Asymmetric distribution of metals in the Xenopus laevis oocyte: a synchrotron X-ray fluorescence microprobe study.

The asymmetric distribution of many components of the Xenopus oocyte, including RNA, proteins, and pigment, provides a framework for cellular specialization during development. During maturation, Xenopus oocytes also acquire metals needed for development, but apart from zinc, little is known about their distribution. Synchrotron X-ray fluorescence microprobe was used to map iron, copper, and zinc and the metalloid selenium in a whole oocyte. Iron, zinc, and copper were asymmetrically distributed in the cytoplasm, while selenium and copper were more abundant in the nucleus. A zone of high copper and zinc was seen in the animal pole cytoplasm. Iron was also concentrated in the animal pole but did not colocalize with zinc, copper, or pigment accumulations. This asymmetry of metal deposition may be important for normal development. Synchrotron X-ray fluorescence microprobe will be a useful tool to examine how metals accumulate and redistribute during fertilization and embryonic development.     

Bioconversion of Phenolic Monomers of Lignin and Lignin-Containing Substrates by the Basidiomycete <Emphasis Type="Italic">Lentinus tigrinus</Emphasis>

The bioconversion of phenolic monomers of lignin (veratrol, vanillin, and vanillyl alcohol), hydrolyzed lignin, and sodium lignosulfonate (a product of the chemical modification of native lignin) by the basidiomycete Lentinus tigrinus was studied. It was found that the growth of the fungi on lignin monomer compounds is suppressed. A noticeable growth of the fungal biomass was observed only on the technical substrate sodium lignosulfonate. A comprehensive physicochemical study of the products of microbial transformation of sodium lignosulfonate was performed. It was established that the main direction of lignin bioconversion is oxidative condensation to form humic substances. In this case, depolymerization of the phenolic skeleton of lignin to monomeric phenol derivatives did not occur. The aromatic carbon atoms of the phenolic skeleton, unlike the carbon atoms of polysaccharides, were not involved in the fungal biomass growth. The observed growth of the fungus on the technical substrate sodium lignosulfonate can be explained by the presence of admixtures of oligomeric polysaccharides hemicellulose and cellulose, which can be used by the fungus as a carbon source.     

Steady-state diffusion and the cell resting potential

The steady-state diffusion of ions through separate, selective channels is described according to irreversible thermodynamics. Ion fluxes thus obtained are the same as those in the parallel conductance model. The equivalent electric circuit set up to describe the system has its electromotive forces expressed by the chemical potentials of the diffusing ions. The expression obtained for the potential differs from the Goldman-Hodgkin-Katz formula, and is reputed to be more accurate. In order for the passive diffusion flows to remain steady, active transport mechanisms must pump the ions up their electrochemical potentials. Such pumps have been incorporated into the equivalent circuit. They supply energy lost in the dissipation caused by preexisting passive forces without affecting the potential, which can thus hardly be called passive diffusion potential. Ion pumps can also create an electric potential in excess of that by passive forces, especially when secondary active transport is involved. The same equivalent circuit is, however, able to describe the whole range of seemingly different situations – from passive diffusion of an electrolyte to active extrusion of anions from the living cell. It has been applied to explain the measured plasma membrane potential of cells, especially those whose potential does not behave as the potassium electrode. Received: 6 July 1998 / Revised version: 7 November 1998 / Accepted: 10 November 1998     

Electronic properties and stability phase diagrams for cubic BN surfaces

This contribution investigates structural and electronic properties as well as stability phase diagrams of surfaces of the cubic boron nitride (c-BN). Our calculated parameters for bulk c-BN agree reasonably well with both experimental and computed values available in the literature. Based on the energies of the three experimentally recognised phases of bulk boron, i.e. α-B₃₆, β-B₁₀₅ and γ-B₂₈, we estimate enthalpy of formation of c-BN to be ?2.8 eV. The c-BN(1?0?0) surface offers separate B and N terminations (denoted as c-BN(1?0?0)_B and c-BN(1?0?0)_N), whereas c-BN(1?1?1) and c-BN(1?1?0) are truncated with combinations of boron and nitrogen atoms (denoted as c-BN(1?1?1)_BN and c-BN(1?1?0)_BN). Optimised geometries of surfaces display interlayer displacements up to the three topmost layers. Downward displacement of surface boron atoms signifies a common geometric feature of all surfaces. Bulk c-BN and its most stable surface c-BN(1?0?0)_N possess no metallic character, with band gaps of 5.46 and 2.7 eV, respectively. We find that, only c-BN(1?0?0)_B configuration exhibits a metallic character. c-BN(1?1?0)_BN and c-BN(1?1?1)_BN surfaces display corresponding band gaps of 2.5 and 3.9 eV and, hence, afford no metallic property.     

Design and Comparative Evaluation of the Anticonvulsant Profile,Carbonic-Anhydrate Inhibition and Teratogenicity of Novel Carbamate Derivatives of Branched Aliphatic Carboxylic Acids with 4-Aminobenzensulfonamide

