GTI-space : the space of generalized topological indices

A new extension of the generalized topological indices (GTI) approach is carried out torepresent 'simple' and 'composite' topological indices (TIs) in an unified way. Thisapproach defines a GTI-space from which both simple and composite TIs represent particular subspaces. Accordingly, simple TIs such as Wiener, Balaban, Zagreb, Harary and Randićconnectivity indices are expressed by means of the same GTI representation introduced for composite TIs such as hyper-Wiener, molecular topological index (MTI), Gutman index andreverse MTI. Using GTI-space approach we easily identify mathematical relations between some composite and simple indices, such as the relationship between hyper-Wiener and Wiener index and the relation between MTI and first Zagreb index. The relation of the GTI space with the sub-structural cluster expansion of property/activity is also analysed and some routes for the applications of this approach to QSPR/QSAR are also given

Absence of Scaling in the Integer Quantum Hall Effect

We have studied the conductivity peak in the transition region between the two lowest integer Quantum Hall states using transmission measurements of edge magnetoplasmons. The width of the transition region is found to increase linearly with frequency but remains finite when extrapolated to zero frequency and temperature. Contrary to prevalent theoretical pictures, our data does not show the scaling characteristics of critical phenomena.These results suggest that a different mechanism governs the transition in our experiment.Comment: Minor changes and new references include

Crystal growth and preliminary X-ray study of glutamic acid specific serine protease from Bacillus intermedius

The glutamic acid specific protease (glutamyl-endopeptidase) from Bacillus intermedius, strain 3-19, was isolated and purified using ion exchange chromatography on CM-cellulose and Mono-S FPLC column. The conditions for crystallization of the enzyme have been discussed. The crystals of enzyme were grown using hanging-drop vapor-diffusion technique. Crystals belong to the space group C2 with unit cell parameters of a = 61.62 Å, b = 55.84 Å, c = 60.40 Å, β = 117.6° X-ray diffraction data to 1.68 Å resolution were collected using synchrotron radiation (EMBL, Hamburg) and an imaging plate scanner. © 1999 Elsevier Science B.V. All rights reserved

Optimization of cultivation medium for the production of Bacillus intermedius 3-19 glutamyl endopeptidase | Optimizatsiia sredy kul'tivirovaniia dlia produktsii glutamiléndopeptidazy Bacillus intermedius 3-19.

The effect of some components of cultivation medium on the growth of the streptomycin-resistant Bacillus intermedius strain 3-19 and on the production of glutamyl endopeptidase was investigated using factorial experimental design, which allowed the concentrations of peptone and inorganic phosphate to be optimized for the maximum production of the enzyme. Experiments with different peptones and casamino acids showed that the enzyme production is maximum with peptone 3 of plant origin. The addition of casamino acids or amino acids to the peptone-containing cultivation medium inhibited the production of glutamyl endopeptidase

Effect of nutrients on the accumulation of glutamyl endopeptidase in the culture liquid of Bacillus intermedius 3-19

The effect of nutrients and growth conditions on the accumulation of glutamyl endopeptidase in the culture liquid of Bacillus intermedius 3-19 was studied. Glucose and other readily metabolizable carbon sources were found to suppress the production of the enzyme, whereas inorganic phosphate and ammonium cations enhanced it. Protein substrates, such as casein, gelatin, and hemoglobin, did not affect enzyme production. Some bivalent cations (Ca2+, Mg2+, Co2+) increased the production of glutamyl endopeptidase, but others (Zn2+, Fe2+, Cu2+) acted in the opposite way. The rate of enzyme accumulation in the culture liquid increased as the growth rate of the bacterium decreased, so that the maximum enzyme activity was observed in the stationary growth phase. Based on the results of this investigation, an optimal medium for the maximum production of glutamyl endopeptidase by B. intermedius 3-19 was elaborated. © 2000 MAIK "Nauka/Interperiodica"

Effect of nutrients on the accumulation of glutamyl endopeptidase in the culture liquid of bacillus intermedium 3-19

The effect of nutrients and growth conditions on the accumulation of glutamyl endopeptidase in the culture liquid of Bacillus intermedius 3-19 was studied. Glucose and other readily metabolizable carbon sources were found to suppress the production of the enzyme, while inorganic phosphate and ammonium cations enhanced it. Protein substrates, such as casein, gelatin, and hemoglobin, did not affect enzyme production. Some bivalent cations (Ca2+, Mg2+, Co2+) increased the production of glutamyl endopeptidase, but others (Zn2+, Fe2+, Cu2+) acted in the opposite way. The rate of enzyme accumulation in the culture liquid increased as the growth rate of the bacterium decreased, so that the maximum enzyme activity was observed in the stationary growth phase. Based on the results of this investigation, an optimal medium for the maximum production of glutamyl endopeptidase by B. intermedius 3-19 was elaborated

