Development of a Flow Immunoassay System for the Detection of Salmonella Typhimurium

Abstract

A flow immunoassay system has been developed for the detection of Salmonella typhimurium by immobilization of antibody to Salmonella onto tygon tubing by adsorption and onto polyethylene tubing, by covalent binding. After liquid containing Salmonella cells or Salmonella antigen was allowed to interact with the immobilized. antibody, glucose oxidase labeled antibody to Salmonella was injected to the system. The bound antigen was quantified by electrochemical detection of H₂O₂ produced from the enzymic oxidation of glucose to gluconic acid. In view of the low non-specific binding, sensitivity and reusability, the polyethylene immunoreactor provided a better performance. The system was capable of detecting as low as 10⁵ ? 10⁶ Salmonella cells/ml in less than 10 minutes. The immunoreactor could be regenerated for at least 50 times during one month of the experiment. The detection limit of the tygon immunoreactor was somewhat higher (10⁶ ? 10⁹ cells/ml). Even though the anti-Salmonella antibody was easily immobilized on the tygon tubing, the system was not reusabl and exhibited a very high non-specific binding.     

The Ambiguity of the Viscometric Method for the Deter-Mination of Dextranase Activity

Abstract

In earlier studies it was found that the tissue pellets of Avena seedlings decrease the viscosity of dextran solutions. By the use of direct methods for investigating the breakage of these molecules, it is shown that the lowering of viscosity of dextran solutions under the influence of tissue pellets of Avena coleoptiles is not due to an intramolecular process of molecular breakage (dextranase-like activity) but rather to an intermolecular process of still unknown nature. This conclusion is supported by the finding that solutions of entirely different macromolecules than dextrans are also affected by the tissue pellets. The observed changes in viscosity can therefore not be due to dextranase activity and the viscometric method for the determination of this activity is clearly ambiguous.     

Base-Catalyzed Rate and Arrhenius Activation Energy for t-Butyl Isothiocyanate Hydrolysis in Dioxane-H2O and Ethanol-H2O Mixtures by Gas Chromatography

Abstract

N-bonded tertiary-butyl isothiocyanate hydrolyzes via a mechanism that differs from the normal, or S-bonded linkage isomer. The diminutive amount of published kinetic data for the former compound prompted a redetermination of the base-catalyzed rate of hydrolysis of the isothiocyanate in 2% dioxane, ethanol water mixtures at several temperatures using gas-liquid chromatography.     

Influence of Methyl Substitution on mass Spectra of Diphenylmethanes: Analytical Applications

Abstract

In connection with other studies we synthesized and obtained low resolution electron impact spectra of the 2,2′-, 2,3′-, 2,4′-, 3,3′-, 3,4′-, and 4,4′-dimethyl substituted diphenylmethanes. The results suggest that caution should be exercised in using the characteristic even mass rearrangement fragment (m/e = 104) produced by the “ortho-effect” as the only method to distinguish between ortho and non-ortho methyl substituted diphenyl-methanes. The relationship between the stability of the diphenylmethane isomers and the substitution patterns at the meta and para positions does not parallel that observed for the dimethyl substituted biphenyls.     

Special Report Chemical Sensors for In Vivo Monitoring: Clinical Aspects

Abstract

The origins and purpose of a new European Community Concerted Action on “Chemical Sensors for In Vivo Monitoring” are described: the overall aim is to promote the development and application of chemical sensors for in vivo monitoring. A report is presented on the first Workshop Meeting entitled “Clinical Aspects of In Vivo Sensing”, which addressed the question of the analyte to be sensed, specific and general problems of in vivo sensing, and future prospects.     