Epilepsy is one of the most common neurological diseases, with between 34 and 76 per 100,000 people developing epilepsy annually. Epilepsy therapy for the past 100⁺ years is based on the use of antiepileptic drugs (AEDs). Despite the availability of more than twenty old and new AEDs, approximately 30% of patients with epilepsy are not seizure-free with the existing medications. In addition, the clinical use of the existing AEDs is restricted by their side-effects, including the teratogenicity associated with valproic acid that restricts its use in women of child-bearing age. Thus, there is an unmet clinical need to develop new, effective AEDs. In the present study, a novel class of carbamates incorporating phenethyl or branched aliphatic chains with 6–9 carbons in their side-chain, and 4-benzenesulfonamide-carbamate moieties were synthesized and evaluated for their anticonvulsant activity, teratogenicity and carbonic anhydrase (CA) inhibition. Three of the ten newly synthesized carbamates showed anticonvulsant activity in the maximal-electroshock (MES) and 6 Hz tests in rodents. In mice, 3-methyl-2-propylpentyl(4-sulfamoylphenyl)carbamate(1), 3-methyl-pentan-2-yl-(4-sulfamoylphenyl)carbamate (9) and 3-methylpentyl, (4-sulfamoylphenyl)carbamate (10) had ED₅₀ values of 136, 31 and 14 mg/kg (MES) and 74, 53, and 80 mg/kg (6 Hz), respectively. Compound (10) had rat-MES-ED₅₀?=?13 mg/kg and ED₅₀ of 59 mg/kg at the mouse-corneal-kindling test. These potent carbamates (1,9,10) induced neural tube defects only at doses markedly exceeding their anticonvuslnat-ED₅₀ values. None of these compounds were potent inhibitors of CA IV, but inhibited CA isoforms I, II and VII. The anticonvulsant properties of these compounds and particularly compound 10 make them potential candidates for further evaluation and development as new AEDs.     

Biomineralization of gold by Mucor plumbeus: The progress in understanding the mechanism of nanoparticles’ formation

This contribution describes the deposition of gold nanoparticles by microbial reduction of Au(III) ions using the mycelium of Mucor plumbeus. Biosorption as the major mechanism of Au(III) ions binding by the fungal cells and the reduction of them to the form of Au(0) on/in the cell wall, followed by the transportation of the synthesized gold nanoparticles to the cytoplasm, is postulated. The probable mechanism behind the reduction of Au(III) ions is discussed, leading to the conclusion that this process is nonenzymatic one. Chitosan of the fungal cell wall is most likely to be the major molecule involved in biomineralization of gold by the mycelium of M. plumbeus. Separation of gold nanoparticles from the cells has been carried out by the ultrasonic disintegration and the obtained nanostructures were characterized by UV‐vis spectroscopy and transmission electron micrograph analysis. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1381–1392, 2017     

2.5-Dimensional numerical simulation of a high-current ion linear induction accelerator

Results are presented from numerical particle simulations of the transport and acceleration of a high-current tubular ion beam through one to five magnetically insulated accelerating gaps. The ion beam is neutralized by an accompanying electron beam. The possibility of transporting a high-current neutralized ion beam through five cusps is demonstrated. It is shown that the quality of the distribution function of a high-current ion beam at the exit from the accelerator can be substantially improved by optimizing the energy of the neutralizing electron beam. It is also shown that, by injecting additional high-current electron beams into the cusps, the accelerated ion beam can be made more monoenergetic and its divergence can be reduced.     

Genetic diversity of ornamentalAllium species and cultivars assessed with isozymes

The aim of the study was to verify the similarity of 13 species and 5 cultivars of ornamental alliums and classify them into groups based on morphological and isozyme variation. The work embraced: Allium aflatunense, A. caeruleum, A. christophii, A. giganteum, A. karataviense, A. moly, A. nigrum, A. pyrenaicum, A. rosenbachianum, A. schubertii, A. siculum (syn. Nectaroscordum siculum), A. sphaerocephalon, A. strictum, A. stipitatum 'Album', A. 'Ivory Queen', A. 'Lucy Ball', A. 'Mont Blanc', and A. 'Purple Sensation'. Scape length, inflorescence diameter, and flowering period were recorded. Isozyme marker polymorphism was assessed by starch gel electrophoresis. Eight polymorphic isozyme systems (AAT, GPI, PGM, ALAT, ACP, DIAP, ALDO, PGD) were selected from 16 analysed in the taxa. Besides the differences between the taxa, the isozymes revealed intraspecific polymorphism in 5 systems. A total of 37 markers were obtained and used for dendrogram construction. The most similar taxa were A. karataviense with A. 'Ivory Queen', and A. karataviense with A. christophii (similarity level 0.78). A high similarity of 11 taxa belonging to one group (A. aflatunense, A. christophii, A. giganteum, A. karataviense, A. nigrum, A. schubertii, A. 'Ivory Queen', A. 'Lucy Ball', A. stipitatum 'Album', A. 'Mont Blanc', A. 'Purple Sensation') suggested that this group could be identified with the subgenus Melanocrommyum.     

Mechanisms and consequences of persistence of intracellular pathogens: leishmaniasis as an example

Lifelong persistence after clinical cure of the primary infection is a characteristic feature of many intracellular pathogens, including viruses, bacteria and protozoa. The underlying mechanisms are complex and range from the passive protection against toxic effector molecules of the host and the remodelling of intracellular compartments as safe niches to the active modulation of the immune response at multiple levels. Parasites of the genus Leishmania have been particular helpful in unravelling some of the basic processes and form therefore the centre of the discussion.     

Protecting groups transfer: unusual method of removal of tr and tbdms groups by transetherification

The triphenylmethyl (Tr) group undergoes a transfer (transetherification or disproportionation) between the molecules of 5'-O-Tr-2'-deoxynucleosides in a process mediated by anhydrous sulfates of Cu(+2), Fe(+2), or Ni(+2) to yield mixtures of 3',5'-bis-O-Tr and 3'-O-Tr products. If phenylmethanol is present in a reaction medium, detritylation results with concomitant formation of phenylmethyl triphenylmethyl ether. The behavior of t-butyldimethylsilyl (TBDMS) group in 5'-O-TBDMS-2'-deoxynucleosides is exactly the same. Such type of transetherifications was not observed before for the O-Tr and O-TBDMS groups.