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  • Articles  (41,324)
  • Chemistry  (41,324)
  • Inorganic Chemistry  (3,415)
  • 1985-1989  (41,324)
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  • Articles  (41,324)
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  • 1
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1988-08-19
    Description: The question of how the primary amino acid sequence of a protein determines its three-dimensional structure is still unanswered. One approach to this problem involves the de novo design of model peptides and proteins that should adopt desired three-dimensional structures. A systematic approach was aimed at the design of a four-helix bundle protein. The gene encoding the designed protein was synthesized and the protein was expressed in Escherichia coli and purified to homogeneity. The protein was shown to be monomeric, highly helical, and very stable to denaturation by guanidine hydrochloride (GuHCl). Thus a globular protein has been designed that is capable of adopting a stable, folded structure in aqueous solution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Regan, L -- DeGrado, W F -- New York, N.Y. -- Science. 1988 Aug 19;241(4868):976-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉E. I. du Pont de Nemours & Company, Central Research & Development Department, Wilmington, DE 19898.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3043666" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Chemical Phenomena ; Chemistry ; Chromatography, Gel ; Escherichia coli/genetics ; Molecular Sequence Data ; Plasmids ; *Protein Conformation ; *Proteins/genetics
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1989-03-03
    Description: Monoclonal antibodies have been induced that are capable of catalyzing specific hydrolysis of the Gly-Phe bond of peptide substrates at neutral pH with a metal complex cofactor. The antibodies were produced by immunizing with a Co(III) triethylenetetramine (trien)-peptide hapten. These antibodies as a group are capable of binding trien complexes of not only Co(III) but also of numerous other metals. Six peptides were examined as possible substrates with the antibodies and various metal complexes. Two of these peptides were cleaved by several of the antibodies. One antibody was studied in detail, and cleavage was observed for the substrates with the trien complexes of Zn(II), Ga(III), Fe(III), In(III), Cu(II), Ni(II), Lu(III), Mg(II), or Mn(II) as cofactors. A turnover number of 6 x 10(-4) per second was observed for these substrates. These results demonstrate the feasibility of the use of cofactor-assisted catalysis in an antibody binding site to accomplish difficult chemical transformations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Iverson, B L -- Lerner, R A -- New York, N.Y. -- Science. 1989 Mar 3;243(4895):1184-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, CA 92037.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2922606" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; *Antibodies, Monoclonal ; Antigens/immunology ; Binding Sites, Antibody ; Catalysis ; Chemical Phenomena ; Chemistry ; Cobalt/immunology/metabolism ; Glycine/metabolism ; Haptens/immunology ; Hydrogen-Ion Concentration ; Hydrolysis ; Immunization ; Metals/metabolism ; Mice ; Molecular Sequence Data ; Molecular Structure ; Oligopeptides/*metabolism ; Phenylalanine/metabolism ; Trientine/immunology
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  • 3
    Publication Date: 1989-11-17
    Description: The surface forces apparatus technique was used for measuring the adhesion, deformation, and fusion of bilayers supported on mica surfaces in aqueous solutions. The most important force leading to the direct fusion of bilayers is the hydrophobic interaction, although the occurrence of fusion is not simply related to the force law between bilayers. Bilayers do not need to "overcome" some repulsive force barrier, such as hydration, before they can fuse. Instead, once bilayer surfaces come within about 1 nanometer of each other, local deformations and molecular rearrangements allow them to "bypass" these forces.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Helm, C A -- Israelachvili, J N -- McGuiggan, P M -- New York, N.Y. -- Science. 1989 Nov 17;246(4932):919-22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemical and Nuclear Engineering, University of California, Santa Barbara 93106.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2814514" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Lipid Bilayers ; Models, Biological ; Models, Structural ; Phosphatidylcholines ; Phosphatidylethanolamines
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  • 4
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1989-07-28
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Waldrop, M M -- New York, N.Y. -- Science. 1989 Jul 28;245(4916):354-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2756423" target="_blank"〉PubMed〈/a〉
    Keywords: *Catalysis ; Chemical Phenomena ; Chemistry ; *Enzymes ; Technology, Pharmaceutical
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  • 5
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1989-05-26
    Description: Methods for the design and synthesis of ligands intended to be specific for a metal ion have been a recent chemical development. This article describes how this process can be inverted so that the specifics of the coordination environment around the metal ion can be used as a template in large-scale ligand synthesis. The synthesis of macrobicyclic ligands for ferric ion has been accomplished by using active esters of catechol ligands in which catecholate coordination to iron is a prelude to the organic chemical reactions that link the coordination subunits together into one ligand system surrounding a central metal ion coordination site. The lanthanide(III) ions, which are among the most labile metal ions known, have coordination numbers of 8 or higher, and thus their encapsulation into a macrobicyclic structure is a challenging problem. Lanthanide amine complexes have been used as metal templates in the synthesis of such macrobicyclic lanthanide complexes. There is evidence that such a complex is inert to exchange in aqueous solution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McMurry, T J -- Raymond, K N -- Smith, P H -- New York, N.Y. -- Science. 1989 May 26;244(4907):938-43.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Radiation Oncology Branch, National Cancer Institute, Bethesda, MD 20892.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2658057" target="_blank"〉PubMed〈/a〉
    Keywords: Cations ; Chemical Phenomena ; Chemistry ; Iron/metabolism ; *Ligands ; Macromolecular Substances ; Metals/*metabolism ; Metals, Rare Earth/metabolism ; Molecular Structure ; Templates, Genetic
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  • 6
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1989-02-17
    Description: Mechanistic and synthetic studies in organometallic chemistry have provided considerable insight into olefin metathesis and Ziegler-Natta polymerization. New homogeneous olefin metathesis catalysts based on high oxidation state transition metals have opened new opportunities in polymer synthesis by providing unprecedented control in ring-opening polymerization of cyclic alkenes. The recent development of living coordinative polymerization systems has led to the preparation of a number of new, interesting materials, including block copolymers, conducting polymers or precursors, and ionophoric polymeric substrates.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Grubbs, R H -- Tumas, W -- New York, N.Y. -- Science. 1989 Feb 17;243(4893):907-15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉California Institute of Technology, Pasadena 91125.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2645643" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Organometallic Compounds ; *Polymers
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  • 7
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1988-09-02
    Description: Study of proteins that recognize specific DNA sequences has yielded much information, but the field is still in its infancy. Already two major structural motifs have been discovered, the helix-turn-helix and zinc finger, and numerous examples of DNA-binding proteins containing either of them are known. The restriction enzyme Eco RI uses yet a different motif. Additional motifs are likely to be found as well. There is a growing understanding of some of the physical chemistry involved in protein-DNA binding, but much remains to be learned before it becomes possible to engineer a protein that binds to a specific DNA sequence.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schleif, R -- New York, N.Y. -- Science. 1988 Sep 2;241(4870):1182-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Graduate Department of Biochemistry, Brandeis University, Waltham, MA 02254.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2842864" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acids/metabolism ; Binding Sites ; Chemical Phenomena ; Chemistry ; DNA/metabolism ; DNA Restriction Enzymes/metabolism ; DNA-Binding Proteins/*metabolism ; Deoxyribonuclease EcoRI ; Electrochemistry ; Nucleic Acids/metabolism ; Protein Conformation ; Zinc
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  • 8
    Publication Date: 1988-11-18
    Description: A general chemical strategy has been developed whereby antibody combining sites can be selectively derivatized with natural or synthetic molecules, such as catalytic groups, drugs, metals, or reporter molecules. Cleavable affinity labels were used to selectively introduce a thiol into the combining site of the immunoglobulin A MOPC 315. This thiol acted both as a nucleophile to accelerate ester thiolysis 60,000-fold and as a handle for selectively derivatizing the antibody with additional functional groups. For example, derivatization of the antibody with a fluorophore made possible a direct spectroscopic assay of antibody-ligand complexation. This chemistry should not only extend our ability to exploit antibody specificity in chemical catalysis, diagnostics, and therapeutics, but may also prove generally applicable to the functional modification of other proteins for which detailed structural information is unavailable.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pollack, S J -- Nakayama, G R -- Schultz, P G -- AI24695-02/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1988 Nov 18;242(4881):1038-40.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of California, Berkeley 94720.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3194752" target="_blank"〉PubMed〈/a〉
    Keywords: Affinity Labels ; Animals ; *Antigen-Antibody Reactions ; *Binding Sites, Antibody ; Chemical Phenomena ; Chemistry ; Dinitrobenzenes ; Immunoglobulin Fab Fragments ; Mice ; Spectrometry, Fluorescence ; Sulfhydryl Compounds
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  • 9
    Publication Date: 1986-09-19
    Description: WIN 51711 and WIN 52084 are structurally related, antiviral compounds that inhibit the replication of rhino (common cold) viruses and related picornaviruses. They prevent the pH-mediated uncoating of the viral RNA. The compounds consist of a 3-methylisoxazole group that inserts itself into the hydrophobic interior of the VP1 beta-barrel, a connecting seven-membered aliphatic chain, and a 4-oxazolinylphenoxy group (OP) that covers the entrance to an ion channel in the floor of the "canyon." Viral disassembly may be inhibited by preventing the collapse of the VP1 hydrophobic pocket or by blocking the flow of ions into the virus interior.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Smith, T J -- Kremer, M J -- Luo, M -- Vriend, G -- Arnold, E -- Kamer, G -- Rossmann, M G -- McKinlay, M A -- Diana, G D -- Otto, M J -- New York, N.Y. -- Science. 1986 Sep 19;233(4770):1286-93.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3018924" target="_blank"〉PubMed〈/a〉
    Keywords: Antiviral Agents/metabolism/*pharmacology ; Binding Sites ; Chemical Phenomena ; Chemistry ; Humans ; Isoxazoles/metabolism/pharmacology ; Poliovirus/drug effects/metabolism ; Rhinovirus/*drug effects/metabolism ; X-Ray Diffraction
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  • 10
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1987-03-06
    Description: Ribonuclease mitochondrial RNA processing, a site-specific endoribonuclease involved in primer RNA metabolism in mammalian mitochondria, requires an RNA component for its activity. On the basis of copurification and selective inactivation with complementary oligonucleotides, a 135-nucleotide RNA species, not encoded in the mitochondrial genome, is identified as the RNA moiety of the endoribonuclease. This finding implies transport of a nucleus-encoded RNA, essential for organelle DNA replication, to the mitochondrial matrix.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chang, D D -- Clayton, D A -- GM-33088-16/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1987 Mar 6;235(4793):1178-84.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2434997" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Base Sequence ; Cell Nucleus/*physiology ; Chemical Phenomena ; Chemistry ; Drug Resistance ; Endonucleases/isolation & purification/metabolism ; Enzyme Activation/drug effects ; *Genetic Code ; Humans ; Mammals/*genetics/metabolism ; Micrococcal Nuclease/pharmacology ; Mitochondria/*metabolism ; Oligonucleotides/pharmacology ; Organoids/physiology ; RNA/*biosynthesis/genetics/isolation & purification/physiology ; Ribonucleases/metabolism ; Subcellular Fractions/metabolism
