bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of potassium and calcium in milk powder by energy‐dispersive x‐ray fluorescence spectrometry
Authors: Alvarez M. , Mazo‐Gray V. 
Published: May 2005

AbstractA rapid method for the simultaneous determination of potassium and calcium in milk powder by energy‐dispersive x‐ray fluorescence (EDXRF) spectrometry was developed. The measurement system consists of a Si(Li) detector, an x‐ray tube coupled with titanium as a secondary target, a DEC‐350 computer and a nonlinear fitting least‐squares program. The methods of calibration and standard preparation are discussed. Milk powder was analysed as pressed pellets using counting times of 100 s. Concentrations were determined by a standard calibration graph method using synthetic standards. The minimum detection limits are 0.011% and 0.007% for potassium and calcium, respectively. The accuracy was ascertained by analysing standard reference materials from the International Atomic Energy Agency. Good agreement was found between the certified and measured values. Potential applications of this method are indicated.
Monte Carlo simulation of the grain size and edge effects in x‐ray fluorescence microanalysis of geological samples
Authors: Lankosz Marek 
Published: May 2005

AbstractA Monte Carlo model was developed for simulation of x‐ray fluorescence from cylindrical mineral grains in geological samples including primary and secondary fluorescence events. The inter‐element and geometrical effects in XRF microanalysis of mineral grains were studied. Calculations were performed for grains of ZnS located in a CaCO3 matrix. The results of calculation indicated that the intensities of excited characteristic x‐rays depend strongly on the diameter and thickness of the irradiated grains.
Validation of sulphide‐bearing certified reference samples by primary calibration as applied to x‐ray fluorescence
Authors: Staats Gotthard , Strieder Stefan 
Published: May 2005

AbstractSulphide‐bearing certified reference samples were validated by multi‐element wavelength‐dispersive XRF based on the SI units kilogram and mole. An oxidizing borate fusion ensured complete oxidation of the test samples and provided for identical physical and chemical conditions for reference and test samples. Matrix effects were successfully overcome by computer‐aided generation and production of perfectly adapted multi‐element calibration samples. The trueness of the validated results was achieved by the application of pure elements or their compounds having quality assured assays. Detailed and accurate analytical information on certified reference samples CCu‐19 and CZN‐1 (CANMET, Canada) and BCR 26, 27, 28 (Community Bureau of Reference, Belgium) are reported.
A comparative radiorespirometric study of glucose metabolism in yeasts
Authors: Bruinenberg Peter M. , Waslander Gerrit W. , Van Dijken Johannes P. , Scheffers W. Alexander 
Published: May 2005

AbstractA comparative radiorespirometric study of glucos emetabolism in glucose‐limited chemostat cultures of Saccharomyces cerevisiae, Candida utilis and Rhodosporidium toruloides was performed in an attempt to estimate the contribution of the hexose monophosphate (HMP) pathway to glucose metabolism. Radioactively labelled glucose was administered directly to the cultures in a constant substrate feed, without disturbance of the steady state. The 14CO2 yields from [1‐14C]‐ and [6‐14C]‐glucose demonstrated that the HMP pathway activities for the three yeasts were very similar. Furthermore, a quantitative analysis of results indicated that the HMP pathway activities were close to the theoretical minimum needed to cover the NADPH requirement for biomass formation.
Reduced efficiency in the glycosylation of the first sequon of Saccharomyces cerevisiae exoglucanase leads to the synthesis and secretion of a new glycoform of the molecule
Authors: Basco Ricardo D. , Muñoz M. Dolores , Hernández Luis M. , De Aldana Carlos Vazquez , Larriba Germán 
Published: May 2005

