Analyte and label binding assay read by flow cytometry

A new immunometric two-site sandwich assay is introduced, in which a label-scavenging binding partner is added to the sample in addition to the analyte-binding partner. The scavenger binding partner binds excess label antibody, giving a signal proportional to the amount of excess label antibody in the sample solution. A set of two calibration curves is obtained from the two binding partners simultaneously, and a combination of the two signals gives an unambiguous determination of the analyte concentration, even for high analyte concentrations where the hook effect may occur. Two-particle immunofluorometric assays developed for placental alkaline phosphatase and human chorionic gonadotropin on the basis of this principle and yielding signals measured by flow cytometry gave rapid results (2 h) and had working ranges in excess of 5 and 6 orders of magnitude for the respective analytes.     

Self-consistent framework for standardising mobilities in free solution capillary electrophoresis: applications to oligoglycines and oligoalanines

A theoretical analysis of deviations from ideality in ionic transport is presented to correct mobilities, mu, measured in free solution capillary electrophoresis (CE) to mobility at infinite dilution, mu degree (limiting mobility). Non-ideality is treated at the same level of approximation as in equilibrium, using a correction factor for the sum of the analyte and counter-ion radius originally suggested by Robinson and Stokes (Electrolyte Solutions, 1961). Unlike previous corrections using Debye-Hückel-Onsager theory, which are strictly applicable only at very low ionic strengths, this treatment is expected to be valid for univalent ions migrating in a uni-univalent background electrolyte for ionic strengths up to 0.075 mol kg-1, a range typical of CE experiments. The analysis is applied to the determination of mu degree in acidic and basic buffers for oligoalanines and oligoglycines with degree of polymerisation 2 to 6. Limiting mobilities for the fully protonated and deprotonated peptides are found to be numerically equal but opposite in sign, consistent with a change in charge from +1 to -1. In all uni-univalent buffers studied (borate, citrate, low pH lithium phosphate and sodium phosphate) mu degree values established using data over a range of pH and ionic strength are found to be identical and in excellent agreement with previous values from isotachophoresis. Values of mu degree in high pH sodium phosphate buffer are systematically 0.2.10(-8) m2 V-1 s-1 higher than those in other buffers; this may be attributed to limitations of the model for a buffer with 1+:2- and 1+:3- ions. This self-consistent framework for standardising mobilities in free solution CE is expected to be widely applicable to univalent analytes migrating in a 1:1 background electrolyte.     

Multicultural considerations in the use of advance directives

Capillary zone electrophoresis with indirect UV-detection was used to separate mixtures containing both positively and negatively charged species. In order to understand the dependence of detector response patterns on the changes in compositions of the background electrolytes and the charge of marker ions (UV-absorbing ions), the separations were performed in two different systems. In a three-ion system (analyte ion, coion and counterion) a marker ion was the major ionic component of a buffer solution and in a two-coion or counterion system the marker ion was used as an additive. In the three-ion system the response profile of an analyte was in good agreement with the mathematical treatment based on the Kohlrausch regulation function. In the two-coion or counterion system the response patterns were more complicated; however, the experimental results agree well with data obtained from a computer simulation program. Peak directions of the analytes were not only determined by their relative charge to the marker ion, but were also associated with their relative mobilities to the buffer coion and the marker ion. The analytes with higher effective mobilities compared to the marker ion were detected as positive peaks and the ones with lower effective mobilities as negative peaks. Similarly to the three-ion system, the detector response of an analyte was stronger by applying a marker coion compared to a counterion. An interesting result was obtained in the separation of a mixture of quaternary ammonium ions and sugars by using a cationic marker ion. The highest and most symmetrical peak was not a cation, but raffinose anion, which appeared most closely to the system peak. The observation suggests that the electromigration dispersion in its zone was eliminated by migrating close to the electroosmosis. A system peak with the mobility corresponding to the electroosmotic flow was obtained in both systems, and an additional system peak with a mobility close to that the marker ion was present in the systems using marker ions as additives.     

