bluuebunny/crossref_metadata_2025_split huggingface dataset:
1H and 13C NMR Characterization of Hemiamidal Isoniazid‐NAD(H) Adducts as Possible Inhibitors Of InhA Reductase of Mycobacterium tuberculosis
Authors: Broussy Sylvain , Coppel Yannick , Nguyen Michel , Bernadou Jean , Meunier Bernard 
Published: May 2003

AbstractIsoniazid (INH) is easily oxidized with manganese(III) pyrophosphate, a chemical model of the KatG protein involved in activation of INH inside the bacteria Mycobacterium tuberculosis. Performed in the presence of NAD+, this oxidation generates a family of isomeric INH–NAD(H) adducts, which have been shown to be effective inhibitors of InhA, an enzyme essential in mycolic acid biosynthesis. In this work, we fully characterized by 1H and 13C NMR spectroscopy four main species of INH–NAD(H) adducts that coexist in solution. Two of them are open diastereoisomers consisting of the covalent attachment of the isonicotinoyl radical at position four of the nicotinamide coenzyme. The other two result from a cyclization involving the amide group from the nicotinamide and the carbonyl group from the isonicotinoyl radical to give diastereoisomeric hemiamidals. Although an INH–NAD(H) adduct with a 4S configuration has been characterized within the active site of InhA from Xray crystallography and this bound adduct interpreted as an open form (Rozwarski et al., Science 1998, 279, 98–102), it is legitimate to raise the question about the effective active form(s), open or cyclic, of INH–NAD(H) adduct(s). Is there a single active form or are several forms able to inhibit the InhA activity with different levels of inhibitory potency?
Alternative Heterocycles for DNA Recognition: The Benzimidazole/Imidazole Pair
Authors: Briehn Christoph A. , Weyermann Philipp , Dervan Peter B. 
Published: May 2003

AbstractBoc‐protected benzimidazole‐pyrrole, benzimidazole‐imidazole, and benzimidazole‐methoxypyrrole amino acids were synthesized and incorporated into DNA binding polyamides, comprised of N‐methyl pyrrole and N‐methyl imidazole amino acids, by means of solid‐phase synthesis on an oxime resin. These hairpin polyamides were designed to determine the DNA recognition profile of a side‐by‐side benzimidazole/imidazole pair for the designated six base pair recognition sequence. Equilibrium association constants of the polyamide‐DNA complexes were determined at two of the six base pair positions of the recognition sequence by quantitative DNase I footprinting titrations on DNA fragments each containing matched and single base pair mismatched binding sites. The results indicate that the benzimidazole‐heterocycle building blocks can replace pyrrole‐pyrrole, pyrrole‐imidazole, and pyrrole‐hydroxypyrrole constructs while retaining relative site specifities and subnanomolar match site affinities. The benzimidazole‐containing hairpin polyamides represent a novel class of DNA binding ligands featuring tunable target recognition sequences combined with the favorable properties of the benzimidazole type DNA minor groove binders.
Cover Picture: Hydrogen–Hydrogen Bonding: A Stabilizing Interaction in Molecules and Crystals (Chem. Eur. J. 9/2003)
Authors: Matta Chérif F. , Hernández‐Trujillo Jesús , Tang Ting‐Hua , Bader Richard F. W. 
Published: May 2003

AbstractThe cover picture shows a schematic representation of the change in structure accompanying the planarization of biphenyl through the formation of bond paths between the pairs of ortho‐hydrogen atoms. The top figure for the twisted equilibrium structure portrays four of the rings of hydrogen atoms, each shown as a spatial region defined by the intersection of its C|H interatomic surface with the van der Waals surface defined by the 0.001 au electron density envelope, the surfaces for the pairs of ortho‐hydrogen atoms touching at the geometry of the equilibrium structure. Planarization results in a lengthening of the CC separation between the rings by ∼0.01 Å, and the ortho‐hydrogen atoms are brought to separations ∼0.04 Å less than twice their van der Waals radii. The resulting increase in the energy of the carbon atoms is, however, largely negated by HH bonding, that is, the formation of an interatomic surface and an associated bond path linking each pair of ortho‐hydrogen atoms. Thus the ortho‐hydrogen atoms in planar biphenyl do not experience “steric nonbonded repulsions”, but rather, like all interactions denoted by a bond path, make a stabilizing contribution to the energy of ∼10 kcal mol−1 per HH interaction. HH bonding is present between the corresponding hydrogen atoms in polybenzenoids, such as phenanthrene and chrysene, and it is the presence of such interactions between the hydrogens of methyl groups in neighboring tetra‐tert‐butyl groups that encapsulate and stabilize the otherwise unstable tetrahedrane and cyclobutadiene molecules. For further details see the article by R. F. W. Bader et al. on p. 1940 ff.
Deletion of mdmB impairs mitochondrial distribution and morphology in Aspergillus nidulans
Authors: Koch Katrin V. , Suelmann Rüdiger , Fischer Reinhard 
Published: May 2003

