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  • Chemistry  (43,793)
  • 2000-2004  (484)
  • 1980-1984  (33,715)
  • 1930-1934
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  • 1
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2003-05-31
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Demaine, Linda J -- Fellmeth, Aaron X -- New York, N.Y. -- Science. 2003 May 30;300(5624):1375-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉RAND, Santa Monica, CA 90401, USA. demaine@rand.org〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12775825" target="_blank"〉PubMed〈/a〉
    Keywords: Aluminum Oxide ; Chemical Phenomena ; Chemistry ; Natural Science Disciplines ; Patents as Topic/*legislation & jurisprudence ; Plant Extracts ; Plant Roots ; Titanium ; United States
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  • 2
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2002-03-16
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Eisner, Thomas -- Berenbaum, May -- New York, N.Y. -- Science. 2002 Mar 15;295(5562):1973.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11896239" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biochemical Phenomena ; *Biochemistry ; *Biological Factors/chemistry ; *Biology ; Chemical Phenomena ; Chemistry ; *Ecology ; Ecosystem ; *Molecular Biology ; Research Support as Topic ; United States
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2004-05-29
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Malakoff, David -- New York, N.Y. -- Science. 2004 May 28;304(5675):1283.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15166364" target="_blank"〉PubMed〈/a〉
    Keywords: Biotechnology ; Career Choice ; Chemistry ; Emigration and Immigration ; History, 20th Century ; History, 21st Century ; Siberia ; United States
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  • 4
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-08-14
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Klotz, I M -- Haney, D N -- King, L C -- New York, N.Y. -- Science. 1981 Aug 14;213(4509):724-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7256275" target="_blank"〉PubMed〈/a〉
    Keywords: Anemia, Sickle Cell/*drug therapy ; Aspirin/analogs & derivatives/therapeutic use ; Chemical Phenomena ; Chemistry ; *Hemoglobin, Sickle ; Humans ; Protein Binding/drug effects ; Protein Conformation ; Salicylates/*therapeutic use ; Solubility ; Structure-Activity Relationship
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  • 5
    Publication Date: 1982-09-10
    Description: Alkyl-Substituted gamma-butyrolactones were synthesized and tested for their convulsant and anticonvulsant actions in mice and guinea pigs. The alpha-substituted compounds, alpha, alpha-dimethyl-, and alpha-ethyl-alpha-methyl-gamma-butyrolactone were anticonvulsant compounds with a spectrum of activity similar to that of ethosuximide. In contrast, beta-substituted compounds were convulsant agents similar to picrotoxinin. The alpha-substituted-gama-butyrolactones represent a new class of anticonvulsant drug with experimental and clinical potential.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Klunk, W E -- McKeon, A -- Covey, D F -- Ferrendelli, J A -- GM-07200/GM/NIGMS NIH HHS/ -- GM-24483/GM/NIGMS NIH HHS/ -- NS-14834/NS/NINDS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1982 Sep 10;217(4564):1040-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6810462" target="_blank"〉PubMed〈/a〉
    Keywords: *4-Butyrolactone/analogs & derivatives/*therapeutic use/toxicity ; Animals ; *Anticonvulsants ; Chemical Phenomena ; Chemistry ; Convulsants ; Drug Evaluation, Preclinical ; Electroencephalography ; Epilepsy, Absence/drug therapy ; Ethosuximide/pharmacology ; *Furans/*therapeutic use ; Guinea Pigs ; Mice ; Structure-Activity Relationship ; Trimethadione/pharmacology
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  • 6
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-05-06
    Description: Crystalline cholesterol undergoes a phase transition a few degrees below human body temperature. The high-temperature form has an unusually complex structure with 16 independent molecules. In the transition two molecules change side chain conformation, four reorient about their long axes, and ten remain unchanged. The transition mechanism implies relatively nonspecific intermolecular interactions, qualitatively consistent with the behavior of cholesterol in biomembranes. The transition preserves a remarkably closely obeyed pseudosymmetry present in the structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hsu, L Y -- Nordman, C E -- GM15259/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1983 May 6;220(4597):604-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6836303" target="_blank"〉PubMed〈/a〉
    Keywords: Body Temperature ; Chemical Phenomena ; Chemistry ; *Cholesterol ; Crystallization ; Humans ; Magnetic Resonance Spectroscopy ; Molecular Conformation
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  • 7
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-07-20
    Description: The iron-carbon monoxide stretching mode and the iron-carbon-oxygen bending mode in carbon monoxide-bound cytochrome oxidase have been assigned at 520 and 578 cm-1, respectively. The frequencies, widths, and intensities of these modes show that the Fe-C-O grouping in carbon monoxide-cytochrome a3 is linear but tilted from the normal to the heme plane; that the iron-histidine bond in both five- and six-coordinate cytochrome a3 is strained; and that the carbon monoxide and the proximal histidine each have characteristic, well-defined orientations in all molecules. These data can account for the binding affinities of carbon monoxide and dioxygen under physiological conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Argade, P V -- Ching, Y C -- Rousseau, D L -- New York, N.Y. -- Science. 1984 Jul 20;225(4659):329-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6330890" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Carbon Monoxide/metabolism ; Cattle ; Chemical Phenomena ; Chemistry ; Electron Transport Complex IV/*metabolism ; Myoglobin/metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Spectrum Analysis, Raman
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  • 8
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-05-06
    Description: Arachidonic acid plays a central role in a biological control system where such oxygenated derivatives as prostaglandins, thromboxanes, and leukotrienes are mediators. The leukotrienes are formed by transformation of arachidonic acid into an unstable epoxide intermediate, leukotriene A4, which can be converted enzymatically by hydration to leukotriene B4, and by addition of glutathione to leukotriene C4. This last compound is metabolized to leukotrienes D4 and E4 by successive elimination of a gamma-glutamyl residue and glycine. Slow-reacting substance of anaphylaxis consists of leukotrienes C4, D4, and E4. The cysteinyl-containing leukotrienes are potent bronchoconstrictors, increase vascular permeability in postcapillary venules, and stimulate mucus secretion. Leukotriene B4 causes adhesion and chemotactic movement of leukocytes and stimulates aggregation, enzyme release, and generation of superoxide in neutrophils. Leukotrienes C4, D4, and E4, which are released from the lung tissue of asthmatic subjects exposed to specific allergens, seem to play a pathophysiological role in immediate hypersensitivity reactions. These leukotrienes, as well as leukotriene B4, have pro-inflammatory effects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Samuelsson, B -- New York, N.Y. -- Science. 1983 May 6;220(4597):568-75.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6301011" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Arachidonic Acids/metabolism/pharmacology/physiology ; Bronchi/drug effects ; Cats ; Chemical Phenomena ; Chemistry ; Cricetinae ; Guinea Pigs ; Haplorhini ; Humans ; Hypersensitivity, Immediate/*physiopathology ; Inflammation/*physiopathology ; Leukocytes/drug effects/metabolism ; Leukotriene B4/pharmacology/*physiology ; Mice ; Microcirculation/drug effects ; Rabbits ; Rats ; SRS-A/*physiology
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  • 9
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-01-20
    Description: Peptide synthesis can be used for elucidating the roles of secondary structures in the specificity of hormones, antigens, and toxins. Intermediate sized peptides with these activities assume amphiphilic secondary structures in the presence of membranes. When models are designed to optimize the amphiphilicity of the secondary structure, stronger interactions can be observed with the synthetic peptides than with the naturally occurring analogs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kaiser, E T -- Kezdy, F J -- HL-18577/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1984 Jan 20;223(4633):249-55.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6322295" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Apolipoprotein A-I ; Apolipoproteins ; Binding Sites ; Calcitonin ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone ; Endorphins ; Glucagon ; Growth Hormone-Releasing Hormone ; *Hormones/pharmacology ; Lipoproteins, HDL ; Melitten ; Models, Structural ; *Peptides/chemical synthesis/metabolism/pharmacology ; Protein Conformation ; Structure-Activity Relationship ; beta-Endorphin
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  • 10
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-10-19
    Description: Fourier transform mass spectrometry will play an important role in the future because of its unique combination of high mass resolution, high upper mass limit, and multichannel advantage. These features have already found application in gas chromatography-mass spectrometry, multiphoton ionization, laser desorption, and secondary ion mass spectrometry. However, its most notable feature is the ability to store ions. This characteristic, when combined with the others, will allow expeditious study of the interaction of gas-phase ions with both photons (photodissociation) and neutral molecules, and the convenient application of this fundamental information for chemical analysis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gross, M L -- Rempel, D L -- 2-8423576/PHS HHS/ -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):261-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6385250" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Fourier Analysis ; Ions ; Lasers ; *Mass Spectrometry/instrumentation/methods
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  • 11
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-08-31
    Description: High-resolution carbon-13 nuclear magnetic resonance (NMR) spectra of enzyme-inhibitor and enzyme-substrate complexes provide detailed structural and stereochemical information on the mechanism of enzyme action. The proteases trypsin and papain are shown to form tetrahedrally coordinated complexes and acyl derivatives with a variety of compounds artificially enriched at the site or sites of interest. These results are compared with the structural information derived from x-ray diffraction. Detailed NMR studies have provided a clearer picture of the ionization state of the residues participating in enzyme-catalyzed processes than other more classical techniques. The dynamics of enzymic catalysis can be observed at sub-zero temperatures by a combination of cryoenzymology and carbon-13 NMR spectroscopy. With these powerful techniques, transient, covalently bound intermediates in enzyme-catalyzed reactions can be detected and their structures rigorously assigned.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mackenzie, N E -- Malthouse, J P -- Scott, A I -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):883-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6433481" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Carbon Isotopes ; Carboxypeptidases/metabolism ; Carboxypeptidases A ; Catalysis ; Chemical Phenomena ; Chemistry ; Coenzymes/*metabolism ; Endopeptidases/metabolism ; Enzymes/*metabolism ; Freezing ; Fructose-Bisphosphate Aldolase/metabolism ; Magnetic Resonance Spectroscopy ; Papain/metabolism ; Pepsin A/metabolism ; Peptide Hydrolases/*metabolism ; Protease Inhibitors ; Pterins/metabolism ; Pyridoxal Phosphate/metabolism ; Serine Endopeptidases
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  • 12
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-03-09
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maugh, T H 2nd -- New York, N.Y. -- Science. 1984 Mar 9;223(4640):1051-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6695193" target="_blank"〉PubMed〈/a〉
    Keywords: *Air Pollutants ; *Atmosphere ; Carbon Tetrachloride ; Chemical Phenomena ; Chemistry ; *Chlorofluorocarbons, Methane ; Free Radicals ; Nitrogen Dioxide ; Nitrous Oxide ; Oxygen ; *Ozone ; Photochemistry ; Risk ; Singlet Oxygen ; Trichloroethanes ; Ultraviolet Rays
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  • 13
    Publication Date: 1984-10-19
    Description: Pyrolysis mass spectrometry in combination with computerized multivariate statistical analysis enables qualitative and quantitative analysis of nonvolatile organic materials containing molecular assemblies of a complexity and size far beyond the capabilities of direct mass spectrometry. The state of the art in pyrolysis mass spectrometry techniques is illustrated through specific applications, including structural determination and quality control of synthetic polymers, quantitative analysis of polymer mixtures, classification and structural characterization of fossil organic matter, and nonsupervised numerical extraction of component patterns from complex biological samples.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meuzelaar, H L -- Windig, W -- Harper, A M -- Huff, S M -- McClennen, W H -- Richards, J M -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):268-74.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6484572" target="_blank"〉PubMed〈/a〉
    Keywords: Biochemical Phenomena ; Biochemistry ; Chemical Phenomena ; Chemistry ; Coal ; Enterobacteriaceae/analysis/isolation & purification ; Hot Temperature ; Mass Spectrometry/*methods ; Polymers
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  • 14
    Publication Date: 1984-08-31
    Description: The splicing of messenger RNA precursors in vitro proceeds through an intermediate that has the 5' end of the intervening sequence joined to a site near the 3' splice site. This lariat structure, which has been characterized for an adenovirus 2 major late transcript, has a branch point, with 2'-5' and 3'-5' phosphodiester bonds emanating from a single adenosine residue. The excised intervening sequence retains the branch site and terminates in a guanosine residue with a 3' hydroxyl group. The phosphate group at the splice junction between the two exons originates from the 3' splice site at the precursor.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Padgett, R A -- Konarska, M M -- Grabowski, P J -- Hardy, S F -- Sharp, P A -- P01-CA14051/CA/NCI NIH HHS/ -- P01-CA26717/CA/NCI NIH HHS/ -- R01-GM32467/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):898-903.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6206566" target="_blank"〉PubMed〈/a〉