AbstractIn addition to exoglucanases (EXGs) I and II, old cultures of Saccharomyces cerevisiae secreted into the culture medium a new immunologically‐related material that exhibited exoglucanase activity. The new exoglucanase (EXGII1/2) was purified from stationary‐phase cultures. It turned out to be a glycoprotein whose protein portion was identical to that of the other two isoenzymes in terms of ionic properties, size, amino acid composition and NH2‐terminal sequence (25 residues). Disruption of the structural gene encoding EXGs I and II resulted in a strain unable to secrete all three isoenzymes. EXGII1/2 was indistinguishable in terms of molecular weight from the single intermediate detected during the deglycosylation (mediated by endo H) of EXGII by sodium dodecyl sulphate–polyacrylamide gel electrophoresis. Thus, the new isoenzyme contains only one of the two slightly elongated mannan inner cores present in enzyme II. Two intermediates were, however, detected when the deglycosylation of EXGII was monitored by ion‐exchange chromatography (high‐pressure liquid chromatography). Site‐directed mutagenesis indicated that the major intermediate, which eluted at about the same position as enzyme II1/2, corresponded to protein molecules carrying the oligosaccharide attached to the Asn of the second sequon, whereas the minor one carried the oligosaccharide in the first potential glycosylation site. Several lines of evidence indicate that EXGII1/2 is a biosynthetic product resulting from an imbalance between the rate of protein synthesis and the glycosylation capabilities of the glycosylation machinery.
Nuclear pore complex antigens delineate nuclear envelope dynamics in vegetative and conjugating Saccharomyces cerevisiae
Authors: Copeland Connie S. , Snyder Michael 
Published: May 2005

AbstractIn the yeast Saccharomyces cerevisiae, the nucleus undergoes dramatic shape changes during mitosis and mating. We have studied nuclear envelope dynamics during the processes of mitosis and conjugation using nuclear pore complexes as a marker for the nuclear envelope in wild‐type cells and several cell‐division‐cycle (cdc) mutants.Three monoclonal antibodies are described that recognize nuclear pore complex‐related antigens in S. cerevisiae. One of these antibodies, RL1, has been extensively characterized by Gerace and colleagues and recognizes nuclear pore complexes in mammalian and amphibian cells. By indirect immunofluorescence of yeast cells, all three antibodies yield a discontinuous nuclear rim stain. All three react with multiple nuclear‐enriched proteins in immunoblots, including the nucleoporin protein encoded by the NSP1 gene.When the antibodies were used in immunofluorescence experiments on mating cells, the nuclear pore complex staining pattern proved to be a sensitive indicator of nuclear fusion. Nuclei with closely apposed spindle pole bodies and unfused nuclear envelopes could be readily distinguished. Marked shape changes were observed in nuclei during fusion and segregation of the diploid nucleus into the zygotic bud.In cdc14 and cdc15 mutants that arrest late in mitosis, the elongated nuclear envelope extension that stretches between daughter nuclei during telophase was preserved. In cytokinesis‐defective mutants (cdc3, cdc10, cdc11 and cdc12), the elongated nuclear envelope was usually resolved into two daughter nuclei in the absence of cytokinesis. These results indicate that nuclear envelope division is mechanistically distinguishable from chromosome segregation, nucleolar segregation and cytokinesis.
Sequence of a 4·8 kb fragment of Saccharomyces cerevisiae chromosome II including three essential open reading frames
Authors: Baur Axel , Schaaff‐Gerstenschläger Ine , Boles Eckhard , Miosga Thomas , Rose Matthias , Zimmermann Friedrich K. 
Published: May 2005

AbstractThe nucleotide sequence of a fragment of 4867 base pairs of Saccharomyces cerevisiae chromosome II has been determined. The sequence contains three complete open reading frames. In addition to the already known gene RPB5, coding for a subunit shared by all three DNA directed RNA polymerases, two new open reading frames could be identified. YBR12.03 codes for a protein of 183 amino acids with homology to one of the proteins of the Bacillus subtilis riboflavin biosynthesis operon (RibG). Deletion mutants of YBR12.03 can germinate but stop growing after five to seven cell divisions on YPD. Supplementation with high concentrations of riboflavin does promote growth. YBR12.05 codes for a protein of 386 amino acids with homology to STI1, a stress‐inducible protein of S. cerevisiae. Deletion mutants of YBR12.05 are not viable.
YMC1, a yeast gene encoding a new putative mitochondrial carrier protein
Authors: Graf Roney , Baum Bobby , Braus Gerhard H. 
Published: May 2005

