protein expression was up-regulated with the concentration of thrombin increased. TRAP can mimic the effect of thrombin to induce apoptosis on hippocampal neurons. These data demonstrated that thrombin induced hippocampal neuron apoptosis in a dose-dependent manner through activating protease-activated protein-1 (PAR-1). The change in expression of Bcl-2 and Bax was related with the effect of high concentration thrombin induced apoptosis on hippocampal neurons.     

Synthesis and characterization of a new water-soluble sodium 5, 7, 4＇-trihydroxyflavone-6, 3＇-disulfonate

Aim To synthesize a new water-soluble Na 2(C15H8O5)(SO3) 2 and determine its structure.Method The new water-soluble apigenin sulfonated derivative was synthesized by sulfonation with concentrated sulfuric acid at 40℃for half an hour and the products were obtained in ethanol-water(V∶V =1∶1).The structure of the product was identified by IR,NMR spectrum and elemental analysis.Results and Conclusion After highly selective introduced two - SO 3 groups at C3′and C6of the substrate,the new water-soluble apigenin sulfonated derivative,sodium 5,7,4 '-trihydroxyflavone-6,3′-sulfonate was obtained in good yield(78%) at moderate conditions.This method is an ideal synthesis way because of its simple operation,mild reaction conditions,high selectivity,easy separation of the product and higher yield.     

Label-free selective sensing of Pb2＋ lead（II） sensors based on the aggregation of a pyrene fluorescent probe

In the present work, we report a label-free fluo- rescence turn-on approach for the sensitive and selective sensing of Pb2＋. Pyrene with one positive charge was used as the fluorescent probe, and thrombin aptamer （TBA）, which was a G-rich oligonucleotide, was employed to form G-quadruplex with lead（II）. When TBA and Pb2＋ were mixed with lead（II） in an aqueous solution, it was folded into a stable G-quadruplex. Subsequently, a single-stranded nucleic acid-specific nuclease S1 was added. The G-quad- ruplex stabilized by Pb2＋ lead（II） had markedly a significant resistant ability to nuclease S1 digestion. However, in the absence of Pb2＋ lead（II）, no quadruplex or less stable quadruplex was formed and TBA was digested by nuclease S1 in 3 min under the optimized experimental conditions. Finally, pyrene probe was Pb2＋ lead（II）. Electrostatic mixed with oligonucleotide in interactions between oligonu- cleotide （a polyanion） and the probe induced the aggregation of the probe, which in turn produced strong emission of the strong pyrene excimer emission. The intensity of the induced excimer emission was directly proportional to the amount of Pb2＋ added. Our approach shows good selectivity and sen- sitivity for the detection of Pb2＋ with a limit of detection limit as low as 800 nmol/L.     

Silica-Based Solid Phase Extraction of DNA on a Microchip

Micro total analysis systems for chemical and biological analysis have attracted much attention. However, microchips for sample preparation and especially DNA purification are still underdeveloped. This work describes a solid phase extraction chip for purifying DNA from biological samples based on the adsorption of DNA on bare silica beads prepacked in a microchannel. The chip was fabricated with polydimethylsiloxane. The silica beads were packed in the channel on the chip with a tapered microchannel to form the packed bed. Fluorescence detection was used to evaluate the DNA adsorbing efficiency of the solid phase. The polymerase chain reaction was used to evaluate the quality of the purified DNA for further use. The extraction efficiency for the DNA extraction chip is approximately 50% with a 150-nL extraction volume, Successful amplification of DNA extracted from human whole blood indicates that this method is compatible with the polymerase chain reaction.     

Study on the specific interaction between angiogenin and aptamer by atomic force microscopy （AFM）

The specific interaction between angiogenin and aptamer has been investigated by using AFM. The specificity of the interaction is revealed by comparing the binding probability of aptamer to other elements in a series of control experiments. The results have shown that there is specific interaction force between angiogenin and aptamer. Moreover, the single molecular pull-off force between angiogenin and aptamer has also been determined using the Poisson statistical method to be 133.7±11.7 pN. These findings obtained are helpful to the better revelation of recognition mechanism between angiogenin and aptamer, which provided basis for further understanding the inhibition of the aptamer to angiogenic activity.     