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  • 11
    Publication Date: 1987-08-14
    Description: Toxic chlorinated dibenzo-p-dioxins are known to be formed in incinerators that burn municipal refuse. These compounds were synthesized by surface-catalyzed reactions on fly ash particulates taken from incinerators. Dioxins were produced catalytically from chlorinated phenol precursors, from non-chlorinated compounds that were chemically dissimilar to dioxins, and from reaction of phenol with inorganic chlorides. The relative amounts of dioxins formed from [13C6]pentachlorophenol with different fly ashes that had been cleaned of all organic compounds corresponded well with those amounts originally found on the samples as received from the incinerators. The optimum temperature range for the formation of dioxins from pentachlorophenol was 250 degrees to 350 degrees C.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Karasek, F W -- Dickson, L C -- New York, N.Y. -- Science. 1987 Aug 14;237(4816):754-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3616606" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Dioxins/*chemical synthesis ; Gas Chromatography-Mass Spectrometry ; *Hot Temperature ; Pentachlorophenol ; Polyvinyl Chloride ; *Refuse Disposal ; Tetrachlorodibenzodioxin/analogs & derivatives/*chemical synthesis
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  • 12
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1987-08-28
    Description: A monoclonal antibody elicited by a transition-state analog that is representative of an intramolecular six-membered ring cyclization reaction acted as a stereospecific, enzyme-like catalyst for the appropriate substrate. Formation of a single enantiomer of a delta-lactone from the corresponding racemic delta-hydroxyester was accelerated by the antibody by about a factor of 170, which permitted isolation of the lactone in an enantiomeric excess of about 94 percent. This finding demonstrates the feasibility of catalytic-antibody generation for chemical transformations that require stereochemical control.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Napper, A D -- Benkovic, S J -- Tramontano, A -- Lerner, R A -- GM 13306/GM/NIGMS NIH HHS/ -- GM 35318/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1987 Aug 28;237(4818):1041-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3616626" target="_blank"〉PubMed〈/a〉
    Keywords: *Antibodies, Monoclonal ; Catalysis ; Chemical Phenomena ; Chemistry ; Cyclization ; *Stereoisomerism
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  • 13
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1987-08-28
    Description: Chemical evidence is needed in both insect endocrinology and sensory physiology to understand hormone and pheromone action at the molecular level. Radiolabeled pheromones and hormones have been synthesized and used to identify binding and catabolic proteins from insect tissues. Chemically modified analogs, including photoaffinity labels and enzyme inhibitors, are among the tools used to covalently modify the specific acceptor or catalytic sites. Such targeted agents can also provide leads for the design of growth and mating disruptants by allowing manipulation of the physiologically important interactions of the chemical signals with macromolecules.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Prestwich, G D -- GM-30899/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1987 Aug 28;237(4818):999-1006.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3616631" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bees/metabolism ; Chemical Phenomena ; Chemistry ; Cockroaches/metabolism ; Female ; Insect Hormones/*metabolism ; Insects/metabolism ; Juvenile Hormones/metabolism ; Male ; Methoprene/metabolism ; Moths/metabolism ; Pheromones/*metabolism
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  • 14
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1987-10-16
    Description: Chromatographic retention is determined by a relatively small number of amino acids located in a chromatographic contact region on the surface of a polypeptide. This region is determined by the mode of separation and the amino acid distribution within the polypeptide. The contact area may be as small as a few hundred square angstroms in bioaffinity chromatography. In contrast, the contact region in ion exchange, reversed phase, hydrophobic interaction and the other nonbioaffinity separation modes is much broader, ranging from one side to the whole external surface of a polypeptide. Furthermore, structural changes that alter the chromatographic contact region will alter chromatographic properties. Thus, although immunosorbents can be very useful in purifying proteins of similar primary structure, they will be ineffective in discriminating between small, random variations within a structure. Nonbioaffinity columns complement affinity columns in probing a much larger portion of solute surface and being able to discriminate between protein variants.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Regnier, F E -- GM25431/GM/NIGMS NIH HHS/ -- GM33644/GM/NIGMS NIH HHS/ -- GM34759/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1987 Oct 16;238(4825):319-23.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, Purdue University, West Lafayette, IN 47907.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3310233" target="_blank"〉PubMed〈/a〉
    Keywords: Adsorption ; Amino Acids ; Chemical Phenomena ; Chemistry ; *Chromatography ; Chromatography, Affinity ; Chromatography, High Pressure Liquid ; Chromatography, Ion Exchange ; Protein Conformation ; Protein Denaturation ; *Proteins ; Recombinant Proteins ; Surface Properties
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  • 15
    Publication Date: 1988-03-04
    Description: Kinetic analysis and protein mutagenesis allow the importance of individual amino acids in ligand binding and catalysis to be assessed. A kinetic analysis has shown that the reaction catalyzed by dihydrofolate reductase is optimized with respect to product flux, which in turn is predetermined by the active-site hydrophobic surface. Protein mutagenesis has revealed that specific hydrophobic residues contribute 2 to 5 kilocalories per mole to ligand binding and catalysis. The extent to which perturbations within this active-site ensemble may affect catalysis is discussed in terms of the constraints imposed by the energy surface for the reaction.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Benkovic, S J -- Fierke, C A -- Naylor, A M -- GM24129/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1988 Mar 4;239(4844):1105-10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Pennsylvania State University, University Park 16802.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3125607" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Catalysis ; Chemical Phenomena ; Chemistry ; Escherichia coli/enzymology ; Kinetics ; Lactobacillus casei/enzymology ; *Mutation ; Structure-Activity Relationship ; Tetrahydrofolate Dehydrogenase/genetics/*metabolism ; Thermodynamics
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  • 16
    Publication Date: 1988-09-02
    Description: Catalysis of amide bond hydrolysis is of singular importance in enzymology. An antibody was induced to an analog of a high-energy intermediate anticipated along the reaction coordinate of amide hydrolysis. This antibody is an amidase with high specificity and a large rate enhancement (250,000) relative to the uncatalyzed reaction. This reaction represents the kinetically most difficult hydrolysis reaction yet catalyzed by an antibody.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Janda, K D -- Schloeder, D -- Benkovic, S J -- Lerner, R A -- New York, N.Y. -- Science. 1988 Sep 2;241(4870):1188-91.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, CA 92037.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3413482" target="_blank"〉PubMed〈/a〉
    Keywords: Amidohydrolases/metabolism ; Animals ; Antibodies, Monoclonal/biosynthesis/*physiology ; Antibody Specificity ; Antigens/immunology ; *Catalysis ; Chemical Phenomena ; Chemistry ; Hemocyanin/analogs & derivatives/immunology ; Hydrolysis ; Immunization ; Kinetics ; Mice ; Organophosphorus Compounds/immunology ; Substrate Specificity
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  • 17
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1988-09-30
    Description: Homopurine-homopyrimidine sequences that flank certain actively transcribed genes are hypersensitive to single strand-specific nucleases such as S1. This has raised the possibility that an unusual structure exists in these regions that might be involved in recognition or regulation. Several of these sequences, including d(C-T)n.d(A-G)n, are known to undergo a transition in plasmids to an underwound state that is hypersensitive to single strand-specific nucleases; this transition occurs under conditions of moderately acid pH and negative supercoiling. Chemical probes were used to examine the reactivity of a restriction fragment from a human U1 gene containing the sequence d(C-T)18.d(A-G)18 as a function of supercoiling and pH, and thus analyze the structure in this region. Hyperreactivity was seen in the center and at one end of the (C-T)n tract, and continuously from the center to the same end of the (A-G)n tract, in the presence of supercoiling and pH less than or equal to 6.0. These results provide strong support for a triple-helical model recently proposed for these sequences and are inconsistent with other proposed structures.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Johnston, B H -- New York, N.Y. -- Science. 1988 Sep 30;241(4874):1800-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2845572" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; Chemical Phenomena ; Chemistry ; *Dna ; DNA, Superhelical ; Endonucleases/*metabolism ; Hydrogen-Ion Concentration ; Molecular Sequence Data ; *Nucleic Acid Conformation ; Plasmids ; Single-Strand Specific DNA and RNA Endonucleases
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  • 18
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1988-01-15
    Description: Glycosylated forms of phosphatidylinositol, which have only recently been described in eukaryotic organisms, are now known to play important roles in biological membrane function. These molecules can serve as the sole means by which particular cell-surface proteins are anchored to the membrane. Lipids with similar structures may also be involved in signal transduction mechanisms for the hormone insulin. The utilization of this novel class of lipid molecules for these two distinct functions suggests new mechanisms for the regulation of proteins in biological membranes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Low, M G -- Saltiel, A R -- DK33804/DK/NIDDK NIH HHS/ -- GM35873/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1988 Jan 15;239(4837):268-75.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology and Cellular Biophysics, College of Physicians and Surgeons of Columbia University, New York, NY 10032.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3276003" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Membrane/*physiology ; Chemical Phenomena ; Chemistry ; Glycolipids/biosynthesis/*physiology ; Glycosylation ; Humans ; Hydrolysis ; Insulin/physiology ; Membrane Lipids/physiology ; Membrane Proteins/physiology ; Phosphatidylinositols/biosynthesis/*physiology ; Phospholipases/metabolism ; Phospholipid Ethers/biosynthesis/physiology ; Trypanosoma brucei brucei/metabolism
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  • 19
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1985-05-03
    Description: In the recent literature on nucleoside phosphorothioate anions the structural formulas show a double bond between phosphorus and sulfur and a single bond between phosphorus and oxygen with a negative charge localized on oxygen. However, a review of physical data on these compounds shows the reverse to be the case; that is, in phosphorothioate anions the P-S bond is a single bond with a negative charge localized on sulfur, while the P-O bond order for exocyclic and nonbridging oxygens is greater than 1, approaching 2 in O-alkyl phosphorothioate monoanions and O,O-dialkyl phosphorothioates. The P-O bond orders in phosphorothioate dianions and trianions approach 1 1/2 and 1 1/3, respectively, owing to delocalization of negative charge among two or three oxygens. These conclusions are based on bond lengths obtained from x-ray crystallographic data and electron diffraction, the magnitudes of the effects of 18O on the 31P-nuclear magnetic resonance chemical shifts of phosphorus in nucleoside [18O]phosphorothioates, the pH-dependence of 17O-NMR chemical shifts in [17O]phosphate and [17O]thiophosphate, the vibrational spectra of thiophosphate di- and trianions, and the pKa (dissociation constant) values for phosphoric and thiophosphoric acids.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Frey, P A -- Sammons, R D -- GM30480/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1985 May 3;228(4699):541-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2984773" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Chemistry, Physical ; Cyclic AMP/metabolism ; Magnetic Resonance Spectroscopy ; Phosphates/metabolism ; Phosphoric Acids/metabolism ; Physicochemical Phenomena ; *Thionucleotides/metabolism