Rapid Detection of Escherichia Coliform Using A Series Electrode Piezoelectric Crystal Sensor

Abstract

A series electrode piezoelectric crystal sensor was used to determine Escherichia coliform (E. coli.). This method is simple and rapid, and requires only a single sample dilution. E. coli. in the range of 10 - 10⁶ cells per ml can be estimated by this method. The procedure is a frequency detection time (FDT) method. The factors which affect the determination are discussed. Thirty samples in pure culture were tested by this method and the results fell within the 95% confidence limits of the standard plate count values. A correlation coefficient of 0.93 was obtained between the frequency detection time and logarithm of initial bacterial concentration. This corresponds to the criteria used to evaluate E. coli. with the added advantage of single dilution and more rapid results.     

A Direct Spectrophotometric Assay for Pyruvic Oxime Hydrolase

Abstract

A sensitive spectrophotometric method, which directly measures the formation of pyruvic oxime from pyruvate and NH₂OH in the UV, is described for the detection of pyruvic oxime hydrolase activity in biochemical systems. The method was used in an attempt to detect pyruvic oxime hydrolase activity in cell-free extracts from an Alcaligenes sp. which can grow on pyruvic oxime. Although substantial pyruvic oxime + nitrite oxidative activity was detected in cells and cell-free extract of this bacterium, catalysis of pyruvic oxime formation was not observed within the error of the method (～20% of the uncatalyzed rate constant of 1.9x10^?3 s^?1 at pH 7, 22°C). The rate of pyruvic oxime oxidation by cells and cell-free extract was at least 10⁵?10⁶ times greater than the rate of its hydrolysis, thus implying that oxidation of pyruvic oxime need not require prior hydrolysis. The method would appear to be applicable to hydrolases directed toward a variety of oximes.     

Fluorescence Behavior of Phenolic Compounds in Solutions Containing Micelles

Abstract

The effects of micelles on the fluorescence detection of phenolic compounds are described. Micelles were found to enhance the fluorescence of the drugs apomorphine (APO), and N-n-propylnorapomorphine (NPA), and a series of model hydroxybiphenyls. The fluorescence enhancements were pH dependent and biphasic behavior in hexadecyltrimethylamnonium chloride was observed for APO and NPA. Multiple equilibria and formation of zwitterions of the phenolic aporphines in the micellar environment is proposed to explain this behavior. Micellar fluorescent enhancements should be useful in improving the sensitivity of fluorometric determinations of polar compounds.     

Spectrophotometric Determination of Nickel(II) with O-hydroxyhydroquinonephthalein in the Mixed Micellar Media of Zephiramine and Tween 20

Abstract

The effect of mixed surfactants on the color reaction between nickel(II) and o-hydroxyhydroquinonephthalein(Qnph) was examined in weakly basic media. The color development of the metal complex in the presence of cationic and nonionic surfactants (mixed micellar media of Zephiramine (Zp) and Tween 20) was very stable and exhibited a high and reproducible absorbance. The calibration curve was linear in the ranges of 0 – 7.0 μg nickel(I1) in a final volume of 10 ml at 545 or 536 nm. The method developed does not require an organic solvent extraction step. The apparent molar absorptivity and Sandell sensitivity were 1.26 × 10⁵ 1 per mol per crn and 0.0045 μg per cmL nickel(II), respectively, at 545 nm.     

Spectrophotometric Determination of Manganese with 4(5)-Imidazolealdoxime (Imalox)

Abstract

A method is described for the spectrophotometric determination of manganese by means of its complex with 4(5)-imidazolealdoxime, IMALOX, formed in alkaline medium. The colour system has its absorption maximum at 350 nm and obeys Beer's law over the range 0.8–8.0 μg of Mn per ml. The optimum range is 1–5 μg m^?1. The molar absorptivity is 7850 1 mol^?1 cm^?1. Relatively few ions interfere, and these can be masked with cyanide, tartrate and NTA. The experimental results have been critically analyzed and a comparison with the main spectrophotometric reagents for manganese is presented.     