    Keywords: Adenoviruses, Human/metabolism ; Base Sequence ; Chemical Phenomena ; Chemistry ; Nucleic Acid Conformation ; Nucleic Acid Precursors/analysis/*metabolism ; Oligoribonucleotides/metabolism ; Phosphates/metabolism ; RNA/analysis/*metabolism ; RNA Precursors ; *RNA Splicing ; RNA, Messenger/analysis/*metabolism ; RNA, Viral/analysis/*metabolism
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  • 15
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-05-11
    Description: The mechanism of lipid peroxidation and the manner in which antioxidants function is reviewed. beta-Carotene is a purported anticancer agent, which is believed by some to have antioxidant action of a radical-trapping type. However, definitive experimental support for such action has been lacking. New experiments in vitro show that beta-carotene belongs to a previously unknown class of biological antioxidants. Specifically, it exhibits good radical-trapping antioxidant behavior only at partial pressures of oxygen significantly less than 150 torr, the pressure of oxygen in normal air. Such low oxygen partial pressures are found in most tissues under physiological conditions. At higher oxygen pressures, beta-carotene loses its antioxidant activity and shows an autocatalytic, prooxidant effect, particularly at relatively high concentrations. Similar oxygen-pressure-dependent behavior may be shown by other compounds containing many conjugated double bonds.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Burton, G W -- Ingold, K U -- New York, N.Y. -- Science. 1984 May 11;224(4649):569-73.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6710156" target="_blank"〉PubMed〈/a〉
    Keywords: Antioxidants/*metabolism ; Carotenoids/*metabolism ; Chemical Phenomena ; Chemistry ; Free Radicals ; Humans ; Linoleic Acids/metabolism ; *Lipid Metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Partial Pressure ; Peroxides/metabolism ; Tetrahydronaphthalenes/metabolism ; beta Carotene
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  • 16
    Publication Date: 1983-12-16
    Description: Aplysiatoxin and debromoaplysiatoxin, which are isolated from the seaweed, Lyngbya gracilis, differ in their chemical structure only by the presence or absence of a bromine residue in the hydrophilic region. The function and the structure-activity relation of the hydrophilic region are not known. Aplysiatoxin increased malignant transformation, stimulated DNA synthesis, and inhibited the binding of phorbol-12,13-dibutyrate and epidermal growth factor to cell receptors. Debromoaplysiatoxin inhibited the binding of these two substances as strongly as aplysiatoxin but did not increase malignant transformation or stimulate DNA synthesis. These results indicate that a slight change in the chemical structure of the hydrophilic region of aplysiatoxin affects its abilities to increase cell transformation and stimulate DNA synthesis and that the abilities of the tumor promoters to inhibit the binding of phorbol-12,13-dibutyrate and epidermal growth factor are dissociable from their abilities to increase cell transformation and stimulate DNA synthesis under some circumstances.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shimomura, K -- Mullinix, M G -- Kakunaga, T -- Fujiki, H -- Sugimura, T -- New York, N.Y. -- Science. 1983 Dec 16;222(4629):1242-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6316505" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Caenorhabditis elegans Proteins ; Carcinogens/*pharmacology ; Carrier Proteins ; Cell Line ; Cell Transformation, Neoplastic/*drug effects ; Chemical Phenomena ; Chemistry ; DNA/biosynthesis ; Epidermal Growth Factor/metabolism ; Lactones/analysis/*pharmacology ; *Lyngbya Toxins ; Mice ; Phorbol 12,13-Dibutyrate ; Phorbol Esters/metabolism ; *Protein Kinase C ; Receptor, Epidermal Growth Factor ; Receptors, Cell Surface/metabolism ; *Receptors, Drug ; Structure-Activity Relationship
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  • 17
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-03-16
    Description: Yeast phenylalanine transfer RNA was subjected to a 12-picosecond molecular dynamics simulation. The principal features of the x-ray crystallographic analysis are reproduced, and the amplitudes of atomic displacements appear to be determined by the degree of exposure of the atoms. An analysis of the hydrogen bonds shows a correlation between the average length of a bond and the fluctuation in that length and reveals a rocking motion of bases in Watson-Crick guanine X cytosine base pairs. The in-plane motions of the bases are generally of larger amplitude than the out-of-plane motions, and there are correlations in the motions of adjacent bases.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harvey, S C -- Prabhakaran, M -- Mao, B -- McCammon, J A -- New York, N.Y. -- Science. 1984 Mar 16;223(4641):1189-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6560785" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Computers ; Cytosine ; Guanine ; Hydrogen Bonding ; Nucleic Acid Conformation ; *RNA, Fungal ; *RNA, Transfer, Amino Acyl ; Yeasts/analysis
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  • 18
    Publication Date: 1984-11-16
    Description: Sequence-dependent variations in DNA revealed by x-ray crystallographic studies have suggested that certain DNA-reactive drugs may react preferentially with defined sequences in DNA. Drugs that wind around the helix and reside within one of the grooves of DNA have perhaps the greatest chance of recognizing sequence-dependent features of DNA. The antitumor antibiotic CC-1065 covalently binds through N-3 of adenine and resides within the minor groove of DNA. This drug overlaps with five base pairs for which a high sequence specificity exists.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hurley, L H -- Reynolds, V L -- Swenson, D H -- Petzold, G L -- Scahill, T A -- New York, N.Y. -- Science. 1984 Nov 16;226(4676):843-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6494915" target="_blank"〉PubMed〈/a〉
    Keywords: Antibiotics, Antineoplastic/*metabolism ; *Base Sequence ; Binding Sites ; Chemical Phenomena ; Chemistry ; DNA/*metabolism ; *Indoles ; Leucomycins/*metabolism ; Molecular Conformation ; X-Ray Diffraction
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  • 19
    Publication Date: 1984-06-15
    Description: A new class of synthetic antifungal agents, the allylamines , has been developed by modification of naftifine , a topical antimycotic. SF 86-327, the most effective of these compounds so far, is highly active in vitro against a wide range of fungi and exceeds clinical standards in the oral and topical treatment of guinea pig dermatophytoses. SF 86-327 is a powerful specific inhibitor of fungal squalene epoxidase, a key enzyme in sterol biosynthesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Petranyi, G -- Ryder, N S -- Stutz, A -- New York, N.Y. -- Science. 1984 Jun 15;224(4654):1239-41.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6547247" target="_blank"〉PubMed〈/a〉
    Keywords: Allylamine/analogs & derivatives/*chemical synthesis/pharmacology ; Amines/*chemical synthesis ; Animals ; Antifungal Agents/*chemical synthesis/pharmacology ; Chemical Phenomena ; Chemistry ; Dermatomycoses/drug therapy ; Fungi/*drug effects/enzymology ; Guinea Pigs ; Naphthalenes/chemical synthesis/pharmacology ; Oxygenases/*antagonists & inhibitors ; Squalene Monooxygenase
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  • 20
    Publication Date: 1984-11-02
    Description: By recombinant DNA techniques, a disulfide bond was introduced at a specific site in T4 lysozyme, a disulfide-free enzyme. This derivative retained full enzymatic activity and was more stable toward thermal inactivation than the wild-type protein. The derivative, T4 lysozyme (Ile3----Cys), was prepared by substituting a Cys codon for an Ile codon at position 3 in the cloned lysozyme gene by means of oligonucleotide-dependent, site-directed mutagenesis. The new gene was expressed in Escherichia coli under control of the (trp-lac) hybrid tac promoter, and the protein was purified. Mild oxidation generated a disulfide bond between the new Cys3 and Cys97, one of the two unpaired cysteines of the native molecule. Oxidized T4 lysozyme (Ile3----Cys) exhibited specific activity identical to that of the wild-type enzyme when measured at 20 degrees C in a cell-clearing assay. The cross-linked protein was more stable than the wild type during incubation at elevated temperatures as determined by recovered enzymatic activity at 20 degrees C.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perry, L J -- Wetzel, R -- New York, N.Y. -- Science. 1984 Nov 2;226(4674):555-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6387910" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; DNA, Recombinant/metabolism ; Escherichia coli/enzymology ; *Genetic Engineering ; Kinetics ; Muramidase/*genetics/metabolism ; Protein Denaturation
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  • 21
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-09-09
    Description: The structures of three proteins that regulate gene expression have been determined recently and suggest how these proteins may bind to their specific recognition sites on the DNA. One protein (Cro) is a repressor of gene expression, the second (CAP) usually stimulates gene expression, and the third (lambda repressor) can act as either a repressor or an activator. The three proteins contain a substructure consisting of two consecutive alpha helices that is virtually identical in each case. Structural and amino acid sequence comparisons suggest that this bihelical fold occurs in a number of proteins that regulate gene expression, and is an intrinsic part of the DNA-protein recognition event. The modes of repression and activation by Cro and lambda repressor are understood reasonably well, but the mode of action of CAP is still unclear.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Takeda, Y -- Ohlendorf, D H -- Anderson, W F -- Matthews, B W -- GM20066/GM/NIGMS NIH HHS/ -- GM28138/GM/NIGMS NIH HHS/ -- GM30894/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1983 Sep 9;221(4615):1020-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6308768" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Chemical Phenomena ; Chemistry ; *DNA Helicases ; DNA-Binding Proteins ; Escherichia coli/genetics ; Gene Expression Regulation ; Models, Chemical ; Protein Conformation
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  • 22
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-06-08
    Description: The effect of a partial pressure of nitrogen of 50 atmospheres (5065 kilopascals ) on the hydrogen evolution reaction of nitrogenase has been investigated. Evolution of hydrogen was not blocked completely by 50 atmospheres of nitrogen in any of four experiments; rather, 27.3 +/- 2.4 percent of the total electron flux through nitrogenase was directed toward production of hydrogen. The ratio of hydrogen evolved to nitrogen fixed was close to 1:1, which implies that hydrogen evolution is obligatory in the fixation of molecular nitrogen by nitrogenase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Simpson, F B -- Burris, R H -- AI-00848/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1984 Jun 8;224(4653):1095-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6585956" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Hydrogen ; *Nitrogen ; Nitrogen Fixation ; *Nitrogenase ; Partial Pressure
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  • 23
    Publication Date: 1980-01-04
    Description: In concentrates of water produced in a laboratory simulation of a drinking water treatment process, direct-acting, nonvolatile mutagens were readily detected by means of the Ames Salmonella test. The mutagens were shown to be produced by the chlorination process. Treatment of the water with chloramine resulted in less mutagenic activity than treatment with free chlorine. Dechlorination of drinking water with sulfite sharply reduced the mutagenic activity. Treatment with sulfur dioxide is proposed as an effective, inexpensive method of reducing the direct-acting mutagenic activity of drinking water and of aqueous industrial effluents.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cheh, A M -- Skochdopole, J -- Koski, P -- Cole, L -- New York, N.Y. -- Science. 1980 Jan 4;207(4426):90-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6985746" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Chloramines ; Chlorine ; Mutagens/*analysis ; Salmonella typhimurium/genetics ; Sulfites ; Water Pollutants/*analysis ; Water Pollutants, Chemical/*analysis ; Water Supply/*analysis
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  • 24
    Publication Date: 1981-10-16
    Description: The DNA/RNA Synthesizer provides a complete and automated procedure for the synthesis of DNA sequences. Each base unit is added in a 30-minute cycle, permitting a tetradecamer to be constructed in 6 1/2 hours. The complete procedure is described, including a practical procedure for isolation and purification of the desired DNA sequence.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Alvarado-Urbina, G -- Sathe, G M -- Liu, W C -- Gillen, M F -- Duck, P D -- Bender, R -- Ogilvie, K K -- New York, N.Y. -- Science. 1981 Oct 16;214(4518):270-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6169150" target="_blank"〉PubMed〈/a〉
    Keywords: Automation ; Chemical Phenomena ; Chemistry ; DNA/*chemical synthesis ; *Genes, Synthetic ; RNA/*chemical synthesis ; Solubility
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  • 25
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-05-15
    Description: Research on chitin as a marine resource is pointing to novel applications for this cellulose-like biopolymer. Discovery of nondegrading solvent systems has permitted the spinning of filaments, for example, for use as surgical sutures. New methods for preparing the bioactive alkyl glycoside of N-acetyl-D-glucosamine (the monomer unit of chitin) and a microcrystalline chitin has encouraged their use as promoters for growth of bifidobacteria and as an aid in digestion of high-lactose cheese whey by domestic animals. Chitin-protein complexes of several crustacean species show great variability in ratios of chitin to covalently bound protein and in residual protein in the "purified" chitins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Austin, P R -- Brine, C J -- Castle, J E -- Zikakis, J P -- New York, N.Y. -- Science. 1981 May 15;212(4496):749-53.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7221561" target="_blank"〉PubMed〈/a〉
    Keywords: Animal Feed ; Animals ; Cheese ; Chemical Phenomena ; Chemistry ; Chickens ; *Chitin ; Crystallography ; Lactose/metabolism ; Proteins/analysis ; Sutures ; *Technology
