bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrolyse und Kondensation von Si(OEt)4: Trennung und massenspektrometrische Charakterisierung der Zwischenprodukte
Authors: Söger N. , Binnewies M. 
Published: February 2003

AbstractReaktionsgemische, die bei der Hydrolyse von Si(OEt)4 entstehen, wurden mittels Kapillargaschromatographie getrennt. Durch GC‐MS‐Kopplung konnten so die Massenspektren der reinen Ethoxysiloxane und ‐siloxanole erhalten werden. Zur Identifizierung dieser Verbindungen wurde deren Retentions‐ und Fragmentierungsverhalten untersucht. Es zeigte sich, daß Moleküle mit derselben Anzahl an Silicium‐Atomen nahezu identische Fragmentierungsmuster aufweisen. Eine massenspektrometrische Identifizierung der Siloxane und Siloxanole mit gleicher Anzahl an Silicium‐Atomen, aber unterschiedlicher Anzahl an Sauerstoff‐Atomen ist nur nach vorheriger Isolierung und nur für niedermolekulare Spezies möglich.
Unexpected Formation of the Mixed Ligand Complexes [Cu(OAc)(bipy)2]Cl·4H2O·1/2MeOH and [Co(OH2)2(phen)2](OAc)2·6H2O, and their Crystal Structures
Authors: Carballo R. , Covelo B. , Vázquez‐López E. M. , García‐Martínez E. 
Published: February 2003

AbstractThe mononuclear compounds [Cu(OAc)(bipy)2]Cl·4H2O·1/2MeOH(1) and [Co(OH2)2(phen)2](OAc)2·6H2O(2) were unexpectedly obtained as single crystals from mother liquors left following isolation of the expected products of the reactions, in ethanol of Cu(OAc)2, benzylic acid and 2, 2'‐bipyridine (for 1) and Co(OAc)2, D, L‐mandelic acid and 1, 10‐phenanthroline (for 2). The complexes were characterized by elemental analysis, IR and electronic spectroscopy and magnetic measurements at room temperature and their structures were determined by single‐crystal X‐ray analysis. In 1, the pentacoordinated copper atom has a basically square pyramidal coordination polyhedron, while in 2 the cobalt atom has a distorted octahedral environment. In both cases, the complexes are linked by hydrogen bonds and aromatic‐aromatic interactions.
Synthetic, Spectroscopic and Structural Studies of the Rhenium(I) Dicarbonyl Complexes of Phosphite, Phosphonite, and Phosphinite Ligands: cis, mer‐[ReBr(CO)2{PPh3‐n(OR)n}3] (R = Me, Et; n = 1—3)
Authors: Carballo Rosa , Losada‐González Pilar , Vázquez‐López Ezequiel M. 
Published: February 2003

AbstractThe reaction of [ReBr(CO)5] with phosphite and phosphonite ligands in toluene yielded cis, mer‐[ReBr(CO)2L3] (2: L = P(OMe)3 2a: P(OEt)3 2b: PPh(OMe)2 2c: PPh(OEt)2 2d). Compounds 2c and 2d were also obtained, as were the phosphinite complexes 2e [L = PPh2(OMe)] and 2f [L = PPh2(OEt)], by reaction of the corresponding phosphorus ligand with trans, mer‐[ReBr(CO)3L2]. Compounds 2 were all characterized by elemental analysis, mass spectrometry and NMR spectroscopy, and the structures of 2b, 2c and 2d were determined by X‐ray diffractometry. Compounds 2a‐d are stable in chloroform and dichloromethane, but 2e and 2f are transformed into the corresponding trans, mer‐[ReBr(CO)3L2] complexes by a reaction for which a partial mechanism is put forward.
Synthesis, Spectroscopic and Structural Aspects of Mono‐ and Diorganothallium(III) Complexes of 2, 6‐Diacetylpyridine Bis(thiosemicarbazone) (H2DAPTSC) — A New Coordination Mode of the HDAPTSC— Anion
Authors: Casas José. S. , Castellano Eduardo E. , Ellena Javier , García‐Tasende María S. , Sánchez Agustín , Sordo José , Vázquez‐López Ezequiel M. , Vidarte María J. 
Published: February 2003

