ALBERT

Notes: Abstract Small α-iron particles with diameter less than 10 nm and enlarged lattice constant have been obtained by low temperature oxidation and reduction of an amorphous Fe91Zr9 alloy.In-situ X-ray diffraction has been used to study the transformation of the alloy at 300 °C which is far below the crystallization temperature. Scanning electron microscopy showed that the reacted sample consisted mainly of aggregates of small iron particles. This might offer a promising method for the effective preparation of heterogeneous catalysts.

Notes: Abstract: In a recent series of papers (see Goldman [1–3]), B-splines of negative degree were introduced and partially investigated. The main purpose of the present paper is to continue and to extend these investigations. In the first part, we look more deeply onto the negative degree B-splines; we present an explicit representation for them, as well as a degree elevation formula; this solves a problem posed in [3]. Moreover, in the second part we look (probably for the first time in the literature) at the structure of the space of negative degree spline functions, spanned by the negative degree B-splines. As a main result here, we obtain a truncated power function representation of these splines.

Notes: Summary Extrapolation methods are well-known to be very efficient tools for the acceleration of the convergence of certain sequences of numbers or functions, cf. [2, 3, 4, 8, 9]. In this note we present a representation of linear extrapolation procedures in terms of complex contour integrals. For the proof we make use of a complete characterization of these procedures as linear functionals, which is itself of some interest and can be found, for example, in [2] or [8].

Notes: Summary Streptomyces griseus TÜ 6 produces the sideromycin antibiotic albomycin δ2 in concentrations of approximately 1 mg/l. The production depends on the phosphate, iron, and ornithine concentrations in the medium. In optimized conditions, the production of albomycin could be increased to 25 mg/l in a fedbatch fermentation. Isolation and purification could be achieved by reversed-phase and size-exclusion chromatography and preparative high-performance liquid chromatography (HPLC). The detection limit in quantitative determination of albomycin by HPLC was reached at a concentration of 1 μg/ml, which was 100 times less sensitive than biological testing, but this method, although time-consuming, was more selective.

Notes: Summary A phylogenetic tree was constructed from 245 globin amino acid sequences. Of the six plant globins, five represented the Leguminosae and one the Ulmaceae. Among the invertebrate sequences, 7 represented the phylum Annelida, 13 represented Insecta and Crustacea of the phylum Arthropoda, and 6 represented the phylum Mollusca. Of the vertebrate globins, 4 represented the Agnatha and 209 represented the Gnathostomata. A common alignment was achieved for the 245 sequences using the parsimony principle, and a matrix of minimum mutational distances was constructed. The most parsimonious phylogenetic tree, i.e., the one having the lowest number of nucleotide substitutions that cause amino acid replacements, was obtained employing clustering and branch-swapping algorithms. Based on the available fossil record, the earliest split in the ancestral metazoan lineage was placed at 680 million years before present (Myr BP), the origin of vertebrates was placed at 510 Myr BP, and the separation of the Chondrichthyes and the Osteichthyes was placed at 425 Myr BP. Local “molecular clock” calculations were used to date the branch points on the descending branches of the various lineages within the plant and invertebrate portions of the tree. The tree divided the 245 sequences into five distinct clades that corresponded exactly to the five groups plants, annelids, arthropods, molluscs, and vertebrates. Furthermore, the maximum parsimony tree, in contrast to the unweighted pair group and distance Wagner trees, was consistent with the available fossil record and supported the hypotheses that the primitive hemoglobin of metazoans was monomeric and that the multisubunit extracellular hemoglobins found among the Annelida and the Arthropoda represent independently derived states.

Notes: Abstract Photoreceptor cells of the honeybee drone fire, in the presence of the polycationic aminoglycoside neomycin, repetitive slow spike-like potentials superimposed on the receptor potential plateau phase. We have used conventional intracellular recordings and microfluorometric intracellular Ca2+ measurements to characterize these spike potentials. We have shown that the spike frequency increases in a light-intensity-dependent manner. The spikes are fired only when light stimuli depolarize the cell from a resting potential of −50 to −60 mV to at least −40 to −45 mV; they are tetrodotoxin insensitive and blocked by the Ca2+ channel blockers Ni2+, Cd2+, ω-agatoxin TK, verapamil and methoxyverapamil. Depolarization of the photoreceptors with high extracellular K+ in the presence of neomycin in darkness does not generate spikes. Small intracellular Ca2+ oscillations superimposed on the plateau phase of the light-induced increase in intracellular free Ca2+ concentration have a similar temporal pattern as the spike-like potentials. We conclude that the spike-like potentials require stimulation by light and are generated by voltage-dependent Ca2+ channels localized on the soma of the photoreceptors, distal to the basal lamina.