Temperature-sensitive gold-nanotube array membranes modified with poly（N-isopropylacrylamide）

A kind of temperature-sensitive nanotube array membrane was developed by modifying gold-nanotube array membranes with poly（N-isopropylacrylamide） （PNIPAm）. The permeation ability of the mem-branes at different temperatures was investigated using sodium fluorescein and quantum dots as probes. The results showed that the pore diameter of nanotube was changed due to the reversible response of PNIPAm-modified membranes to temperature, and then the permeation ability of the mem-branes was changed. The permeation of fluorescence probes was slow and even almost blocked at 25℃ （below the lower critical solution temperature, LCST）, since PNIPAm formed expanded structures and decreased the pore size. While at 40℃ （above the LCST）, the permeation was increased, since PNIPAm became compact structures and the pore diameter was increased. Furthermore, the permeation ability of the temperature-sensitive nanotube array membranes could be adjusted reversibly and it is possible to use the membranes in nanofluidic devices, nanogates, etc.     

On the development of the GRAPES——A new generation of the national operational NWP system in China

Numerical weather prediction （NWP） has become one of the most important means for weather forecasts in the world. It also mirrors a nation＇s comprehensive strength in meteorology. In 2000, China Meteorological Administration （CMA） established the National Innovative Base for Meteorological Numerical Prediction in the Chinese Academy of Meteorological Sciences （CAMS）, to work on developing a new generation of the national operational NWP system-Global/Regional Assimilation and PrEdiction System （GRAPES）, to enhance meteorological services in China in the new century. In recent years, the GRAPES has witnessed a fast development. The GRAPES has been set up as an integration of the model framework, data assimilation, regional and global NWP system, which can be commonly used for both operation and research. In this paper, a brief review is made for illustrating the GRAPES system, including the advanced designs of the GRAPES, its diverse applications in multi-fields, and efficiencies of the regional and global GRAPES in operational applications based on hindcast results.     

mRNA detection in living cell using phosphorothioate-modified molecular beacon

In this study, GFP mRNA in COS-7 cell and GFP-transfected COS-7 cell was detected in real time using phosphorothioate-modified molecular beacon based on living cell imaging method. Results showed that phosphorothioate-modified molecular beacon still kept the advantages of molecular beacon, such as, excellent selectivity, high sensitivity, and no separation detection. In addition, this modification could significantly increase the nuclease resistance of molecular beacon. Phosphorothioate-modified molecular beacon can efficiently reduce the false positive signal and improve the accuracy of living cell mRNA detection. Supported by the National Key Basic Research Program (Grant No. 2002CB513110), International Technologies Collaboration Program of China (Grant No. 2003DF000039), and National Natural Science Foundation of China (Grant Nos. 90606003 and 20620120107)     

Photovoltaic properties of MEH-PPV/TiO2 nanocomposites

Photovoltaic properties of photodiodes based on nano-TiO2 and poly[2-methoxy,5-（2＇-ethlhexyloxy）-p-phenylenevinylene] （MEH-PPV） composites are investigated. By comparing composite devices with the same weight of TiO2 （nanoparticles and nanotubes）：MEH-PPV, it was found that the device with TiO2 nanotubes exhibited better performance. By further optimizing the weight radio of TiO2 nanotubes： MEH-PPV, we gained the device with a short circuit current density of 9.27μA/cm^2 with a light intensity of 16.7mW/cm^2 at the 500 nm wavelength, the highest open-circuit voltage of 1.1V, and a photosensitivity of 332 at reverse bias of -0.6V. The photosensitivity is improved by a factor of 33 compared with the undoped MEH-PPV device.     