AbstractWe have cloned and sequenced a Saccharomyces cerevisiae gene coding for a protein with significant similarities to the mitochondrial carrier family. The gene we termed YMC1 (yeast mitochondrial carrier) is located on chromosome XVI, closely downstream of ARO7 encoding chorismate mutase.
Targeting of heterologous membrane proteins into proliferated internal membranes in Saccharomyces cerevisiae
Authors: Wittenkindt Nicola E. , Würgler Friedrich E. , Sengstag Christian 
Published: May 2005

AbstractOverproduction of chimeric proteins containing the HMG2/1 peptide, which comprises the seven transmembrane domains of Saccharomyces cerevisiae 3‐hydroxy‐3‐methylglutaryl‐CoA reductase isozymes 1 and 2, has previously been observed to induce the proliferation of internal endoplasmic reticulum‐like membranes. In order to exploit this amplified membrane surface area for the accommodation of heterologous microsomal proteins, we fused sequences coding for human cytochrome P4501A1 (CYP1A1) to sequence encoding the HMG2/1 peptide and expressed the hybrid genes in yeast. The heterologous hybrid proteins were targeted into strongly proliferated membranes, as shown by electron microscopic and immunofluorescent analysis. Fusion proteins comprising the whole CYP1A1 polypeptide (HMG2/1‐CYP1A1) exhibited 7‐ethoxyresorufin‐O‐deethylase activity, whereas fusion proteins lacking the N‐terminal 56 amino acids of CYP1A1 (HMG2/1‐ΔCYP1A1) were inactive and appeared to be unable to incorporate protoheme. Similar amounts of heterologous protein were detected in cells expressing HMG2/1‐CYP1A1, HMG2/1‐ΔCYP1A1 and CYP1A1, respectively. Replacement of the N‐terminal membrane anchor domain of human NADPH‐cytochrome P450 oxidoreductase by the HMG2/1 peptide also resulted in a functional fusion enzyme, which was able to interact with HMG2/1‐CYP1A1 and the yeast endogenous P450 enzyme lanosterol‐14α‐demethylase.
Scp160p, a new yeast protein associated with the nuclear membrane and the endoplasmic reticulum, is necessary for maintenance of exact ploidy
Authors: Wintersberger Ulrike , Kühne Christian , Karwan Anneliese 
Published: May 2005

AbstractWe have cloned a new gene, SCP160, from Saccharomyces cerevisiae, the deduced amino acid sequence of which does not exhibit overall similarity to any known yeast protein. A weak resemblance between the C‐terminal part of the Scp160 protein and regulatory subunits of cAMP‐dependent protein kinases from eukaryotes as well as the pstB protein of Escherichia coli was observed. The SCP160 gene resides on the left arm of chromosome X and codes for a polypeptide of molecular weight around 160 kDa. By immunofluorescence microscopy the Scp160 protein appears to be localized to the nuclear envelope and to the endoplasmic reticulum (ER). However, no signal sequence or membrane‐spanning region exists, suggesting that the Scp160 protein is attached to the cytoplasmic surface of the ER–nuclear envelope membranes. Disruption of the SCP160 gene is not lethal but results in cells of decreased viability, abnormal morphology and increased DNA content. This phenotype is not reversible by transformation with a plasmid carrying the wild‐type gene. Crosses of SCP160 deletion mutant strains among each other or with unrelated strains lead to irregular segregation of genetic markers. Taken together the data suggest that the Scp160 protein is required during cell division for faithful partitioning of the ER–nuclear envelope membranes which in S. cerevisiae enclose the duplicated chromosomes.
Assignment of Phosphorus NMR Parameters to Absolute Configurations in Chiral Phosphorus Sulfide Cage Compounds, using Ab Initio Methods
Authors: Tattershall Bruce W. 
Published: May 2005