Notes: Abstract Complex planar splines were introduced by Opfer and Puri [4] and further investigated by several authors, cf. [3, 5, 6, 8]. These papers were mainly concerned with the properties of piecewise linear or quadratic polynomials. In the present paper polynomial planar splines of arbitrary degree are investigated. Our results are mainly concerned with their interpolatory properties on polygonal regions and contain those of [3, 4, 5] for triangular and rectangular regions as special cases.

Notes: Summary We have performed a comparative transcript analysis with RNA from two different strains of Cephalosporium acremonium, using synthetic oligonucleotides as specific probes for the isopenicillin N-synthetase gene (pcbC). Strain DSM 2353 shows a considerably higher amount of the pcbC transcript than strain ATCC 14553. Subsequently, a genomic library from C. acremonium strain DSM 2353 DNA was constructed using lambda vector EMBL4. We have isolated five recombinant clones containing identical copies of the pcbC gene as was confirmed by partial DNA sequencing. The 5′ region of the pcbC gene was fused with the prokaryotic gene for hygromycin B phosphotransferase (hph) using a synthetic oligonucleotide linker. The resulting plasmid pMW1 can be used for high frequency transformations of the filamentous fungus Aspergillus niger (about 10000 transformants/μg plasmid DNA). From Southern hybridization analysis it can be concluded that all transformants tested contain vector DNA integrated into the genomic DNA. The expression of the prokaryotic hph gene in A. niger was conclusively demonstrated with an assay specific for hygromycin B phosphotransferase.