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  • 20
    Publication Date: 1985-06-28
    Description: The search for new congeners of the leading anticancer drug doxorubicin has led to an analog that is approximately 1000 times more potent, noncardiotoxic at therapeutic dose levels, and non-cross-resistant with doxorubicin. The new anthracycline, 3'-deamino-3'-(3-cyano-4-morpholinyl)doxorubicin (MRA-CN), is produced by incorporation of the 3' amino group of doxorubicin in a new cyanomorpholinyl ring. The marked increase in potency was observed against human ovarian and breast carcinomas in vitro; it was not accompanied by an increase in cardiotoxicity in fetal mouse heart cultures. Doxorubicin and MRA-CN both produced typical cardiac ultrastructural and biochemical changes, but at equimolar concentrations. In addition, MRA-CN was not cross-resistant with doxorubicin in a variant of the human sarcoma cell line MES-SA selected for resistance to doxorubicin. Thus antitumor efficacy was dissociated from both cardiotoxicity and cross-resistance by this modification of anthracycline structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sikic, B I -- Ehsan, M N -- Harker, W G -- Friend, N F -- Brown, B W -- Newman, R A -- Hacker, M P -- Acton, E M -- CA 24543/CA/NCI NIH HHS/ -- CA 32250/CA/NCI NIH HHS/ -- CA 33303/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1985 Jun 28;228(4707):1544-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/4012308" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Antineoplastic Agents ; Breast Neoplasms/drug therapy ; Cell Line ; Chemical Phenomena ; Chemistry ; Dose-Response Relationship, Drug ; Doxorubicin/adverse effects/*analogs & derivatives/therapeutic use ; Female ; Heart/drug effects ; Humans ; Isoenzymes ; L-Lactate Dehydrogenase/analysis ; Mice ; Myocardium/enzymology ; Ovarian Neoplasms/drug therapy ; Pregnancy
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  • 21
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1986-12-19
    Description: Monoclonal antibodies elicited to haptens that are analogs of the transition state for hydrolysis of carboxylic esters behaved as enzymic catalysts with the appropriate substrates. These substrates are distinguished by the structural congruence of both hydrolysis products with haptenic fragments. The haptens were potent inhibitors of this esterolytic activity, in agreement with their classification as transition state analogs. Mechanisms are proposed to account for the different chemical behavior of these antibodies with two types of ester substrates. The generation of an artificial enzyme through transition state stabilization by antibodies was thus demonstrated. These studies indicate a potentially general approach to catalyst design.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tramontano, A -- Janda, K D -- Lerner, R A -- GM35318/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1986 Dec 19;234(4783):1566-70.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3787261" target="_blank"〉PubMed〈/a〉
    Keywords: *Antibodies, Monoclonal/immunology ; Binding Sites ; Carboxylic Ester Hydrolases ; *Catalysis ; Chemical Phenomena ; Chemistry ; Esters/immunology/metabolism ; Haptens/immunology ; Hydrolysis ; Kinetics
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  • 22
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1987-03-06
    Description: Phosphate esters and anhydrides dominate the living world but are seldom used as intermediates by organic chemists. Phosphoric acid is specially adapted for its role in nucleic acids because it can link two nucleotides and still ionize; the resulting negative charge serves both to stabilize the diesters against hydrolysis and to retain the molecules within a lipid membrane. A similar explanation for stability and retention also holds for phosphates that are intermediary metabolites and for phosphates that serve as energy sources. Phosphates with multiple negative charges can react by way of the monomeric metaphosphate ion PO3- as an intermediate. No other residue appears to fulfill the multiple roles of phosphate in biochemistry. Stable, negatively charged phosphates react under catalysis by enzymes; organic chemists, who can only rarely use enzymatic catalysis for their reactions, need more highly reactive intermediates than phosphates.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Westheimer, F H -- New York, N.Y. -- Science. 1987 Mar 6;235(4793):1173-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2434996" target="_blank"〉PubMed〈/a〉
    Keywords: Amides ; Animals ; Arsenates ; Chemical Phenomena ; Chemistry ; Citrates ; Citric Acid ; Electrochemistry ; Humans ; Hydrolysis ; Ions ; Nucleic Acids/metabolism ; Phosphates/metabolism/*physiology ; RNA/metabolism ; Silicic Acid
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  • 23
    Publication Date: 1987-03-06
    Description: Cross-polarization magic-angle-spinning nuclear magnetic resonance spectroscopy has been used to determine insect cuticle composition and cross-link structure during sclerotization or tanning. Unsclerotized cuticle from newly ecdysed pupae of the tobacco hornworm, Manduca sexta L., had a high protein content with lesser amounts of lipid and chitin. Concentrations of chitin, protein, and catechol increased substantially as dehydration and sclerotization progressed. Analysis of intact cuticle specifically labeled with carbon-13 and nitrogen-15 revealed direct covalent linkages between ring nitrogens of protein histidyl residues and ring carbons derived from the catecholamine dopamine. This carbon-nitrogen adduct was present in chitin isolated from cuticle by alkaline extraction and is probably bound covalently to chitin. These data support the hypothesis that the stiffening of insect cuticle during sclerotization results primarily from the deposition of protein and chitin polymers and their crosslinking by quinonoid derivatives of catecholamines.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schaefer, J -- Kramer, K J -- Garbow, J R -- Jacob, G S -- Stejskal, E O -- Hopkins, T L -- Speirs, R D -- New York, N.Y. -- Science. 1987 Mar 6;235(4793):1200-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3823880" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Carbon Isotopes ; Chemical Phenomena ; Chemistry ; Cross-Linking Reagents/*metabolism ; Insects/*metabolism ; Magnetic Resonance Spectroscopy ; Nitrogen Isotopes ; Skin/*metabolism
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  • 24
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1986-04-18
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Merrifield, B -- New York, N.Y. -- Science. 1986 Apr 18;232(4748):341-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3961484" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Chemical Phenomena ; Chemistry ; In Vitro Techniques ; Methods ; Nucleotides/*chemical synthesis ; Peptide Fragments/metabolism ; Peptides/*chemical synthesis ; Ribonuclease, Pancreatic/chemical synthesis/metabolism ; Structure-Activity Relationship
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  • 25
    Publication Date: 1987-10-23
    Description: Monoclonal antibodies linked to toxic proteins (immunotoxins) can selectively kill some tumor cells in vitro and in vivo. However, reagents that combine the full potency of the native toxins with the high degree of cell type selectivity of monoclonal antibodies have not previously been designed. Two heretofore inseparable activities on one polypeptide chain of diphtheria toxin and ricin account for the failure to construct optimal reagents. The B chains (i) facilitate entry of the A chain to the cytosol, which allows immunotoxins to efficiently kill target cells, and (ii) bind to receptors present on most cells, which imparts to immunotoxins a large degree of non-target cell toxicity. This report identifies point mutations in the B polypeptide chain of diphtheria toxin that block binding but allow cytosol entry. Three mutants of diphtheria toxin have 1/1,000 to 1/10,000 the toxicity and 1/100 to 1/8,000 the binding activity of diphtheria toxin. Linking of either of two of the inactivated mutant toxins (CRM103, Phe508; CRM107, Phe390, Phe525) to a monoclonal antibody specific for human T cells reconstitutes full target-cell toxicity--indistinguishable from that of the native toxin linked to the same antibody--without restoring non-target cell toxicity. This separation of the entry function from the binding function generates a uniquely potent and cell type-specific immunotoxin that retains full diphtheria toxin toxicity, yet is four to five orders of magnitude less toxic than the native toxin is to nontarget cells.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Greenfield, L -- Johnson, V G -- Youle, R J -- New York, N.Y. -- Science. 1987 Oct 23;238(4826):536-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbial Genetics, Cetus Corporation, Emeryville, CA 94608.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3498987" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antibodies, Monoclonal ; Antigens, Differentiation, T-Lymphocyte/immunology ; Antigens, Surface/immunology ; Cell Line ; Cell Survival/drug effects ; Chemical Phenomena ; Chemistry ; Diphtheria Toxin/genetics/*metabolism/pharmacology ; Heparin-binding EGF-like Growth Factor ; Immunotoxins/*pharmacology ; Intercellular Signaling Peptides and Proteins ; *Mutation ; *Receptors, Cell Surface ; Receptors, Cholinergic/metabolism ; Ricin/metabolism ; Structure-Activity Relationship ; T-Lymphocytes/immunology ; Vero Cells
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  • 26
    Publication Date: 1987-03-06
    Description: A DNA cross-link adduct of the antitumor agent mitomycin C (MC) to DNA has been isolated and characterized; the results provide direct proof for bifunctional alkylation of DNA by MC. Exposure of MC to Micrococcus luteus DNA under reductive conditions and subsequent nuclease digestion yielded adducts formed between MC and deoxyguanosine residues. In addition to the two known monoadducts, a bisadduct was obtained. Reductive MC activation with Na2S2O4 (sodium dithionite) leads to exclusive bifunctional alkylation. The structure of the bisadduct was determined by spectroscopic methods that included proton magnetic resonance, differential Fourier transform infrared spectroscopy, and circular dichroism. Formation of the same bisadduct in vivo was demonstrated upon injection of rats with MC. Computer-generated models of the bisadduct that was incorporated into the center of the duplex B-DNA decamer d(CGTACGTACG)2 indicated that the bisadduct fit snugly into the minor groove with minimal distortion of DNA structure. A mechanistic analysis of the factors that govern monofunctional and bifunctional adduct formation is presented.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tomasz, M -- Lipman, R -- Chowdary, D -- Pawlak, J -- Verdine, G L -- Nakanishi, K -- CA 11572/CA/NCI NIH HHS/ -- CA 28681/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1987 Mar 6;235(4793):1204-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3103215" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Cross-Linking Reagents/*isolation & purification ; DNA/*metabolism ; Mass Spectrometry ; Mitomycin ; Mitomycins/*metabolism ; Models, Molecular
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  • 27
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1988-05-06
    Description: The origins, definitions, tools, and guiding principles of host-guest chemistry are developed. Perching, nesting, and capsular complexes are exemplified through molecular model and crystal structure comparisons. The degree of preorganization of a host for binding is a central determinant of its binding power. Complementarity of binding site placement in host and guest is a central determinant of structural recognition in complexation. Examples are given of chiral recognition in complexation, of partial transacylase mimics, of caviplexes, and of a synthetic molecular cell.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cram, D J -- New York, N.Y. -- Science. 1988 May 6;240(4853):760-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, University of California, Los Angeles 90024.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3283937" target="_blank"〉PubMed〈/a〉
    Keywords: Acylation ; Binding Sites ; Chemical Phenomena ; Chemistry ; Crystallization ; Enzymes ; *Models, Chemical ; Models, Molecular ; Nucleic Acids ; Thermodynamics
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  • 28
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1988-04-29