AbstractMitochondria form a dynamic network of interconnected tubes in the cells of Saccharomyces cerevisiae or filamentous fungi such as Aspergillus nidulans, Neurospora crassa, or Podospora anserina. The dynamics depends on the separation of mitochondrial fragments, their movement throughout the cell, and their subsequent fusion with the other parts of the organelle. Interestingly, the microtubule network is required for the distribution in N. crassa and S. pombe, while S. cerevisiae and A. nidulans appear to use the actin cytoskeleton. We studied a homologue of S. cerevisiae Mdm10 in A. nidulans, and named it MdmB. The open reading frame is disrupted by two introns, one of which is conserved in mdm10 of P. anserina. The MdmB protein consists of 428 amino acids with a predicted molecular mass of 46.5 kDa. MdmB shares 26% identical amino acids to Mdm10 from S. cerevisiae, 35% to N. crassa, and 32% to the P. anserina homologue. A MdmB‐GFP fusion protein co‐localized evenly distributed along mitochondria. Extraction of the protein was only possible after treatment with a non‐ionic and an ionic detergent (1% Triton X‐100; 0.5% SDS) suggesting that MdmB was tightly bound to the mitochondrial membrane fraction. Deletion of the gene in A. nidulans affected mitochondrial morphology and distribution at 20°C but not at 37°C. mdmB deletion cells contained two populations of mitochondria at lower temperature, the normal tubular network plus some giant, non‐motile mitochondria. Cell Motil. Cytoskeleton 55:114–124, 2003. © 2003 Wiley‐Liss, Inc.
Dynamic association of a tumor amplified kinase, Aurora‐A, with the centrosome and mitotic spindle
Authors: Stenoien D. L. , Sen S. , Mancini M.A. , Brinkley B. R. 
Published: May 2003

AbstractAurora‐A kinase, also known as STK15/BTAK kinase, is a member of a serine/threonine kinase superfamily that includes the prototypic yeast Ipl1 and Drosophila aurora kinases as well as other mammalian and non‐mammalian aurora kinases involved in the regulation of centrosomes and chromosome segregation. The Aurora‐A gene is amplified and overexpressed in a wide variety of human tumors. Aurora‐A is centrosome‐associated during interphase, and binds the poles and half‐spindle during mitosis; its over‐expression has been associated with centrosome amplification and multipolar spindles. GFP‐Aurora‐A was used to mark centrosomes and spindles, and monitor their movements in living cells. Centrosome pairs labeled with GFP‐Aurora‐A are motile throughout interphase undergoing oscillations and tumbling motions requiring intact microtubules and ATP. Fluorescence recovery after photobleaching (FRAP) was used to examine the relative molecular mobility of GFP‐Aurora‐A, and GFP‐labeled α‐tubulin, γ‐tubulin, and NuMA. GFP‐Aurora‐A rapidly exchanges in and out of the centrosome and mitotic spindle (t1/2∼3 sec); in contrast, both tubulins are relatively immobile indicative of a structural role. GFP‐NuMA mobility was intermediate in both interphase nuclei and at the mitotic spindle (t1/2∼23–30 sec). Deletion mapping identifies a central domain of Aurora‐A as essential for its centrosomal localization that is augmented by both the amino and the carboxyl terminal ends of the protein. Interestingly, amino or carboxy terminal deletion mutants that maintained centrosomal targeting exhibited significantly slower molecular exchange. Collectively, these studies contrast the relative cellular dynamics of Aurora‐A with other cytoskeletal proteins that share its micro‐domains, and identify essential regions required for targeting and dynamics. Cell Motil. Cytoskeleton 55:134–146, 2003. © 2003 Wiley‐Liss, Inc.
Universal instability of dust ion‐sound waves and dust‐acoustic waves
Authors: Tsytovich V. N. , Watanabe K. 
Published: May 2003