AbstractThe closo cage molecules α‐ and β‐P4S3(μ‐NCH(Me)Ph) were modelled at the RHF/3‐21G* and MPW1PW91/DZVP levels. For each, the conformational space corresponding to rotation about the C–N bond was explored, and relative average electronic energies were calculated. The β‐isomer was more stable than the α‐isomer by 10.7 kJ mol−1, according to the DFT calculations, in contrast to the unsubstituted model compounds α‐ and β‐P4S3(μ‐NH), where the α‐isomer was more stable. GIAO calculations of phosphorus isotropic NMR shieldings, in the rotamers, led to relative average chemical shifts in the diastereomers. Comparison with experimental chemical shift differences gave an assignment to absolute configuration for α‐P4S3(μ‐NCH(Me)Ph), which agreed with the assignment obtained by comparing calculated relative diastereomer stability with observations. For β‐P4S3(μ‐NCH(Me)Ph), the GIAO calculations allowed relative assignment of observed chemical shifts to the nitrogen bridgehead phosphorus atoms.
Strukturen der Alkalimetallsalze aromatischer, heterocyclischer Amide: Synthese und Struktur von Kronenether‐Addukten der Alkalimetall‐Carbazolide
Authors: Esbak Hoda , Behrens Ulrich 
Published: May 2005

Structures of Alkali Metal Salts of Aromatic, Heterocyclic Amides: Synthesis und Structure of Crown Ether Adducts of the Alkali Metal CarbazolidesThe synthesis of six alkali metal carbazolide crown ether complexes is reported: Potassium‐carbazolide(18‐crown‐6) (1), rubidium‐carbazolide(18‐crown‐6) (2), rubidium‐carbazolide(15‐crown‐5) (3), cesium‐carbazolide(18‐crown‐6) (4), cesium‐carbazolide‐bis(15‐crown‐5) (5), and cesium‐carbazolide‐bis(benzo‐15‐crown‐5) (6). The complexes 1 to 6 were synthesized from the alkali metal carbazolide (obtained in solution by metalation of carbazole with KH or Rb‐ and Cs‐hexamethyldisilazide) and the corresponding crown ether. The structures of 1, 3, 4, and 5 could be determined by X‐ray diffraction. Complex 1 is mononuclear, the carbazolide anion shows an η1(N)‐coordination to the metal cation. The complexes 3 and 4 are dinuclear with a central metal2N2‐ring. Compound 5 has a salt‐like structure with a sandwich‐like [Cs(15‐crown‐5)2]+ cation and an uncoordinated carbazolide anion.
Reversible Lithium Intercalation into the Three‐Dimensional Cluster Network Structure of Ta6Cl15
Authors: Kuhn Alois , Dill Simone , Meyer H.‐Jürgen 
Published: May 2005

AbstractA crystalline powder of Ta6Cl15 was synthesized through solid state reaction of Ta powder, and TaCl5 at 700 °C. The structure contains [Ta6Cl12]3+ clusters which are three‐dimensionally interconnected by Cl bridges, leaving cavities which are shown to be suitable for lithium insertion. Reversible lithium intercalation into Ta6Cl15 involves 1 mol of lithium per formula unit under equilibrium conditions, when cells are discharged between 3 and 1.8 V, leading to the upper composition LiTa6Cl15. Although capacity values within this reversible voltage range are small (ca. 25 Ah·kg−1), the cycle life of such Li/Ta6Cl15 cells is excellent, and the initial capacity value is maintained over 1500 cycles. On the other hand, a maximum of 15 moles of lithium can be reacted with one mole Ta6Cl15 when lithium cells were deep‐discharged. This process is likely due to the complete and irreversible reduction of the parent by lithium.
Chirale 1,3,2‐Oxazaborolidine aus chiralen 2,3‐Dihydro‐1H‐1,3,2‐diazaborolen und Diphenylketen
Authors: Weber L. , Rausch A. , Stammler H.‐G. , Neumann B. 
Published: May 2005