    Description: Exposure of Escherichia coli to low concentrations of hydrogen peroxide results in DNA damage that causes mutagenesis and kills the bacteria, whereas higher concentrations of peroxide reduce the amount of such damage. Earlier studies indicated that the direct DNA oxidant is a derivative of hydrogen peroxide whose formation is dependent on cell metabolism. The generation of this oxidant depends on the availability of both reducing equivalents and an iron species, which together mediate a Fenton reaction in which ferrous iron reduces hydrogen peroxide to a reactive radical. An in vitro Fenton system was established that generates DNA strand breaks and inactivates bacteriophage and that also reproduces the suppression of DNA damage by high concentrations of peroxide. The direct DNA oxidant both in vivo and in this in vitro system exhibits reactivity unlike that of a free hydroxyl radical and may instead be a ferryl radical.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Imlay, J A -- Chin, S M -- Linn, S -- GM19020/GM/NIGMS NIH HHS/ -- P30ES01896/ES/NIEHS NIH HHS/ -- New York, N.Y. -- Science. 1988 Apr 29;240(4852):640-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, University of California, Berkeley 94720.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2834821" target="_blank"〉PubMed〈/a〉
    Keywords: Bacteriophage lambda ; Chemical Phenomena ; Chemistry ; *DNA Damage ; DNA Repair ; DNA, Bacterial/*drug effects ; Escherichia coli/drug effects/*genetics ; Ferrous Compounds ; Free Radicals ; Hydrogen Peroxide/administration & dosage/*pharmacology ; Hydrogen-Ion Concentration ; Hydroxides ; Hydroxyl Radical ; Oxidation-Reduction
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  • 29
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1988-06-03
    Description: A major portion of the toxicity of hydrogen peroxide in Escherichia coli is attributed to DNA damage mediated by a Fenton reaction that generates active forms of hydroxyl radicals from hydrogen peroxide, DNA-bound iron, and a constant source of reducing equivalents. Kinetic peculiarities of DNA damage production by hydrogen peroxide in vivo can be reproduced by including DNA in an in vitro Fenton reaction system in which iron catalyzes the univalent reduction of hydrogen peroxide by the reduced form of nicotinamide adenine dinucleotide (NADH). To minimize the toxicity of oxygen radicals, the cell utilizes scavengers of these radicals and DNA repair enzymes. On the basis of observations with the model system, it is proposed that the cell may also decrease such toxicity by diminishing available NAD(P)H and by utilizing oxygen itself to scavenge active free radicals into superoxide, which is then destroyed by superoxide dismutase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Imlay, J A -- Linn, S -- New York, N.Y. -- Science. 1988 Jun 3;240(4857):1302-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉University of California, Berkeley.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3287616" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *DNA Damage ; DNA, Bacterial/*drug effects ; Escherichia coli/drug effects/*genetics ; Free Radicals ; Hydrogen Peroxide/*pharmacology ; Iron ; NAD/metabolism ; Oxidation-Reduction ; Oxygen/*metabolism
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  • 30
    Publication Date: 1988-08-05
    Description: The x-ray structures of the allosteric enzyme aspartate transcarbamylase from Escherichia coli have been solved and refined for both allosteric forms. The T form was determined in the presence of the heterotropic inhibitor cytidine triphosphate, CTP, while the R form was determined in the presence of the bisubstrate analog N-phosphonacetyl-L-aspartate. These two x-ray structures provide the starting point for an understanding of how allosteric enzymes are able to control the rates of metabolic pathways. Insights into the mechanisms of both catalysis and homotropic cooperativity have been obtained by using site-directed mutagenesis to probe residues thought to be critical to the function of the enzyme based on these x-ray structures.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kantrowitz, E R -- Lipscomb, W N -- GM 06920/GM/NIGMS NIH HHS/ -- GM26237/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1988 Aug 5;241(4866):669-74.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Boston College, MA 02167.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3041592" target="_blank"〉PubMed〈/a〉
    Keywords: Allosteric Regulation ; Allosteric Site ; Aspartate Carbamoyltransferase/*physiology ; Binding Sites ; Chemical Phenomena ; Chemistry ; Escherichia coli/*enzymology ; Macromolecular Substances ; Protein Conformation ; Structure-Activity Relationship
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  • 31
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1987-02-27
    Description: The diversity of monomers available for synthesis of high polymers makes it possible to prepare a wide variety of long-chain macromolecular compounds. It is instructive to consider a hierarchical organization of structure in polymers at four successive levels--the molecular, nano-, micro-, and macrolevels--and to examine how interactions at and between these various levels of structure have important and often quite specific influences. Examples are drawn from semicrystalline polymers with flexible chains, liquid-crystalline polymers composed of rigid macromolecules, and amorphous polymers. Structural hierarchies in biocomposite systems are also discussed, particularly in soft connective tissues such as tendon and intervertebral disk.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Baer, E -- Hiltner, A -- Keith, H D -- New York, N.Y. -- Science. 1987 Feb 27;235(4792):1015-22.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3823866" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Chemical Phenomena ; Chemistry ; Connective Tissue/physiology/ultrastructure ; Crystallization ; Humans ; Intervertebral Disc/physiology/ultrastructure ; Macromolecular Substances ; Microscopy, Electron ; Phenols ; *Polymers/chemical synthesis ; Polystyrenes ; Tendons/physiology/ultrastructure
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  • 32
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1987-03-13
    Description: Vascular endothelium plays an active role in preventing blood clot formation in vivo. One mechanism by which prevention is achieved involves a cell surface thrombin-binding protein, thrombomodulin, which converts thrombin into a protein C activator. Activated protein C then functions as an anticoagulant by inactivating two regulatory proteins of the coagulation system, factors Va and VIIIa. The physiological relevance of the protein C anticoagulant pathway is demonstrated by the identification of homozygous protein C--deficient infants with severe thrombotic complications. Recent studies suggest that this pathway provides a link between inflammation and coagulation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Esmon, C T -- R01 HL-29807/HL/NHLBI NIH HHS/ -- R01 HL-30340/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1987 Mar 13;235(4794):1348-52.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3029867" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Blood Coagulation ; Chemical Phenomena ; Chemistry ; Glycoproteins ; *Homeostasis ; Humans ; Liposomes/metabolism ; Papio ; Protein C/*physiology ; Protein S ; Receptors, Cell Surface/metabolism ; Receptors, Thrombin ; Shock, Septic/blood ; Thrombin/metabolism ; Thrombosis/blood ; Vitamin K/pharmacology
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  • 33
    Publication Date: 1988-11-11
    Description: The crystal structure of a complex containing the DNA-binding domain of lambda repressor and a lambda operator site was determined at 2.5 A resolution and refined to a crystallographic R factor of 24.2 percent. The complex is stabilized by an extensive network of hydrogen bonds between the protein and the sugar-phosphate backbone. Several side chains form hydrogen bonds with sites in the major groove, and hydrophobic contacts also contribute to the specificity of binding. The overall arrangement of the complex is quite similar to that predicted from earlier modeling studies, which fit the protein dimer against linear B-form DNA. However, the cocrystal structure reveals important side chain-side chain interactions that were not predicted from the modeling or from previous genetic and biochemical studies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jordan, S R -- Pabo, C O -- GM-31471/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1988 Nov 11;242(4880):893-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biophysics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3187530" target="_blank"〉PubMed〈/a〉
    Keywords: Base Composition ; Base Sequence ; Binding Sites ; Chemical Phenomena ; Chemistry ; Crystallization ; DNA/*metabolism ; *DNA-Binding Proteins ; Glutamine/metabolism ; Hydrogen Bonding ; Molecular Sequence Data ; Molecular Structure ; Nucleic Acid Conformation ; *Operator Regions, Genetic ; Protein Binding ; Protein Conformation ; Repressor Proteins/genetics/*metabolism ; Sugar Phosphates/metabolism ; Transcription Factors/*metabolism ; Viral Proteins ; Viral Regulatory and Accessory Proteins
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  • 34
    Publication Date: 1985-10-11
    Description: A new, competitive, nonpeptide cholecystokinin (CCK) antagonist, asperlicin, was isolated from the fungus Aspergillus alliaceus. The compound has 300 to 400 times the affinity for pancreatic, ileal, and gallbladder CCK receptors than proglumide, a standard agent of this class. Moreover, asperlicin is highly selective for peripheral CCK receptors relative to brain CCK and gastrin receptors. Since asperlicin also exhibits long-lasting CCK antagonist activity in vivo, it should provide a valuable tool for investigating the physiological and pharmacological actions of CCK.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chang, R S -- Lotti, V J -- Monaghan, R L -- Birnbaum, J -- Stapley, E O -- Goetz, M A -- Albers-Schonberg, G -- Patchett, A A -- Liesch, J M -- Hensens, O D -- New York, N.Y. -- Science. 1985 Oct 11;230(4722):177-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2994227" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Aspergillus/*metabolism ; Benzodiazepinones/*isolation & purification/pharmacology ; Chemical Phenomena ; Chemistry ; Cholecystokinin/*antagonists & inhibitors/pharmacology/physiology ; Dose-Response Relationship, Drug ; Gallbladder/drug effects ; Guinea Pigs ; Ileum/drug effects ; Pancreas/drug effects ; Rats ; Receptors, Cell Surface/drug effects ; Receptors, Cholecystokinin
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  • 35
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1985-09-27
    Description: The three-dimensional structure of poliovirus has been determined at 2.9 A resolution by x-ray crystallographic methods. Each of the three major capsid proteins (VP1, VP2, and VP3) contains a "core" consisting of an eight-stranded antiparallel beta barrel with two flanking helices. The arrangement of beta strands and helices is structurally similar and topologically identical to the folding pattern of the capsid proteins of several icosahedral plant viruses. In each of the major capsid proteins, the "connecting loops" and NH2- and COOH-terminal extensions are structurally dissimilar. The packing of the subunit "cores" to form the virion shell is reminiscent of the packing in the T = 3 plant viruses, but is significantly different in detail. Differences in the orientations of the subunits cause dissimilar contacts at protein-protein interfaces, and are also responsible for two major surface features of the poliovirion: prominent peaks at the fivefold and threefold axes of the particle. The positions and interactions of the NH2- and COOH-terminal strands of the capsid proteins have important implications for virion assembly. Several of the "connecting loops" and COOH-terminal strands form prominent radial projections which are the antigenic sites of the virion.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hogle, J M -- Chow, M -- Filman, D J -- AI-20566/AI/NIAID NIH HHS/ -- AI-22346/AI/NIAID NIH HHS/ -- NS-07078/NS/NINDS NIH HHS/ -- R01 AI020566/AI/NIAID NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1985 Sep 27;229(4720):1358-65.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2994218" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Antigens, Viral/immunology ; Capsid/physiology ; Chemical Phenomena ; Chemistry ; HeLa Cells/microbiology ; Mutation ; Poliovirus/physiology/*ultrastructure ; Protein Conformation ; Virus Replication ; X-Ray Diffraction
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  • 36
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1985-05-31