AbstractIt is shown that the dust ion‐sound waves (DISW) and the dust‐acoustic waves (DAW) are universally unstable for wave numbers less than some critical wave number. The basic dusty plasma state is assumed to be quasineutral with balance of the plasma particle absorption on the dust particles and the ionization with the rate proportional to the electron density. An analytical expression for the critical wave numbers, for the frequencies and for the growth rates of DISW and DAW are found using the hydrodynamic description of dusty plasma components with self‐consistent treatment of the dust charge variations and by taking into account the change of the ion and electron distributions in the dust charging process. Most of the previous treatment do not take into account the latter process and do not treat the basic state self‐consistently. The critical lengths corresponding to these critical wave numbers can be easily achieved in the existing experiments. It is shown that at the wave numbers larger than the critical ones DISW and DAW have a large damping which was not treated previously and which can be also measured. The instabilities found in the present work on their non linear stage can lead to formation of different types of dust self‐organized structures.
Axial structure of plasma column sustained by non‐symmetric electromagnetic surface wave
Authors: Olefir V.P. , Azarenkov N.A. , Sporov A.E. 
Published: May 2003

AbstractThis article presents the results of theoretical study of the axial structure of gas discharge that is sustained by a non‐symmetric electromagnetic surface wave (SW) with azimuth wavenumberm= –2. The phase and attenuation characteristics of the wave, and the spatial wave field structure were studied as well. The wave considered propagates along the magnetized slightly nonuniform in axial direction plasma column and sustains it. The influence of external magnetic field value and finite plasma column radius on the discharge stability, on the plasma density axial profile and on the SW properties has been studied in the case of the diffusion regime of gas discharge sustaining.
Study of uniformity of plasmas produced in a wall‐stabilized arc
Authors: Książek I. , Pawelec E. 
Published: May 2003

AbstractIn this contribution the plasma of an arc discharge in a mixture of helium and argon is studied. The gas mixture is introduced uniformly along the arc column between each of the stabilizing plates. From the measured lateral distribution of radiation (HeI, HI, ArI, ArII, NI, FI line intensity and width measurements), after Abel inversion, the radial temperature distributions were obtained at various positions of the arc column. Beside the expected radial temperature gradients, a distinct temperature gradient along the arc column was found.
Investigation of the electrical breakdown mechanism in neon at 13.3 mbar pressure using the time delay method
Authors: Radović M.K. , Jovanović T.V. , Maluckov Č.A. , Stepanović O.M. 
Published: May 2003

AbstractThe results of the investigation of electrical breakdown in neon filled diode at 13.3 mbar pressure in function of distances between electrodes (0.1 < d < 20 mm), using electrical breakdown time delay method, are presented in this paper. The Paschen curve, as well as the electrical breakdown time delay mean values, and discharge formative time dependence of distance between electrodes are analyzed. The electrical breakdown time delay distributions and Laue diagrams, both as the functions of the distances between electrodes, were used in consideration. The shapes of the established distributions indicate the complex nature of the discharge formation mechanism. The results also indicate that on the right hand side of the Paschen curve (pd > 15 mbar · cm) the transition regime between Townsend and streamer mechanism of electrical breakdown is dominant.
Role of the wall ablation in the operation of a 46.9 nmAr capillary discharge soft x‐ray laser
Authors: Ritucci A. , Tomassetti G. , Reale A. , Palladino L. , Reale L. , Limongi T. , Flora F. , Mezi L. , Khuklevsky S.V. , Faenov A. , Pikuz T. , Kaiser J. 
Published: May 2003

AbstractA capillary discharge pumped soft x‐ray laser operating at 46.9 nm on the 3p–3s transition of the Ne‐like Ar has been realized by pumping the active medium with a relatively slow current pulse (dI/dt ≈ 6 · 1011 A/s). In order to study the role of the ablation in the production of the laser effect, the intensity of the amplified 46.9 nm line has been investigated using the same pumping current pulses in the plastic (polyacetal) and ceramic (Al2O3). We showed that the ablation of the capillary walls is unfavorable both for the compression and stability of the plasma and consequently for the soft x‐ray laser production. The amplification and lasing effects are observed only in the ceramic channel. The measurements of the line intensity at 46.9 nm showed the lasing with a gain‐length product of ≈ 9, a laser pulse energy of ≈ 5 μJ, a pulse duration of 1.3 ns and a beam divergence of ≈ 3.5 mrad. In addition, effect of the scaling of the time of lasing with the initial plasma diameter was demonstrated experimentally and compared with a one‐dimensional MHD model.
Similarity rules for collisionless hot‐filament discharges
Authors: Jelić N. , Kuhn S. , Schrittwieser R. 
Published: May 2003