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  • 26
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-12-18
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gilbert, W -- New York, N.Y. -- Science. 1981 Dec 18;214(4527):1305-12.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7313687" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; Chemical Phenomena ; Chemistry ; DNA/*genetics ; Eukaryotic Cells/physiology ; *Genes ; Hydrazines ; Lac Operon ; Methylation ; Prokaryotic Cells/physiology ; Sulfuric Acid Esters
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  • 27
    Publication Date: 1982-07-09
    Description: A new process has been developed which is called "Boradeption" to signify boronic acid--dependent phase transfer of water-insoluble agents. Highly fluorescent boronic acid dervatives, FluoroBoras, are solubilized with a physiologically compatible carrier buffer containing a receptor group for boronate adduct formation. The system can be used to stain living cells. In another variation of the Boradeption concept, an insoluble reporter molecule containing a boronate receptor is solubilized with a carrier buffer containing a boronic acid functional group. The boronate-receptor complexes, which are in dynamic equilibrium, can be designed as vital stains and reagents for a variety of biological and medical applications.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gallop, P M -- Paz, M A -- Henson, E -- AG-00376-07/AG/NIA NIH HHS/ -- HL-20764-04A1/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1982 Jul 9;217(4555):166-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6178158" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Biological Transport ; *Boron Compounds/therapeutic use ; *Boronic Acids/therapeutic use ; *Cell Membrane Permeability ; Cells, Cultured ; Chemical Phenomena ; Chemistry ; Chromogenic Compounds/metabolism ; Cricetinae ; Fibroblasts ; Fluorescent Dyes/metabolism ; Humans ; Rats ; Staining and Labeling
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  • 28
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-12-11
    Description: The scrapie agent causes a degenerative nervous system disease in sheep and goats. Studies with extensively purified preparations demonstrated that the agent contains a protein that is required for infectivity. Chemical modification of the scrapie agent by diethyl pyrocarbonate reduced the titer 1000-fold. Exposure of the inactivated agent to hydroxylamine, a strong nucleophile, resulted in complete restoration of infectivity. Presumably, nucleophilic residues within a scrapie agent protein undergo carbethoxylation on reaction with diethyl pyrocarbonate, and subsequent addition of hydroxylamine displaces these carbethoxy groups.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McKinley, M P -- Masiarz, F R -- Prusiner, S B -- NS14069/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1981 Dec 11;214(4526):1259-61.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6795721" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Assay ; Brain/microbiology ; Chemical Phenomena ; Chemistry ; Cricetinae ; Diethyl Pyrocarbonate/pharmacology ; Histidine/pharmacology ; *Prions ; Ribonucleases/pharmacology ; Serum Albumin, Bovine/pharmacology ; Viral Proteins/*isolation & purification/pharmacology
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  • 29
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-01-30
    Description: The incubation of lens proteins with reducing sugars leads to the formation of fluorescent yellow pigments and cross-like similar to those reported in aging and cataractous human lenses. Called nonenzymatic browning or the Maillard reaction, this aging process also occurs in stored foods. Reducing sugars condense with the free amino group of proteins, then rearrange and dehydrate to form unsaturated pigments and cross-linked products. Although most proteins in living systems turn over with sufficient rapidity to avoid nonenzymatic browning, some, such as lens crystallins and skin collagen, are exceptionally long-lived and may be vulnerable.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Monnier, V M -- Cerami, A -- AM 19655/AM/NIADDK NIH HHS/ -- New York, N.Y. -- Science. 1981 Jan 30;211(4481):491-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6779377" target="_blank"〉PubMed〈/a〉
    Keywords: *Aging ; Animals ; Cattle ; Chemical Phenomena ; Chemistry ; *Crystallins ; Diabetes Mellitus/physiopathology ; Glucose ; Glucosephosphates ; In Vitro Techniques ; Lysine ; *Proteins ; Spectrophotometry, Ultraviolet
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  • 30
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-03-13
    Description: Great advances have been made in fundamental scientific research in recent years. The new knowledge gathered, in addition to deepening our understanding of the physical universe, contributes a range of abilities and opportunities to society that would not otherwise be available. Much research that may be called applied because it addresses needs of society is quite fundamental in character, and support of such research at the National Science Foundation is to be handled in tandem by the research directorates. Other areas that require a refocusing of support are engineering science and education, at all levels, in science and engineering. Increasing our strength in these areas is essential to achieve our national economic, social, and political goals. Steps are being taken by the National Science Foundation to make its structure better able to deal with engineering and applied research and to provide greater mutual reinforcement between applied and basic research.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Slaughter, J B -- New York, N.Y. -- Science. 1981 Mar 13;211(4487):1131-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7466384" target="_blank"〉PubMed〈/a〉
    Keywords: Cell Biology ; Chemical Phenomena ; Chemistry ; *Forecasting ; Geological Phenomena ; Geology ; *Government Agencies ; Molecular Biology ; Neurochemistry ; Physical Phenomena ; Physics ; Research Support as Topic ; United States
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  • 31
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1982-12-10
    Description: The discovery that cis-diamminedichloroplatinum(II) (cis-DDP) has clinically useful antitumor properties and can form platinum blues spawned an extensive investigation of its chemistry in water. Several new molecules have been synthesized, some rather old ones have been characterized for the first time, and clues have begun to emerge about the chemical interaction of cis-DDP with its likely biological target, DNA.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lippard, S J -- New York, N.Y. -- Science. 1982 Dec 10;218(4577):1075-82.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6890712" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Cisplatin ; *Dna ; Hydrolysis ; Pigments, Biological
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  • 32
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1982-12-03
    Description: The visual response is initiated by light reception and transduction into chemical and electrical energy in the outer-segment membranes of rod and cone cells. Recent research on the molecular events controlled by light has clarified the roles of some of the rod outer-segment biomolecules. These developments and the current unresolved questions are described.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉O'Brien, D F -- New York, N.Y. -- Science. 1982 Dec 3;218(4576):961-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6291153" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Blood Proteins/metabolism ; Calcium/metabolism ; Chemical Phenomena ; Chemistry ; Enzyme Activation ; Enzymes/metabolism ; GTP-Binding Proteins ; Light ; Membranes/metabolism ; Models, Biological ; Phosphoric Diester Hydrolases/biosynthesis ; Photoreceptor Cells/*metabolism ; Receptors, Cell Surface/metabolism ; Rhodopsin/metabolism ; Rod Cell Outer Segment/*metabolism ; Vision, Ocular/*physiology
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  • 33
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-06-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krenitsky, T A -- Beauchamp, L -- New York, N.Y. -- Science. 1983 Jun 10;220(4602):1106.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6857236" target="_blank"〉PubMed〈/a〉
    Keywords: Acyclovir/metabolism ; *Antiviral Agents/metabolism ; Chemical Phenomena ; Chemistry ; Humans ; Vidarabine/metabolism
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  • 34
    Publication Date: 1983-05-06
    Description: Resonance Raman spectra of photolyzed carbonmonoxyhemoglobin obtained with 10-nanosecond pulses are compared with the spectra of photolyzed carbonmonoxyhemoglobin stabilized at 80 K. In comparing the deoxy with the photodissociated species, the changes in the Raman spectra are the same for these two experimental regimes. These results show that at ambient and cryogenic temperatures the heme pocket in liganded hemoglobin is significantly different from that of deoxyhemoglobin. It is concluded that measurements of the properties of intermediate species from photodissociated hemoglobin stabilized at low temperatures can be used to probe the short-lived metastable forms of hemoglobin present after photodissociation under biologically relevant solution conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ondrias, M R -- Friedman, J M -- Rousseau, D L -- New York, N.Y. -- Science. 1983 May 6;220(4597):615-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6836305" target="_blank"〉PubMed〈/a〉
    Keywords: Carboxyhemoglobin ; Chemical Phenomena ; Chemistry ; Freezing ; *Hemoglobins ; Humans ; Ligands ; Spectrum Analysis, Raman ; Temperature
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  • 35
    Publication Date: 1983-04-15
    Description: Alkylating agents that display strong selectivity for opiate receptor types delta or mu were prepared by appropriate modification of the structures of the strong analgesics fentanyl, etonitazene, and endoethenotetrahydrooripavine. The availability of these substances should facilitate studies of the structural basis of receptor specificity and of the physiologic roles of these receptors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rice, K C -- Jacobson, A E -- Burke, T R Jr -- Bajwa, B S -- Streaty, R A -- Klee, W A -- New York, N.Y. -- Science. 1983 Apr 15;220(4594):314-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6132444" target="_blank"〉PubMed〈/a〉
    Keywords: Alkylation ; Animals ; Benzimidazoles/analogs & derivatives/metabolism ; Brain/physiology ; Cells, Cultured ; Chemical Phenomena ; Chemistry ; Enkephalin, Methionine/analogs & derivatives/metabolism ; Fentanyl/analogs & derivatives/metabolism ; *Isothiocyanates ; Ligands ; Rats ; Receptors, Opioid/*metabolism/physiology ; Thebaine/analogs & derivatives/pharmacology
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  • 36
    Publication Date: 1980-10-01
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bumb, R R -- Crummett, W B -- Cutie, S S -- Gledhill, J R -- Hummel, R H -- Kagel, R O -- Lamparski, L L -- Luoma, E V -- Miller, D L -- Nestrick, T J -- Shadoff, L A -- Stehl, R H -- Woods, J S -- New York, N.Y. -- Science. 1980 Oct;210(4468):385-90.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6159682" target="_blank"〉PubMed〈/a〉
    Keywords: Air Pollutants/analysis ; Chemical Phenomena ; Chemistry ; Chromatography, High Pressure Liquid ; *Dioxins/analysis ; *Fires ; Power Plants ; Smoke/analysis ; Soil Pollutants/analysis ; Tetrachlorodibenzodioxin/analysis ; Vehicle Emissions/analysis ; Water Pollutants, Chemical/analysis
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  • 37
    Publication Date: 1984-05-25
    Description: Polypeptide analogs of the known members of the corticotropin-releasing factor (CRF) family were synthesized and tested in vitro and in vivo for enhanced potency or competitive antagonism. Predictive methods and physicochemical measurements had suggested an internal secondary alpha-helical conformation spanning about 25 residues for at least three members of the CRF family. Maximization of alpha-helix-forming potential by amino acid substitutions from the native known sequences (rat/human and ovine CRF, sauvagine, and carp and sucker urotensin 1) led to the synthesis of an analog that was found to be more than twice as potent as either of the parent peptides in vitro. In contrast, certain amino-terminally shortened fragments, such as alpha-helical CRF or ovine CRF residues 8 to 41, 9 to 41, and 10 to 41, were found to be competitive inhibitors in vitro. Selected antagonists were examined and also found to be active in vivo.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rivier, J -- Rivier, C -- Vale, W -- AA03504/AA/NIAAA NIH HHS/ -- AM20917/AM/NIADDK NIH HHS/ -- AM26741/AM/NIADDK NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1984 May 25;224(4651):889-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6326264" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenocorticotropic Hormone/secretion ; Animals ; Binding, Competitive ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone/*antagonists & inhibitors ; Rats
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  • 38
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 118 (1980), S. 128-151 
    ISSN: 1420-9136
    Keywords: Galactic cosmic rays ; Solar proton events ; Particle precipitation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An assessment is made of the relative contribution of certain classes of energetic particle precipitation to the chemical composition of the middle atmosphere with emphasis placed on the production of odd nitrogen and odd hydrogen species and their subsequent role in the catalytic removal of ozone. Galactic cosmic radiation is an important source of odd nitrogen in the lower stratosphere but since the peak energy deposition occurs below the region where catalytic removal of O3 is most effective, it is questionable whether this mechanism is important in the overall terrestrial ozone budget. The precipitation of energetic solar protons can periodically produce dramatic enhancement in upper stratospheric NO. The long residence time of NO in this region of the atmosphere, where catalytic interaction with O3 is also most effective, mandates that this mechanism be included in future modelling of the global distribution of O3. Throughout the mesosphere the precipitation of energetic electrons from the outer radiation belt (60°≲Λ≲70°) can sporadically act as a major local source of odd hydrogen and odd nitrogen leading to observable O3 depletion. Future satellite studies should be directed at simultaneously measuring the precipitation flux and the concomitant atmosphere modification, and these results should be employed to develop more sophisticated models of this important coupling.