    Description: The herb Artemisia annua has been used for many centuries in Chinese traditional medicine as a treatment for fever and malaria. In 1971, Chinese chemists isolated from the leafy portions of the plant the substance responsible for its reputed medicinal action. This compound, called qinghaosu (QHS, artemisinin), is a sesquiterpene lactone that bears a peroxide grouping and, unlike most other antimalarials, lacks a nitrogen-containing heterocyclic ring system. The compound has been used successfully in several thousand malaria patients in China, including those with both chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum. Derivatives of QHS, such as dihydroqinghaosu, artemether, and the water-soluble sodium artesunate, appear to be more potent than QHS itself. Sodium artesunate acts rapidly in restoring to consciousness comatose patients with cerebral malaria. Thus QHS and its derivatives offer promise as a totally new class of antimalarials.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Klayman, D L -- New York, N.Y. -- Science. 1985 May 31;228(4703):1049-55.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3887571" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Antimalarials ; *Artemisinins ; Brain Diseases/therapy ; Chemical Phenomena ; Chemistry ; Humans ; Liver/metabolism ; Malaria/*drug therapy ; Medicine, Chinese Traditional ; Metabolic Clearance Rate ; Plants, Medicinal/analysis ; Plasmodium berghei ; Plasmodium falciparum ; *Sesquiterpenes/isolation & purification/metabolism/therapeutic use/toxicity
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 37
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1985-02-22
    Description: Organic chemistry as a discipline derives from and impacts on the biological and abiological world in which we live. Its challenges lie in the areas of structure, reactivity, techniques, and concepts. Powerful structural tools reveal structures from biology that range from control of insect development and behavior to whole new metabolic pathways in humans. Unnatural products create beautiful new molecular shapes whose properties cannot be predicted as well as catalysts that function with enzyme-like control. From structure flows reactivity. Exploration of known reactions points to new directions, and development of new reactions offers the opportunity of streamlined synthetic design. Emerging new techniques offer new dimensions for performing and studying reactions as well as the hope for developing new ones. Merging disparate facts into unified concepts increases predictive capabilities. The extraordinary difficulty of finding the resultant of many small effects may obscure the presence of general theories, creates the art in the practice of the science, and challenges the practitioner. From these general themes derives the quest for selectivity--chemo-, regio-, diastereo-, and enantio-. An examination of the fundamental underpinnings of the applications of organic chemistry reveals that, while impressive strides have been made, the science is best described as being between infancy and childhood. The cross-fertilization between organic chemistry and molecular biology vividly illustrates a merging of chemistry and biology.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Trost, B M -- New York, N.Y. -- Science. 1985 Feb 22;227(4689):908-16.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3969569" target="_blank"〉PubMed〈/a〉
    Keywords: Alkylation ; Animals ; Chemical Phenomena ; Chemistry ; *Chemistry, Organic ; Enzymes ; Humans ; Insects ; Mammals ; Organic Chemistry Phenomena ; Research ; Stereoisomerism
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  • 38
    Publication Date: 1986-05-30
    Description: For many drugs, only racemic mixtures are available for clinical use. Because different stereoisomers of drugs often cause different physiological responses, the use of pure isomers could elicit more exact therapeutic effects. Differential complexation of a variety of drug stereoisomers by immobilized beta-cyclodextrin was investigated. Chiral recognition and racemic resolution were observed with a number of compounds from such clinically useful classes as beta-blockers, calcium-channel blockers, sedative hypnotics, antihistamines, anticonvulsants, diuretics, and synthetic opiates. Separation of the diastereomers of the cardioactive and antimalarial cinchona alkaloids and of two antiestrogens was demonstrated as well. Three dimensional projections of beta-cyclodextrin complexes of propanolol, which is resolved by this technique, and warfarin, which is not, are compared. These studies have improved the understanding and application of the chiral interactions of beta-cyclodextrin, and they have demonstrated a means to measure optical purity and to isolate or produce pure enantiomers of drugs. In addition, this highly specific technique could also be used in the pharmacological evaluation of enantiomeric drugs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Armstrong, D W -- Ward, T J -- Armstrong, R D -- Beesley, T E -- RR1081/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1986 May 30;232(4754):1132-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3704640" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Cinchona Alkaloids/isolation & purification ; *Cyclodextrins ; *Dextrins ; Propranolol/isolation & purification ; *Starch ; *Stereoisomerism ; Warfarin/isolation & purification ; *beta-Cyclodextrins
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  • 39
    Publication Date: 1985-01-25
    Description: Ancient Mexican botanical literature was systematically searched for new plant sources of intensely sweet substances. Lippia dulcis Trev., a sweet plant, emerged as a candidate for fractionation studies, and hernandulcin, a sesquiterpene, was isolated and judged by a human taste panel as more than 1000 times sweeter than sucrose. The structure of the sesquiterpene was determined spectroscopically and confirmed by chemical synthesis. Hernandulcin was nontoxic when administered orally to mice, and it did not induce bacterial mutation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Compadre, C M -- Pezzuto, J M -- Kinghorn, A D -- Kamath, S K -- N01-DE-02425/DE/NIDCR NIH HHS/ -- New York, N.Y. -- Science. 1985 Jan 25;227(4685):417-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3880922" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bibliography as Topic ; Botany/history ; Chemistry ; History, 16th Century ; Humans ; Magnetic Resonance Spectroscopy ; Mexico ; Mice ; Molecular Conformation ; Mutagenicity Tests ; *Plants/analysis ; *Sesquiterpenes/chemical synthesis/isolation & purification/toxicity ; *Sweetening Agents/chemical synthesis/history/isolation & purification/toxicity
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  • 40
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1985-04-26
    Description: The planning of alternative routes for the synthesis of complex organic molecules has been facilitated by the formulation of guiding strategies that can be applied to a broad range of problems. Analysis of organic synthesis can be carried out in the retrosynthetic direction, opposite to the actual process of chemical synthesis, or bidirectionally, that is, as a combined retrosynthetic and synthetic search. An interactive computer program is described which utilizes the general strategies of retrosynthetic analysis and an appropriate database to generate pathways of chemical intermediates for chemical synthesis of a particular target structure. Computer graphics and standard chemical structures are used for man-machine communication.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Corey, E J -- Long, A K -- Rubenstein, S D -- New York, N.Y. -- Science. 1985 Apr 26;228(4698):408-18.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3838594" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Chemistry, Organic/*methods ; *Computers ; Forecasting ; Software
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  • 41
    Publication Date: 1985-03-15
    Description: A theoretical methodology for use in conjunction with experiment was applied to the neurohypophyseal hormone lysine vasopressin for elucidation of its accessible molecular conformations and associated flexibility, conformational transitions, and dynamics. Molecular dynamics and energy minimization techniques make possible a description of the conformational properties of a peptide in terms of the precise positions of atoms, their fluctuations in time, and the interatomic forces acting on them. Analysis of the dynamic trajectory of lysine vasopressin shows the ability of a flexible peptide hormone to undergo spontaneous conformational transitions. The excursions of an individual phenylalanine residue exemplify the dynamic flexibility and multiple conformational states available to small peptide hormones and their component residues, even within constraints imposed by a cyclic hexapeptide ring.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hagler, A T -- Osguthorpe, D J -- Dauber-Osguthorpe, P -- Hempel, J C -- New York, N.Y. -- Science. 1985 Mar 15;227(4692):1309-15.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3975616" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Chemistry, Physical ; Energy Metabolism ; Hydrogen Bonding ; Lypressin/*metabolism ; Phenylalanine/metabolism ; Physicochemical Phenomena ; Protein Conformation
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  • 42
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1985-03-08
    Description: Methanogenic and acetogenic bacteria metabolize carbon monoxide, methanol, formate, hydrogen and carbon dioxide gases and, in the case of certain methanogens, acetate, by single-carbon (C1) biochemical mechanisms. Many of these reactions occur while the C1 compounds are linked to pteridine derivatives and tetrapyrrole coenzymes, including corrinoids, which are used to generate, reduce, or carbonylate methyl groups. Several metalloenzymes, including a nickel-containing carbon monoxide dehydrogenase, are used in both catabolic and anabolic oxidoreductase reactions. We propose biochemical models for coupling carbon and electron flow to energy conservation during growth on C1 compounds based on the carbon flow pathways inherent to acetogenic and methanogenic metabolism. Biological catalysts are therefore available which are comparable to those currently in use in the Monsanto process. The potentials and limitations of developing biotechnology based on these organisms or their enzymes and coenzymes are discussed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zeikus, J G -- Kerby, R -- Krzycki, J A -- 144-T263/PHS HHS/ -- New York, N.Y. -- Science. 1985 Mar 8;227(4691):1167-73.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3919443" target="_blank"〉PubMed〈/a〉
    Keywords: Acetates/*metabolism ; Acetobacter/metabolism ; Bacteria/*metabolism ; Carbon Dioxide/metabolism ; Carbon Monoxide/metabolism ; Chemical Phenomena ; Chemistry ; Clostridium/metabolism ; Eubacterium/metabolism ; Euryarchaeota/*metabolism ; Formates/metabolism ; Methane/metabolism ; Methanol/metabolism
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  • 43
    Publication Date: 1985-03-22
    Description: Glutathione reductase from trypanosomes and leishmanias, unlike glutathione reductase from other organisms, requires an unusual low molecular weight cofactor for activity. The cofactor was purified from the insect trypanosomatid Crithidia fasciculata and identified as a novel glutathione-spermidine conjugate, N1,N8-bis(L-gamma-glutamyl-L-hemicystinyl-glycyl)spermidine, for which the trivial name trypanothione is proposed. This discovery may open a new chemotherapeutic approach to trypanosomiasis and leishmaniasis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fairlamb, A H -- Blackburn, P -- Ulrich, P -- Chait, B T -- Cerami, A -- 1 R01 A127429/PHS HHS/ -- 1 R01 AI19428/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1985 Mar 22;227(4693):1485-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3883489" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Chemical Phenomena ; Chemistry ; Coenzymes/analysis/*isolation & purification/metabolism ; Crithidia/*enzymology ; Glutathione/*analogs & derivatives/analysis/isolation & purification/metabolism ; Glutathione Reductase/*metabolism ; Leishmania/*enzymology ; Oxidation-Reduction ; Spermidine/*analogs & derivatives/analysis/isolation & purification/metabolism ; Terminology as Topic ; Trypanosoma/*enzymology ; Trypanosoma brucei brucei/enzymology ; Trypanosoma cruzi/enzymology
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  • 44
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1985-02-22
    Description: Coenzyme B12 serves as a cofactor in various enzymatic reactions in which a hydrogen atom is interchanged with a substituent on an adjacent carbon atom. Measurement of the dissociation energy of the coenzyme's cobalt-carbon bond and studies of the rearrangement of model free radicals related to those derived from methylmalonyl-coenzyme A suggest that these enzymatic reactions occur through homolytic dissociation of the coenzyme's cobalt-carbon bond, abstraction of a hydrogen atom from the substrate by the coenzyme-derived 5'-deoxyadenosyl radical, and rearrangement of the resulting substrate radical. The only role thus far identified for coenzyme B12 in these reactions--namely, that of a free radical precursor--reflects the weakness, and facile dissociation, of the cobalt-carbon bond.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Halpern, J -- New York, N.Y. -- Science. 1985 Feb 22;227(4689):869-75.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2857503" target="_blank"〉PubMed〈/a〉