Pyrocatechol-1-Aldehyde 2-Benzothiazolylhydrazone As Reagent for the Spectrofluorimetric Determination of Nanogram Amounts of Gallium in Urine and Blood Serum

Abstract

A method is developed for the spectrofluorimetric determination of 1–80 ng.ml^?1 of gallium with pyrocatechol-1-aldehyde 2-benzothiazolylhydrazone, in a 50% (v/v) DMSO-Water medium at apparent pH 4.0 (monochloracetic/monochloracetate buffer). Λ_ex = 400nm, Λ_em = 504 nm (corrected). Interferences have been evaluated and the method applied to the determination of gallium in human urine and blood serum samples.     

A Fluorometric Assay of L-Aspartate: 2-oxoglutarate Aminotransferase in Human Serum with N-(9-Acridinyl) maleimide

Abstract

A new assay of L-aspartate:2-oxoglutarate aminotransferase (EC 2, 6, 1, 1) (glutamic-oxaloacetic transaminase: GOT) is reported. Substrate L-aspartate was replaced with L-cysteine sulfinic acid (CSA) which yields sulfite and pyruvate. The enzyme activity was determined by measuring the sulfite with the aid of a fluorescent reagent, N-(9-acridinyl)maleimide (NAM). The method presents a extremely sensitive GOT assay in the range of 4 to 140 U/l using less than 10 μl of human serum.     

Quantitative Determination of Nortriptyline And Desmethylnortriptyline In Human Plasma By Combined Gas Ciiromatography - Mass Spectrometry

Abstract

A quantitative method has been developed for the determination of the tricyclic antidepressant drug nortriptyline in plasma, utilizing a combined technique of gas chromatography - mass spectrometry called mass fragmentography. A metabolite, desmethylnortriptyline, may be analyzed in the same run. The compounds are first converted to their heptafluorobutyranide derivatives. A complete chromatogram takes less than five minutes. Quantitive determinations under the present conditions are possible down to a few nanograms of nortriptyline per milliliter. There is a good correlation between the new method and that previously used which was based upon in vitro ³ 11-acetylation labelling.     

Adsorption behavior of polymers having phosphoric acid group on γ-Fe2O3 and magnetic characteristics in magnetic coatings

Polymers having phosphoric acid groups were prepared as a model binder for magnetic coatings, and the correlation among the adsorption behavior of the polymers onto-Fe₂O₃ particles and the dispersibility, the orientation, and the packing density of-Fe₂O₃ particles in the magnetic coatings was investigated.PMMA homopolymer molecules hardly adsorbed on-Fe₂O₃, and the interfacial tension at a water/polymer solution (toluene) interface ( _W/T) was scarcely changed compared with a water/toluene interface. Increasing with the content of polymeric phosphoric acid group, the adsorbance of polymer increased and the interfacial tension ( _W/T) decreased. When the content of polymeric phosphoric acid groups was over 0.4 mol%, the adsorbance of polymer and interfacial tension ( _W/T ) remained constant. When these polymers were used as a binder for magnetic tapes, the dispersibility of-Fe₂O₃ in the magnetic coatings was improved, increasing with the content of polymeric phosphoric acid group; however, when the content of phosphoric acid group was over 0.2 mol%, its dispersibility decreased abruptly.Studies on Recording Magnetic Materials and Magnetic Composite. XVIII.     

X-ray diffraction studies on homologous thallium soaps below the temperature range of the neat phase 2. Structure models of crystalline modifications in the temperature range below the neat phase