AbstractThe reaction of 2, 6‐diacetylpyridine bis(thiosemicarbazone) (H2DAPTSC) with dimethylthallium hydroxide yielded the complexes [(TlMe2)2(DAPTSC)] and [TlMe2(HDAPTSC)]. The structure of [TlMe2(HDAPTSC)], determined by X‐ray diffractometry, exhibits a hitherto unknown coordination mode of the HDAPTSC— anion in which its deprotonated thiosemicarbazone chain coordinates one metal atom through its sulphur and hydrazinic N atoms while a second metal atom is weakly coordinated through the S atom of the undeprotonated thiosemicarbazone chain. Each thallium atom is coordinated in both ways, with the result that the [TlMe2(HDAPTSC)] units are linked in infinite helical chains in the direction of the b axis.When reacting with diphenylthallium(III) hydroxide, H2DAPTSC induced a dephenylation process which led to the monophenylthallium(III) complex [TlPh(DAPTSC)]. Recrystallization from acetone yielded crystals of [TlPh(DAPTSC)]·C3H6O in which X‐ray diffractometry showed DAPTSC2— to be pentadentate, coordinating through its sulphur, azomethine N and pyridine N atoms.The 1H, 13C and 205Tl NMR data of [TlPh(DAPTSC)] indicate that its solid state molecular structure persists in DMSO solution, while those of [TlMe2(HDAPTSC)] indicate rapid alternation between coordination of the metal atom to one of the HDAPTSC— thiosemicarbazone chains and its coordination to the other.
Tricarbonyl Complexes of Rhenium(I) with Acetylpyridine Benzoylhydrazone and Related Ligands
Authors: Grewe Jacqueline , Hagenbach Adelheid , Stromburg Brigitte , Alberto Roger , Vazquez‐Lopez Ezequiel , Abram Ulrich 
Published: February 2003

AbstractNovel rhenium(I) tricarbonyl complexes have been prepared by reactions of (Et4N)2[Re(CO)3Br3] with acetylpyridine benzoylhydrazone, Hapbhyd, di(2‐pyridyl)ketone benzoylhydrazone, Hpy2bhyd, bis(2‐pyridine)ketone, py2CO, and pyridinealdehyde terephtalaldehydebishydrazone, pytehyd. The ligands remain protonated when no supporting base is added and the following complexes have been isolated: [Re(CO)3Br(Hapbhyd)], [Re(CO)3Br(Hpy2bhyd‐py, hyd)], [Re(CO)3Br(Hpy2bhyd‐py1, py2)], [Re(CO)3Br(py2CO‐N, N)] and [Re(CO)3Br(pytehyd)]. Addition of triethyl amine results in deprotonation of Hapbhyd and the formation of [Re(CO)3(OH2)(apbhyd)], whereas Hpy2bhyd is hydrolysed and a rhenium complex with the monoanionic bis(2‐pyridyl)hydroxymethanolato ligand, {py2C(OH)O}‐, is formed. The same compound, [Re(CO)3{py2C(OH)O}], is obtained when triethyl amine and water are added to a mixture of (Et4N)2[Re(CO)3Br3] and py2CO.The air‐stable products have been studied by spectroscopic methods and X‐ray crystallography.
Die Kristallstrukturen von KNdTe4, RbPrTe4 und RbNdTe4 — Untersuchungen zur thermischen Stabilität von KNdTe4 sowie Bemerkungen zu einigen anderen Vertretern der Zusammensetzung ALnTe4 (A = K, Rb, Cs und Ln = Seltenerd‐Metall)
Authors: Stöwe Klaus , Napoli Christian , Appel Stephan 
Published: February 2003

