Characteristic features of electron-ion collisions in strong electric fields

The classical motion of an electron in the Coulomb field of an ion and in a uniform external electric field is analyzed. A nondimensionalization method that makes it possible to study electron motion in arbitrarily strong electric fields is proposed. The possible electron trajectories in the plane of motion in a static field are classified. It is noted that, from a practical standpoint, the most interesting trajectories are snakelike trajectories, which are absent in the problem with a weak external field. An adiabatic approximation for transverse electron motions in quasistatic (strong) fields is constructed. A one-dimensional equation of motion is derived that accounts for transverse electron oscillations and the increase in the effective electron mass as an electron approaches an ion. An analytic model is used to calculate the spectra of bremsstrahlung generated by individual electrons. The calculated results are shown to agree well with the results of direct numerical integration of the basic equations. It is predicted that, at frequencies higher than the frequency of the incident light, pronounced peaks can appear in the spectrum of the transverse dipole moment of an electron; as a result, an electron is expected to effectively emit radiation at these frequencies in the direction of the external field.     

Biosynthesis and use of coproporphyrins and uroporphyrins and their metal complexes in immune analysis and diagnostic methods]

Methods of synthesis of coproporphyrin and uroporphyrin by using bacteria of the genus Arthrobacter are proposed. Metal complexes of coproporphyrin and uroporphyrin with Pt, Pd, and Zn were synthesized. Their structures were identified by spectrophotometry, IR spectrometry, 1H-NMR, mass spectrometry, and HPLC. Data showing the possibility to use coproporphyrin III-metal complexes as luminophores for fluorescence detection of tumors. The current and prospective uses of metal complexes of water-soluble natural porphyrins in advanced immunofluorescence assays are discussed.     

Effective method for physical mapping the DNA molecule

The method of DNA molecules physical mapping based on the algorithms of discrete optimization and graph theory was proposed. The input information consisted of the sizes of single and double restrictions fragments and the level of their measurement errors. The method presents possibilities for optimal planning of experiments and step by step construction of physical maps. Efficiency of the method and examples of its application are discussed.     

Pattern recognition in the computer analysis of nucleotide sequences

We have used an algorithm from the pattern recognition theory "generalized portrait" to find a distinguishing vector for Escherichia coli promoters. We have made an attempt to solve closely linked problems for choosing significant signs of that signal, multiple alignment and for calculation of the recognition vector (matrix). The promoters with known strength have been ranged with this vector. The analysis of the occurrence of predicted promoters has been carried out. The promoters search program for IBM-compatible computers is available from the authors.     

Effect of trophoblast-specific beta 1-glycoprotein on the ratio of cellular forms in a mast cell population

The influence of trophoblast-specific beta 1-glycoprotein (TSG) on the degranulation of mast cells and their saturation with heparin was studied. Introduction of the TSG into the population of mast cells of the rat peritoneal fluid practically does not change their degranulation, but lowers the degree of their saturation with heparin. An antibiotic alone increases the saturation of the cells with heparin. The serum of an allergic animal markedly stimulates the degranulation and lowers the degree of saturation of the mast cells with heparin. In an experimental model (antibiotic--the serum of the allergic mast cells) the mast cells transform into very clear (heparin-free) cells and the degree of saturation is at minimum. The TSG introduction into this system stabilizes the population of mast cells and markedly increases the degree of their saturation with heparin. Although the degranulation is rather intensive, it is less expressed, than in the experimental model. This suggests the presence of TSG receptors on the mast cells (targets of allergic reactions). The possibility to use TSG preparations in the therapy of allergic diseases is discussed.     