Notes: Summary We investigated the binding of azure B to DNA (calf thymus) over a wide range of concentrations of the dye (C F) and the nucleic acid (C N) using absorption spectroscopy [C Fand C Nrepresent the total concentrations of the dye (F) and the mononucleotide units (N) of the DNA, respectively]. The binding isotherms of the dye to DNA in aqueous solutions were determined. In addition, we analysed the composition of insoluble DNA/azure B precipitates that are formed in presence of an excess of azure B. These precipitates are of particular interest, because Giemsa staining is usually performed using high dye concentrations. Azure B easily forms dimers in aqueous solutions. When determining the binding isotherms, the equilibrium between free monomers and dimers must be taken into account. Therefore, we determined the dimerisation constant (K d) of azure B from the concentration dependency of its absorption spectra in water at the standard temperature T=298 K (25°C), K d=6.5·103 M −1 (experimental conditions: tris buffer, pH 7.2; concentration of Na⊕ ions, C Na=0.002 M). As the C Na value increases, the dimerisation constant rises rapidly. When the azure B concentration is very low and there is an excess of DNA, ordinary Scatchard and Langmuir isotherms are observed. Monomer dye cations are bound to DNA, these cations being in equilibrium with free monomers in the solution. In order to obtain the Scatchard binding constant (K S) and the binding parameter (n) spectroscopically, it is necessary to determine the extinction coefficient (ε Fb ) of the monomer bound (b) dye molecules (F) at one analytical wave number $$(\tilde v_a )$$ . The three constants can be determined simultaneously using an iterative technique that combines Scatchard isotherms and the Benesi-Hildebrand extrapolation, C N→∞. We obtained K S=1.8·105 M −1 and n=0.18 (25°C; tris buffer, pH 7.2; C Na=0.002 M). At very low dye (C F) and competitor (C Na) concentrations, only 18% of the anionic binding sites of the DNA are capable of binding the dye cations. With increasing C Na values the concentration of bound azure B cations decreases rapidly. The Na⊕ cations displace the bound dye cations and act as a competitor. The K Svalue also greatly depends on the competitor concentration (C Na). This dependency can be used to determine the binding constant of intercalation, K 1=2.7·103 M −1, the binding constant of pre-intercalative or external binding, K 2=1.9·105 M −1, and the binding constant of the competitor cations (Na⊕), K 3=24 M −1 (25°C; tris buffer, pH 7.2). The binding constant of intercalation (K 1) is very small compared with the constant of pre-intercalative binding (K 2). Therefore, at low dye and competitor concentrations, azure B behaves like a non-intercalating compound. With increasing dye concentrations (C F), pronounced positive deviations from the ordinary Scatchard and Langmuir isotherms are observed. Many more dye molecules are bound to DNA than would be expected. These positive deviations are caused by cooperative binding (q). Each anionic phosphodiester residue of DNA is a binding site for dye cations, g=1.0. Using a spectroscopic technique, we were able to determine the extinction coefficient (ε Fb ) of the cooperatively bound dye molecules at low DNA concentrations, C N→0. Using a method involving two analytical wave numbers $$(\tilde v_a , \tilde v'_a )$$ , we were able to evaluate experimentally the binding isotherm in the range of cooperative dye binding (25°C; tris buffer, pH 7.2; C Na=0.002 M). The binding isotherm was calculated by applying the theory of cooperative binding as proposed by Schwarz. Three constants characterize the binding isotherm: 1. K n=1.5·103 M −1 (the constant of nucleation); this describes the binding of a monomer dye molecule to one binding site of DNA that has unoccupied neighbour sites. 2. K q=1.2·105 M −1 (the constant of aggregation or growth); this describes the binding of a dye cation in the immediate neighbourhood of an already bound dye molecule. 3. q=K q/Kn=80 (the cooperativity parameter); this describes the interaction of the nearest neighbouring dye molecules on the DNA. It can be shown that the monomer bound azure B cations of the Scatchard or Langmuir isotherm do not represent the nucleation step of cooperative dye binding. The two binding mechanisms are different and are competitive with each other. Bearing this in mind, it was possible to calculate the isotherm over the entire concentration range of non-cooperative and cooperative dye binding. The spectra of the bound dye species could be separated from the total absorption of the solutions by using a combination of absorption spectroscopy and equilibrium dialysis. The bound monomers (M), dimers (D) and higher aggregates (A) of azure B have different absorption spectra. The first two have absorption maxima at 15 200 cm−1 (657 nm) and 17 200 cm−1 (582 nm), respectively. The higher aggregates (A) have a main peak at 18 000 cm−1 (556 nm) with two shoulders at approximately 15 300 cm−1 (654 nm) and 16 800 cm−1 (596 nm) that need to be distinguished from the absorption bands of M and D in the same spectral regions. At very low C F/CNratios, only bound monomers are observed. At somewhat higher C F/CNratios, monomers and dimers are detected. However, when the C F/CNratio increases beyond a certain point, the monomers and dimers disappear completely; instead, we observed higher aggregates of bound azure B cations exhibiting a characteristic broad absorption band at 18 000 cm−1 and two long wave-length shoulders at 15 300 and 16 800 cm−1. This behaviour is in agreement with the cooperativity parameter, q=80: Cooperative binding favours the formation of higher aggregates with increasing C F/CNratios. At relatively high dye and DNA concentrations, insoluble DNA/azure B precipitates (P) are formed. We analysed the composition of these precipitates, r P=(CFb/CN)P, as a function of C F/CN(C N=1.56·10−4 M). At a ratio C F/CN=1.8, each anionic binding site of DNA is occupied by an azure B cation, r P=1.0. The nucleic acid is saturated with dye cations, and the DNA/azure B complex is uncharged. At C F/CN〉1.8, rP〉1: dye cations are bound in excess as compared with the number of anionic binding sites of the DNA. At C F/CN=5.28 (CF=8.22·10−4 M), we found r P=1.37: The DNA/azure B complex now has a positive charge. Finally, we measured the microspectra of fine fibres or films of DNA/azure B precipitates at different C F/CNratios. In all spectra, the intense maximum of the bound higher aggregates (A) at 18 000 cm−1 (556 nm) is dominant. At relatively low C F/CNratios, the absorption of bound dimers at 17 100 cm−1 (585 nm) is also detectable. With increasing C F/CNratios, the absorption of the dimers disappears; the only remaining spectrum is that of A, with its intense maximum at 18 000 cm−1 and the two weaker bands at approximately 15 400 cm−1 (651 nm) and 16 500 cm−1 (606 nm). Again, cooperativity favours the formation of higher aggregates with growing azure B concentrations. These higher DNA-bound azure B polymers are present under the conditions prevailing during Giemsa staining. The positively charged DNA/azure B complexes are the target of eosin Y anions during the formation of the DNA/azure B/eosin Y complex, resulting in the purple colouration of the cell nuclei produced by Giemsa staining.