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  • 39
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    Accreditation and quality assurance 5 (2000), S. 409-413 
    ISSN: 1432-0517
    Keywords: Key words Metrology ; Comparisons ; Chemistry ; Standards
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  After stressing the importance in the modern world of accurate and reproducible measurements, the actions taken by the Bureau International des Poids et Mesures to set up, together with the regional metrology organizations, a series of key comparisons are described. They are the technical foundation of a mutual recognition of national measurement standards arrangement prepared in conjunction with the National Metrology Institutes (NMIs). This arrangement also includes the recognition of calibration and measurement certificates issued by these institutes. Then, the consequences of this arrangement for trade are described. The case of chemical analysis is illustrated by the application of the Kyoto protocol on the reduction of greenhouse gases. But the global workload to be taken up by the International Committee of Weights and Measures, its Consultative Committee for Amount of Substance and the NMIs is huge.
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  • 40
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    Journal of molecular evolution 15 (1980), S. 79-101 
    ISSN: 1432-1432
    Keywords: Molecules ; Interstellar ; Chemistry ; Isotopes ; Solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The study of interstellar molecules broadly includes two areas of interest. One area uses the unique ability of molecules to act as probes of the physical conditions in the cold, dense, visually opaque component of the interstellar medium. The physical properties of this and other components of the interstellar medium are summarized. The other area deals with the chemistry of interstellar molecules, recent aspects of which are emphasized in this review. Gas-phase chemistry, shock chemistry, and grain surface chemistry are discussed in the context of recent observations. No present observations suggest that surface reactions are relevant, but neither can they be ruled out. Ion-molecule reactions are clearly operative, at least for the simpler species. Chemical isotope fractionation is reviewed, andd it is concluded that the complexities of the chemistry allow no cosmological conclusions to be drawn from observations of deuterium in interstellar molecules, while the presence of13C in interstellar molecules permits an estimate of the12C/13C ratio which is consistent with the current concepts of the nucleosynthesis history of the Galaxy. Possible connections between interstellar molecules and the early molecular history of the solar system are discussed.
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  • 41
    ISSN: 1432-0827
    Keywords: Bacterial amphophile ; Purification ; Chemistry ; Resorption ; Ca influx ; Cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The bone resorptive factor and amphipathic antigen (AcA) previously identified by us in preparations fromActinomyces viscosus have been partially purified, characterized chemically, and compared. They elute at the same location on chromatography with Ac 22. The fatty acid composition of AcA and the bone resorptive factor is the same. Some differences in carbohydrate composition are observed. TheActinomyces factor does not affect calcium influx or cyclic AMP in isolated bone cells. Therefore it is concluded that AcA stimulates resorption either by gaining entrance into bone cells or by way of a yet undetermined second messenger.
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  • 42
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    Earth, moon and planets 88 (2000), S. 35-58 
    ISSN: 1573-0794
    Keywords: Chemistry ; interplanetary dust particles (IDPs) ; Leonids ; meteor trails ; meteoroids ; meteors ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The cometary Leonid meteoroids represent a size range in between largest carbon-richIDPs and the smallest CI meteorites. Their dustball structure and chemistry offer anopportunity to constrain hierarchical dust accretion inferred from petrologic studies ofaggregate and cluster IDPs. The Leonid shower meteoroids of known ``comet ejection''ages provide an opportunity to study space weathering of cometary dust over periodsof up to several hundred years. The meteors and aggregate and cluster IDPs displaycontinuous thermal modification of organics and volatile element (Na, K-bearing phases), that occur as discrete minerals and amorphous solids each different response during kinetically controlled ablation. Leonid meteoroids are not excessively Na-rich. The occurrences of Leonid meteors can now be accurate predicted and combined withknowledge better models for the settling rates, collections of surviving dust becomea comet nucleus-sampling mission.
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  • 43
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 801-818 
    ISSN: 1434-1948
    Keywords: Zeolites ; Microporous zeolites ; Titanosilicates ; Transition metal ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stable microporous materials, such as zeolites, are extremely important for applications in catalysis, adsorption, ion-exchange, and separation. In this review we describe a new class of stable microporous materials that involves novel mixed octhaedral-tetrahedral framework oxides. The archetypal material is based on titanosilicates, although there is tremendous scope for introducing many other transition metals. These materials not only have potential novel applications in the fields normally associated with zeolites but also possible applications in the areas of optoelectronics, nonlinear optics, batteries, magnetic materials and sensors.
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  • 44
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 827-830 
    ISSN: 1434-1948
    Keywords: Ammonolysis ; Chlorine ; Nitrogen ; Silicon ; Silsesquiazane ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ammonolysis of trichlorosilanes RSiCl3 [R = CH(SiMe3)2 (1a), Ph (1b), Et (1c)] leads to a series of condensed products such as six-membered rings [(Me3Si)2CHSi(OH)NH]3 (2a) and [PhSi(NH2)NH]3 (2b), disilazane [(Me3Si)2CHSi(NH2)2]2NH (3) and the cage compound (EtSi)6(NH)9 (4). The mixed Si-N-O compound 2a was obtained when liquid ammonia was not dried over sodium prior to use. The reaction with sodium gives NaCl instead of NH4Cl as a by-product which is easily removed by filtration.
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  • 45
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 835-837 
    ISSN: 1434-1948
    Keywords: Gold ; Clusters ; Quantum dots ; Monolayers ; Amphiphiles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Extended ordered monolayers of ligand stabilized Au55 clusters are formed at the phase boundary between water and dichloromethane. The water phase, containing amphiphilic molecules like per-6-deoxy-6-thio-α-cyclodextrin (1) or poly(vinylpyrrolidone) (2), is covered by a thin film of a solution of [Au55(PPh3)12Cl6] in dichloromethane. The interaction of the cluster molecules with the thiol functions of 1 or the polymer chains of 2 form perfect cluster orders of hexagonal and cubic structure. The monolayers can be transferred onto solid substrates by a simple dipping process. The use of carbon coated copper grids allows the investigation of the monolayers by transmission electron microscopy (TEM). Electron diffraction experiments under a microscope prove the hexagonal and cubic arrangements. The reason for the formation of the one or the other modification is still unknown.
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  • 46
    ISSN: 1434-1948
    Keywords: Triosmium cluster ; Biphosphinine ; Crystal structure ; Cyclic voltammetry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of the novel cluster [Os3(CO)10(4,4′,5,5′-tetramethyl-2,2′-biphosphinine)] reveals an unprecedented coordination mode of the biphosphinine ligand that occupies a doubly-bridging position spanning the open osmium triangle. The cluster is photostable, pointing to a localization of the lowest-energy electronic transition largely on the negatively charged biphosphinine ligand.
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  • 47
    ISSN: 1434-1948
    Keywords: Photochemistry ; Electrochemistry ; Ruthenium compounds ; α-Diimine complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photophysical, photochemical and redox properties of the title complexes were investigated. Resonance Raman measurements revealed the lowest-energy electronic transition to possess σ→π* character. At low temperatures, long-lived near-IR emission was observed. Irradiation in solution results in homolytic splitting of a Ru-Ru bond as the primary step, followed by secondary reactions of the radical fragments depending on the experimental conditions. (Spectro)electrochemical investigations of the title species proved that the axial [RuCp(CO)2] groups exert a stabilising influence on the corresponding radical cations, while destabilising the corresponding radical anions, compared to the redox behaviour of other ruthenium complexes of this type.
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  • 48
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 889-894 
    ISSN: 1434-1948
    Keywords: Rhodium hydride complexes ; Parahydrogen ; Tin ligands ; Hydrogenations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidative addition of dihydrogen to the [RhH(SnCl3)5]3-/PR3 system (PR3 = PPh3, PEtPh2, PEt3) leads to the formation of previously unknown dihydride complexes, the 1H-NMR spectra of which have been studied by means of the ParaHydrogen Induced Polarization (PHIP) method. The composition of the resulting complexes crucially depends on the type of the added phosphane. With PEt3 as the phosphane and acetonitrile as the solvent, a complex with a SnCl2L ligand (L = CD3CN) can be detected. All systems examined catalyze the hydrogenation of phenylacetylene. During these reactions, both the 1H-NMR resonances of the dihydride complexes and those of styrene, the hydrogenation product of phenylacetylene, can be detected simultaneously. In the case of SnBr3 ligands, hydrogen addition in the presence of phosphanes leads to similar dihydride complexes, which were also identified via 1H-NMR spectroscopy. Furthermore, a mixed complex of the structure [Rh(SnBr3)nBr6-n]3- has been isolated.
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  • 49
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 857-877 
    ISSN: 1434-1948
    Keywords: Crystal packing ; Neural networks ; Pattern recognition ; Organometallic compounds ; Close packing ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structures of hundreds of thousands of molecular compounds have now been determined with the quantitative information being stored in large databases. Chemists are generally interested in that specific part of this information which refers to individual molecules. The packing of molecules and their spatial relation to each other is not the focus of interest, even though the material properties of a molecular crystal are determined by both the packing arrangement of the molecules and their specific properties. The lack of interest in packing has at least one obvious reason. It is difficult for the non-expert to find the appropriate packing categories when looking at a principally infinite lattice. A tool performing this search for individual categories of packing in an automatic manner would therefore be of general importance. The development and application of such a tool is described in this paper. Novel strategies to extract a set of n points forming a specific n-point polyhedron from a set of p points (p 〉 n) is at its basis. Neural networks and second moment analysis are used as the methods of pattern recognition. In order to correlate packing and shape, second moment analysis of molecular shape is also used. This novel method is applied to three classes of organometallic compounds to determine whether the crystals formed by these compounds belong to any of the three classes fcc, bcc, or hcp in an idealized sense. A strong correlation is found between molecular shape and the membership or nonmembership of these classes. The corresponding program, including appropriate tools for visual representation, is available from the authors.
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  • 50
    ISSN: 1434-1948
    Keywords: Arenetricarbonyl chromium complexes ; Palladium ; Cross coupling reaction ; Thiophenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cross coupling reaction of (p-chloroanisole)tricarbonylchromium complex (1) with thiophene derivatives under palladium-catalyzed conditions leads to the selective formation of tricarbonyl-η6-[(2-thiophenyl)arene]- or -η6-[(2-thiophenyl)carbonylarene]chromium complexes (2 or 3) depending on reaction conditions. The conformation of complexes 2 and 3 in the solid state as well as in solution are reported.
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  • 51
    ISSN: 1434-1948
    Keywords: Ruthenium ; Phenanthroline ; Luminescence ; Sterically hindered ligands ; Terpyridine ; Cyclometallation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two series of cyclometallated and noncyclometallated ruthenium(II) complexes incorporating mono- or disubstituted 1,10-phenanthroline- and 2,2′:6′,2′′-terpyridine-type ligands have been synthesized and characterized. An X-ray crystal structure for one of the complexes, Ru(ttpy)(mapH)-(Cl)(PF6), has been obtained (mapH = 2-p-anisyl-1,10-phenanthroline; ttpy = 4′-tolyl-2,2′:6′,2′′-terpyridine). Distinct electrochemical and photophysical properties have been observed for the two series: a remarkable feature is the observation of relatively long-lived MLCT excited states (from 70 to 106 ns at room temperature in CH3CN) for three of the cyclometallated complexes. A discussion is given on the role of factors like sigma donation by the cyclometallating ligands, interligand steric hindrance and interligand π-π interactions that affect the electrochemical and spectroscopic properties.
