Microdialysis sampling and monitoring of uric acid in vivo by a chemiluminescence reaction and an enzyme on immobilized chitosan support membrane

A new detection system based on microdialysis sampling and chemiluminescence (CL) reaction was developed for in vivo monitoring of uric acid (UA) with high sensitivity, selectivity and accuracy. The uric acid is indirectly monitored by CL detection of enzymatic reaction product formation (H₂O₂), catalyzed by Uricase. A microprobe was modified and coated with immobilized enzyme through a Streptavidin-biotin mediated linker by using a chitosan support membrane, polyurethane trapped ferrocene film is employed to protect the probe surface and diminish the interference from reductant molecules, which often are present in the blood (e.g. ascorbic acid). The earlier mentioned probe and the constructed sensor can detect uric acid in the range of 0.01-1 mM with detection limit (3σ) of 5 μM. Finally, the system is used to monitor uric acid (UA) variation through an acute myocardial infarction (AMI) model. Following AMI-induced oxidative stress, the UA level decreases continuously, thus suggesting that UA plays a protective role as a substitute antioxidant. Furthermore, the in vivo monitoring results show good agreement with those obtained by a standard method, and the procedure is recommended for in vivo and real time monitoring of UA. In addition, the proposed method can be more accurate since the UA may be potentially oxidized by in vitro exposure to oxygen in the presence of a catalyst.     

固液相变的分子动力学研究Ⅰ─—(KI)_(108)离子簇的熔化和凝固(英)

通过分子动力学模拟，考查并分析了（KI）108离子簇的结构、能量和相变的动力学行为．在加热和冷却过程中，离子簇再现了熔化和凝固现象，而且熔化起始于立方体的其一顶点，熔化的离子簇不是球形的，说明了离子簇的非湿特征．根据结晶的成核速率，讨论了电子衍射实验中观察KI凝固的可能性     

Preparation and crystal structure of Nb6.74 Ta5.26S4 – a new compound in the ternary system Ta?Nb?S

Nb_6.74Ta_5.26S₄ has been prepared by high temperature techniques. The crystal structure has been determined from single crystal X-ray diffraction data (R/R_w = 0.0588/0.0655). The compound crystallizes in the orthorhombic space group Pnma with unit cell dimensions a = 959.11 (26) pm, b = 336.37 (10) pm, and c = 3282.51 (74) pm. The orthorhombic cell contains four formula units. Its structure is similar to that of Nb-rich sulfides, rather than to that of Ta-rich sulfides. The metal coordinations are capped distorted cubic prisms and pentagonal prisms while the coordinations of sulfur are capped trigonal prisms.     

Quantum dot nanocrystals for in vivo molecular and cellular imaging

Semiconductor quantum dots (QD) are nanometer-sized crystals with unique photochemical and photophysical properties that are not available from either isolated molecules or bulk solids. In comparison with organic dyes and fluorescent proteins, QD are emerging as a new class of fluorescent labels with improved brightness, resistance against photobleaching and multicolor fluorescence emission. These properties could improve the sensitivity of biological detection and imaging by at least 10- to 100-fold. Further development in high-quality near-infrared-emitting QD should allow ultrasensitive and multicolor imaging of molecular targets in deep tissue and living animals. Here, we discuss recent developments in QD synthesis and bioconjugation, applications in molecular and cellular imaging as well as promising directions for future research.     

Kinetic investigation of the textile bleaching process

Volumetric H₂-uptake measurements on an Mo₂N (79 m²g^–1) sample reduced at 673 K have been carried out and the uptake isotherms in the temperature range of 308–623 K have been determined. Both the total and reversible hydrogen uptake increased with the uptake temperature. The irreversible hydrogen uptake increased abruptly when the uptake temperature was raised up to 423 K. The maximum of irreversible hydrogen uptake was measured at 473 K. The H_IR/Mo ratio calculated from the uptakes obtained in the temperature range of 308–623 K varies in the range of 0.0010–0.0202. One possible mechanism for hydrogen adsorption is proposed to be heterolytic dissociation on Mo-N paris, in which the molybdenum atoms are in unsaturated coordination.     

两个具有PTP1B抑制活性的4-羟基丁内酯化合物的全合成研究

Two new naturally 4-hydroxylated butenolides were concisely synthesized in excellent enantiomeric purities. An aldol condensation and a Suzuki reaction served successfully as the key steps in the synthesis.     

Determination of lead by selective chelatometric titration with HEDTA after separation as its sulphate by an improved method of precipitation

A selective titrimetric determination of Pb after separation by a modified method of precipitation as its sulphate is proposed. Pb(II), present as the perchlorate, is precipitated by gentle boiling in 3.6M H(2)SO(4) presaturated with PbSO(4) and free from any extraneous anions. The customary time-consuming evaporation to fumes of sulphuric acid is dispensed with. The precipitate is collected, and dissolved in excess of HEDTA, the surplus of which is back-titrated with Zn(II) at pH 5.0-5.5. Use of Catechol Violet and Xylenol Orange as a mixed indicator gives a sharper end-point. The standard deviation of the proposed method for 60 mg of lead is 0.35 mg. The method has been successfully used to determine Pb in non-ferrous alloys.     

核-壳型聚丙烯酸酯复合乳液

简述了核-壳型聚丙烯酸酯复合乳液的合成方法、形态及其影响因素与判断方法、结构与性能等方面的研究进展;认为核-壳型复合乳液膜机械性能优良的原因是:核、壳两相间存在的过渡区适当地抑制了二者的相分离。     

Swelling kinetics and release characteristic of crosslinked chitosan: Polyether polymer network (semi-IPN) hydrogels

The aqueous swelling kinetics of a series of crosslinked chitosan (cr-CS) with glutaraldehyde (GA) interpenetrating polyether hydrogels have been studied as functions of pH, the N-deacetylation degree of chitosan, the amount of crosslinking agent, the electrolyte composition in solution, temperature, and gel composition. Based on these results, the swelling mechanism of the hydrogels was discussed. The release profiles of chlorhexidini acetas from the semi-IPN were also investigated. © 1994 John Wiley & Sons, Inc.     

氢化物发生石墨炉原子吸收光谱法直接测定高温镍基合金中的硒

在６ｍｏｌ／Ｌ盐酸介质和０．１％ＫＢＨ４条件下，不但能有效地发生硒的氢化物，而且５ｍｇ／ｍｌＮｉ和３ｍｇ／ｍｌＦｅ都不干扰硒的测定。利用涂钯石墨；管作为氢化物的原子化器，直接测定了高温镍基合金中的硒，特征质量为４０ｐｇ，相对标准偏差在６．１％以内，回收率在９７％－１１０％之间。