AbstractVon den Verbindungen der Zusammensetzung ALnQ4 (A = Na, K, Rb, Cs, mit Ln = Seltenerd‐Metall und mit Q = S, Se und Te) konnten die Strukturen der drei neuen Telluride KNdTe4, RbPrTe4 und RbNdTe4 durch Einkristallstrukturanalyse und des weiteren die der drei neuen Telluride KCeTe4, KPrTe4 und CsNdTe4 durch röntgenographische Untersuchungen an Pulvern bestimmt werden. Alle sechs neuen Verbindungen kristallisieren isotyp zu KCeSe4. Kennzeichnend für die Kristallstruktur der genannten Verbindungen sind Schichten mit (Q2)2—‐Hanteln in Form von 4.32.4.3‐Netzen, zwischen die die Kationen A+ und Ln3+ eingelagert sind und dort achtfach in Form von quadratischen Antiprismen von Q koordiniert sind. Der Te‐Te‐Abstand innerhalb der Hanteln liegt für alle untersuchten Telluride im Bereich von 277.8(2)pm. Röntgenographische und differenzthermoanalytische Untersuchungen zeigen, dass die Verbindung KNdTe4 bei Raumtemperatur metastabil ist und einen begrenzten Existenzbereich zwischen 260 und 498 °C hat.
Synthesis and Structure of Ln2(H4IO6)(I2O10)·H3O·5 H2O (Ln=Pr, Nd, Sm), a Lanthanide Periodate Diperiodate
Authors: Fischer Andreas 
Published: February 2003

AbstractBy slow evaporation of solutions containing Ln(ClO4)3 (Ln=Pr, Nd, Sm), H5IO6 and an excess of HClO4, crystals of the title compounds could be obtained. Their structures were determined by single‐crystal X‐ray diffraction. The compounds crystallize in the monoclinic crystal system, space group I2/a. They contain two types of periodate ions: octahedral H4IO6 groups and two crystallographically different I2O10 groups, which consist of two edge‐sharing octahedra. These anions coordinate to the cations as bridging groups yielding a three‐dimensional network. Together with some water of crystallization, a coordination number of 9 is achieved around the lanthanide ions with a tri‐capped trigonal prismatic geometry.
Synthesis and Structure of a One‐Dimensional Aluminum Phosphate, [NH3(CH2)2NH2(CH2)3NH3]3+[Al(PO4)2]3—
Authors: Natarajan Srinivasan , Klein Wilhelm , Nuss Jürgen , van Wüllen Leo , Jansen Martin 
Published: February 2003

AbstractA one‐dimensional aluminum phosphate, [NH3(CH2)2NH2(CH2)3NH3]3+ [Al(PO4)2]3—, has been synthesized hydrothermally in the presence of N‐(2‐Aminoethyl‐)1, 3‐diaminopropane (AEDAP) and its structure determined by single crystal X‐ray diffraction. Crystal data: space group = Pbca (no. 61), a = 16.850(2), b = 8.832(1), c = 17.688(4)Å, V = 2632.4(2)Å3, Z = 8, R1 = 0.0389 [5663 observed reflections with I > 2σ(I)]. The structure consists of anionic [Al(PO4)2]3— chains built up from AlO4 and PO4 tetrahedra, in which all the AlO4 vertices are shared and each PO4 tetrahedron possesses two terminal P=O linkages. The cations, which balances the negative charge of the chains, are located in between the chains and interact with the oxygen atoms through strong N—H···O hydrogen bonds. Additional characterization of the compound by powder XRD and MAS‐NMR has also been performed and described.
Crystal Structure and Properties of Strontium Phosphate Apatite with Oxocuprate Ions in Hexagonal Channels
Authors: Kazin Pavel E. , Karpov Andrey S. , Jansen Martin , Nuss Jürgen , Tretyakov Yury D. 
Published: February 2003