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  • 52
    ISSN: 1434-1948
    Keywords: Polymeric copper complexes ; Group-subgroup relationships ; 2D-sheets ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterisation of two new polymeric CuII complexes is described, i.e. {[Cu(btp)2(CH3CN)(H2O)](CF3SO3)2}n (1) and {[Cu(btp)2(CH3CN)2](ClO4)2}n (2), in which btp = [1,3-bis(1,2,4-triazol-1-yl)propane]. Compound 1 crystallizes in space group P21/c with a = 11.9337(15) Å, b = 20.108(6) Å, c = 12.748(6) Å, β = 92.247(14)°, and Z = 4. Compound 2 crystallizes in space group Pna21 with a = 18.770(8) Å, b = 12.648(8) Å, and c = 12.019(8) Å. The structures refined to R1 values of 0.0683 for 1 and 0.0846 for 2. In both structures the CuII ions are linked by the bridging ligands, resulting in two-dimensional networks. Two such curved layers are arranged on top of each other with center-to-center of layer distances of 2.12 Å in 1 and 1.98 Å in 2. Such double layers are separated from each other by 10.05 Å in 1 and 9.385 Å in 2. The space between the double layers is occupied with interstitial anions. No significant interaction between CuII ions is observed by EPR and magnetic susceptibility measurements. The compounds form a new class of a lattice engineered system held together by the CuII ions. - The coordination geometry of the copper ions is distorted octahedral, with the equatorial plane formed by the N4 nitrogens of the four triazole groups and the axial sites occupied by solvent molecules; acetonitrile and water in structure 1 and two acetonitrile molecules in structure 2. The two structures are related by a group-subgroup relationship, which appears to be the first such case in supramolecular chemistry. - The Cu-N vibrations in the FIR region are found at 274 cm-1 for 1, and at 276 cm-1 for 2. The ligand-field maxima are observed at about 16·103 cm-1, with a shoulder at about 12·103 cm-1. The νCN stretching vibrations of the acetonitrile molecules are found at 2303 and 2261 cm-1 for 1, and at 2313, 2294, 2278, and 2260 cm-1 for 2.Supporting information for this article is available on the WWW under -//_/_http://www.wiley-vch.de/contents/jc_2005/2000/99211_s.pdf or from the author.
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 217-224 
    ISSN: 1434-1948
    Keywords: Reaction mechanisms ; Cyclopalladation ; Acetic acid ; Pd-C bond stability ; Polynuclear species ; Palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The processes operating during the synthetic cyclopalladation reactions of imines in acetic acid have been studied from a kinetico-mechanistic point of view. These reactions include a fast initial coordination to the palladium through the N-donor atom of the imine, followed by the proper C-H bond activation to produce the acetato bridged dimeric species. At this point, the lability of the bridging acetato groups, the hydrolysis of the C-Pd bonds, and/or the hydrolysis of C=N exo bonds contribute to the generation of dark red polynuclear compounds. The processes occurring after the C-H activation have been followed kinetically, both from palladium acetate plus imine, and the synthetically pure isolated acetato dimers as starting materials. The kinetic and activation parameters have been found identical within experimental error whatever the starting material was (k323 = 1.5 × 10-4 s-1; ΔH# = 51 kJ mol-1; ΔS# = -163 JK-1 mol-1 ΔV# = +19 cm3 mol-1 for the 4-ClC6H4-CH=N-CH2-C6H5 imine derivative 1a). Acidolysis of C-Pd bonds has been found to occur in these polynuclear species. When alternative monomeric Cbenzylic-Pd bond-containing complexes are possible follow ups of the reactions produce them as final dead-end complexes (k323 = 2.2 × 10-5 s-1; ΔH# = 61 kJ mol-1; ΔS# = JK-1 mol-1 ΔV# ≈ 0 cm3 cm-1 for the [2,4,6-(CH3)3]C6H2-CH=N-CH2-[2-(CH3]C6[H4] imine derivative 3d). The same study has been carried out with primary amines in order to check the validity of the data if C=N bond hydrolysis is taking place in the imine derivatives with exo C=N bonds. For complexes with similar type of metallacycles, the results agree reasonably well with the proposed mechanism [k323 = 1.2·10-4 s-1, ΔH# = 46 kJ·mol-1, ΔS# = -180 J·K-1mol-1, ΔV# = -16 cm3·mol-1 for the polynuclear formation of the C6H5-CH2-NH2 derivative 4e; k323 = 3.0·10-4 s-1, ΔH# = 55 kJ·mol-1, ΔS
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  • 54
    ISSN: 1434-1948
    Keywords: Phosphanylphenolate ; Cyclopentadienylnickel complexes ; Chelates ; Ethylene polymerization ; Crystal structure ; Polymerizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Diphenylphosphanyl- and 2-alkylphenylphosphanyl-4-methylphenols 1 or their silyl ethers 2 and equimolar amounts of nickelocene react in benzene preferably to give orange-brown diamagnetic cyclopentadienylnickel chelate complexes [η-CpNi(P∩O)] (3). Addition of a second equivalent of 1 or 2 affords (RR) and (SS) diastereoisomers of cis-bis(P∩O-chelates) 4a-c (R = Ph, Me, iPr) or the unsymmetrical cis-bis(P∩O-chelate) 5, whereas with bulkier substituted derivatives 1d or 2d (R = tBu) the second step is hindered or retarded. The reactivity of 1d remains high towards nickel salts in polar solvents, but in contrast to 1a-c, yielding 4, a sparingly soluble green trans-bis(P-O-chelate) nickel complex 6d is formed. Complexes formed in situ from 1 or 2 and Ni(COD)2 in toluene catalyze the polymerization of ethylene. The cyclopentadienyl (P∩O) complexes 3, however, are too stable to be active in this process. The crystal and molecular structure of 3c and 4c are described.Supporting information for this article is available on the WWW under -//_/_http://www.wiley-vch.de/contents/jc_2005/2000/99035_s.pdf or from the author.
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 287-297 
    ISSN: 1434-1948
    Keywords: Enolates ; Nucleophilic additions ; Ruthenium ; S ligands ; Sulfenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the chiral racemic complex [CpRu(mppe)(SO2)]PF6 (1, mppe = Me2PC2H4PPh2) with diazomethane or -ethane gave the sulfene complexes [CpRu(mppe)(RHC/SO2)]PF6 (R = H, 2a; R = Me, 2b). Treatment of 2a with prochiral enamines or deprotonated β-oxo esters yielded C-C coupling products with 32-60% de. An analog of 2a, [NmcpRu(mppe)(H2C/SO2)]PF6 (8, Nmcp = neomenthylcyclopentadienyl) was prepared in a four-step synthesis starting from LiNmcp and [RuCl2(PPh3)3]. Repeated crystallization of the intermediate [NmcpRu(mppe)Cl] (6) provided diastereomerically pure 6′ which added methylene stereospecifically to give diastereomerically pure 8′. Compound 8 turned out to be much less reactive towards nucleophiles than 2a, but still added deprotonated ethyl 2-methyl-3-oxobutanoate with 44% de. The chiral, enantiomerically pure sulfur dioxide complex [CpRu(chir)(SO2)]PF6 [10, chir = (S,S)-Ph2PCHMeCHMePPh2] was synthesized from [CpRu(chir)Cl] and SO2 and was characterized by X-ray crystallography. Reaction of 10 with diazomethane gave the enantiomerically pure sulfene complex [CpRu(chir)(H2C/SO2)]PF6 (11). Addition reactions of 11 with N-(1-cyclopentenyl)morpholine, as well as with various enolates derived from β-oxo esters or 1,3-diesters proceeded with high yields and 20-90% de. The structure of a diastereomerically pure addition product, [CpRu(chir)(SO2CH2C(Me){C(O)Me}{C(O)OtBu}] (13d′), was determined crystallographically and was shown to have (R) configuration at the quaternary carbon atom. After alkylation of one of the S/O functions, the sulfinate ligand was cleaved from the metal center by ligand substitution with acetonitrile, and the resulting acetonitrile complex 15 was converted back into 10 by treatment with SO2.
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  • 56
    ISSN: 1434-1948
    Keywords: Metal-rich antimonides ; Magnetism ; Structure and bonding ; Conductivity ; LMTO ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compounds can be synthesized in quantitative yields by arc-melting of stoichiometric amounts of HfSb2, Hf and one of the 3d metals V, Cr, Mn, Fe, Co, Ni, and Cu. These antimonides crystallize in a substitution variant of the W5Si3 type, in which one position is statistically mixed, occupied by the 3d metal atom M or the Sb2 atom in different ratios. Within the linear (M,Sb) chain, the M:Sb ratio may vary between 3:1 and 2:3. According to calculations of the electronic structures of Hf10MδSb6-δ with δ = 1, these phases are metallic compounds stabilized by strong Hf-Hf, Hf-M, and Hf-Sb bonds, and to a smaller extent by bonding interactions within the linear (M,Sb) chain. The metallic character was confirmed by measurements of the electrical resistivity and the magnetism of selected samples. Whereas Pauli paramagnetism was observed experimentally for M = V, Co, and Ni, Hf10FeSb5 is apparently the only phase with localized magnetic moments and magnetic coupling. This is in agreement with the magnetic ground state obtained solely for the ordered structure model of Hf10FeSb5 with spin-polarized calculation within the local spin density approximation.
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  • 57
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 323-330 
    ISSN: 1434-1948
    Keywords: Amino acids ; Alkynes ; Ferrocene ; Palladium ; Catalysis ; Bioorganometallic chemistry ; Biosensors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work describes a Pd-catalyzed coupling of ferrocene alkyne derivatives to iodo amino acids. Ferrocene carboxylic acid propargyl amides were easily obtained in high yield. The crystal structures of the propargyl amine derivative 3 and the 1,1-diethylpropargylamine derivative 4 have been determined by X-ray diffraction. Pd-catalyzed coupling to p-iodoanilide amino acids gave the corresponding ferrocene-labeled amino acid derivatives, which were easily purified by diethyl ether extraction in the case of the 1,1-diethyl derivatives 8. The coupling reaction did not require anhydrous solvents and tolerated a variety of functional groups present in peptides such as alcohols (8a, Ser), thioethers (8d, Met), disulfide bonds (cystine, 12) esters (as in the N-labeled Leu derivative 10) and of course amides. A minor by-product of the coupling reaction, namely the homo-dimer bis(ferrocene carboxylic acid propargylamide) 9, was identified in the crude reaction mixtures by mass spectrometry and independently synthesized by oxidative coupling (Glaser and Eglington) of 3. All new compounds were completely characterized spectroscopically, including 15N- and 2D NMR spectroscopy, Mössbauer spectroscopy and electrochemistry. This work introduces a versatile procedure for a selective functionalization of amino acids with organometallics at the C-terminus which is expected to be of general applicability to peptide chemistry.
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  • 58
    ISSN: 1434-1948
    Keywords: Palladium ; Insertion reactions ; Tridentate ligands ; Hydrazones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Potentially tridentate hydrazonic ligands of the type HNNO have been used in the synthesis of some methyl palladium(II) complexes. Depending on the applied experimental conditions two different kinds of complexes are obtained. Thus, the reactions between HL1-HL5 and (COD)PdMeCl in diethyl ether led to the formation of bidentate methyl complexes of the type Pd(HNN)MeCl (1-5), where the ligands maintain a neutral character. However, in the presence of a base such as Et3N or NaOMe, the ligands are deprotonated with the consequent formation of tridentate methyl complexes of the type Pd(NNO)Me (7-10). In solution, complexes 1-5 tend to lose the hydrazonic proton with elimination of methane and formation of a tridentate chloride complex Pd(NNO)Cl (6); this tendency can be correlated with the acidity of the free ligands, which has been determined. On bubbling carbon monoxide through solutions of 1-5, the corresponding acetyl complexes Pd(HNN)[C(O)Me]Cl (11-15) are formed, in which both the cis and trans isomers are present. Their molar ratio is rationalised from the results of a molecular modelling study on the basis of electronic considerations. A remarkably different reactivity has been found in the carbonylation of the tridentate complexes 7-10: they decompose rapidly and quantitatively to palladium black and an organic product corresponding to the ligand with an acetyl group bonded to the hydrazonic nitrogen. The X-ray structures of a methyl complex (3) and its corresponding acetyl (13) derivative have been determined.
