微波消解测定水样中总磷

研究了以H2O2-HNO3为氧化剂，用微波消解测定水样中总磷的分析方法。通过正交试验选择合适的消解条件与氧化剂投入量，选择合适的显色酸度及测定波长，方法对自然水样测定平均相对标准偏差为3．3％，平均回收率为100．3%。     

Preparation of luminescent Cy5 doped core-shell SFNPs and its application as a near-infrared fluorescent marker

Cy5 dye is widely used as a biomarker in the research fields of life science because of its excitation at wavelengths above 600 nm where autofluorescence of bio-matter is much reduced. However, Cy5 dye could not be encapsulate into silica directly to form stable nanoparticles by using of the traditional methods. In this paper, an improved method had been developed to prepare Cy5 dye doped core-shell silica fluorescent nanoparticles (SFNPs), employing biomolecules conjugated Cy5 as the core material and silica coating produced from the hydrolysis TEOS (tetraethyl orthosilicate) in the water-in-oil microemulsion. To obtain stable Cy5 dye doped SFNPs with core-shell structure, five kinds of biomolecules with different iso-electric point (pI) have been selected to conjugate Cy5 for preparation of core-shell SFNPs. Results demonstrated that very bright and photostable Cy5 doped core-shell SFNPs could be both prepared by use of positive polysine conjugated Cy5 or IgG conjugated Cy5 as the core material, respectively. IgG conjugated Cy5 doped core-shell SFNPs was selected as a demonstration to be characterized and applied as a near-infrared fluorescent marker in cell recognition. The results showed that Cy5 doped core-shell SFNPs prepared by conjugating with a positive biomolecules IgG as the core material were luminescent and stable. About 110 Cy5 dye molecules could be doped in one nanoparticle with size of 42 ± 5 nm. The breast cancer cells had been selectively recognized by use of the near-infrared fluorescent marker based on the Cy5-IgG doped core-shell SFNPs. And the results demonstrated that this Cy5 doped core-shell SFNPs fluorescence marker was superior to the pure Cy5 dye marker for cell recognition in photostability and detection sensitivity.     

Automatic initialisation of buffer composition estimation for on-line analysis of unknown buffer solutions

An automatic initialisation procedure for extracting useful information about buffer composition from a titration experiment is presented in this paper. The initialisation procedure identifies which buffering components are present in the sample from a relatively long list of buffers expected in the system monitored. The procedure determines approximate pK _a values of the buffers and evaluates their maximum and minimum concentrations. This information is then used to start an optimisation procedure to fit the model of the buffer components to the titration data and to accurately determine buffer concentrations and pK _a values. The procedure has been integrated as a software layer around the buffer capacity optimum model builder (BOMB) that fits a buffer-capacity model to a measured buffer-capacity curve to estimate model properties (pK _a values and concentrations). The reliability and robustness of the resulting buffer capacity software (BCS) were tested using a titrimetric analyser simulator (TAS). The BCS was then validated off-line and on-line.     

Glycine-rich proteins

Glycine-rich proteins (GRPs) containing more than 60% glycine have been found in different tissues from many eukaryotic species. Despite the availability of literature on different groups of GRPs, there are few reports in which they are all considered and compared together. Some of these proteins are components of the cell walls of many higher plants. In most cases, it has been shown that they are accumulated in the vascular tissues and that their synthesis is part of the plant’s defense mechanism. Other distinct types of GRPs are characterized by having structures and functions similar to animal cytokeratins or by a domain with typical RNA-binding motifs. The availability of cloned GRP genes facilitates the study of the function of this diverse class of proteins, which is expected to enhance the understanding of cell physiology.     

Modification of surface properties of oral streptococci by α-1,6 glucans

Several members of the genus Streptococcus, including S. sobrinus, S. cricetus, S. sanguis and S. mutans, are known to produce proteins capable of complexing with α-1,6 glucans. Of all the oral streptococcal groups, S. sobrinus and S. cricetus are the most readily aggregated by high molecular weight glucan (glucan T-2000), but the aggregation may be inhibited by low molecular weight glucans (glucan T-10). Some of the oral streptococci are also known to express surface hydrophobins, molecules which impart hydrophobic characteristics to their cell surfaces. When glucan T-10 was added to suspensions of S. cricetus or S. sobrinus, the bacteria were less able to adhere to hexadecane, to bind to plastics or to be aggregated by ammonium sulfate. It is concluded that the glucan rendered the bacteria more hydrophilic. In contrast, streptococci such as S. sanguis and S. mutans, incapable of aggregation by high molecular weight α-1,6 glucan, retained their hydrophobic characteristics in the presence of glucan T-10. Other bacteria, such as Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa, exhibited their same abilities to bind to hexadecane, to adhere to plastics or to be aggregated by ammonium sulfate, regardless of the presence of α-1,6 glucan. When S. cricetus or S. sobrinus were grown under conditions to minimize expression of glucan-binding lectin or when glucan-binding lectin was denatured, glucan T-10 had no effect on their hydrophobic characteristics. It appears that the complexing of α-1,6 glucan by streptococci bearing glucan-binding lectin causes the bacteria to assume a more hydrophilic character.     