AbstractThe plasma parameters of a collisionless hot‐filament discharge are investigated theoretically and experimentally as functions of a dimensionless variable called the discharge efficiency, which is a product of several relevant external parameters. It is found that the main plasma parameters, as measured in plasma chambers that are either geometrically different or filled with different working gases, depend on this variable in approximately the same way. Consequently, the number of experimental data necessary for discharge characterization may be drastically reduced.
Effects of electron‐absorbing boundaries on the plasma parameters of a hot‐filament discharge
Authors: Jelić N. , Schrittwieser R. , Kuhn S. 
Published: May 2003

AbstractIn this paper we investigate theoretically and experimentally the plasma parameters in a double‐plasma device in the presence of an additional electron‐absorbing boundary. The latter is formed by an electrode of variable size immersed in the plasma. It is found that, depending on its size and bias potential, such an anode can considerably influence the plasma parameters. Good qualitative and fair quantitative agreement between theoretical predictions and laboratory measurements of the plasma parameters is found for various discharge conditions. In addition we discuss the consequences of our results with respect to the existence conditions of anode‐type double layers in double‐plasma devices.
A high‐speed‐execution method for a program written in factory‐automation‐cell control language
Authors: Koyama Masahiro , Miyake Norihisa , Fujii Kenjiro , Komoda Norihisa 
Published: May 2003

AbstractA new programming method called Cell Control Language (CCL) for factory‐automation systems has been developed. In CCL programming, an action sequence of each functional unit in each operation mode is first described as a net module. This net module is a subclass of Petri nets, and this subclass is equivalent to a state‐transition diagram (a conventional design method). Several net modules are merged and translated into an internal code program, which is executed in a cell controller. To improve the ability of the controller to respond to state changes, we developed two new methods based on CCL. One is that for efficiently describing a CCL program, which needs a quick response to state changes, and the other is that for executing the program in a short cycle. The execution method was applied to an actual cell controller, which confirmed that it can improve the ability to respond to state changes without reducing the total control performance. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(2): 34–42, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10167
Changes of vitamin E content in rice bran with different heat treatment
Authors: Ko Soon‐Nam , Kim Chul‐Jin , Kim Chong‐Tai , Kim Hakryul , Chung Soo‐Hyun , Lee Sun‐Mi , Yoon Hye‐Hyun , Kim In‐Hwan 
Published: May 2003

AbstractOil yield from unheated rice bran was 17.6% whereas that of microwave‐heated rice bran increased to up to 18.4%. Content and composition of vitamin E in rice bran oil were affected by microwave heating. Especially, contents of α‐tocopherol, α‐tocotrienol, and γ‐tocotrienol as well as total vitamin E were significantly (P <0.05) increased when the rice bran was subjected to microwave heating for up to 30 s. When rice bran was heated in an electric roaster up to 20 min at 170 °C, 5 min at 180 °C, and 3 min at 190 °C, the total vitamin E content in rice bran oil increased significantly (P <0.05) followed by a considerable decline beyond those time points. Microwave heating was more effective for an increase in the vitamin E content than electric roaster heating. However, longer heating with both microwave and electric roaster caused a significant degradation of vitamin E resulting in a decreased content of total vitamin E.
A Convenient Synthesis of 1‐Deoxy‐8a‐epi‐Castanospermine Diastereoisomers (6R,7R,8S,8aS)‐6,7,8‐Trihydroxyindolizidine and (6R,7R,8R,8aS)‐6,7,8‐Trihydroxyindolizidine
Authors: Zhang Honglu , Ni Yi‐Ke , Zhao Gang , Ding Yu 
Published: May 2003

AbstractAn efficient synthesis of (6R,7R,8S,8aS)‐6,7,8‐trihydroxyindolizidine and (6R,7R,8R,8aS)‐6,7,8‐trihydroxyindolizidine is described from readily available N‐BOC‐L‐proline, (BOC = tert‐butoxycarbonyl) which involves the addition of ethyl lithiopropiolate to the aldehyde derived from N‐BOC‐L‐proline as a key step, then cyclization to construct indolizidine skeletons and asymmetric dihydroxylation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
To What Extent Can Nine‐Membered Monocycles Be Aromatic?
Authors: von Ragué Schleyer Paul , Nyulászi László , Kárpáti Tamás 
Published: May 2003