酸盐分离技术在镍电积阳极液中的应用

目前酸盐分离技术主要有树脂吸附法、离子交换法和膜分离技术三大类,但将其应用于镍湿法冶炼中镍电积阳极液的报道较少。总结了三大类酸盐分离技术的原理和应用,并分别采用树脂吸附法、扩散渗析法、特种纳滤膜和电渗析结合的方法对镍电积阳极液进行酸盐分离试验。结果表明,三种方法对镍电积阳极液均有一定的分离效果,其中树脂吸附法易饱和,需反洗再生,造成体积膨胀;扩散渗析法对硫酸的回收率在80%以上,镍的截留率在90%以上,但回收的硫酸浓度较低,同样存在体积膨胀问题;特种纳滤膜和电渗析结合法对镍离子的截留率可达90%以上,氢离子去除率可达70%以上,同时浓缩后的氢离子浓度可提高400%以上,镍离子浓度可提高500%以上,淡化液中各种离子浓度小于50 mg/L,可用作纯水,并且该方法不会造成系统体积膨胀,具有工业化应用价值。     

Designed protein pores as components for biosensors

BACKGROUND: There is a pressing need for new sensors that can detect a variety of analytes, ranging from simple ions to complex compounds and even microorganisms. The devices should offer sensitivity, speed, reversibility and selectivity. Given these criteria, protein pores, remodeled so that their transmembrane conductances are modulated by the association of specific analytes, are excellent prospects as components of biosensors. RESULTS: Structure-based design and a separation method that employs targeted chemical modification have been used to obtain a heteromeric form of the bacterial pore-forming protein staphylococcal alpha-hemolysin, in which one of the seven subunits contains a binding site for a divalent metal ion, M(II), which serves as a prototypic analyte. The single-channel current of the heteromer in planar bilayers is modulated by nanomolar Zn(II). Other M(II)s modulate the current and produce characteristic signatures. In addition, heteromers containing more than one mutant subunit exhibit distinct responses to M(II)s Hence, a large collection of responsive pores can be generated through subunit diversity and combinatorial assembly. CONCLUSIONS: Engineered pores have several advantages as potential sensor elements: sensitivity is in the nanomolar range; analyte binding is rapid (diffusion limited in some cases) and reversible; strictly selective binding is not required because single-channel recordings are rich in information; and for a particular analyte, the dissociation rate constant, the extent of channel block and the voltage-dependence of these parameters are distinguishing, while the frequency of partial channel block reflects the analyte concentration. A single sensor element might, therefore, be used to quantitate more than one analyte at once. The approach described here can be generalized for additional analytes.     

A rapid electrochemical method for measuring the concentration of active glue in copper refinery electrolyte which contains thiourea

Good cathode quality in copper electrorefining depends on maintaining an optimum level of glue and other leveling reagents in the electrolyte. A rapid electrochemical method has been developed for measuring the concentration of active glue in the electrolyte. It is based on the fact that glue strongly influences the polarization (currentvs potential) curve of a copper cathode in such electrolyte. The polarization curve is also influenced by the concentrations of copper, nickel, and thiourea (another leveling reagent) in the solution; the concentrations of these substances also can vary. With the present method a cathodic scan curve of a copper electrode is measured in the fresh, test electrolyte and again after the electrolyte is heated such as to destroy the active glue by hydrolysis; the heating does not affect the thiourea, Cu⁺² or Ni⁺² ions. The glue concentration is determined from the difference in the scan curves for the fresh and heated electrolytes. The difference may be quantified if needed by making standard glue additions to the cooked electrolyte and measuring the corresponding scan curves. The methods given by Refs. 2 and 4 are useful, despited the limitations stated, for tankhouse application in which Ni⁺² and Cu⁺² ion concentrations change very little or are monitored separately.     