In Part 1 were discussed the results of X-ray diffraction measurements on homologous thallium soaps, the lattice parameters and the unit cells of the different phases: phase C₁, phase C₂, phase I, phase II, and the neat phase.The aim of Part 2 is the development of structural models, based on data on lattice parameters, packing densities of hydrocarbon chains and head groups. In order to supplement our experimental data we carried out infrared-spectroscopic measurements at different temperatures within the existence regions of these phases to get additional information on alterations in configurations of head groups and hydrocarbon chains of thallium soaps in these phase regions.By comparing the structural models we can generalize that the phase C₁, phase C₂, phase I, and phase II have some properties in common: they form crystalline structures, their unit cells are monoclinic, and the angles and are orthogonal. The amount of the lattice parametersc is equal to the distances of two molecular bilayers and/or twice the distance between the lamellae.Among the normal lamella, the molecules form a herring-bone-like packing. This indicates that the lamellar structure of the liquid-crystalline neat phase is already preformed in these crystalline modifications of phase C₁, phase C₂, phase I, and phase II. These crystalline phases differ in their lattice parameters and their packing coefficients. The transition from the crystalline phase I or phase II into the neat phase is accompanied by a temperature-dependent contraction of the distances between the lamellae, which originates in the fluidity of the hydrocarbon chains. Simultaneously, the lattice parametersa andb are drastically shortened and attain dimensions considerably lower than the values obtained in crystalline modifications. The X-ray scattering properties of the Tl⁺-ions suggest that the Tl⁺-ions exist in a fluid-like state within the head groups region of the neat phase.We came to the conclusion that the thallium-oxygen-bond is remarkably less polar than the bonds between alkali ions and oxygen resulting from the electro-negativity of the metal-oxygen-bonds of the alkali soaps, in comparison to the thallium soaps. Hence, the absence of polymorphic liquid-crystalline semiphases of thallium soaps is due to the low polarity of the thallium-oxygen-bond. Structure formation of Tl-soaps is mainly influenced by the hydrocarbon chain packing.     

Transient photocapacitance study in 4-nitro-4′-aminodiphenyl layers

In 4-nitro-4-aminodiphenyl (NAD) layers the photocapacitance (PhC) transients were investigated. PhC spectral distribution as well as the temperature dependences of time constants (under/_on/or after/_off/illumination) have been measured. The photocapacitance spectral distribution possesses maxima at 350, 500, and 750 nm. It was shown that _on (T) is of exponential form while _off (T) is more complicated. The values of thermal activation energies (0.65±0.05) eV of both time constants coincide. The mechanism of photocapacitance process has been disclosed in NAD layers.     

Micropore filling of NO,SO2, NH3, and CO2 onα-FeOOH dispersed activated carbon fibers

Adsorption isotherms of NO, SO₂, NH₃, and CO₂ on-FeOOH dispersed activated carbon fibers at 303 K were examined to determine the role of surface modification in micropore filling. The parameters on micropore structures were obtained from both nitrogen adsorption at 77 K and benzene adsorption at 303 K; both isotherms were of BDDTI type and gave the same micropore volume. The preoxidation conditions of ACF, prior to the deposition of-FeOOH against the NO adsorptivity were examined. The dispersion of-FeOOH on ACF was effective in enhancement of micropore filling, irrespective of the adsorbate molecule. We determined the degree of volume filling for each gas by the use of a DR plot. The modified DR plot for an NO gas, of which the critical temperature was much lower than 303 K, was proposed. The degree of volume filling for various gases was correlated with the deviation of each boiling point from 303 K and with the van der Waalsa constant.     

Thermoanalytical investigations of extended and annealed keratins

DSC investigations have been used to characterize the microfibril-matrix complex of keratin consisting of helical low-sulfur microfibrils in a nonhelical high-sulfur matrix. The corresponding DSC curves display one or two endothermic peaks in the temperature range 230°–255°C. The first peak is a microfibrillar peak and the second one a matrix peak (cystine decomposition peak). DSC investigations of extended keratins have shown that the microfibrillar peak is a helix peak. DSC investigations of annealed keratins confirm our earlier assumption that the helix peak is no helix melting peak but an irreversible helix unfolding, superimposed by various decomposition reactions. The matrix peak of the above described keratin samples is less reproducible than the corresponding helix peak and cannot be used for further characterization studies of keratins.Dedicated to Professor E. G. Klesper on the occasion of his 60th birthday.