AbstractAb initio and density functional computations have been used to characterize the heteronins. New targets for synthesis are suggested on the basis of the results. The aromaticity of the heteronins was evaluated via numerous criteria such as magnetic properties (NICS and δH), geometric indices (Bird, BDSHRT and HOMA), aromatic stabilization energies (ASE), and the barriers to planarity. Along with the experimentally characterized cyclononatetraenyl (1CH−) and azonide (1N−) anions, the phosphonide ion (1P−, which has not been reported before), favors planar (C2v) symmetry. All the other heteronins are nonplanar in order to alleviate ring strain. Comparisons of the neutral planar heteronins (constrained to C2v symmetry) show the extent to which heteroatoms like P and S, as well as N and O (in oxonin, 1O), can participate in the cyclic electron delocalization. Due to hyperconjugation, the C2v‐symmetric 9,9‐distannylcyclononatetraene 1C(SnH3)2 is moderately aromatic, in contrast to 1CH2, which is a nonaromatic, conjugated system. The planar C2v‐symmetric 1BH and 1AlH and 1CF2 are antiaromatic, like the planar form of 1CH+. Annelation with three‐membered rings resulted in planar heteronins. The sole exception was phosphonin (8PH), but the barrier to planarity decreased to 1.8 kcal/mol in 8PR, due to the bulky R: 2,6‐di‐tert‐butylphenyl substituent at the phosphorus atom. Among the 8π heteronins, only the previously reported 1CH+ is Möbius‐aromatic; 1BH, 1AlH and 1CF2 also have C2 structures but are nonaromatic due to large torsional angles which preclude cyclic delocalization. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Catalysis through Induced Intramolecularity: What Can Be Learned by Mimicking Enzymes with Carbonyl Compounds that Covalently Bind Substrates?
Authors: Pascal Robert 
Published: May 2003

AbstractProtein engineering and the use of catalytic antibodies have given substance to the possibility of making artificial enzymes, whereas chemical design has provided functional, though not yet useful, enzyme mimics. This article is devoted to a class of mimics that uses covalent binding to substrates at a site different from the reaction center and that exhibits turnover. These molecular devices are capable of converting the bimolecular reaction of a substrate into a fast intramolecular one and may be defined by the concept of catalysis by induced intramolecularity. As examples of such systems, several reactions of bifunctional substrates that involve catalysis by carbonyl compounds are brought together in this review. Their ability to catalyze difficult reactions such as the hydrolysis of unactivated amides by mimicking enzyme−substrate complementarity is the result of a uniform stabilization of bound species, including both the transition state and also encounter complexes, which is the specific feature of these systems. They allow quantitative analysis of differences between intramolecular and bimolecular processes and support the explanation based on the entropic disadvantage of bimolecular reactions that can be compensated by binding energy as in enzymes. Three‐dimensional energy diagrams are proposed as valuable tools to describe these systems, as well as enzymatic mechanisms and other catalytic mechanisms that take advantage of induced intramolecularity. Unexpectedly, these diagrams are appropriate to a wide field of applications, such as the description of intramolecular and bimolecular reactions, resulting in a dynamic description of the notion of “tight” binding. In addition, the high efficiency of catalysts that covalently bind substrates raises the question of what their contribution may have been in early enzyme evolution. Their potential association with primitive enzymes as catalytic cofactors is considered. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Using the COSYMA System for the Discovery of Synthesis Strategies by Analogy
Authors: Jauffret Philippe , Ostermann Claude , Kaufmann Gérard 
Published: May 2003

AbstractCOSYMA is a computer program whose use is to suggest synthesis strategies for complex organic molecules. During a learning stage, which has been presented in previous papers, strategies (sequences of key reaction steps) are automatically extracted from total syntheses, described in the literature, and stored in a knowledge base. This paper presents the storage of strategies and the use of COSYMA to solve synthetic problems: how strategies applicable to a submitted target molecule are selected, and “instanciated” according to the structural specificities of this target. We provide an example of using COSYMA for discovering synthesis strategies for acromelic acid. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)