Binding study of Flos Lonicerae Japonicae with bovine serum albumin using centrifugal ultrafiltration and liquid chromatography

The screening and analysis of bioactive components in traditional Chinese medicines (TCMs) is very important not only for the quality control of Chinese herbs but also for elucidating the therapeutic principles. This study developed a new method for screening and analyzing bioactive compounds from TCMs using centrifugal ultrafiltration coupled with high-performance liquid chromatography. The method was successfully applied in the binding study of Flos Lonicerae Japonicae with bovine serum albumin (BSA), and 11 compounds were found to be bound with the BSA. Eight of them were positively identified as chlorogenic acid, caffeic acid, rutin, quercetin-3-O-glucoside, luteolin-7-O-glucoside, lonicerin, 3, 5-di-O-caffeoyl quinic acid and 3,4-di-O-caffeoyl quinic acid. Another three compounds were tentatively identified as two isomers of chlorogenic acid and one isomer of di-O-caffeoyl quinic acid by comparing the UV data and MS data with the previous reports. Based on modern pharmacological study, these compounds are the major bioactive components in Lonicera japonica. Therefore, the proposed method could be a good approach to predicting the potential bioactivities of multiple compounds in TCMs simultaneously.     

Screen-printed microfluidic device for electrochemical immunoassay

In this paper, a new microfluidic array device has been fabricated with screen printing technology. In contrast to traditional microfabrication processes, our method is simple, inexpensive and also suitable for mass production. The device is used for sandwich-type electrochemical immunoassay, in which probes are covalently attached to the electrode surface via electropolymerized polypyrrole propylic acid (PPA) film. This novel microfluidic system enables the whole array preparation and detection processes, including the probe immobilization, sample injection, enzyme incubation and electrochemical detection, to be conducted in the sealed microchannels. For a demonstration, mouse IgG is selected as the target analyte and its detection is realized by sandwich ELISA with goat anti-mouse IgG, rat anti-mouse IgG (conjugated to alkaline phosphatase) and p-aminophenyl phosphate (PAPP) as the primary antibody, second antibody, and enzyme substrate, respectively. A detection limit of 10 ng mL(-1) (67 pM) is achieved with a dynamic range of 100 ng mL(-1)-10 microg mL(-1). In addition, anti-goat IgG is also immobilized as an alternative probe to test mouse IgG in the solution, in order to demonstrate the multiplexing capability as well as the specificity of the device. As expected, the electrochemical responses are much lower than that using anti-mouse IgG as the probe, indicating good selectivity of the immunoassay device. These results indicate a great promise toward the development of miniaturized, low-cost protein biochips for clinical, forensics, environmental, and pharmaceutical applications.     

本征及掺杂石墨烯对2,3,7,8-四氯二苯并呋喃吸附机理的计算模拟研究

二噁英对人类和环境具有较高的毒性,因此,研制出有效的二噁英有机污染物的去除和检测方法尤为重要.本研究采用密度泛函理论模拟方法详细探讨了本征及Ti,Fe及Pt掺杂石墨烯对2,3,7,8-四氯二苯并呋喃(2,3,7,8-tetrachlorodibenzofuran,TCDF)二噁英污染物的吸附机理.研究结果表明,本征石墨烯及掺杂石墨烯表面对TCDF均有一定程度的吸附,而Ti和Fe掺杂石墨烯对TCDF的吸附远大于本征石墨烯对TCDF的吸附.主要原因是TCDF与本征石墨烯之间主要形成了π…π,C-H…π和C-Cl…π非共价的相互作用,而与掺杂石墨烯之间主要形成了metal-O共价相互作用.研究结果有望为石墨烯材料在二噁英污染物TCDF吸附方面的应用提供有价值的理论指导.     

分子动力学模拟研究方解石表面润湿性反转机理

利用分子动力学模拟技术从分子尺度探究方解石表面润湿性反转机理.首先,研究方解石表面润湿性反转过程;而后,从原油分子-方解石表面与原油分子-原油分子/水分子相互作用两个方面系统揭示方解石表面润湿性反转机理.结果:(1)水分子能够驱离方解石表面弱吸附的非极性分子造成润湿性的改变,但不能驱离强吸附的极性分子使润湿性反转难以实现;(2)原油分子极性越强与方解石表面相互作用越强,极性分子与方解石表面之间主要为静电力,非极性分子与方解石表面之间主要为范德华力;(3)原油分子极性越相近分子之间的相互作用越强,分子极性相差越大分子之间的相互作用越弱.非极性分子之间主要是范德华力,极性分子之间主要是静电力;(4)原油分子在方解石表面和水分子的共同作用下形成乙酸-吡啶-水-甲苯-己烷的稳定吸附序列.本研究为靶向提高采收率技术的设计与应用提供理论基础.     