AbstractStrontium phosphate apatites containing different amounts of copper were prepared by a solid state reaction at 1100 °C or by arc melting above 1600 °C in air. The samples were characterized by X‐ray diffraction, ICP analysis, scanning electron microscopy, IR spectroscopy, MAS—1H—NMR, diffuse reflectance spectroscopy, and SQUID magnetometry. X‐ray crystal structure determination was carried out for a single crystal obtained from the melt. The compound is formulated as Sr5(PO4)3(CuO2)1/3 and has an apatite structure (space group P63/m, a = 9.7815(4)Å, c = 7.3018(4)Å, Z = 2) with linear CuO23— ions occupying hexagonal channels. For solid state synthesized samples, Rietveld refinement of powder XRD patterns was performed. The samples obtained at 1100 °C acquire the composition Sr5(PO4)3CuxOHy, with x changing from 0.01 to 0.62 and y < 1—x. The copper content can be increased to x = 0.85 by annealing in argon at 950 °C. The compounds represent a hydroxyapatite in which part of the protons is substituted by Cu+ and Cu2+ ions. The ions form linear O—Cu—O units which are progressively condensed creating the Cu—O—Cu bridges on increasing copper content. IR and NMR data testify existence of OH groups, non‐disturbed and disturbed by neighboring Cu atoms. In the electron spectra, the samples exhibit absorption bands at 7800‐7900, 14200‐14500 and 17500‐17550 cm—1, which were assigned to Cu2+ d‐electron transitions. By annealing the sample with x = 0.1 in oxygen at 800 °C copper is fully oxidized while retaining in channels in unusual for Cu2+ linear coordination.
Comparative Genetic Diversity of the
narG
,
nosZ
, and 16S rRNA Genes in Fluorescent Pseudomonads
Authors: Delorme Sandrine , Philippot Laurent , Edel-Hermann Veronique , Deulvot Chrystel , Mougel Christophe , Lemanceau Philippe 
Published: February 2003

ABSTRACT

The diversity of the membrane-bound nitrate reductase (
narG
) and nitrous oxide reductase (
nosZ
) genes in fluorescent pseudomonads isolated from soil and rhizosphere environments was characterized together with that of the 16S rRNA gene by a PCR-restriction fragment length polymorphism assay. Fragments of 1,008 bp and 1,433 bp were amplified via PCR with primers specific for the
narG
and
nosZ
genes, respectively. The presence of the
narG
and
nosZ
genes in the bacterial strains was confirmed by hybridization of the genomic DNA and the PCR products with the corresponding probes. The ability of the strains to either reduce nitrate or totally dissimilate nitrogen was assessed. Overall, there was a good correspondence between the reductase activities and the presence of the corresponding genes. Distribution in the different ribotypes of strains harboring both the
narG
and
nosZ
genes and of strains missing both genes suggests that these two groups of strains had different evolutionary histories. Both dissimilatory genes showed high polymorphism, with similarity indexes (Jaccard) of between 0.04 and 0.8, whereas those of the 16S rRNA gene only varied from 0.77 to 0.99. No correlation between the similarity indexes of 16S rRNA and dissimilatory genes was seen, suggesting that the evolution rates of ribosomal and functional genes differ. Pairwise comparison of similarity indexes of the
narG
and
nosZ
genes led to the delineation of two types of strains. Within the first type, the similarity indexes of both genes varied in the same range, suggesting that these two genes have followed a similar evolution. Within the second type of strain, the range of variations was higher for the
nosZ
than for the
narG
gene, suggesting that these genes have had a different evolutionary rate.
Cloning, Sequencing, and Expression of the Chitinase Gene
chiA74
from
Bacillus thuringiensis
Authors: Barboza-Corona J. Eleazar , Nieto-Mazzocco Elizabeth , Velázquez-Robledo Rocio , Salcedo-Hernandez Rubén , Bautista Mayela , Jiménez Beatriz , Ibarra Jorge E. 
Published: February 2003