Chiral 1,3,2‐Oxazaborolidines from the Reaction of Chiral 2,3‐Dihydro‐1H‐1,3,2‐diazaboroles and DiphenylketeneReaction of equimolar amounts of diphenylketene with 1,3‐di‐tert‐butyl‐2‐isobutyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborole ${\rm{\it t}Bu\overline{NCH=CHN({\it t}Bu)B}-{\it i}Bu}$ (1) regioselectively afforded 1,3,2‐oxazaborolidine ${\rm{\it t}Bu\overline{N-CH(CH=N{\it t}Bu)C(=CPh_{2})OB}-{\it i}Bu}$ (2). The employment of a series of chiral diazaboroles ${\rm{\it (S,S)}-Me(Cy)CH-\overline{NCH=CH-N\{CH(Cy)Me\}B}X}$ (3a: X = nBu; b: iBu; c: CH2SiMe3; d: NHtBu) led to the formation of the diastereoisomeric oxazaborolidines ${\rm Me(Cy)CH\overline{N-CH\{CH=NCH(Cy)Me\}C(=CPh_{2})OB}X}$ (4a–d) with diastereomeric excesses de, which increase with the steric demand of X from de = 55 % (X = nBu) to de ≥ 95 % (X = NHtBu). Under comparable conditions the treatment of the enantiomerically pure diazaborole ${\rm{\it (S)}-{\it t}Bu\overline{N CH=CHN({\it t}Bu)B}-NHCH(Ph)Me}$ (6) with the ketene yielded oxazaborolidine ${\rm{\it t}Bu\overline{N CH(CH=N{\it t}Bu)C(=CPh_{2})OB}NHCH(Ph)Me}$ (7) with a de‐value of only 52 %. The new compounds, with exception of 2 and 4d, are thermolabile solids, which were characterized mainly by spectroscopy (1H‐, 11B{1H}‐, 13C{1H}‐NMR, MS). The X‐ray structure analysis of 2 revealed a slightly puckered five‐membered heterocycle with a long B–O bond.
A Novel Mixed‐Ligand Manganese(II) Complex Containing a V‐shape Water Trimer: Synthesis, Structure and Magnetic Properties of {[Mn(azpy)2(dca)(H2O)2](ClO4)(azpy)(H2O)2}n
Authors: Zhu Li‐Na , Ou‐Yang Yan , Liu Zhan‐Quan , Liao Dai‐Zheng , Jiang Zong‐Hui , Yan Shi‐Ping , Cheng Peng 
Published: May 2005

AbstractA novel mixed‐ligand complex {[Mn(azpy)2(dca)(H2O)2](ClO4)(azpy)(H2O)2}n (1) has been synthesized and characterized by single crystal X‐ray analysis, elemental analysis, IR spectroscopy and variable temperature magnetic measurement. The 4,4′‐azopyridine and dicyanamide ligands are abbreviated as azpy and dca, respectively. The crystal structure of 1 revealed that the 1D covalent bonding chains constructed by μ1,5‐dca bridging the MnII ions are linked together via O–H···N and O–H···O hydrogen bonds and π‐π stacking interactions into a 3D supramolecular structure. V‐shape (bent) water trimers were also found in the structure. The water clusters play an important role in the formation of the 3D supramolecular structure. The determination of the variable temperature magnetic susceptibilities (2–300 K) shows the existence of a very weak antiferromagnetic interaction with a J value of −0.16 cm−1.
TAS‐Indolid und TAS‐Carbazolid: Strukturen von [TAS]+[IndHInd]− und [TAS]+[Carb]−·½CarbH
Authors: Müller Marco , Lork Enno , Mews Rüdiger 
Published: May 2005

TAS Indolide and TAS Carbazolide: Structures of [TAS]+[IndHInd]− and [TAS]+[Carb]−·½CarbHFrom the reaction of TAS‐fluoride [(Me2N)3S]+[Me3SiF2]− with trimethylsilyl‐indole and trimethylsilyl‐carbazole TAS‐indolide and TAS‐carbazolide are formed. During crystallisation partially protonation to indole and carbazole occurs, resulting in the formation of [TAS]+[IndHInd]− (3a) and [TAS]+[Carb]−·½CarbH (5a) according to X‐ray analysis.
Synthese und Charakterisierung der 1,2‐Diphosphanyldisilane [Me4Si2(PH2)2] und [Me4Si2(PHMe)2] sowie deren Reaktionen mit n‐Butyllithium
Authors: von Hänisch Carsten , Matern Eberhard 
Published: May 2005