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  • 59
    ISSN: 1434-1948
    Keywords: Vanadyl arsenate ; Hydrates ; Layered compounds ; Vibrational spectroscopy ; X-ray scattering ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The course of the intercalation and deintercalation of water molecules in vanadyl arsenate has been studied by X-ray diffraction analysis and by infrared and Raman spectroscopies. The formation of VOAsO4 hydrates at ambient temperature has been found to depend on relative humidity (r.h.): VOAsO4 · 5 H2O (basal spacing c = 10.48 Å) is formed at r.h. above 76%, VOAsO4 · 3 H2O (c = 8.03 Å) at 43-76% r.h., VOAsO4 · 2 H2O (c = 7.33 Å) at 11-43% r.h.; dehydrated VOAsO4 (c = 4.18 Å) exists near 0% r.h. Like the thermal dehydration of VOPO4 · 2 H2O, the thermal dehydration of VOAsO4 · 3 H2O proceeds in a stepwise manner so that the dihydrate and monohydrate are formed en route to the anhydrous compound. The arsenate monohydrate is gradually dehydrated over a broad temperature range. The broad diffraction lines observed can be explained in terms of the existence of a disordered phase containing monohydrated and anhydrous forms of vanadyl arsenate. A similar phenomenon has been observed during the dehydration of VOAsO4 · 3 H2O over phosphorus pentoxide at ambient temperature. The hydration of VOAsO4 is different from that of VOPO4. The first step, i.e. the insertion of water that coordinates to the vanadium atoms, is very slow. On the contrary, the uptake of further water molecules with the formation of higher hydrates is fast. It thus seems likely that the filling of one interlayer space with water facilitates the intercalation of further water into neighboring interlayer spaces. Therefore, only higher hydrates together with the original anhydrous phase are observed. Impedance spectral measurements indicate that the conductivity of the trihydrate has a mixed ionic/electronic character.
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  • 60
    ISSN: 1434-1948
    Keywords: Coordination chemistry ; α-Imino ketones ; CO complexes ; Iron complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of Fe2(CO)9 at room temperature in THF or toluene with the α-imino ketones R1N=C(R2)-C(R3)=O (L) (R1 = alkyl, R2 = H, Me, Ph, R3 = Me, Ph) (a-k), initially results in the formation of the mononuclear chelate Fe(CO)3(α-imino ketone) complexes 6 which can be isolated in moderate (6h) to high (6e-g) yield. Under these reaction conditions, complexes 6 subsequently react with [Fe(CO)4] fragments or dimerise, to form the dinuclear complexes Fe2(CO)6(α-imino ketone) (7a-j) or Fe2(CO)4(L-L) (8a,b,k), respectively. The complexes 8 contain two α-imino ketone ligands C-C coupled at the ketone carbon atoms. Complexes 8a,b react with CO at elevated temperatures to quantitatively yield Fe(CO)3(α-imino ketone) (6a,b). This reaction can be reversed photochemically. Irradiation of a solution of 6a,b in the low-energy band results in the reformation of 8a,b in almost quantitative yield. The extremely air-sensitive complexes 6 and the dinuclear complexes 7 and 8 have been characterised spectroscopically (IR, UV/Vis, 1H and 13C NMR) and by elemental analysis. The solid state structures of complexes 6g and 8a have been determined by single-crystal X-ray diffraction. The molecular structure of 6g confirms the flat σ-O,σ-N chelate coordination of the α-imino ketone. The structure of 8a consists of two metal-metal-bonded Fe(CO)2 units, bridged by a formally 10e-donating dianionic C-C coupled (tBu-ADO) ligand. A mechanism for the formation of complexes 8 is discussed.Supporting information for this article is available on the WWW under -//_/_http://www.wiley-vch.de/contents/jc_2005/2000/99351_s.pdf or from the author.
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  • 61
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 929-932 
    ISSN: 1434-1948
    Keywords: Titanium ; Cyclopentadienes ; Arene complexes ; Cations ; Bridging ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The half-sandwich titanium trimethyl complex (η5-C5H4CMe2Ar)TiMe3 (Ar = 3,5-Me2C6H3) reacts with the Lewis acid B(C6F5)3 to give the ionic TiIV ansa-cyclopentadienyl-arene complex [(η5,η6-C5H4CMe2Ar)TiMe2][MeB(C6F5)3]. In bromobenzene solvent, addition of more B(C6F5)3 leads to C6F5/Me exchange and, subsequently, to formation of an unusual dimeric TiIII dicationic species, {[(η5,η6-C5H4CMe2Ar)Ti(μ-Br)]2}[B(C6F5)4]2, which was structurally characterized. Its formation involves reduction of the transition-metal center, solvent C-Br cleavage and perfluoroaryl-group scrambling.Supporting information for this article is available on the WWW under -//_/_http://www.wiley-vch.de/contents/jc_2005/2000/99383_s.pdf or from the author.
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  • 62
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 939-941 
    ISSN: 1434-1948
    Keywords: Germanium ; Germanol ; Hydrogen bonds ; X-ray structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydrolysis of tBu2Ge(OEt)2 is described. Depending on the amount of water used either tBu2Ge(OH)2 (1) or a mixture of the latter and (tBu2GeOH)2O (2) were obtained. A cocrystallate consisting of 2tBu2Ge(OH)2, (tBu2GeOH)2O and water was the subject of a single crystal X-ray diffraction study. In the solid state the individual molecules are connected by hydrogen bonds giving rise to the formation of a polymeric double chain ribbon.
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  • 63
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 959-969 
    ISSN: 1434-1948
    Keywords: Bipyridyldiphosphane ligands ; Macrocycles ; Metallacyclophanes ; Platinum ; Supramolecular chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 5,5′-bis(hydroxyalkyl)-2,2′-bipyridines 4a-c (Scheme 1) were prepared either in one step (4b, 4c) or in four steps (4a) starting with 5,5′-dimethyl-2,2′-bipyridine in each case. Reaction of 4a-c with mesyl chloride afforded the bis(mesylates) [-C5H3N-(CH2)n-CH2-OSO2Me]2 5a-c [n = 1 (a), 2 (b), 3 (c)], which could easily be transformed into the diphosphanes 6a-c by reaction with LiPPh2. Treatment of 6c, 6b with Cl2Pt(NCPh)2 and (RC6H4)2Pt(COD) according to the high-dilution method resulted in the formation of the tetraphosphadiplatinacyclophanes [-C5H3N-(CH2)4-PPh2PtCl2PPh2-(CH2)4-C5H3N-]2 (7c) and [-C5H3N-(CH2)3-PPh2Pt(C6H4R)2PPh2-(CH2)3-C5H3N-]2 (8b, 9b) (8b: R = H, 9b: R = tBu), respectively (Scheme 2). The molecular structures of 8b and 9b were elucidated by X-ray structural analyses. The noncoordinated bipyridine moieties in 8b were employed to encapsulate copper(I) to give the host/guest complex 10b (Scheme 3), which was investigated by FAB-MS, NMR spectroscopy, and cyclovoltammetry. 10b exhibited a quasi-reversible oxidation at E1/2 = -0.31 V and an electrodeposition-redissolution redox system at E1/2 = -0.79 V, owing to the formation of copper at the surface of the working electrode.
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  • 64
    ISSN: 1434-1948
    Keywords: Lanthanides ; Ytterbium ; MRI contrast agents ; Solid-state structures ; Hydration ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The low temperature (-100 °C) X-ray structure of the complex K2[Yb(DTPA)(H2O)] has been determined. The metal ion is at the center of a tricapped trigonal prism and is nine-coordinate, binding to the three nitrogens and five oxygens of the ligand and one water molecule. From the structure obtained, three well-defined hydration shells can be observed consisting of: i) one coordinated water molecule; ii) several water molecules in the outer coordination sphere of the YbIII ion and iii) one water molecule surprisingly close to the metal center and hydrogen-bonded to proximate carboxylate groups. A variable-field and temperature NMRD study of the corresponding Gd complex has been performed and the data interpreted by taking into account the presence of second-sphere water molecule(s). The results of the analysis are in excellent agreement with the X-ray structural data.
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  • 65
    ISSN: 1434-1948
    Keywords: Catalysis ; Densitiy functional theory ; Epoxidation ; Reaction mechanisms ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Seven-coordinated molybdenum oxobisperoxo complexes with chelate nitrogen donors like pyrazolylpyridines are catalysts for the epoxidation of olefins. An NMR spectroscopic and quantumchemical study on the fluxionality of the chelate ligand proves that during this process partial ligand dissociation takes place. This gave rise to a detailed theoretical study on the activation of CH3OOH at the model complex (NH3)2MoO(O2)2 including dissociation of one of the ammonia ligands and proton transfer from the hydroperoxide to one of the peroxo ligands.Supporting information for this article is available on the WWW under -//_/_http://www.wiley-vch.de/contents/jc_2005/2000/99429_s.pdf or from the author.
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  • 66
    ISSN: 1434-1948
    Keywords: Palladium ; Tripodal ligands ; O ligands ; Fluxionality ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of [PdCl2(CH3CN)2] with the silver salt of the tripodal oxygen ligand L- = [(C5H5)Co{P(O)(OMe)2)}3]- yields the homoleptic oxygen ligand complex [PdL2] (1). The molecular structure of 1 was determined by single-crystal X-ray diffraction: monoclinic space group P21/n; a = 8.515(1), b = 13.627(2), c = 15.828(2) Å; β = 92.44(1)°; V = 1834.9(7) Å3; Z = 2. The complexes [Pd(PPh3)XL] [X = Cl (2a), Br (2b), I (2c)] have been prepared starting from 1. Complex 2a reacts with PPh3 to form [Pd(PPh3)2L]Cl (3a) and [Pd(PPh3)2L]L (3b). Treatment of 2a with CO in MeOH yields the carboxymethyl complex [{(PPh3)(COOMe)Pd(μ-Cl)}2] (4) and the protonated ligand HL. The carboxymethyl complex 4 shows some catalytic activity for the copolymerization of CO and ethene. Complex 4 reacts with AgL to yield [Pd(PPh3)(COOMe)L] (6). Alkylation of 2a with Me4Sn leads to the methyl complexes [Pd(PPh3)MeL] (7) and [Me2ClSnL] (8). CO insertion in the palladium-carbon bond of 7 gives the stable acetyl complex [Pd(PPh3){C(O)Me}L] (10). The palladium(II) complexes 1, 2, 3, 6, 7, and 10 of the tripodal oxygen ligand L are all fluxional molecules that have been studied by temperature-dependent 1H- and 31P-NMR spectroscopy.
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  • 67
    ISSN: 1434-1948
    Keywords: Tripod ligands ; Hindered rotation of vinylidene ligands ; CpML2 chelate ligands ; Ruthenium ; Carbenes ; Carbene-type ligands ; Cyclic voltammetry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tripodal ligand [CH3C(CH2C5H4)(CH2PPh2)2]- reacts with RuCl2(PPh3)3 to produce CH3C(CH2-η5-C5H4)(CH2-η1-PPh2)2RuCl, [tripodCpL2RuCl], 1. Complex 1 undergoes substitution of the chlorine function with various nucleophiles L′ to produce [tripodCpL2RuL′]+. The carbonyl derivative (L′ = CO) 2, isonitrile (L′ = RNC) 3, nitrile compounds (L′ = RCN) 4, and a tolane adduct (L′ = η2-PhC≡CPh) 5 are obtained when 1 is treated with the appropriate ligands in polar solvents. Halide acceptors (e.g. TlPF6) are generally needed to promote these reactions. The cyanide derivative tripodCpL2RuCN (3a) is alkylated by F3CSO3CH3 to give the isonitrile derivative [tripodCpL2RuCNMe]+3b. Terminal alkynes HC≡CR produce vinylidene compounds [tripodCpL2RuL′]+, where L′ = C=CHR (R = tBu, 7b; R = Ph, 7c), or allenylidene derivatives, L′ = C=C=CPh2 (6), depending on the nature of R (R = CPh2OH for synthesis of 6). Trimethylsilylacetylene gives the parent vinylidene species, L′ = C=CH2 (7a), which is transformed to the Fischer-type carbene compound, L′ = C(OMe)Me (8), upon treatment with methanol. The vinylidene species 7 are deprotonated by NaOMe to produce the alkynyl compounds tripodCpL2RuC≡CR (9). Methylation of 9 with F3CSO3CH3 results in the vinylidene derivatives L′ = C=C(Me)R (R = tBu, 7d; R = Ph, 7e), having two organic substituents at the terminal carbon centre. For all vinylidene compounds with two different substituents at their terminal carbon atom, hindered rotation of the single-faced vinylidene π-ligand about its Ru-C bond is observed. Analysis by 31P-NMR spectroscopic coalescence measurements as well as line-shape analyses reveals activation enthalpies of around 40 kJmol-1 for this rotation, with small activation entropies of around ±10 Jmol-1K-1. Solid-state structures of nine compounds of the type [tripodCpL2RuL′]+n (n = 0, 1) demonstrate the remarkable conformational rigidity of the tripodCpL2Ru template. They also show that the possible strain imposed by linking the Cp ligand and the two donor groups L in one and the same chelate scaffolding does not appear to impose a serious steric strain on these templates.
