[Changes in electrophysical characteristics of Azospirillum brasilense Sp7 cells during their interaction with polyclonal antibodies].

Electrooptical characteristics of Azospirillum brasilense Sp7 cells during their specific interaction with polyclonal rabbit antibodies were studied. Dependence of optical density of cell suspension during electroorientation of cells from frequency of orienting field in interval 10, 100, 250, and 500 kHz was evaluated. Itwas shown that electrooptical (EO) characteristics of bacterial suspensions change during interaction of A. brasilense cells with antibodies, and maximal changes occur when frequency of oriented field amounts 100-250 kHz. During interaction of A. brasilense Sp7 with strain-specific polyclonal antibodies in the presence of Escherichia coli K-12 and Pseudomonas putida C-11 decrease of amplitude of analytic signal was observed but detection of A. brasilense Sp7 cells was possible. Possibility of detection of microorganisms by EO analysis during their interaction with antibodies was shown.

[The electrooptical parameters of suspensions of Escherichia coli XL-1 cells interacting with helper phage M13K07].

The electrophysical properties of Escherichia coli XL-1 cells interacting with helper phage M13K07 were studied as a function of the phage-to-cell ratio and the contact time. The electro-optical signal of bacterial cells changed considerably as soon as 10 min after the onset of their incubation with phage particles, presumably due to phage adsorption on the cell surface. The maximum changes in the orientational spectra of cell suspensions were observed when the phage-to-cell ratio was 20. Selectivity studies showed that E. coli XL-1 cells interacting with the helper phage M13K07 in the presence of foreign microflora, such as E. coli K-12 or Azospirillum brasilense Sp7, can be identified by using their electrophysical properties. Changes in the orientational spectra of cell suspensions are interpreted with the stage of phage-bacterium interaction taken into account. The results obtained can probably be used to devise a new rapid method for identification of microorganisms and to study the particular stages of cell infection by bacteriophages.

[Investigation of electrophysical properties of Listeria monocytogenes cells during the interaction with monoclonal antibodies].

An electrooptical approach was used in studies of Listeria monocytogenes-antibody binding. An electrooptical analyzer, which has been developed at the State Research Center for Applied Microbiology (Obolensk, Russia), was used as a basic instrument for electrooptical measurements. The analyzer consists of the following modules: a sample preparation module, a mixer, an AC field generator, an EO-flow cell, a microcontroller for transfer of liquid, a thermal system, an operator interface, and an image processor. The sample preparation module includes a unit for an automatic filter changing device and a hydraulic system. Since the AC electrokinetic effects depend on the dielectric properties of bioparticles, their composition, morphology, phenotype, the medium, and the frequency of applied electrical field, the electroorientational spectra were used for discrimination of different types of bacteria, a given type being "controlled" (and identified) by the selective choice of binding agents (antibodies). The measurements were performed using a discrete set of frequencies of the orienting electric field (10, 100, 250, and 500 kHz). During biospecific interactions, an antibody is bound to the microorganism, causing a change in the dielectric properties of the microorganism-antibody complex, and the electrooptic signal reaches its maximum at 100-200 kHz. It was shown that the biospecific interactions of Listeria monocytogenes cells with anti-Listeria antibody in the presence of E. coli K-12, and A. brasilense sp7 significantly change the electrooptical signals. Thus, the determination of the presence of particular bacteria within a mixed sample may be achieved by selection and matching of antibodies specific to individual bacterium types and by comparing the spectra of bacterium in the presence and in the absence of specific binding agent (antibody).

[A highly sensitive immunoenzyme analysis using electrochemical detection]. / Vysokochuvstvitel'nyi immunofermentnyi analiz s élektrokhimicheskim detektirovaniem.

The authors have developed a method for improving the sensitivity of electrochemical enzyme immunoassay, based on binding the enzymatic reaction volatile component to a complexone, followed by destruction of the complex in a flow-type amperometric detector. The lowest limit of the measured levels of blood serum antibodies and antigens is 10(-11)-10(-12) M. The method was tried in enzyme immunoassay of the blood serum IgE in patients with asthma and chronic obstructive bronchitis. Reduction of IgE level after therapy was found to be a regular feature; the authors claim that it may be considered as one of the criteria indicating the treatment efficacy.

[An electrochemical method of determining peroxidase in saliva]. / Elektrokhimicheskii metod opredeleniia peroksidazy v sliune.

Electrochemical method has been developed for measuring human salivary peroxidase. Salivary peroxidase levels were measured in donors in various hours of the day, in girls in various periods of the cycle, and in myocardial infarction patients. The results may be used to develop rapid methods for assessment of ovarian functional activity and for prediction of myocardial infarction outcome. Electrochemical analysis productivity is 360 samples per hour, the minimal peroxidase concentration detectable is 5.10(-12) M.

[Immunochemical study of modified forms of L-asparaginase]. / Immunokhimicheskoe izuchenie modifitsirovannykh form L-asparaginazy.

Certain catalytic and immunological properties of L-asparaginase modified by polyglucin were studied. It was shown that the modified forms of L-asparaginase maintained high catalytic activity (Km 0.80.10(-5)-1.89.10(-5) M) and at the same time appeared to be more resistant to inactivation under the effect of antibodies.

[Determining the peroxidase level using tubular coal electrodes in flow-type systems]. / Opredelenie peroxidazy s ispol'zovaniem trubchatykh ugol'nykh elektrodov v protochnykh sistemakh.

An amperometric transducer with tubular coal electrodes has been worked out to determine the microquantity of peroxidase. The hydrodynamic parameters of the transducer were studied as were the relationship of the output signal to the concentration of the electroactive substance, the length of the electrode, the speed of the background electrolyte movement and the diffusion coefficient. The line section of the relationship between the strength of current and the peroxidase concentration is observed within the interval of the enzymic concentration 1-32 ng/ml with the exposure time of the enzymic reaction of 5-10 min.

[Amperometric sensor for recording the results of immunoenzyme analysis]. / Amperometricheskii datchik dlia registratsii rezul'tatov immunofermentnogo analiza.

A technique for quantitative determining horseradish peroxidase was developed using an amperometric sensor that makes it possible to register up to 50 pM of the enzyme in the reaction of the peroxidase oxidation of iodide ions by hydrogen peroxide. The sensor, composed of combined carbon and Ag/AgCl electrodes, is intended for enzyme immunoassay and may be used for registering the results in the very wells of the polystyrene plates widely used in clinics and laboratories. The dependences of the initial rate of the enzymatic reaction on the substrate concentration and pH of the medium were determined, on the basis of which the conditions for the optimal operation of the sensor were found. The amperometric and spectrophotometric methods of registration on a model system for determining antibodies against X-virus of potato were compared in order to show a possibility of the sensor applying to enzyme immunoassay.