    Keywords: Carbon/metabolism ; Chemical Phenomena ; Chemistry ; Chemistry, Physical ; Cobalt/metabolism ; Cobamides/*metabolism ; Energy Metabolism ; Free Radicals ; Methylmalonyl-CoA Mutase/metabolism ; Physicochemical Phenomena
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  • 45
    Publication Date: 1985-08-09
    Description: Hemocyanins are large multi-subunit copper proteins that transport oxygen in many arthropods and molluscs. Comparison of the amino acid sequence data for seven different subunits of arthropod hemocyanins from crustaceans and chelicerates shows many highly conserved residues and extensive regions of near identity. This correspondence can be matched closely with the three domain structure established by x-ray crystallography for spiny lobster hemocyanin. The degree of identity is particularly striking in the second domain of the subunit that contains the six histidines which ligate the two oxygen-binding copper atoms. The polypeptide architecture of spiny lobster hemocyanin appears to be the same in all arthropods. This structure must therefore be at least as old as the estimated time of divergence of crustaceans and chelicerates, about 540 to 600 million years ago.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Linzen, B -- Soeter, N M -- Riggs, A F -- Schneider, H J -- Schartau, W -- Moore, M D -- Yokota, E -- Behrens, P Q -- Nakashima, H -- Takagi, T -- GM 21314/GM/NIGMS NIH HHS/ -- GM 28410/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1985 Aug 9;229(4713):519-24.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/4023698" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Arachnida/genetics ; *Arthropods/genetics ; Binding Sites ; Biological Evolution ; Chemical Phenomena ; Chemistry ; Copper ; Crustacea/genetics ; *Hemocyanin/genetics ; Models, Molecular ; Protein Conformation ; Species Specificity
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  • 46
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1985-02-22
    Description: A strategy for the synthesis of chiral molecules that receives growing popularity among organic chemists employs the photochemically mediated [2 + 2] cycloaddition reaction. These reactions can be performed on a multigram scale and often proceed with high yield and with stereocontrol. These features, in combination with the useful properties of the four-membered ring photoproducts in subsequent chemical transformations, make them attractive options in the early stage of a synthesis design. Various combinations of unsaturated functional groups can participate in this reaction process. Accordingly, these chemical reactions can be economical solutions to problems relating to the synthesis of a variety of target molecules.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schreiber, S L -- GM-32527/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1985 Feb 22;227(4689):857-63.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/4038558" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Anti-Bacterial Agents/chemical synthesis ; Antifungal Agents/chemical synthesis ; Chemical Phenomena ; Chemistry ; Cockroaches ; Female ; Furans/chemical synthesis ; Lactones/chemical synthesis ; Male ; Mycotoxins/chemical synthesis ; *Photochemistry ; Pyrones/chemical synthesis ; Sex Attractants/chemical synthesis/isolation & purification ; Stereoisomerism
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  • 47
    Publication Date: 1985-04-12
    Description: Computerized pattern recognition techniques can be applied to the study of complex chemical communication systems. Analysis of high resolution gas chromatographic concentration patterns of the major volatile components of the scent marks of a South American primate, Saguinus fuscicollis, demonstrates that the concentration patterns can be used to predict the gender and subspecies of unknown donors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Smith, A B 3rd -- Belcher, A M -- Epple, G -- Jurs, P C -- Lavine, B -- 5 T32 NSO7176-03/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1985 Apr 12;228(4696):175-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3975636" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Chemical Phenomena ; Chemistry ; Chromatography, Gas ; *Computers ; Female ; Male ; *Pattern Recognition, Automated ; Pheromones/*physiology ; Saguinus/physiology ; Scent Glands/physiology ; Sex Attractants/*physiology ; Structure-Activity Relationship
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  • 48
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic sciences 51 (1989), S. 108-128 
    ISSN: 1420-9055
    Keywords: Chemistry ; mountain lakes ; silica ; acidity ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Alpine lakes in siliceous catchments of Tyrol and Carinthia (Austria) show signs of acidification. About 9% of the studied lakes have no alkalinity, more than 20% are below pH 6. About two thirds of all lakes have acid neutralizing capacities below 100 μeq 1−1. In spite of moderate precipitation acidity, some lakes show considerable concentrations of dissolved reactive aluminum during or shortly after snowmelt. High altitude lakes of the Alps are definitely more acidic than high mountain lakes in remote areas. Large differences in water and soil chemistry of nearby situated lakes were attributed to heterogeneities of bedrock geology. Paleolimnological investigations on former pH values of five lakes, based on diatom assemblages in the sediment, showed different developments: recent and past acidification, stable conditions, and alkalinization.
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    Pharmacy world & science 8 (1986), S. 245-251 
    ISSN: 1573-739X
    Keywords: Analysis ; Antineoplastic agents ; Biosynthesis ; Botany ; Chemistry ; Cytotoxins ; Eupatorium cannabium ; Sesquiterpenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A review onEupatorium cannabinum L. is given, including botany, history and constituents. The sesquiterpene lactones are discussed in more detail, covering their biosynthesis, isolation, analysis and biological activity. Special attention is paid to the cytotoxic and antitumour activities of the sesquiterpene lactones.
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  • 50
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    Pharmacy world & science 9 (1987), S. 305-314 
    ISSN: 1573-739X
    Keywords: Atrial natriuretic factor ; Blood pressure ; Chemistry ; Diuresis ; Homeostasis ; Kidney ; Muscle, smooth ; Natriuresis ; Receptors, endogenous compounds ; Renin-angiotensin system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is now known that cardiac atria play an important role in blood pressure and volume regulation. Mechanical distension of the atria results in the release of a potent diuretic and natriuretic agent or agents termed the atrial natriuretic factor (ANF). Several structurally related forms of ANF exist in man and it is thought that these represent precursory forms of a single optimally active molecule and/or the presence of more than one form of active ANF. The chemical structure of ANF between different mammalian species is similar. ANF receptors have been identified in kidney, brain, vascular endothelial and smooth muscle cells, tracheal and bronchial smooth muscle and the adrenal glands of many mammalian species, including man. This would suggest that ANF influences blood pressure and volume homoeostasis by affecting any one of a number of biochemical or physiological mechanisms via different target tissues. ANF is now considered a potentially valuable therapeutic agent for the treatment of hypertension and congestive heart failure. Synthesis of potent receptor antagonists could be extremely useful in the treatment of various clinical situations which are produced or complicated by endogenously produced ANF, such as chronic orthostatic hypotension.
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    Pharmacy world & science 10 (1988), S. 93-95 
    ISSN: 1573-739X
    Keywords: Anthracyclines ; Chemistry ; Drug stability ; Mitomycins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 52
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    Pharmacy world & science 10 (1988), S. 101-116 
    ISSN: 1573-739X
    Keywords: Chemistry ; Chromatography ; Etoposide ; Immunoassay ; Metabolism ; Podophyllotoxin ; Pharmacokinetics ; Teniposide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Etoposide (VP 16-213) and teniposide (VM 26) are semisynthetic epipodophyllotoxin derivatives active against a variety of tumours. The clinical efficacy has led to an increasing interest in these compounds. This review presents information on the mechanism of action, biochemical pharmacology, bioanalysis, metabolism and pharmacokinetics of etoposide and teniposide.
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  • 53
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    Biological Mass Spectrometry 14 (1987) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Biological Mass Spectrometry 14 (1987), S. i 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Topics: Chemistry and Pharmacology
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  • 55
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino acids can be identified unambiguously in form of their dansylated methyl esters by combination of thin-layer chromatography on polyamide and subsequent mass spectrometry without prior substance elution from the chromatographic polyamide carrier. The evaporation intensity of the amino acid derivatives is sufficient to get excellent mass spectra with significant structural information also with very small amounts of starting material (picomole level), which guarantee a high separation power in the TLC step. Besides the methylester derivatives, in part, products additionally methyl substituted at the sulfonamide nitrogen could be separated.
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  • 56
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The simple combination of thin-layer chromatography on polyamide with subsequent mass spectrometry of the separated compounds together with the carrier material has been employed for unambiguous identification of individual dipeptides in a mixture. The dipeptides were analysed in the form of their dansyl methyl ester derivatives. The appearance of molecular ions in the electron impact mass spectra simultaneously with the ions dans-NH=CHR⌝+ indicating the corresponding N-terminal amino acid residue enables a rapid and sensitive structure elucidation of the dipeptides. The chromatography and mass spectrometry can be performed with 0.2-0.3 nmol dipeptide.
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    Biological Mass Spectrometry 14 (1987), S. 357-362 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several classes of environmentally significant compounds were introduced into an ion trap detector (ITD) by capillary column gas chromatography, and the performance of the device as a gas chromatography/mass spectrometry (GC/MS) system was studied. The experiments conducted included studies of the precision of selected ion monitoring (SIM) measurements, the precision of relative ion abundance measurements in full mass range scans, the sensitivity and instrument detection limits in SIM and full mass range data acquisition, and the linear range of concentration calibration. It was observed that resolution may be lost and saturation may occur under certain conditions, and that the data system can report artifact ions under these conditions.
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  • 58
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Brominated dioxins and dibenzofurans (PBDDs and PBDFs) are known contaminants in commercial fire retardant preparations. Further, they are formed in incineration processes involving polybrominated biphenyl and diphenylether fire retardants. This report presents the characterization of polybrominated dioxins and dibenzofurans. In particular, environmental monitoring methodology for PBDDs and PBDFs has been developed, and confirmation criteria for GC/MS analyses are presented.
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  • 59
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    Biological Mass Spectrometry 14 (1987), S. 473-477 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analysis of reports in the world's literature suggests that average sperm densities for groups of unselected males were relatively constant at about 108 million cells per ml prior to 1950. Subsequent to that time mean sperm densities appear to have declined. Regression analysis indicates the existence of significant negative correlations between mean sperm densities and production of synthetic organic chemicals among other parameters. Phthalate esters are one class of large volume organic chemicals that are known to disturb testicular function in laboratory animals. These compounds are also the most abundant man-made chemicals in the environment. Plots of the concentration of dibutylphthalate in the cellular fraction of ejaculates against either the sperm density or the total number of sperm for the same ejaculates gave two clusters of points. These clusters suggest the existence of two or more populations vis à vis phthalate metabolism; both of which show a negative correlation between phthalate concentration and sperm production.