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  • 68
    ISSN: 1434-1948
    Keywords: (R)-(+)-2,3-Epoxy-1-propanol ; 2,3-Dihydroxyalkyl phosphanes ; 1,3,2-Dioxaborolane ; 1,3-Dioxolane ring ; Enantiopure phosphanes ; Complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of (R)-(+)-2,3-epoxy-1-propanol with Ph2PH, Ph(Me)PH, or PhPH2 in the superbasic medium KOH/DMSO affords the novel chiral phosphanes 1a-1c. While 1a is obtained enantiomerically pure, 1b and the secondary phosphane 1c are formed as mixtures of diastereoisomers (RPRC, SPRC) with homochiral β carbon atoms. Derivatization of 1a with phenylboronic acid or 2,2-dimethoxypropane yields 2a and 3a with 1,3,2-dioxaborolane and 1,3-dioxolane ring systems, respectively. The X-ray structure of 2a (space group P21) reveals the presence of four molecules of R configuration in the unit cell. Nucleophilic phosphanylation of (R)-(-)-2,3-O-isopropylideneglycerol tosylate with Ph2PH, Ph(Me)PH, or PhPH2 yields chiral 3a-3d. Compound 3b was obtained enantiomerically pure. The secondary phosphane 3c has been employed in syntheses of the hydrophilic tertiary phosphanes 3e, 3f and of the novel bidentate phosphane ligands 3g, 3h, all of which have homochiral β carbon atoms. PdII complexes PdL2Cl2 of 1a, 2a, 3a (L) are formed as mixtures of cis/trans isomers. RhI complexes of 1a, 3a, and bidentate 3h have also been synthesized.
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  • 69
    ISSN: 1434-1948
    Keywords: Macrocycles ; Nickel ; Redox chemistry ; Schiff bases ; S ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A single crystal X-ray analysis of [Ni2L1](ClO4)2· MeCN · 1/4 H2O, 1a [formed directly from a mixture of nickel(II) template ions, 2,6-diformyl-4-methyl-thiophenolate, and 1,4-diaminobutane] reveals that the nickel(II) ions are in square-planar N2S2 environments and that the four “bowed” dinickel macrocycles in the asymmetric unit pack around a single central perchlorate template ion encapsulating it to form “star” clusters of stoichiometry {[Ni2L1]4(ClO4)}7+. These “stars” stack together, via π-π-stacking interactions, to form two-dimensional sheets, which are separated from one another by layers of the remaining perchlorate anions and solvent molecules. Reduction, by NaBH4, of the four imine bonds in [Ni2L2](ClO4)22a (analogous to 1a but formed from 1,3-diaminopropane not 1,4-diaminobutane) or [Ni2L2](CF3SO3)22b to amine bonds produces the corresponding tetra-amine complex, [Ni2L3](ClO4)23. These complexes are shown to contain diamagnetic nickel(II) ions by a combination of magnetic, NMR and UV/Vis spectroscopic results. The 1H NMR spectra of 1-3 run in [D3]MeNO2 and in [D3]MeCN are consistent with increasing axial binding ability in the order: 3 〈 2 〈 1. Thiocyanate ion binding studies reveal that 1 and 2 are able to coordinate two thiocyanate ions, forming [Ni2L1(NCS)2] 4 and [Ni2L2(NCS)2] 5 respectively, whereas 3 does not. Single crystal X-ray analyses of complexes 4· 2 MeCN and 5· MeCN show that adjacent square-planar and octahedral nickel(II) ions result. Two one-electron oxidations and two one-electron reductions are a feature of the electrochemistry of 1-3 in MeCN: curiously, the potentials for the oxidation processes are almost invariant whereas those for the reduction processes vary as anticipated. EPR spectroscopy shows that the first one-electron reduction process and the first one-electron oxidation process are metal centred. Spectroelectrochemical studies and redox titrations indicate that a purplish-coloured complex is produced by one-electron oxidation of 2 (λ = 870 nm, ε = 1320 L mol cm-1). The synthesis of a phenolate analogue, [Ni2L′(MeCN)4](ClO4)2 (6), of the thiophenolate complex 2a is also detailed. Complex 6 undergoes two one-electron oxidations in MeCN, but, in contrast to the thiophenolate complexes 1-3, these occur at much higher potentials. Only a single one-electron reduction process is observed and this occurs at a more negative potential than for any of 1-3.
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  • 70
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 195-203 
    ISSN: 1434-1948
    Keywords: Acid derivatives ; Cyclen and cyclam derivatives ; Phosphinic acid ; Potentiometry ; Protonation and stability constants ; 31P-NMR titration ; Hydrogen bonding ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two phenylphosphinic acid derivatives of tetraaza macrocycles, (1,4,7,10-tetraazacyclododecanetetrayl)tetrakis(methylene)tetrakis(phenylphosphinic acid) [(H4L1) and (1,4,8,11-tetraazacyclotetradecanetetrayl)tetrakis(methylene)tetrakis(phenylphosphinic acid)] (H4L2), were synthesised and the crystal structures of H4L2 and its bis(1-adamantylammonium) salt were determined. In both the structures, the ring conformation is virtually the same and is stabilised by hydrogen bonds. Protonation constants of the acids and stability constants of their Zn2+ and Cd2+ complexes were determined pH-metrically at 25 °C and at an ionic strength of 0.1 mol dm-3 (KNO3). The pKA values found for both the compounds are lower than those for their carboxylic analogues and correspond to the expected electron-withdrawing ability of the -P(Ph)O2H moiety. The value pK1 of the last dissociation constant of H4L1 is surprisingly high. The complexes of Zn2+ and Cd2+ with (L1)4- and (L2)4- are less stable than those with other similar ligands, which is in accordance with lower overall basicity of H4L1 and H4L2. A pronounced drop in the stability of the complexes of H4L2 can be explained by partial coordination of the ligand to the metal ions. The solution properties of the ligands were also investigated by 31P-NMR spectroscopy. The spectra observed suggest stable (on the NMR time scale) conformations of the protonated ligands in solution. A comparison of NMR spectra in solution and CP/MAS-NMR spectra indicates that the structures of the conformers roughly correspond to the structures observed in the solid state. The conformations are stabilised by intramolecular hydrogen bonds and by hydrophobic interactions of phenylphosphinic moieties. The conformers are stable even at 90 °C, but not in the presence of complexing metal ions.Supporting information for this article is available on the WWW under -//_/_http://www.wiley-vch.de/contents/jc_2005/2000/99149_s.pdf or from the author.
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  • 71
    ISSN: 1434-1948
    Keywords: Rare earth complexes ; Naphthalocyaninato ligand ; Double-decker complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of rare earth(III) double-deckers RE[Nc(tBu)4]2 [RE = La, Ce, Pr, Nd, Eu, Gd, Tb, Y, Er; Nc(tBu)4 = dianion of tetra(tert-butyl)-2,3-naphthalocyanine] (1-9) have been prepared by treating RE(acac)3·n H2O (acac = acetylacetonate) with 6-tert-butylnaphthalonitrile in refluxing n-octanol in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). These novel sandwich-type complexes have been spectroscopically characterized. The electrochemical studies show that the first oxidation and the first reduction potentials increase with the size of the central metal ions with a relatively small separation (0.28-0.33 V), reflecting the narrow HOMO-LUMO gap.
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  • 72
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 229-239 
    ISSN: 1434-1948
    Keywords: Pyridine derivatives ; Bipyridine derivatives/Metal complexes ; Chromophores ; Nonlinear optics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal complexes of pyridine and bipyridine-type ligands represent an important class of nonlinear optical (NLO) materials: (i) They can incorporate a variety of functionalised ligands with a wide range of metals which can give rise to tuneable NLO properties; (ii) they are generally associated with intense low-lying charge-transfer excitations such as metal to ligand charge-transfer (MLCT) or intraligand charge-transfer (ILCT); (iii) bipyridyl ligands are also good building blocks that allow the construction of octupolar complexes with a defined geometry and symmetry. This review describes the recent developments in the design of such dipolar and octupolar chromophores for second-order nonlinear optics.
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  • 73
    ISSN: 1434-1948
    Keywords: Heterobimetallics ; Hydride complexes ; Alkenyl complexes ; μ-Isonitrile complexes ; Silicon ; Iron ; Platinum ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The heterobimetallic hydride complexes [(OC)3Fe{Si(OMe)3}(μ-Ph2PXPPh2)Pt(H)(PR3)] (1a: X = CH2, PR3 = PPh3; 1b: X = NH, PR3 = PPh3; 1c: X = CH2, PR3 = PMePh2) have been prepared by the oxidative addition of [(OC)3Fe(H){Si(OMe)3}(η1-Ph2PXPPh2)] to [Pt(H2C=CH2)(PPh3)2] or by reaction of K[(OC)3Fe{Si(OMe)3}(η1-dppm)] with trans-[Pt(Cl)(H)(PPh3)2]. The solid-state structure of compound 1b has been determined by single-crystal X-ray diffraction. 1-Alkynes such as methylpropiolate or phenylacetylene insert in a regiospecific manner into the Pt-H bond of 1 to yield the σ-alkenyl complexes [(OC)3Fe{μ-Si(OMe)2(OMe)}(μ-Ph2PXPPh2)Pt{C(R)=CH2}] (2a: X = CH2, R = CO2Me; 2b: X = NH, R = CO2Me; 3a: X = CH2, R = Ph). Addition of the Pt-H bond of 3a across the triple bond of [D1]phenylacetylene affords [(OC)3Fe{μ-Si(OMe)2(OMe)}(μ-dppm)Pt{C(Ph)=C(D)H}] (3a*) having the deuteron trans to platinum (cis addition). This insertion reaction is accompanied by dissociation of the platinum-bonded PR3 ligand and saturation of the vacant coordination site by a dative μ-η2-Si-O→Pt interaction. When 3 is treated with PR3 again, a subsequent phosphane-induced rearrangement leading to vinylidene-bridged complexes [(OC)3Fe{μ-C=C(H)R′}(μ-Ph2PXPPh2)Pt(PR3)] (4a: X = CH2, R′ = Ph, PR3 = PPh3; 4b: X = NH, R′ = Ph, PR3 = PPh3; 4c: X = CH2, R′ = Ph, PR3 = PMePh2; 4d: X = CH2, R′ = p-tolyl, PR3 = PPh3) occurs. Upon purging a solution of 3a with carbon monoxide, the labile CO adduct [(OC)3Fe{Si(OMe)3}(μ-dppm)-Pt(CO){C(Ph)=CH2}] 5a is formed, addition of 2,6-xylyl isocyanide to 2a and 3a affords the isonitrile adducts [(OC)3Fe{Si(OMe)3}(μ-dppm)Pt(CNxylyl){C(R)=CH2}] (5b: R = CO2Me; 5c: R = Ph), respectively. When hydride complex 1a is allowed to react with stoichiometric amounts of aromatic isonitriles, formal elimination of HSi(OMe)3 occurs, yielding the heterodinuclear isonitrile-bridged complexes [(OC)3Fe(μ-C=N-R)(μ-dppm)Pt(PPh3)] (6a: R = 2,6-xylyl; 6b: R = o-anisyl; 6c: R = p-anisyl; 6d: R = p-C6H4NH2) and the bis(isonitrile) complexes [(OC)2(RN≡C)Fe(μ-C=N-R)(μ-dppm)Pt(PPh3)] (7a: R = 2,6-xylyl; 7b: R = p-anisyl). Single-crystal X-ray diffraction studies perfomed on 6a and 6b reveal that the molecular structures of these μ-isonitrile complexes closely resemble the μ-vinylidene complexes 4. The two metal centers are bridged in a symmetric manner by strongly bent CNR ligands, the aromatic groups R being oriented towards the Fe(CO)3 moiety. Electrophilic addition of HBF4 to the basic nitrogen atom of the μ-CNR ligand transforms 6 to the cationic μ-aminocarbyne complexes [(OC)3Fe{μ-CN(H)R}(μ-dppm)Pt(PPh3)][BF4] (8a: R = 2,6-xylyl; 8b: R = p-anisyl; 8c: R = p-C6H4NH2).