Luminance and color contrast sensitivity and VEP latency in subjects with normal and defective binocularity

The effect of an additive (Brij 35) on the mobilities of a group of porphyrin acids is quantitatively characterized based on a 1:1 dynamic complexation model. Varying additive concentration shifts the equilibrium and changes the viscosity of the background electrolyte. The equilibrium constant, the electrophoretic mobility of the free analyte, and the electrophoretic mobility of the complex are identified as the parameters necessary to describe the analytes' migration behavior. Several statistical methods for obtaining these parameters are discussed. The equilibrium constants and complex mobilities are calculated using three different linear regression methods. The weighted y-reciprocal method was preferred because it gives smaller error, and the data points are evenly distributed along the concentration axis. These values are confirmed using a nonlinear regression to ensure that the proper weighting was used in the linear regression plots. The parameters are then used to predict the apparent mobilities of the analytes over the entire additive concentration range, allowing the optimum separation conditions to be identified. For disc-like molecules, such as porphyrins, the mobility is determined by the orientation of the molecule in an electric field, in addition to their size and charge. The strength of binding between the porphyrins and Brij 35 depends on the number of binding sites and the solvation shell.     

A mathematical model for microbial growth under limitation by conservative substrates

A mathematical model is suggested for growth of microorganisms under limitation by "conservative" substrates such as inorganic ions or vitamins that are not broken down after uptake into the cells, but that wholely or partly remain available for production of biomass. The specific growth rate is expressed here as a function of the intracellular "concentration" of the limiting substrate, defined as the amount of substrate within the cells per unit of cell dry weight. In the model, the intracellular substrate is divided into two parts. One part is a "structural" substrate not available for further growth. The other part is an "excess" or "functional" substrate that is used for biomass production and is assumed to be converted into structural substrate proportionally to growth. The rate of growth is believed to be controlled by the intracellular concentration of excess substrate.     

Determination of ivabradine and its N-demethylated metabolite in human plasma and urine, and in rat and dog plasma by a validated high-performance liquid chromatographic method with fluorescence detection

A sensitive and selective high-performance liquid chromatographic method with native detection of fluorescence was developed and validated for the quantitation of ivabradine and its N-demethylated metabolite in plasma (rat, dog, human) and human urine. The procedure involves the use of an analogue as internal standard, solid-phase extraction on cyano cartridges, separation on a Nova-Pak C8 column and fluorescence detection. Calibration curves are linear in the concentration ranges from 0.5 to 100 ng/ml in plasma and 2.0 to 500 ng/ml in urine with a limit of quantitation set at 0.5 and 2.0 ng/ml in plasma and urine, respectively. The analysis of plasma and urine samples (spiked with the analytes at low, medium and high concentrations of the calibration range) demonstrates that both analytes can be measured with precision and accuracy within acceptable limits. Quality controls spiked with analyte concentrations up to 10000 ng/ml can also be analysed with excellent precision and accuracy after dilution of the samples. The parent drug and its metabolite are stable in plasma and urine after short-term storage (24 h at room temperature and after three freeze-thaw cycles) as well as after long-term storage at -20 degrees C (at least 6 months in animal plasma and 12 months in human plasma and urine). The method has been used to quantify both compounds in plasma and urine samples from clinical and non-clinical studies with ivabradine.     

Application of an automated HS-GC method in partition coefficient determination for xylenes and ethylbenzene in rat tissues

An automated static head space-gas chromatography method was used in the determination of partition coefficients (Kd) for the xylene isomers and ethylbenzene in blood, brain, muscle, kidney, liver and fat of Sprague Dawley rats. Since homogenization resulted in the potential loss of analytes from tissue samples, unhomogenized samples were used. With a few exceptions, tissue:air Kd values were independent of the concentrations of the analytes, singly or as a mixture. The tissue:blood Kd values were determined. For each tissue and analyte, the value obtained for each analyte concentration was within +/- 10% of the mean value calculated for the entire concentration range.     