Biosynthesis and localization of glutamylendopeptidase from Bacillus intermedius strain 3-19

The biosynthesis of glutamylendopeptidase from Bacillus intermedius strain 3-19 and localization of the enzyme in the bacterial cells was studied. The synthesis of the enzyme was suppressed by easily metabolizable carbon sources. Inorganic phosphate and NH+ 4 ions stimulated the production of glutamylendopeptidase. Complicated organic substrates such as casein, gelatine, and haemoglobin did not affect the biosynthesis of the enzyme. The divalent metallic ions Ca2+, Mg2+, Co2+ increased the production of glutamylendopeptidase while Zn2+, Cu2+, and Fe2+ reduced the biosynthesis of proteinase. The rate of synthesis of the enzyme increased when the rate of the bacterial growth decreased. The maximum enzyme activity in the culture fluid was determined at the stationary phase of growth. In the cells glutamylendopeptidase was bound to the cytoplasmic membrane, and the maximal enzyme activity was detected in the stationary growth phase. The results facilitated the development of a medium which yielded the maximum glutamylendopeptidase production by B. intermedius strain 3-19

Secreted hydrolases from streptomycin-resistant strains of Bacillus intermedius

Alkaline phosphatases and serine proteinases have been isolated from the culture liquid of streptomycin-resistant strains of Bacillus intermedius using ion-exchange and affinity chromatography and FPLC. Substrate blotting and electrophoresis revealed two phosphatase forms with molecular masses of 40 and 50 kD. The enzyme had maximal activity at pH 9.5 and 50°C and could cleave the phosphate moiety from a range of substrates. It is suggested that both forms of the phosphatase are products of processing that involves a serine proteinase. Two proteinases, with molecular masses of 29 and 33 kD, were purified to homogeneity from the culture liquid of A. intermedius S7. The protein from the major peak was identical in its properties to an earlier described serine proteinase. The minor peak was 5% of the major one. These enzymes had different pH optima. Inhibitor analysis indicated that the minor peak is also a serine proteinase

Secreted hydrolases from streptomycin-resistant strains of Bacillus intermedius

Alkaline phosphatase and serine proteinase have been isolated from streptomycin-resistant strains of Bacillus intermedius using ion-exchange, affinity and FPLC chromatography. Substrate blotting analysis and electrophoresis revealed two phosphatase forms with molecular weight of 40 and 50 kDa. The pH and temperature optima of phosphatase were at pH 9.5 and 50°C. The enzyme showed a broad substrate specificity. It was suggested that the two forms of phosphatase are the products of processing, in which serine proteinase is the participant. Two proteinase peaks with molecular weights of 29 and 33 kDa were isolated from B. intermedius S7, the first peak having only 5% of the activity of the second peak. The major peak was identical to serine proteinase described earlier. The minor peak was distinct from the major one by the pH-optima. Analysis of inhibitors' effects revealed that the minor peak also corresponded to serine proteinase

Bipolaron Binding in Quantum Wires

A theory of bipolaron states in quantum wires with a parabolic potential well is developed applying the Feynman variational principle. The basic parameters of the bipolaron ground state (the binding energy, the number of phonons in the bipolaron cloud, the effective mass, and the bipolaron radius) are studied as a function of sizes of the potential well. Two cases are considered in detail: a cylindrical quantum wire and a planar quantum wire. Analytical expressions for the bipolaron parameters are obtained at large and small sizes of the quantum well. It is shown that at $R\gg 1$ [where $R$ means the radius (halfwidth) of a cylindrical (planar) quantum wire, expressed in Feynman units], the influence of confinement on the bipolaron binding energy is described by the function $\sim 1/R^{2}$ for both cases, while at small sizes this influence is different in each case. In quantum wires, the bipolaron binding energy $W(R)$ increases logarithmically with decreasing radius. The shapes and the sizes of a nanostructure, which are favorable for observation of stable bipolaron states, are determined.Comment: 17 pages, 6 figures, E-mail addresses: [email protected]; [email protected]