Elastic properties of MBH4 (M=Na, K, Rb, Cs)

The elastic properties of MBH₄ (M=Na, K, Rb, Cs) are studied by first-principles calculations using a projected augmented plane-wave method and finite strain method. KBH₄ is found to be the most isotropic material among MBH₄, which can be attributed to the contribution of C₄₄. The Debye temperatures are also calculated using theoretical elastic constants and the change along the series is explained.     

Adsorption and separation of methane/hydrogen in octaphenylsilsesquioxane based covalently-linked organic-inorganic hybrid framework

The adsorption and separation of CH₄/H₂ in two covalently-linked organic-inorganic hybrid frameworks polyoctaphenylsilsesquioxane (JUC-Z1) were computationally studied using the Grand Canonical Monte Carlo (GCMC) simulations. The results show that JUC-Z1 with Linde type A (LTA) and polycubane (zeolite code ACO) net topologies can adsorb up to 20.32, 18.57 mmol/g of CH₄ and 19.04, 17.89 mmol/g of H₂ at 298 K and 10 MPa, respectively. For the adsorption of binary mixture, the selectivity of CH₄ over H₂ in LTA-JUC-Z1 decrease gradually with the increase of the pressure or the CH₄ mole fraction of the mixture. As to ACO-JUC-Z1, the selectivity first increases at low pressure or CH₄ mole fraction, and then begins to decrease with the further increase of the corresponding amount. Anyhow, the two materials both exhibit excellent adsorption and separation capacities of CH₄/H₂.     

Etching blazed grating into quartz substrate with selectivity 1:1 against photoresist by inductively coupled plasma technology

Inductively coupled plasma (ICP) etching technology is becoming widely used in the fabrication of micro-optical elements. Because of its advantages such as relatively high etching rate and anisotropic etching, ICP technology is receiving more attention. Selectivity 1:1 of the substrate against photoresist is very convenient, because we can easily get the same structures which were designed on the photoresist. Through extensive experiments we have achieved an optimized etching condition under which the transfer process generates fairly smooth etched structures with selectivity 1:1. The first order diffraction efficiency of the etched blazed gratings is 83.5% which is a little bit lower than the theoretical efficiency 88.9%. The diffraction of etched blazed gratings matches the theoretical results well.     

Hydrogen adsorption on Ti containing organometallic structures grafted on silsesquioxanes

The adsorption of hydrogen molecule on a novel structure of Ti containing organometallic complexes grafted on silsequioxanes (SQ, H₈Si₈O₁₂) was investigated by means of DFT method. The hydrogen adsorption properties of the complex structures TiRH₇Si₈O₁₂ (R = C₄H₃, C₅H₄, C₆H₅) keep almost the same as that of corresponding Ti containing organometallic complexes. Moreover, these complex structures can avoid the problem of transition metal clustering which is a disadvantage for hydrogen adsorption. The maximum number of hydrogen molecules adsorbed was still determined by 18 electron rule, that is to say 5, 4, and 4 H₂ molecules for TiRH₇Si₈O₁₂ with R = C₄H₃, C₅H₄, and C₆H₅, respectively. At the same time, all the average binding energy of H₂ is located in 0.2–1.0 eV, which is an advantage for hydrogen storage at ambient conditions. Therefore, the materials studied here may provide some enlightenment for developing new types of hydrogen storage materials.     

Application of high-performance liquid chromatography-electrospray ionization time-of-flight mass spectrometry for analysis and quality control of Radix Astragali and its preparations

A high-performance liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry (HPLC-ESI-TOF-MS) method has been developed for qualitative and quantitative analysis of isoflavonoids and saponins, as well as for the quality control of Radix Astragali and its preparations. The selectivity, reproducibility and sensitivity are compared with HPLC with diode array detection (DAD) and evaporative light scattering detection (ELSD). Limits of detection and quantification fell in ranges of 9-40 and 23-103 ng/mL for 13 analytes with a injection of 10 microL samples, and all calibration curves showed good linear regression (r(2)>0.9938) within the test range. The assay was successfully utilized to analyze the 13 marker components in 20 samples of Radix Astragali products. The quantitative results demonstrated that samples from different localities and manufacturers showed different quality. Advantages, in comparison with conventional HPLC-DAD-ELSD, are that reliable identification of target compounds could be achieved by accurate mass measurements (<3 ppm) along with characteristic retention time, extracted ions chromatograms using a narrow mass window for quantification ensure that the chromatographic peaks are free from background or co-elutes interference, and the great enhancement in selectivity and sensitivity allows identification and quantification of low levels of constituents in complex Radix Astragali matrixes.     

The equality cases for the inequalities of Oppenheim and Schur for positive semi-definite matrices

In this paper, necessary and sufficient conditions for equality in the inequalities of Oppenheim and Schur for positive semidefinite matrices are investigated. Supported by National Natural Science Foundation of China (No. 10531070), National Basic Research Program of China 973 Program (No. 2006CB805900), National Research Program of China 863 Program (No. 2006AA11Z209) and the Natural Science Foundation of Shanghai (Grant No. 06ZR14049).