Two calcium currents in the somatic membrane of mollusc neurons

Two new types of calcium channels were discovered during research in ionic currents in the somatic membrane ofHelix pomatia neurons, using an intracellular perfusion technique. Apart from the principal calcium current described in the literature with a holding potential of about –110 mV, an additional calcium current was observed activated at depolarizations of –40 to –80 mV and was not reduced when the cell was perfused with solutions containing fluoride anions. The kinetics of this current were well described in the context of the Hodgkin and Huxley model with a time constant of activation of 6–8 msec and of inactivation of 300–600 msec. It increased in amplitude as the Ca⁺⁺ rose in the cellular environment but was reduced by extracellular addition of the Ca⁺⁺ antagonists Co⁺⁺, Ni⁺⁺, and Cd⁺⁺, and the organic blockers nifedipine and verapamil. The association constants of these substances with corresponding channels determined from the maximum of the current-voltage relationship were 2 (Ca⁺⁺), 3 (Co⁺⁺), 0.06 (nifedipine), and 0.2 mM (verapamil). The properties detected in this component of calcium conductance are compared with those of calcium channels in other excitatory formations and its possible functional role is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 5, pp. 627–633, September–October, 1985.     

The taxonomy of obligate anaerobic bacteria

Studies on the chemotaxonomy of obligate anaerobic bacteria have been made. The combination of gas chromatography and mass spectrometry with computer-assisted analysis, permitting the multicomponent analysis of all products of bacterial metabolism and bacterial cell components, has been shown to be a research method, quite suitable for such studies. The chromatographic profiles of the end products of metabolism in anaerobic cultures of different age have been found to differ not in the set and number of peaks indicating various metabolites, but only in the concentration of metabolites, increasing in the process of prolonged incubation. The authors believe that the national microbiological "library" of the chromatographic profiles of anaerobic organisms should be created and the album of typing chromatographic profiles should be published; besides, data on new profiles should regularly appear in magazines.     

Economical sequencing of DNA with terminators

We describe several improvements of chain-termination DNA sequencing procedure of Sanger et al. For template preparation we use 0.3 ml cultures of M13 clones, grown in standard 1,5 ml polypropylene tubes. The sequencing experiment differs from the previously described by the use of deoxyNTP, labelled with phosphorus-33 (a low energy isotope with a half-life of 25 days, commercially produced in the USSR), and by a "quasi-end labelling" reaction, preceding the DNA synthesis in the presence of dideoxyNTPs. The combination of the phosphorus-33 and the quasi-end labelling produces very sharp sequencing ladders, that equal or exceed in quality those obtained with sulphur-35, and only an overnight exposure with a conventional X-ray film is required. The use of plastic tubes for bacterial growth and the 60-well microchambers for carrying out sequencing reactions results in substantial saving of time and cost in routine "middle scale" sequencing (both types of plasticware are produced in the USSR).     

Tn10-mediated inversions fuse uridine phosphorylase (udp) and rRNA genes of Escherichia coli.

Two strains carrying metE::Tn10 insertions (upstream of the udp gene) were used to isolate mutants of Escherichia coli overexpressing udp. These strains differ in their gene order; one contains an inversion between the rrnD and rrnE rRNA operons. Selection was based on the ability of overexpressed Udp to complement thymine auxotrophy. Chromosomal rearrangements that connect the udp gene and promoters of different rrn operons were obtained by this selection. Seven of 14 independent mutants selected in one of the initial strains contained similar inversions of the metE-rrnD segment of the chromosome (about 12% of its length). Another mutant contained traces of a more complicated event, inversion between rrnB and rrnG operons, which was followed by reinversion of the segment between metE and the hybrid rrnG/B operon. Similar inversions (udp-rrn) in a strain already carrying an rrnE-rrnD inversion flip the chromosomal segment between metE and rrnD/E in the opposite direction. In this case, inversions are also accompanied by duplications of the chromosomal region between the rrnA and hybrid udp-rrnD/E operons. PCR amplification with a set of oligonucleotides from the rrn, Tn5, and met genes was used for more detailed mapping. Amplified fragments of the rearranged chromosomes connecting rrnD sequences and insertion elements were sequenced, and inversion endpoints were established.