Measurements of sulfur in oil using a pressurised wet digestion technique in open vessels and isotope dilution mass spectrometry

Graz University of Technology has developed a new technique for digesting samples using the well-established high-pressure asher (HPA) from Anton Paar GmbH (Graz, Austria). The digestion is performed in semi-open vessels inside a pressurised autoclave. The new HPA equipment consists of a liner for the autoclave, special sample racks and 30-mL digestion vessels made of quartz, covered with PTFE stoppers. The Laboratory for Isotope Dilution and Nuclear Analysis of the Federal Institute for Materials Research and Testing (BAM, Berlin) tested this new equipment in order to assess its usability for the decomposition of larger sample amounts of gas oils for the measurement of sulfur. Several experiments were carried out using the new sample decomposition technique. In order to test the recovery of the new digestion method, a gas oil material with known sulfur content was chosen, quantified by the validated conventional closed vessel HPA digestion in combination with thermal ionisation mass spectrometry. Isotope dilution mass spectrometry has been applied as analytical method in this investigation. The gas oil was spiked with an isotopic spike material, which is enriched in ³⁴S, and was then wet digested in the HPA. The oxidized sulfur of the dried samples was reduced to H₂S and precipitated as As₂S₃. The sulfur was measured as arsenic monosulfide (AsS⁺). The mass content of sulfur in the gas oil tested is 453.5 mg kg^–1. Recovery tests for increasing masses of gas oils indicate that the recovery using the new measurement technique decreases with increasing mass of gas oil. Results were obtained for approximately 0.3 g sample weight and had less overlap with the result of the old HPA method within the stated uncertainties. At approximately 0.5 g sample weight the yield decreases to about 97% and at approximately 1.0 g sample weight to about 87%. In comparison with the conventional closed vessel HPA digestion, the new technique shows no clear advantages for the certification of the sulfur content in gas oil other than a more convenient handling. The total uncertainty of the sulfur mass fractions (k=2) is about 1.5%. Repeated determination of the oil samples show a relative standard deviation of about 0.8% and indicate that the analytical procedure is robust and reproducible. The demonstrated reproducibility allows the establishment of correction factors for the yield, which in turn enables higher sample masses for routine work. The blank level (0.26×10^-6 g) was within the range of the conventional closed HPA digestion procedure·(0.28×10^-6 g). Cross contamination could not be detected. In terms of trace metal analysis a good applicability and more advantages over the conventional closed vessel HPA digestion can be assumed.     

Voltammetric Determination of Platinum in Plant Material

A very sensitive procedure for the determination of platinum in hydroponically cultivated plant samples (Sinapis alba L and Lolium perenne) is presented. A microwave digestion with HNO₃, HClO₄ and HCl acids with additional UV irradiation is followed by the platinum determination by adsorptive stripping voltammetry at hanging mercury drop electrode. The influence of HNO₃ acid on voltammetric determination of platinum is discussed. For validation of the obtained results the recovery of Pt was examined and the Pt determination by ICP MS was carried out. The highest platinum amounts were found in the roots of the plants, nevertheless the effective transport of platinum to the steams and leaves was also observed.     

Stopped-flow kinetic determination of aluminum in Chinese tea leaves by fluoride ion-selective electrode potentiometry

A stopped-flow kinetic potentiometric method for the determination of aluminum is described, based on monitoring the reaction between aluminum and fluoride at pH 3.0 using fluoride ion-selective electrode. The initial rate of the reaction is proportional to the concentration of aluminum present in the solution. The method is simple and rapid and has been applied to the determination of aluminum in Chinese tea leaves after microwave digestion.     

用无乳化剂乳液聚合法制备聚丙烯醛微球

本文应用无乳化剂乳液聚合法合成了粒度均一、具有活泼醛基的聚丙烯醛微球,并对丙烯醛聚合动力学和影响微球直径,活泼醛基含量的因素进行了研究。用合成的微球同不同的氨基酸和午血清白蛋白反应,结果表明:该微球在生理pH条件下同含有伯氨基的化合物具有较高的结合容量。因此,在无乳化剂存在下,采用乳液聚合法制备聚丙烯醛微球是一种合成具有干净表面的聚丙烯醛微球的新方法。     

Nanoscale probes encapsulated by biologically localized embedding (PEBBLEs) for ion sensing and imaging in live cells

This review discusses the development and recent advances of probes encapsulated by biologically localized embedding (PEBBLEs), and in particular the application of PEBBLEs as ion sensors. PEBBLEs allow for minimally intrusive sensing of ions in cellular environments due to their small size (20 to 600 nm in diameter) and protect the sensing elements (i.e. fluorescent dyes) by encapsulating them within an inert matrix. The selectivity and sensitivity of these nanosensors are comparable to those of macroscopic ion selective optodes, and electrodes, while the response time and absolute detection limit are significantly better. This paper discusses the principles guiding PEBBLE design including synthesis, characterization, diversification, the advantages and limitations of the sensors, cellular applications and future directions of PEBBLE research.