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    Biological Mass Spectrometry 14 (1987), S. 481-485 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report a case of n-nonacosane storage disease, which went undiagnosed until the death of a 55-year-old farmer. Clinical, histological, and biochemical features are discussed. n-Nonacosane storage was identified by gas chromato-graphic-mass spectrometric analysis of different tissue extracts, n-nonacosane concentration reaching 1.2 mg g-1 of lung tissue and 0.32 mg g-1 of liver tissue. It was possible to rule out a work-induced intoxication, and n-nonacosane storage appeared to be accounted for by a lifelong, heavy consumption of unpeeled apples and Brussels sprouts.
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  • 61
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new technique known as thermally-assisted fast atom bombardment (TA-FAB) has been applied to the analysis of a series of cyclic tetrapeptide mycotoxins in order to demonstrate the usefulness of the method for structural elucidation. TA-FAB uses saturated aqueous solutions of highly hydroxylated compounds, such as fructose, as alternatives to the usual viscous liquid matrices employed in conventional FAB. During the TA-FAB analysis, the probe tip is resistively heated causing diffeiences to occur in the desorption profiles for the analyte and the matrix ions enabling an optimization for analyte desorption as a function of temperature. In this study, direct comparisons are made between TA-FAB, conventional FAB, and electron impact ionization for the analysis of the Helminthosporium carbonum mycotoxins at the 1.5 μg level. The results demonstrate the superior capacity of TA-FAB to provide both molecular weight confirmation and significant fragmentation to aid in the structural elucidation of these important biomolecules.
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    Biological Mass Spectrometry 14 (1987), S. 517-521 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three glutathione conjugates of acetaminophen were characterized by fast atom bombardment/mass spectrometry (FAB/MS) and fast atom bombardment/mass spectrometry/mass spectrometry (FAB/MS/MS). The conjugates, 3-(glutathion-S-yl)acetaminophen, 3-(glutathion-S-yl)diacetaminophen and 3-(diglutathion-S-yl)diacetaminophen showed intense [MH]+ ions at m/z 457, 606 and 911, respectively. Only 3-(glutathion-S-yl)acetaminophen showed any fragmentation by FAB/MS. Structurally characteristic fragmentation was observed with all three conjugates when the [MH]+ ions were collisionally activated. The loss of the glycine (GLY) and glutamic acid (GLU) moieties indicated the presence of at least one glutathione (GSH) group. Multiple losses, some of which could only occur via cleavages in both GSH moieties, were observed with the diglutathione conjugate.
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    Biological Mass Spectrometry 14 (1987), S. 549-553 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A GC-MS procedure has been developed for the quantitation in plasma and urine of rimantadine, an antiviral drug effective against type A influenza. The assay utilizes selective ion monitoring, methane negative ion chemical ionization (NCI) and stable isotope dilution. Sensitivity to NCI is effected by derivation of rimantadine with pentafluorobenzoyl chloride. The method has been used to quantitate plasma concentrations of rimantadine over a range from 4.2 ng/ml to 416 ng/ml, and urinary concentrations of rimantadine over a range of 21 ng/ml to 2077 ng/ml.
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    Biological Mass Spectrometry 14 (1987), S. 127-129 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described to assign the positional series of methylene interrupted polyenoic acids, in complex mixtures, isolated from hydrolysed lipid extracts. It entails a simple comparison of the intensities of three ions of m/z 108, 150 and 192.
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  • 65
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behaviour of 1,1·,1″-phosphinothioylidinetrisaziridine (thiotepa) in water and aqueous salt solution of various acidity was studied by field ionization mass spectrometry (FI-MS), TLC and potentiometric titration. The rate of thiotepa hydrolysis increased with increasing thiotepa, or sodium chloride concentration, and with decreasing pH. As hydrolysis products of thiotepa, mono- and dichloro derivatives formed in neutral, salt-containing and acidic solution, tepa, and products formed by P—N bond cleavage and release of aziridine have been identified.
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  • 66
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methodology for the qualitative and quantitative analysis of the anthelmintic fenbendazole and its metabolites in goat feces using electron impact (EI)/direct exposure probe (DEP)/mass spectrometric (MS) and tandem mass spectrometric (MS/MS) techniques is presented. Analyses were conducted on extracts from spiked feces and feces from animals treated per os with 5 mg fenbendazole/kg, with samples being collected at zero time and at twelve hour intervals for 144 h. The results of the EI/DEP/MS quantitation of these samples are compared to those for the same samples analysed by high pressure liquid chromatography (HPLC). Mass spectral data for fenbendazole and its metabolites are presented and the advantages of the use of EI/DEP/MS and/or DEP/MS/MS over HPLC are discussed. This methodology may be used as a confirmatory method for the HPLC analysis of fenbendazole and its metabolites or may be used as a method in its own right for the rapid qualitative and quantitative analysis of these compounds.
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  • 67
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Known and possible phenolic and primary and secondary amine metabolites of lidocaine were added to urine from drug-naive rats. These metabolites were derivatized in this aqueous medium by acetylation with acetic anhydride or by pentafluorobenzoylation with pentafluorobenzoyl chloride. The derivatives were simultaneously extracted into an organic solvent. The products were separated by gas chromatography (flame ionization detection for acetates and electron-capture detection for pentafluorobenzoates) and identified by combined gas chromatography/mass spectrometry. Mass spectral fragmentation pathways were readily deduced; diagnostic fragment ions were identified and were valuable for characterization purposes. Structural isomers could be distinguished on the basis of their GC retention times.Extractive derivatization using pentafluorobenzoyl chloride is an attractive analytical procedure for the identification of phenolic and dealkylated metabolites of lidocaine.
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 69
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    Biological Mass Spectrometry 14 (1987), S. 213-220 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray HPLC/MS analysis of the metabolites of arachidonic acid proved to be sensitive and specific. The compounds included were hydroxy-fatty acids (5-HETE, 12-HETE, and 15-HETE) and prostaglandins PGD2, PGE2, PGF2α, PGA2, PGA1, TXB2, and 6-Keto-PGF1α. Thermospray HPLC/MS analysis allows for simultaneous monitoring of each compound without the need for additional sample preparation or derivatization. The thermospray spectra for the metabolites exhibited [M + NH4]+ ions and fragment ions because of sequential loss of equivalents of H2O. HPLC/MS showed detection limits in the 0.5 to 5 ng range when using multiple ion detection for most of the metabolites. Post-column derivatization of these metabolites using trimethylanilinium hydroxide (TMAH) to form the methyl esters is also presented. This derivatization resulted in a gain in ion current by a factor of 3-6 for most compounds while adding potential specificity to the analysis. The thermospray spectra of the derivatives were nearly identical to the spectra of the free acid except the peaks were incremented by 14 daltons due to the methyl ester formation. The derivatization of the carboxylic acid group proved to be complete under thermospray conditions producing the maximum ion current and causing no compromise in operation of the interface.
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    Biological Mass Spectrometry 14 (1987), S. 649-651 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The identified urinary metabolites of male rats exposed to indan are: 1- and 2-indanone; 1-, 2- and 5-indanol; 2-and 3-hydroxyl-1-indanone; and cis- and trans-indan-1,2-diol. Indan causes kidney damage in male rats in a manner similar to the cyclic hydrocarbons cis- and trans-decalin and JP-10. Lesions produced by indan occur only in male rats and not in female or control rats.
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    Topics: Chemistry and Pharmacology
    Notes: Dinucleoside monophosphates bearing usual protecting groups at the exocyclic amino functions of the heterocyclic bases, the 5′-hydroxy group, the phosphate moiety and the O-6-position of the guanine ring have been analysed by FAB mass specrometry in the negative ion mode. These non-charged key intermediates for oligodeoxynucleotide synthesis exhibit very simple spectra in the mass range of m/z 400-1500 using tetra-ethylene glycol as matrix. Most of the observed ions could easily be assigned. Apart from deprotonated molecular ions sequence specific ions arising from C-O-P bond cleavage and ions derived from loss of protecting groups were observed. The simplicity of spectra interpretation makes FAB mass spectrometry to a rapid and valuable tool for unambiguous identification of dimeric synthons for oligonucleotide synthesis.
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    Biological Mass Spectrometry 14 (1987), S. 141-142 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Biological Mass Spectrometry 14 (1987), S. 131-140 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixtures of both synthetic and naturally occurring (human plasma) cholesteryl esters have been examined by capillary gas chromatography/mass spectrometry (GC/MS). A magnetic sector mass spectrometer was used and a variety of ionization modes were assessed with a view to obtaining structural information on intact cholesteryl esters. By employing ammonia as reagent gas, with negative ion scanning, spectra were produced from which the nature of steryl and fatty acyl moieties could be readily deduced. Analyses were performed at an ion source temperature of 300°C in order to maintain the integrity of the gas chromatographic profile. The technique described is of general use for the GC/MS analysis of steryl esters, particularly in conjunction with magnetic sector instruments.
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray spectra on a magnetic sector mass spectrometer, by definition measured at high accelerating voltages, are seen to be highly fragmented. This is rationalised in terms of the necessity to accelerate ions through a region of high pressure in the vicinity of the ion-collecting orifice at the spray volume, where ions may be energized by ion molecule collisions. In this region, a high percentage of the parent ion current is lost through the dispersion of the ion beam and by the collisional activation of molecular ions resulting in extensive fragmentation. The investigation of means by which these effects may be minimized has led to the construction of an improved sector thermospray source. Comparative results for gramicidin S demonstrate that its fragmentation is reduced and that the intensity of the protonated molecular ion is greatly enhanced.
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    Biological Mass Spectrometry 14 (1987), S. 183-185 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetates of 12 positionally isomeric tetradecenols (Δ2-Δ13) have been prepared and their mass spectra measured without any prior chemical modification. Comparison of spectra of all the isomers has shown the variation in intensities of some predominant fragments with the position of the double bond on the 14 carbons chain. The mass spectra were interpreted in terms of the relative intensity ratio of the fragment ion peaks to locate the double bond positions. A procedure for elucidation of the positional isomerism of tetradecenyl acetates is given.
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    Biological Mass Spectrometry 14 (1987) 
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    Biological Mass Spectrometry 14 (1987), S. 207-211 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eight normal subjects ingested 125 mg of p-tyramine-β,β-2H2 hydrochloride and the 3 h and following 21 h urine collections were analysed by mass spectrometry with selected ion monitoring for the deuterated metabolites: free and conjugated p-tyramine-β,β-2H2, free p-octopamine-β-2H1, free and conjugated p-hydroxyphenylacetic acid-α-2H1 and -α,α-2H2, and free p-hydroxymandelic acid-α-2H1. These metabolites accounted for 72% of the ingested label, of which conjugated p-tyramine and free p-hydroxyphenylacetic acid constituted 90%. Approximately 50% of the total deuterated tyramine and 70% of the total deuterated p-hydroxyphenylacetic acid were excreted in the first three hours, although there was considerable variation between individuals. The presence of a small amount of p-hydroxyphenylacetic acid-α-2H1 suggests that some exchange of deuterium occurred at the intermediate p-hydrophenylacetaldehyde stage.These results, based as they are on metabolites labelled with the stable isotope deuterium, ought to be more reliable than earlier studies in which unlabelled tyramine was ingested with the resultant metabolites, indistinguishable from their endogenous metabolic counterparts, being measured by fluorimetry or gas chromatography.