Crystal structures of catalytic and regulatory subunits of rat protein kinase CK2

Protein kinase CK2 consists of two catalytic subunits (CK2α) and two regulatory subunits (CK2β). Here, we report the crystal structures of rat CK2α mutant (rCK2α-△C, 1—335) and CK2β (rCK2β). The overall topology of rCK2α-△C and rCK2β are very similar to the human enzyme, although large structural differences could be observed in the N-terminal domain of rCK2α-△C. Our reported structure of rCK2α-△C is in the close conformation state while the counterpart hCK2α is in the open conformation state, indi- cating ...     

On-line catalytic upgrading of biomass fast pyrolysis products

Pyrolysis-gas chromatography/mass spectrometry （Py-GC/MS） was employed to achieve fast pyrolysis of biomass and on-line analysis of the pyrolysis vapors. Four biomass materials （poplar wood, fir wood, cotton straw and rice husk） were pyrolyzed to reveal the difference among their products. Moreover, catalytic cracking of the pyrolysis vapors from cotton straw was performed by using five catalysts, including two microporous zeolites （HZSM-5 and HY） and three mesoporous catalysts （ZrO2＆TiO2, SBA-15 and AI/SBA-15）. The results showed that the distribution of the pyrolytic products from the four materials differed a little from each other, while catalytic cracking could significantly alter the pyrolytic products. Those important primary pyrolytic products such as levoglucosan, hydroxyacetaldehyde and 1-hydroxy-2-propanone were decreased greatly after catalysis. The two microporous zeolites were ef- fective to generate high yields of hydrocarbons, while the three mesoporous materials favored the formation of furan, furfural and other furan compounds, as well as acetic acid.     

Combining docking and comparative molecular similarity indices analysis （COMSIA） to predict estrogen activity and probe molecular mechanisms of estrogen activity for estrogen compounds

Estrogen compounds are suspected of disrupting endocrine functions by mimicking natural hormones, and such compounds may pose a serious threat to the health of humans and wildlife. Close attention has been paid to the prediction and molecular mechanisms of estrogen activity for estrogen com- pounds. In this article, estrogen receptor a subtype （ERa） -based comparative molecular similarity indices analysis （COMSIA） was performed on 44 estrogen compounds with structural diversity to find out the structural relationship with the activity and to predict the activity. The model with the significant correlation and the best predictive power （R^2= 0.965, Q^2 LOO： 0.599, R^2 pred ： 0.825） was achieved. The COMSIA and docking results revealed the structural features for estrogen activity and key amino acid residues in binding pocket, and provided an insight into the interaction between the ligands and these amino acid residues.     

Measurement of the Newtonian gravitational constant based on the principle of free fall

The Newtonian gravitational constant (G) is one of the fundamental physical constants. This paper introduces a method to determine the Newtonian gravitational constant based on the principle of free fall, through measuring the change of gravity from the disturbed mass with an FG5/112 absolute gravimeter. This method has good repeatability. The measurement precision can be improved by error control and a large number of experiments. The constant G is obtained by two experiments, and the measured value is (6.6665±0.0554)×10⁻¹¹ m³/(kg·s²). Supported by the National Basic Research Program of China (Grant No. 2003CB716300) and Key Project of the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-125)     

Arctic dipole anomaly and summer rainfall in Northeast China

A dipole structure anomaly in summer Arctic atmospheric variability is identified in this study, which is characterized by the second mode of empirical orthogonal function （EOF） analysis of summer monthly mean sea level pressure （SLP） north of 70°N, accounting for 12.94% of the variance. The dipole anomaly shows a quasi-barotropic structure with opposite anomalous centers over the Canadian Arctic and the Beaufort Sea and between the Kara Sea and the Laptev Sea. The dipole anomaly reflects alternating variations in location of the polar vortex between the western and eastern Arctic regions. The positive phase of the dipole anomaly corresponds to the center of the polar vortex over the western Arctic, leading to an increase in summer mean rainfall in Northeast China. The dipole anomaly has a predominant 6-year periodicity, and shows interdecadal variations in recent decades.