ABSTRACT

The endochitinase gene
chiA74
from
Bacillus thuringiensis
serovar kenyae strain LBIT-82 was cloned in
Escherichia coli
DH5αF′. A sequence of 676 amino acids was deduced when the gene was completely sequenced. A molecular mass of 74 kDa was estimated for the preprotein, which includes a putative 4-kDa signal sequence located at the N terminus. The deduced amino acid sequence showed high degree of identity with other chitinases such as ChiB from
Bacillus cereus
(98%) and ChiA71 from
Bacillus thuringiensis
serovar pakistani (70%). Additionally, ChiA74 showed a modular structure comprised of three domains: a catalytic domain, a fibronectin-like domain, and a chitin-binding domain. All three domains showed conserved sequences when compared to other bacterial chitinase sequences. A ca. 70-kDa mature protein expressed by the cloned gene was detected in zymograms, comigrating with a chitinase produced by the LBIT-82 wild-type strain. ChiA74 is active within a wide pH range (4 to 9), although a bimodal activity was shown at pH 4.79 and 6.34. The optimal temperature was estimated at 57.2°C when tested at pH 6. The potential use of ChiA74 as a synergistic agent, along with the
B. thuringiensis
insecticidal Cry proteins, is discussed.
Symbiotic and Genetic Diversity of
Rhizobium galegae
Isolates Collected from the
Galega orientalis
Gene Center in the Caucasus
Authors: Andronov E. E. , Terefework Z. , Roumiantseva M. L. , Dzyubenko N. I. , Onichtchouk O. P. , Kurchak O. N. , Dresler-Nurmi A. , Young J. P. W. , Simarov B. V. , Lindström K. 
Published: February 2003

ABSTRACT

This paper explores the relationship between the genetic diversity of rhizobia and the morphological diversity of their plant hosts.
Rhizobium galegae
strains were isolated from nodules of wild
Galega orientalis
and
Galega officinalis
in the Caucasus, the center of origin for
G. orientalis
. All 101 isolates were characterized by genomic amplified fragment length polymorphism fingerprinting and by PCR-restriction fragment length polymorphism (RFLP) of the rRNA intergenic spacer and of five parts of the symbiotic region adjacent to
nod
box sequences. By all criteria, the
R. galegae
bv. officinalis and
R. galegae
bv. orientalis strains form distinct clusters. The
nod
box regions are highly conserved among strains belonging to each of the two biovars but differ structurally to various degrees between the biovars. The findings suggest varying evolutionary pressures in different parts of the symbiotic genome of closely related
R. galegae
biovars. Sixteen
R. galegae
bv. orientalis strains harbored copies of the same insertion sequence element; all were isolated from a particular site and belonged to a limited range of chromosomal genotypes. In all analyses, the Caucasian
R. galegae
bv. orientalis strains were more diverse than
R. galegae
bv. officinalis strains, in accordance with the gene center theory.
Geographical Variation in Ribotype Profiles of
Escherichia coli
Isolates from Humans, Swine, Poultry, Beef, and Dairy Cattle in Florida
Authors: Scott Troy M. , Parveen Salina , Portier Kenneth M. , Rose Joan B. , Tamplin Mark L. , Farrah Samuel R. , Koo Andrew , Lukasik Jerzy 
Published: February 2003

ABSTRACT

Waters impacted by fecal pollution can exact high risks to human health and can result in financial losses due to closures of water systems used for recreation and for harvesting seafood. Identifying the sources of fecal pollution in water is paramount in assessing the potential human health risks involved as well as in assessing necessary remedial action. Recently, various researchers have used the ribotyping method to identify sources of bacterial indicators (
Escherichia coli
and enterococci) in environmental waters. While these studies have identified genotypic differences between human- and animal-derived indicators that are capable of differentiating organisms isolated from humans and various animal hosts, most have focused on organisms collected from a confined geographic area and have not addressed the question of whether these ribotype profiles are watershed specific or if they can be applied universally to organisms from other geographic locations. In this study,
E. coli
isolates were obtained from humans, beef cattle, dairy cattle, swine, and poultry from locations in northern, central, and southern Florida and were subjected to ribotyping analysis. The intent was to determine (i) if ribotype profiles are capable of discriminating the source of
E. coli
at the host species level and (ii) if the resulting fingerprints are uniform over an extended geographic area or if they can be applied only to a specific watershed. Our research indicated that, using a single restriction enzyme (
Hin
dIII), the ribotyping procedure is not capable of differentiating
E. coli
isolates from the different animal species sampled in this study. Results indicate, however, that this procedure can still be used effectively to differentiate
E. coli
as being either human or animal derived when applied to organisms isolated from a large geographic region.
A Combined Model To Predict the Functionality of the Bacteriocin-Producing
Lactobacillus sakei
Strain CTC 494
Authors: Leroy Frédéric , De Vuyst Luc 
Published: February 2003