Effect of Cl~- on electrochemical corrosion behavior of H_2S

In the process of natural gas transportation in high-sulfur oil and gas fields,the inner wall of the pipeline absorbs large quantities of condensate water due to the different temperatures inside and outside the pipeline. This condensate water dissolves a number of other ions. On one hand,these ions lead to the dissolution of H_2S and reduce the concentration of the acid corrosion reduction due to the ions having the same effect as salt. On the other hand,the ions in the electrochemical corrosion process can promote charge transfer and accelerate electrochemical reactions. Polarization curves and AC impedance measurements were used to investigate the effects of different Cland S~(2-) concentrations on the electrochemical behavior of H_2S.     

Controlling charge states of large ions

The charge state of ions produced in electrospray ionization (ESI) was reduced in a controlled manner to yield predominantly singly charged species by exposure of the aerosol to a bipolar ionizing gas. Analysis of the resulting ions on an orthogonal time-of-flight mass spectrometer yielded mass spectra greatly simplified compared with conventional ESI spectra. The decreased spectral complexity afforded by the charge reduction facilitates the analysis of mixtures by ESI mass spectrometry.     

Study of TRH in the postganglionic sypnasis of the isolated human vas deferens

Cummulative dose-response curves to l-noradrenaline and in presence of different concentrations of TRH (10(-3), 10(-4), 10(-5), 10(-6), 10(-7), and 10(-8) M) were investigated. 25 segments of vas deferens (escrotal tract) were obtained from different surgical patients of urological disorders. At the lower concentration (greater than 10(-7) M), we can not appreciate any influence of TRH on the l-noradrenaline response. Nevertheless there was a reduction of response to l-noradrenaline, with displacement of the curves to the right side, for the high concentrations, and a proportional ratio to the concentration to TRH.     

The role of cupric complex ions in the dissolution and stress-corrosion cracking of α-brass in nontarnishing aqueous ammonia

A study has been made of the dissolution and stress-corrosion cracking of copper and a series of α-brasses in nontarnishing 15 N ammoniacal solutions containing various concentrations of cupric complex ions. Corrosion studies under open-circuit conditions indicated that the dissolution process is controlled by the cathodic reduction of the cupric complexes or, more specifically, by the transport of these ions to the metal surface. Stress-corrosion tests confirmed earlier reports that failure of Cu-30 Zn under open-circuit conditions requires the presence in solution of cupric complexes in excess of a critical concentration. However, potentiostatic experiments demonstrated that cracking occurs in theabsence of significant cupric complex-ion concentrations provided that the dissolution rate of the specimens exceeds a critical value. Thus it is concluded that in stress-corrosion tests under open-circuit conditions the role of the cupric complex ions is simply to provide an efficient cathodic reaction, permitting rapid anodic dissolution. These observations are discussed in terms of the mechanism of cracking in these solutions. E. N. PUGH, formerly with the Research Institute for Advanced Studies (RIAS), martin Marietta Corp., Baltimore. Md.     

A simulation of the NiO/Ag interface with point defects

The NiO/Ag interface has been modelled using established simulation techniques, which have been modified to include the image interactions between the oxide ions and the induced charge in the metal. The energies of point defects near the interface were calculated and it was found that the surface rumpling was such that defects with a negative net charge were favoured. This will result in a space charge layer with excess cation vacancies which will cancel the interfacial potential. A low energy interface was modelled in which the cation sub-lattice of the second oxide plane was saturated with vacancies and Ni³⁺ ions. Such a structure may be responsible for the observed excess of oxygen near the NiO/Ni interface, and also for the low wetting angles of metals on NiO, compared with MgO.     

