Design,Synthesis, and Characterization of Photolabeling Probes for the Study of the Mechanisms of the Antiviral Effects of Ribavirin

Ribavirin, the only small molecule available so far for treating hepatitis‐C‐virus infection, was recently used in an emergency context to treat patients with severe acute respiratory syndrome (SARS) in the early stages of the disease. To study the mechanisms responsible for the antiviral effects of ribavirin by using a photolabeling approach, we designed, synthesized, and characterized the azidotriazole nucleosides 1 and 2 as photolabeling probes of ribavirin. These probes were synthesized either by performing nucleophilic substitution of the corresponding bromotriazole nucleoside with NaN₃ (Scheme 2) or by directly coupling the azidotriazole with the protected ribose sugar (Scheme 4). The azidotriazole nucleosides 1 and 2 showed a fast, clear‐cut photochemical reaction, which suggests that they are promising candidates for use in photolabeling studies.     

Molar mass distributions by gradient liquid chromatography: predicting and tailoring selectivity

Interactive liquid chromatography (iLC) for polymer analysis is usually applied to the characterisation of distributions other than molar mass. In particular, its use for the determination of chemical-composition, functionality-type and tacticity distributions has been demonstrated. The application of iLC for the determination of molar mass distributions (MMDs), however, has not yet been fully explored. An expanded version of the reversed-phase liquid chromatography model has been developed to describe and predict how the retention behaviour of polydisperse polystyrene samples changes with molar mass. The relationship between molar mass and the parameters of the model has been investigated in some detail and non-linear correlations were found. From the model and the relationships between the model parameters and molar mass, calibration curves (retention time versus molar mass) were constructed to predict changes in chromatographic selectivity across a given molar mass range. These calibration curves were compared to experimentally obtained curves and, in most cases, excellent agreement was found. The dramatic enhancement in selectivity that can be obtained with iLC in comparison to size-exclusion chromatography (SEC) was illustrated by measuring matrix-assisted laser desorption ionisation (MALDI) MS spectra of fractions collected during a gradient-LC separation. In the low-molar mass range, essentially monodisperse fractions were obtained. Calibration curves, predicted by the model and validated experimentally using narrow-dispersity standards and MALDI-MS spectra of fractions, were used to determine the molar mass distribution of some narrowly distributed polystyrene samples. Molar mass distributions for such standards were found to be somewhat lower than the values reported by the manufacturers. The results also deviated from those obtained by MALDI-MS.     

A microcalorimetric study of the action of mercuric chloride on the metabolism of mitochondria isolated from Cyprinus carpio liver tissue

After the occurrence of 'Minamata disease' in 1950, mercury aroused much more attention, and lots of studies concerned have been made. The purpose of the present paper is to study the effect of mercuric chloride on the mitochondria suspension isolated from the liver tissue of Cyprinus carpio from the direct viewpoint of energy by using the microcalorimetric method. The metabolic thermogenic curves of the mitochondria suspension at 25°C were obtained, and the mitochondria metabolic thermokinetic equations were established, from which we obtained the thermodynamic and thermokinetic parameters: thermogenic rate constant (k), heat output (Q), average heat power (P_av), etc. Experimental results indicated that low concentration of mercuric chloride (5 nmol Hg²⁺/(mg protein)) stimulates the thermogenesis of mitochondria, suggesting a strong effect of uncoupling action, while high concentration of mercuric chloride (20 nmol Hg²⁺/(mg protein)) inhibits the metabolism of mitochondria completely, suggesting a fatal effect on the phosphorylation system. The effect of Hg²⁺ on mitochondria is concentration-depended, from which the probable reaction mechanism of Hg²⁺ to the mitochondria was proposed. So the microcalorimetric method can be used in the toxicology research.     

化学计量学在分析化学中的应用

从化学定量构效关系、模式识别法、人工神经网络、波谱化学、多元校正分析法等方面对化学计量学在分析化学中的应用进行了综述。阐明了化学计量学在分析化学中的作用及广阔的应用前景。     

Contribution to the certification of B,Cd, Cu,Mg and Pb in a synthetic water sample,by use of isotope-dilution ICP-MS,for Comparison 12 of the International Measurement Evaluation Programme

The contribution of the Institute for Reference Materials and Measurements to the certification of the B, Cd, Cu, Mg, and Pb content of a synthetic water sample used in Comparison 12 of the International Measurement Evaluation Programme (IMEP-12) is described. The aim of the IMEP programme is to demonstrate objectively the degree of equivalence and quality of chemical measurements of individual laboratories on the international scene by comparing them with reference ranges traceable to the SI (Système International d'Unités). IMEP is organized in support of European Union policies and helps to improve the traceability of values produced by field chemical measurement laboratories. The analytical procedure used to establish the reference values for the B, Cd, Cu, Mg, and Pb content of the IMEP-12 sample is based on inductively coupled plasma-isotope-dilution mass spectrometry (ICP-IDMS) applied as a primary method of measurement. The measurements performed for the IMEP-12 study are described in detail. Focus is on the element boron, which is particularly difficult to analyze by ICP-MS because of potential problems of low sensitivity, high mass discrimination, memory effects, and abundance sensitivity. For each of the certified amount contents presented here a total uncertainty budget was calculated using the method of propagation of uncertainties according to ISO (International Organization for Standardization) and Eurachem guidelines. For all investigated elements with concentrations in the low micro g kg(-1) and mg kg(-1) range (corresponding to pmol kg(-1) to the high micro mol kg(-1) level), SI-traceable reference values with relative expanded uncertainties ( k=2) of less than 2 % were obtained.     

Rapid detection of Escherichia coliform with a bulk acoustic wave sensor based on the gelation of Tachypleus amebocyte lysate

A new sensing method (BAW-TAL technique), which combined the bulk acoustic wave (BAW) technique with the gelation reaction of Tachypleus amebocyte lysate (TAL), was used for viscosity and density measurement and applied to the detection of Escherichia coliform (E. coli). This method depended on the fact that the viscosity and density of the mixture increased, and as a result, the resonance frequency decreased correspondingly after TAL was mixed with the heated E. coli solution that contained endotoxin. Results showed that the frequency shift was linearly related to the logarithm of E. coli concentration in the range of 2.7x10(4)-2.7x10(8) cells/ml. The correlation coefficient was 0.996. This BAW-TAL method was compared with the standard pour plate counts (PPC) method. The proposed method was much more rapid and simpler for detection of E. coli than the traditional methods.     

细胞动力学研究VIII.Na2SeO3对黑根菌作用特征

The Characteristics of the action of Na2SeO3 on Rhizopus nigrocans has been studied by means of microcalorimetry, the relationship between growth rate constants and the concentration of Na2SeO3 is
k=0.03608exp[-0.003608(c+8.60)2]
It was found that Na2SeO3 of low concentration has promoting action on the growth of Rhizopus nigrocans cells, and high concentration of Na2SeO3 has inhibitory action. The study has provided a lot of information on the bioaffect of selenium and the research of toxicology.     

When does gradient Ricci soliton have one end?

Annals of Global Analysis and Geometry - In this paper, we study a problem of finding compact hypersurfaces of prescribed mean curvature with free boundary in a ball. We transform the problem to an...     

钼钨铌磷杂多化合物的研究（Ⅰ）：杂多酸的合成和表征

提出了分步酸化一分步加料合成[PNb_2Mo_xW_(10-x)O_(40)]~(5-)(x=0,2,4,6)系列杂多酸的方法,给出了最佳配料比和生成反应的pH值,并进行了红外、紫外、极谱、电位滴定及热稳定性研究。