Capillary gel electrophoresis of single-stranded DNA fragments with UV detection

Capillary gel electrophoresis has proven to be a powerful tool in biomedical research. We report our investigation of some of the critical parameters affecting separations of single-stranded DNA fragments as monitored by ultraviolet (UV) absorbance detection. Although not as sensitive as laser-induced fluorescence (LIF), UV absorbance detection allows one to calculate quite accurately, and inexpensively, the molarity of each separated DNA fragment and, moreover, the signal “fading” effect normally observed with LIF detection can be, in many cases, substituted for fluorescence to detect the many different single-stranded DNAs, as well as for detection of sequencing reactions.     

Carbon fibre electrodes in flow potentiometric stripping analysis

The construction of carbon fibre flow electrodes suitable for use in connection with potentiometric and constant-current stripping is described, and the fibre electrodes are compared with a glassy carbon disc thin layer cell. The signal-to-background ratio is approximately 1.6 times higher for an 8–10 μm carbon fibre compared to the glassy carbon disc electrode. If an Ag/AgCl tube is used as both counter and reference electrode, the signal-to-noise ratio of the fibre electrode is approximately five times better than for a glassy carbon disc electrode with a calomel reference; the latter electrode design, however, gives slightly better precision. The dead volume and internal potential drop of the fibre electrodes are more than one order of magnitude smaller than for the glassy carbon disc electrode. Because of the simplicity of the manufacturing process and low material cost, the fibre cells can be used as disposable electrodes and the polishing process necessary in connection with glassy carbon disc electrodes can be omitted.     

Stability of a dispersion of particles covered by a charge-regulated membrane: effect of the sizes of charged species

The influence of the sizes of charged species on the stability of a colloidal dispersion is investigated theoretically. We consider the case where a particle comprises a rigid core and an amphoteric, charge-regulated membrane layer, which simulates biocolloids and particles covered by artificial membranes. A modified Poisson-Boltzmann equation, which takes the sizes of all the charged species into account, is adopted to describe the electrical field. The effects of other key parameters such as electrolyte concentration, pH, and the valence of counterions on the behavior of a dispersion are also examined. We show that the larger the effective size of the counterions, the greater the stability ratio, which is consistent with experimental observations in the literature.     

Determination of cerium in rare earth ores by fluorescence quenching of rhodamine 6G

A fluorescence quenching method has been developed to determine cerium with rhodamine 6G. The method is based on the oxidation of rhodamine 6G by cerium(IV) in sulfuric acid solution. The linear calibration range is 4.0 × 10^–7 -1.6 × 10^–6mol/L. The detection limit is 1.0 × 10^–7 mol/L. The relative standard deviation was 1.0% (n = 5). The method has been used to determine cerium in rare earth ores, with satisfactory results. The method offers the advantages of simplisity, sensitivity and selectivity.     

Synthesis of graft copolymer of ethyl cellulose through living polymerization and its self-assembly

Copolymers of ethyl cellulose (EC) with polystyrene (PSt) were synthesized through atom transfer radical polymerization (ATRP). The molecular weight of graft copolymers increased without any trace of the EC macro-initiator, and the polydispersity of the side chains was low. The molecular weight of the side chains increased with the monomer conversion. Kinetic study indicated that the polymerization was first order. The micelle characteristics of the graft copolymer in acetone were investigated using dynamic light scattering (DLS), atom force microscopy (AFM) and transmission electron microscopy (TEM). With increasing the concentration, micelles were gradually formed from the solution. The TEM and AFM images indicated that the micelles had spherical shape and showed core-shell structure.     

Preparation of β-cyclodextrin-polyaniline complex in supercritical CO2

A method is proposed to prepare β-cyclodextrin (β-CD)/polyaniline (PANI) inclusion complex. In this route, benzoyl peroxide (BPO, the oxidant) is first encapsulated into the cavity of β-CD. Aniline is then carried into the cavity of β-CD by supercritical (SC) CO₂, which polymerizes in situ to form inclusion complex. The product is characterized by FT-IR, UV-Vis, ¹H NMR and XRD techniques. The results suggest that the columnar inclusion complexes may be formed.     

室温以上磁制冷材料La(Fe1-xCox)11.7Al1.3化合物的研究

通过X射线衍射分析和超导量子干涉磁强计（SQUID）磁性测量,研究了Co替代Fe含量对居里温度在室温以上的磁制冷材料La（Fe1-xCox）11.7Al1.3（x=0.072,0.081）磁结构和磁性能的影响。La（Fe1-xCox）11.7Al1.3材料的居里温度随Co的含量增加而增加,La（Fe0.919Co0.081）11.7Al1.3的居里温度为311 K。当外场变化为1.9 T时磁熵变达到3.6 J·kg^-1·K^-1,RCP值为168.6 J·kg^-1,虽然它的磁熵变小于具有巨磁熵变的磁制冷材料,但是它在磁场为1.9 T时的制冷能力与这些材料相当。     

A novel fluorescent method for determination of peroxynitrite using folic acid as a probe

A novel method for the determination of peroxynitrite using folic acid as a fluorescent probe is described. The method is based on the oxidation of the reduced, low-fluorescent folic acid by peroxynitrite to produce a high-fluorescent emission product. The fluorescence increase is linearly related to the concentration of peroxynitrite in the range of 3 × 10⁻⁸ to 5.0 × 10⁻⁶ mol L⁻¹ with a correlation coefficient of 0.998, and the detection limit is 1 × 10⁻⁸ mol L⁻¹. Interferences from some metal ions normally seen in biological samples, and also some anions structurally similar to peroxynitrite were studied. The optimal conditions for the detection of peroxynitrite were evaluated.     

Neural network studies : Part 3. Prediction of partition coefficients

In a previous paper (N. Bodor, A. Harget and M.-J. Huang, J. Am. Chem. Soc., 113 (1991) 9480) we demonstrated the utility of a neural network approach in the estimation of the aqueous solubility of organic compounds. This approach has now been extended to the prediction of partition coefficients. A training set of AM1 calculated properties and experimental values for 302 compounds was used and, after training, the neural network was tested for its ability to predict the partition coefficients of 21 compounds not included in the training set. We also tested six more compounds with molecular properties out of the training set property range. A comparison was made with the results obtained from a previous study which had used a regression analysis approach (N. Bodor and M.-J. Huang, J. Pharm. Sci., 81 (1992) 272). The neural network results compared favorably with those given by the regression analysis approach, both for the training set and for the new compounds.     

硫胺的燐光研究

硫胺无燐光，在碱中氧化后才产生燐光。 λ激发＝３００ｎｍ，λ发射＝４１０ ｎｍ，燐光寿命为１．３ｓ．硫胺燐光受溶剂极性影响甚小，１５种金属离子中只有铜离子可增强流胺燐光，寿命变短为 ０． ９４ ｓ，但不影响燐光光谱。在开始３０ｍｉｎ内有ＣｕＳＯ４的作用较快，以后逐渐变慢，到 ４ｈ后达平衡与不用ＣｕＳＯ４的燐光相近，启示ＣｕＳＯ４具有催化硫胺的氧化作用，建立了硫胺的燐光分析方法，用于两种维生素Ｂ１片的分析，分别为９８．５％与９８％。