Electroextraction of lead from a lead trilonate solution

Laboratory studies of the cathode process of the electroextraction of zinc from the trilonate electrolyte obtained after the purification of solutions after leaching lead cakes of zinc production are performed. The potential scan rate is determined by recording potentiodynamic curves; the optimal electrolyte acidity, the composition, and the temperature are established. Values of activation energy confirming the concentration nature of process polarization are found.     

Tri-axial recording of event-related potentials during passive cognitive tasks in patients with Alzheimer''s disease

A novel dynamic mathematical microelectrode model (a model of solvent and solute kinetics in electrolyte-filled microelectrodes) was deduced from experimental observations made on standard (single-barrelled, 3.0 M KCl-filled, approximately 10 M[ohm]) electrodes using (a) electrodiffusion, electro-osmosis, and continuity equations that were placed into the constraints of electrode geometry, and (b) handbook/textbook parameter values, only. The model proved to be able to faithfully reproduce all observed electrochemical and electrical electrode properties, i.e. even those that constituted no part of the model's experimental basis. In theoretical tests, the model shows, for the standard electrode that (a) inside the electrode, any profiles in electrical potential and electrolyte concentration are occurring at the most distal part (approximately 50 microm) of the tip region, (b) asymmetrical shifts in electrolyte concentration just inside the electrode tip opening are the true cause of the electrode's current rectification, and (c) strong transelectrode currents are producing water flows across the electrode orifice that may affect the volume of smaller and medium-sized cells. In further tests, the model shows, among other things, for non-standard electrodes that (a) decreasing the electrode electrolyte concentration will give rise to marked decreases in electrolyte leakage from the electrode, but only very minor changes in tip potential, and (b) increasing the surface charge of the electrode glass (increases in zeta potential) and/or decreasing the electrode electrolyte concentration will produce increases in electro-osmotic water transport, which may be desirable for the intracellular injection of water-soluble (electro-neutral) substances.     

Confirmation and quantitation of selected sulfonylurea, imidazolinone, and sulfonamide herbicides in surface water using electrospray LC/MS

A multianalyte method has been developed for the confirmation and quantitation of 16 selected sulfonylurea, imidazolinone, and sulfonamide herbicides in surface water. Samples are acidified, the analytes are extracted using RP-102 extraction cartridges, and the extracts are cleaned-up using an anion-exchange cartridge (SAX) stacked on top of an alumina cartridge. The final extracts are evaporated to dryness, redissolved in 10:90 or 20:80 acetonitrile/water, and analyzed using electrospray LC/MS. Confirmation criteria were defined so that identification of the analytes could be made with a reasonable degree of scientific certainty. Confirmation required that (1) LC/MS retention times of the analytes be within 1% of the retention times of the standards, (2) the molecular ion and two characteristic fragment ions per analyte be present, and (3) ion abundance ratios of the fragment ions relative to the molecular ion be within 20% of the ion ratios obtained for the standards. Each of the analytes in all of the samples used to validate this method met these confirmation criteria. Quantitation of the analytes at 0.1 and 1.0 ppb was demonstrated, with average recoveries between 70% and 114% and relative standard deviations that were less than 13%. The limit of quantitation (LOQ) for this method is 0.1 ppb (ng/mL) for all analytes. Six water types were used for the validation of this method.     

电解质水溶液中钴、镍分离、提纯研究进展

高浓度、高纯度钴盐电解质水溶液是电解或电解精炼生产高纯乃至超高纯金属钴的关键.钴、镍离子深度地分离是制备该种电解质水溶液的核心任务.研究发现目前主要的分离、提纯方法包括:离子交换法、萃取色层法、膜分离法和溶剂萃取法等.研究对象主要集中在含高镍、低钴的硫酸盐水溶液体系.离子交换法、萃取色层法是实现两者深度分离的有效手段，溶剂萃取法则更易实现规模化.研究主要针对有机萃取剂和吸附材料的研发、改性、组合和分离提取工艺的改进等展开.文中对含钴、镍电解质水溶液中钴、镍分离研究进展进行总结评述，并对其发展进行展望.