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  • 74
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 253-264 
    ISSN: 1434-1948
    Keywords: Iron-sulfur clusters ; Crown ethers ; Electrochemical devices ; Host-guest chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of Fe4S4 cluster compounds, I, III, and V, in which the cuboidal cluster core is appended with four crown ether thiolate ligands, and II and IV, bearing thiolate ligands without crown ether parts, has been synthesized and characterized. The spectroscopic and electrochemical properties of these compounds are determined by the electronic nature of the thiolate ligands. Only in the case of III, where a very short α-thioacetyl linker was used to connect the crown ether ligands to the cluster core, was a restricted conformational freedom of the ligand observed. A detailed electrochemical study of the influence of alkali and earth alkali metal ions (Li+, Na+, K+, Mg2+, and Ba2+) on the reversible 2-/3- reduction of the cluster compounds was performed. In the case of the crown ether appended clusters I, III, and V, the addition of these metal ions resulted in an anodic shift, i.e. in positive direction, of the reduction potential (modulation effect) and to larger current responses (promotion effect). The magnitude of the modulation effects is determined by the binding affinity of the metal ions in the crown ether ligands, and by the distance between bound metal ions and the redox active cluster core. Variation of the linker between the cluster core and the metal ion binding site resulted in cluster compounds with almost inverse selectivities for e.g. K+ and Ba2+ in the case of I and III. For the large effects found for compound I a lariat binding mode is proposed.
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  • 75
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    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 281-285 
    ISSN: 1434-1948
    Keywords: NMR spectroscopy ; Zeolites ; Al-coordination ; Mordenite ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 27Al 3Q MAS NMR spectroscopy has been applied to study the coordination state of the species giving the 30 ppm Al NMR signal in the 27Al MAS NMR spectrum of activated mordenite materials. From the 27Al 3Q MAS NMR measurements it is evident that the broad peak at 30 ppm in the 27Al NMR spectrum of the mordenite calcined at temperatures up to 600 °C comes mainly from the distorted four-coordinated Al. By simulation a quadrupolar coupling constant of 5.8 MHz was estimated for the distorted tetrahedral Al. For samples calcined at 650 and 700 °C, a small amount of pentacoordinated Al emerges. The majority of the signal, however, arises from distorted tetrahedral Al. A two-step calcination results in a significant contribution of the pentacoordinated Al to the signal at 30 ppm. From the simulated line-shape, a quadrupole coupling constant of 6.2 MHz is obtained for the latter signal. These data show that during the calcination of the mordenite, the coordination environment at the Al centre gradually becomes distorted to give rise to the shoulder at 30 ppm. With the increase of the calcination temperature, pentacoordinated Al species form
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  • 76
    ISSN: 1434-1948
    Keywords: Copper ; Magnetic properties ; Supramolecular chemistry ; Three-dimensional architecture ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel three-dimensional copper(II) compound of the formula [Cu3(btre)5(H2O)2](ClO4)6·H2O (btre = 1,2-bis(1,2,4-triazol-4-yl)ethane) has been synthesized. The structure has been solved at 150 K by single-crystal X-ray analysis. The compound [C30H44Cu3N30O2·6(ClO4)·H2O] crystallizes in the triclinic space group P1bar with a = 12.488(1), b = 13.195(1), c = 19.756(2) Å, α = 78.959(8), β = 84.553(8), γ = 63.869(7)°, V = 2868.4(5) Å3, Z = 2 (trinuclear CuII units), 6484 reflections [I 〉 4σ(Ι)], RF = 0.0581, wR2 = 0.1214. The structure of this coordination polymer consists of a three-dimensional network built up from linear trinuclear CuII cations of formula [Cu3(btre)5(H2O)2]6+. This crystallographically independent unit comprises a linear array of three CuII ions linked by triple N1,N2-1,2,4-triazole bridges, yielding Cu1-Cu2 = 3.893(1) Å and Cu2-Cu3 = 3.889(1) Å. These linear trinuclear CuII units are linked by various pathways involving tridentate and tetradentate bridging btre ligands, which yields an unprecedented three-dimensional network. The CuII ions are weakly antiferromagnetically coupled with J = -1.01(2) cm-1 (based on the Hamiltonian: H = -J[SCu1·SCu2 + SCu2·SCu3] using the expression for the molar magnetic susceptibility S = 1/2 of a linear trinuclear system). The nature and the magnitude of the antiferromagnetic exchange have been discussed on the basis of the structural features.
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  • 77
    ISSN: 1434-1948
    Keywords: Alkenylcarbynes ; Dinuclear tungsten complexes ; Electrochemistry ; Tungsten NMR ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Neutral trans-cyanide alkenylcarbyne complexes 2a and 2b have been prepared by reaction of the complex 1a and 1b with NaCN or [Bu4N]CN. The reaction of complexes 2a and 2b with an equimolar amount of the acetonitrile complexes 1a and 1b in CH2Cl2 leads to the cationic cyanide-bridged bis(alkenylcarbyne) di-tungsten complexes 3a-d. Diisocyanide-bridged bis(alkenylcarbyne) di-tungsten complexes 4a and 4b have been synthesized by the reaction of complexes 1a and 1b with 0.5 equivalents of the diisocyanide 1,4-(CN)2C6H4. IR as well as 1H-, 31P{1H}-, 13C{1H}-, and 183W-NMR data are reported. The spectroscopic data show that in the dinuclear complexes 3a-d, the bridging CN group and the alkenylcarbyne units are located in trans positions, while in the dinuclear complexes 4a and b, the isocyanide groups of the bridging ligand 1,4-(CN)2C6H4 and the two alkenylcarbyne moieties are cis. The 183W chemical shifts of complexes 2a, 2b, 3a-d, 4a, and 4b were obtained through two-dimensional indirect 31P, 183W NMR recording techniques. A downfield shifting of 183W resonances of the cyanide-bridged dinuclear complexes 3a-d with respect to the mononuclear ones, 2a and 2b, was observed. The δ183W of isocyanide bridging dinuclear complexes 4a and 4b appear at higher field than those of the corresponding mononuclear cyanide 2a and 2b in accordance with the higher π-acceptor electron properties of the isocyanide ligand. The electrochemical behaviour of all the complexes has been investigated by cyclic voltammetry and controlled potential electrolysis in aprotic media and at a Pt (or vitreous C) electrode. Complexes 1, 2, or 3 undergo multi-electron irreversible oxidation processes involving anodically induced proton dissociation from the alkenylcarbyne ligands, and irreversible cathodic processes are also observed for all the complexes. The order of the redox potentials reflects that of the net electron π-acceptor/σ-donor character of the ligands and the ligating alkenylcarbynes are shown to behave as remarkably strong π-electron acceptors (even stronger than CO).
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  • 78
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    AIChE Journal 26 (1980), S. 152-154 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 79
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 80
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    AIChE Journal 26 (1980), S. 148-150 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 81
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    AIChE Journal 26 (1980), S. 174-174 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 82
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    AIChE Journal 26 (1980), S. 175-176 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 83
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    AIChE Journal 26 (1980), S. 177-201 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article reviews the major developments in the engineering and design of three-phase slurry catalytic reactors. A general theoretical analysis for predicting the overall rate of reaction in a slurry reactor for various kinetics is presented, incorporating all the transport effects. Modeling of semi-batch reactors is discussed and design procedures are indicated. Some major correlations and methods for determining gas-liquid and liquid-solid mass transfer coefficients and effective diffusivity in liquid filled pores are reviewed. Slurry reactors are compared with other three-phase reactors, such as trickle bed or packed bed reactors, and relative merits are pointed out.
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  • 84
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    AIChE Journal 26 (1980), S. 201-212 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Intraparticle mass transfer in coal pyrolysis is described by ternary diffusion and viscous flow, in conjunction with a simple pore model to predict concentration profiles for gases and tar. At low pressures, product yields depend on particle size only, while at high pressures they depend on pressure and particle size. Limited experimental data from a subbituminous coal confirm these trends. Data from a bituminous coal show different trends, as expected from the drastic changes the pore structure undergoes during pyrolysis.
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  • 85
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When primary control objectives cannot be measured directly, secondary measurements have to be selected and used in conjunction with estimators to infer the value of the unmeasurable variables. Unmeasured process disturbances (state excitation noise) are assumed to be of major importance, dominating the errors caused by measurement noise. Since the white noise assumption is generally insufficient for the persistent disturbances commonly occuring in the Chemical Engineering, environment, a nonstationary noise model has been employed, and is shown to yield superior estimations under these circumstances. New necessary and sufficient conditions have been developed for the observability of the dynamic system augmented to include the noise model.A variety of new measurement selection criteria is presented here, with the goal of minimizing estimation error. One class of criteria aims at minimizing the transient estimation error when a static estimator is used. The other class minimizes the measurement error caused by the unobservable subspace. The design of state reconstruction procedures (which are able to handle persistent unmeasured process disturbances) is explained in a stochastic and a deterministic framework. Finally, the synthesis of reduced order control schemes is discussed. The power of the selection criteria and the superiority of a Kalman filter design employing a nonstationary noise model is demonstrated in many examples.
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  • 86
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    AIChE Journal 26 (1980), S. 274-281 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A three-parameter model of axial and radial dispersion in a packed tubular reactor is proposed as an alternative to the Fickian dispersion model. Though it is formulated in terms of differential equations, it requires no exit boundary condition, so it is mathematically more convenient than the Fickian model. Examples of its application to chemical reactors are given.
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    AIChE Journal 26 (1980), S. 287-288 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 88
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    AIChE Journal 26 (1980), S. 308-310 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 26 (1980), S. 314-317 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 90
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    AIChE Journal 26 (1980), S. 317-319 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 91
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    AIChE Journal 26 (1980), S. 325-327 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 92
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    AIChE Journal 26 (1980), S. 1-9 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article describes a novel approach to the systematic synthesis of heat exchanger networks. For a given synthesis problem, this approach leads to a complete listing of all solutions which exist, using a prescribed degree of energy recovery, the minimum number of exchangers, heaters and coolers, and no split streams. The approach is combinatorial, with a variety of thermodynamic criteria used to minimize the problem size by preventing infeasible solutions being generated. Two examples (5SPI and 6SPI) are discussed to illustrate complete solution by hand.
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  • 93
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    AIChE Journal 26 (1980), S. 24-30 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For moving-bed solids flow in an inclined pipe leading into a fluidized bed, the pressure drop across the pipe is a retarding force while the gas leakage rate alters the flow properties of the solids. The pressure drop has been related to the pipe exit pressure, which, in turn, can be calculated by integrating the solids bulk density over the bed depth. A correlation for the rate of gas leakage in terms of the geometric features and operating conditions of the system is developed. The correlation agrees with experimental data to within ± 25%. Part II of this paper will deal with solids flow.
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  • 94
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    AIChE Journal 26 (1980), S. 43-51 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Diffusion in concentrated, non-ideal liquid solutions may take place not only through motion of single molecules but also through movement of groups of molecules, or “clusters.” Analyzing this cluster diffusion leads to predictions that the diffusion coefficient can vary with the square root of the usual activity corrections to diffusion. These predictions seem consistent with experiments, particularly in highly non-ideal solutions.
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  • 95
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    AIChE Journal 26 (1980), S. 60-67 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A reactor of fiour crossflow nomolithic blocks is used to approximate a cocurrent and a countercurrent reactor-heat excanger. Essentailly isothermal reaction pass profiles are produced by flowing the coolant and reactant streams cocurrent to each other according to the criteria set down in Part I of this paper. A multiplicy of steady states is shown to exist for the autothermal countercurrent mode, but not for the autothermal cocurrent mode, under identical conditions.
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  • 96
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: There are several ways to remove minral matter from coal-derived liquids: antisolvent agglomeration and subsequent sedimentation is one. Adding antisolvent to coal liquids causes asphaltenes and/or preasphaltenes in the oil to precipitate. The precipitated asphaltenes then agglomerate the paraticles, increasing the sedimentation rate. The magnitude of this increase depend no the mixing conditions used to dispers the antisolvent in the oil.This article discuss the results of sedimentation experiments performed onthe antisolvent addition to coal liquids, using an x-ray detection system. The system has the capacity of high temperature (up to 315°C) and high pressure (up to 2.75 7 × 106 Pa). The important parameters are the mixing time, the impeller speed, and the antisolvent addition rate. These are studied in detail for the antisolvent Soltrol.
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  • 97
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    AIChE Journal 26 (1980), S. 132-134 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 98
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    AIChE Journal 26 (1980), S. 136-139 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: NO Abstract.
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    AIChE Journal 26 (1980), S. 144-148 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Slugging experiments were performed in a semicircular Plexiglas column 5.6 m in height to study the effect of an expanded section on slugging. The bottom section of the column (3.05 m long) is 28.6 cm in inside diameter and the expanded section 40.6 cm. Both the bed height and the fluidizing velocity were varied during the study, and the results were successfully correlated with a theoretically derived equation. The implications in designing a bed with an expanded section to reduce the slugging effectively are also discussed.
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    AIChE Journal 26 (1980), S. 154-157 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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