Synthesis and Characterization of the 1,2‐Diphosphanyldisilanes [Me4Si2(PH2)2] and [Me4Si2(PHMe)2] as well as their Reactions with n‐ButyllithiumThe 1,2‐diphosphanyldisilanes [Me4Si2(PH2)2] (1) and [Me4Si2(PHMe)2] (2) as well as the cyclic silaphosphane [(Me4Si2)2(PMe)2] (3) can be obtained from the reactions of [Me4Si2Cl2] with [LiAl(PH2)4] and [LiAl(PHMe)4], respectively. These compounds were characterized by multinuclear NMR spectroscopy, mass spectrometry and in case of compound 3 by single crystal X‐ray diffraction. The reactions of 1 and 2 with nBuLi yield the Si/P/Li cage compounds [(Me4Si2)2P2Li2(thf)5] (4) und [Me4Si2(PMe)2Li2(tmeda)2] (5). Central structural motif of 4 is a six‐membered P2Si4 ring in boat conformation. The phosphorus atoms of this ring are bridged by one of the Li+ ions. However, compound 5 contains a four‐membered P2Li2 ring whose phosphorus atoms are additionally connected by a Si2Me4 unit.
Über das Donor‐Verhalten von Bis(pyrazolyl)‐Schwefel‐Derivaten
Authors: Schröter Markus , Lork Enno , Mews Rüdiger 
Published: May 2005

The Donor Properties of Bis(pyrazolyl)‐Sulfur DerivativesFrom the reactions of bis(pyrazolyl)sulfane S(pz)2 (1) with the fluoro Lewis acids BF3 and AsF5 in liquid SO2 the 1:2‐adducts S(pz·BF3)2 (2) and S(pz·AsF5)2 (3) are obtained. 1 reacts with [Co(SO2)4(FAsF5)2] to give the doubly bridged FAsF4F dimeric complex [Co{S(pz)2}(FAsF5)(SO2)(μ‐FAsF4F)]2 (5). From F2S(pz)2 and [Ni(SO2)6](AsF6)2, the fluorocubane [Ni4F4{S(pz)2}4(μ‐FAsF4F)2](AsF6)2·4SO2 (8) is isolated. The X‐ray structures of the compounds 2, 3, 5 and 8 are reported.
The intestinal phase hormone
Authors: Orloff Marshall J. , Hyde Paul V. B. , Kosta Louis D. , Guillemin Roger C. L. , Bell Richard H. 
Published: May 2005

AbstractThe existence of a stimulatory intestinal phase of gastric acid secretion has been suspected, but largely ignored, for many years. Recently, however, it has become clear that the intestinal phase plays an important role in acid production during digestion. The intestinal phase is of additional interest in relation to the profound gastric acid hypersecretion associated with portacaval shunt (PCS). Substantial evidence indicates that PCS‐related gastric hypersecretion is due to unmasking of the intestinal phase by hepatic bypass of a humoral stimulant in portal blood that is normally degraded to a considerable extent by the liver. Studies in our laboratory during the past 12 years have provided strong physiologic evidence for humoral mediation of both the intestinal phase of gastric secretion and of PCS‐related hypersecretion by a hormone that arises in the small intestine, particularly in the jejunum. Furthermore, our studies have demonstrated that this intestinal phase hormone (IPH) exists in humans as well as in dogs, rats, and pigs. Additionally, drecent work by a number of investigators, as well as by our group, has provided convincing evidence that IPH is different from any of the known gastric stimulatory hormones.With these physiologic observations as a background, we have used a classical method for extracting acidic peptides to prepare a hog intestinal mucosa extract (HIME) that has all of the known physiologic properties of an IPH. Specifically, HIME contains a potent stimulant of gastric acid secretion that acts according to a linear dose‐response relationship; that is not gastrin in any of its immunoassayable forms; that significantly augments the maximal acid secretory responses to pentagastrin, gastrin, CCK, and histamine; and that is substantially degraded by the liver, in contrast to gastrin and CCK. Efforts at isolating the gastric stimulatory substance in HIME suggest that it is a peptide of low molecular weight. Work directed at isolating IPH in pure form and identifying it is in progress.