ABSTRACT

The use of bacteriocin-producing lactic acid bacteria for improved food fermentation processes seems promising. However, lack of fundamental knowledge about the functionality of bacteriocin-producing strains under food fermentation conditions hampers their industrial use. Predictive microbiology or a mathematical estimation of microbial behavior in food ecosystems may help to overcome this problem. In this study, a combined model was developed that was able to estimate, from a given initial situation of temperature, pH, and nutrient availability, the growth and self-inhibition dynamics of a bacteriocin-producing
Lactobacillus sakei
CTC 494 culture in (modified) MRS broth. Moreover, the drop in pH induced by lactic acid production and the bacteriocin activity toward
Listeria
as an indicator organism were modeled. Self-inhibition was due to the depletion of nutrients as well as to the production of lactic acid. Lactic acid production resulted in a pH drop, an accumulation of toxic undissociated lactic acid molecules, and a shift in the dissociation degree of the growth-inhibiting buffer components. The model was validated experimentally.
Genetic Manipulation ofLactococcus lactisby Using Targeted Group II Introns: Generation of Stable Insertions without Selection
Authors: Frazier Courtney L. , San Filippo Joseph , Lambowitz Alan M. , Mills David A. 
Published: February 2003

ABSTRACTDespite their commercial importance, there are relatively few facile methods for genomic manipulation of the lactic acid bacteria. Here, the lactococcal group II intron, Ll.ltrB, was targeted to insert efficiently into genes encoding malate decarboxylase (mleS) and tetracycline resistance (tetM) within theLactococcus lactisgenome. Integrants were readily identified and maintained in the absence of a selectable marker. Since splicing of the Ll.ltrB intron depends on the intron-encoded protein, targeted invasion with an intron lacking the intron open reading frame disrupted TetM and MleS function, and MleS activity could be partially restored by expressing the intron-encoded protein intrans. Restoration of splicing from intron variants lacking the intron-encoded protein illustrates how targeted group II introns could be used for conditional expression of any gene. Furthermore, the modified Ll.ltrB intron was used to separately deliver a phage resistance gene (abiD) and a tetracycline resistance marker (tetM) intomleS, without the need for selection to drive the integration or to maintain the integrant. Our findings demonstrate the utility of targeted group II introns as a potential food-grade mechanism for delivery of industrially important traits into the genomes of lactococci.
Engineering of Carbon Distribution between Glycolysis and Sugar Nucleotide Biosynthesis in
Lactococcus lactis
Authors: Boels Ingeborg C. , Kleerebezem Michiel , de Vos Willem M. 
Published: February 2003

ABSTRACT

We describe the effects of modulating the activities of glucokinase, phosphofructokinase, and phosphoglucomutase on the branching point between sugar degradation and the biosynthesis of sugar nucleotides involved in the production of exopolysaccharide biosynthesis by
Lactococcus lactis
. This was realized by using a described isogenic
L. lactis
mutant with reduced enzyme activities or by controlled expression of the well-characterized genes for phosphoglucomutase or glucokinase from
Escherichia coli
or
Bacillus subtilis
, respectively. The role of decreased metabolic flux was studied in
L. lactis
strains with decreased phosphofructokinase activities. The concomitant reduction of the activities of phosphofructokinase and other enzymes encoded by the
las
operon (lactate dehydrogenase and pyruvate kinase) resulted in significant changes in the concentrations of sugar-phosphates. In contrast, a >25-fold overproduction of glucokinase resulted in 7-fold-increased fructose-6-phosphate levels and 2-fold-reduced glucose-1-phosphate and glucose-6-phosphate levels. However, these increased sugar-phosphate concentrations did not affect the levels of sugar nucleotides. Finally, an ∼100-fold overproduction of phosphoglucomutase resulted in 5-fold-increased levels of both UDP-glucose and UDP-galactose. While the increased concentrations of sugar-phosphates or sugar nucleotides did not significantly affect the production of exopolysaccharides, they demonstrate the metabolic flexibility of
L. lactis.