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    Biological Mass Spectrometry 14 (1987), S. 221-227 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Human exposure to aromatic amines may be monitored by measuring the amount of sulfinamide adduct bound to hemoglobin. In order to develop a sensitive and selective method for measuring aromatic amines present in low concentrations the mass spectra of the pentafluoropropionamide derivatives of a series of aromatic amines were determined under various ionization conditions. With electron ionization the aromatic amine derivatives typically yield intense molecular ions with fragmentation leading to elimination of C2F5 and COC2F5. Higher molecular weight polycyclic aromatic amines, e.g., 6-aminochrysene, give prominent molecular ions as well as intense ions corresponding to M-174 (loss of CNHCOC2F5). With positive chemical ionization using methane as reagent gas the derivatives give protonated molecular ions as the base peaks, as well as the associated ions at M + 29 and M + 41. Negative ion chemical ionization yields, primarily, peaks corresponding to the loss of HF from the molecular anions. Negative ion chemical ionization with selected ion monitoring is generally more suitable than positive chemical ionization or electron ionization for the quantitative analysis of aromatic amines present in biological samples in the mid femtomolar range. Exposure of human subjects to aromatic amines was determined via basic hydrolysis of the isolated sulfinic acid amide hemoglobin adducts. Analysis of the derivatized extracts by gas chromatography/negative ion chemical ionization/mass spectrometry demonstrated the presence of aniline, ortho-, meta-, and para-toluidine, 2-naphthylamine, and 4-aminobiphenyl. The hemoglobin adduct levels of these amines in both cigarette smokers and nonsmokers were determined. The mean values of the adduct levels of ortho- and para-toluidine, 2-naphthylamine, and 4-aminobiphenyl were higher in smokers than in nonsmokers, while the mean adduct values of aniline and meta-toluidine were similar in both groups. Adducts of 2-, 3-, 4-ethylaniline, 2,3-, 2,4-, 2,5-, 2,6-dimethylaniline, and 3-aminobiphenyl have been detected in smokers' blood. 1-Aminoanthracene, 9-aminophenanthrene, and 6-aminochrysene have not been detected. GC/MS procedures were also used to determine the extent of binding of aniline-2,3,4,5,6-d5 to hemoglobin in rats administered aniline-d5.
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    Biological Mass Spectrometry 14 (1987), S. 479-479 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The single dose pharmacokinetics of deuterium-labelled cannabinol (2H2-CBN) were evaluated in six male cannabis users with different degree of abuse after smoking an average dose of 19 mg and after intravenous administration of 20 mg CBN. Plasma levels were measured for up to 72 h with selected ion monitoring by GC/MS using 2H7-CBN as internal standard. The systemic availability of smoked CBN was found to be 39 ± 26% (min-max 6-65%). The mean plasma clearance was 19.1 ± 2.6 ml min-1 kg-1 and the volume of distribution was determined to 50 ± 23 1 kg-1. The apparent terminal half lives for CBN were 32 ± 17 h and 43 ± 29 h after intravenous administration and smoking, respectively.
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    Biological Mass Spectrometry 14 (1987), S. 533-534 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biological Mass Spectrometry 14 (1987), S. 523-531 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Derivatization of prostaglandins and thromboxane B2 using diethyl amino ethyl chloride and diethyl amino ethyl bromide improved thermospray HPLC/MS sensitivity. The derivatization was evaluated for prostaglandin A1, A2, D2, E2, F1α, F2α, and thromboxane B2. The derivatization reaction, thermospray operating conditions, and mode of detection were optimized to produce the most intense [M + H]+ or [M - H]- ions for the derivative. Derivatization was better than 99% complete in 1 hour at 75°C. No thermal degradation of the prostaglandins was observed. Positive thermospray ionization proved the mode most sensitive, enabling detection from 10 to 300 pg of each prostaglandin under multiple ion detection. The thermospray spectra exhibited intense [M + H]+ ions for the derivative with a few fragment ions from sequential losses of water from the [M + H]+ ion. Detection of a prostaglandin metabolite in plasma over the concentration range from 3 ppm to 30 ppb was possible using this derivatization.
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  • 83
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas chromatographic and mass spectrometric properties of leukotriene B4, 20-hydroxy-leukotriene B4 and 20-carboxy-leukotriene-B4 were investigated as their methyl ester trimethylsilyl, methyl ester allyldimethylsilyl and methyl ester tert-butyldimethylsilyl ethers. The gas chromatographic properties of the trimethylsilyl and tert-butyldimethylsilyl ether derivatives were good with respect to peak shape and sensitivity, whereas the allyldimethylsilyl ether derivative gave a lower sensitivity. The sensitivity defined as the quantity that could be passed through the gas chromatographic column.The three derivatives showed a mass spectrometric fragmentation pattern with cleavage of the C12—C13 bond as an important feature. Particularly, the allyldimethylsilyl ether derivative of the three compounds studied exhibited a high tendency for C12—C13 bond cleavage resulting in a fairly intense ion at m/z 435. However, the mass spectra indicated multiple fragmentation pathways due to the presence of double bonds, leading to decreased intensities of the high mass ions. A quantitative analysis by selected ion monitoring of the most intense high mass ions in the respective mass spectrum demonstrated that neither derivative would allow measurements in the low picogram range. Catalytic hydrogenation of the double bonds was performed and the methyl ester trimethylsiyl, methyl ester allyldimethylsilyl and methyl ester tert-butyldimethylsilyl ether derivatives of the reduced compounds were prepared. Saturation of the double bonds increased the gas chromatographic sensitivity for the three derivatives as well as the intensities of the high mass ions in their mass spectra. The high sensitivity that can be obtained by measurement of such high mass ions was demonstrated by quantification of leukotriene B4 in lung tissue samples by selected ion monitoring.
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    Biological Mass Spectrometry 14 (1987), S. 355-355 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biological Mass Spectrometry 14 (1987), S. 363-367 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The indoor air quality of the offices of smokers and nonsmokers was surveyed for volatile organic compound identities and concentrations. These results were examined to determine whether environmental tobacco smoke contamination could be distinguished from airborne pollutants outgassing from other sources. It was not possible to positively attribute volatile organic contaminants to environmental tobacco smoke. It was possible to distinguish between smokers' and nonsmokers' offices by determining airborne nicotine levels.
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    Biological Mass Spectrometry 15 (1988), S. 291-293 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the process of developing a high-sensitivity negative chemical ionization gas chromatographic/mass spectrometric assay for brain and cerebrospinal fluid (CSF) levels of quinolinic acid (QUIN, 2,3-pyridine dicarboxylic acid), (18O4)QUIN was prepared. Its properties as an internal standard were compared with those of the structural isomer 2,4-pyridine decarboxylic acid (2,4-PDC) previously used by others. All oxygen atoms in QUIN were labeled by heating in 3N HCl/(18O)water for 48 h at 80°C. Back-exchange of (18O4)QUIN was prevented during derivatization to an electron-capturing dihexafluoropropanol ester by using trifluoroacetylimidazole as catalyst instead of perfluroacyl anhydrides. When mixtures of QUIN and (18O4)QUIN and/or 2,4-PDC were followed through a procedure to isolate and quantify brain and CSF QUIN, the variability in the ratio of QUIN:2,4-PDC was greater than for QUIN:(18O)QUIN. We conclude that (18O)QUIN is the preferred internal standard in gas chromatographic/mass spectrometric quantification of brain and CSF QUIN, and that (18O)-labeled carboxylic acids may be esterified effectively without back-exchange using acylimidazole reagents.
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    Biological Mass Spectrometry 15 (1988), S. 305-310 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polycyclic peptide antibiotic, Nisin, has been analysed by plasma desorption mass spectrometry using two different sample preparation techniques and two versions of the commercial plasma desorption mass spectrometer, and a prototype with high resolving power. The spectra obtained allow identification of a major component and two minor analogues. Extensive fragmentation is observed in samples prepared by the electrospray technique, whereas only ions indicating the molecular weight are produced when the sample is adsorbed on nitrocellulose.
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  • 88
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxygen-enhanced negative chemical ionization MS is sensitive and specific for the detection of polychlorinated biphenyls (PCBs) without isobaric interferences (qualitative or quantitative) from congeners of higher levels of chlorination. The collision-induced dissociation (CID) spectra of the [M - Cl + O]- ion of 40 PCB congeners have been acquired on a triple quadrupole mass spectrometer.Qualitative relationships between structure of the congener and its CID spectrum suggest that reliable identification of PCB congeners is possible even where capillary column gas chromatographic separation is incomplete. Congeners with hydrogen atoms located para and meta to the biphenyl linkage show most abundant collision-induced loss of HCl, whereas congeners with a penta-chloro phenyl ring show least CID loss of HCl. Congeners IUPAC 105 and 121 have CID spectra suggesting a pathway for sequential loss of HCl and CO neutrals during the collision-induced dissociation of the [M - Cl + O]- ion of these molecules. Unambiguous identification of PCB congeners in natural materials will require a complete set of pure, synthetic PCB congeners: identification problems are illustrated using an extract of Northern Shark (dogfish) liver oil.
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    Biological Mass Spectrometry 15 (1988), S. 369-374 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C enrichment of the carboxyl carbon of leucine was measured by isotope ratio mass spectrometry after conversion to CO2 by reaction with ninhydrin in a Vacutainer and cryogenic purification using the Finnigan MAT Breath Gas Analysis System designed for processing 13C breath test samples. The sources of error which arise with submicromole samples are examined and corrections provided for suboptimal mass spectrometer signals and contamination of the evolved CO2 with CO2 from the reaction medium. The main limitations to the accuracy and precision of the method are not instrumental but arise from the contamination with residual CO2 in the reaction medium, and this sets a lower limit of around 0.25 μmol leucine on the practical sample size. This is an improvement of about five-fold on the previous manual method of CO2 isolation.
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  • 90
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fragmentation pathways of methyl abscisate and its 2E isomer in methane positive ion chemical ionization (PICI) and methane negative ion chemical ionization (NICI) mass spectrometry have been elucidated using isotopically labelled analogues. It is shown that in PICI the most abundant ions are formed by the loss of water, methanol, both methanol and water and of methyl formate. The PICI mass spectrum of methyl 2E abscisate differs significantly in that the loss of water is much less important. In NICI, the most abundant ions from methyl abscisate are due to the molecular anion, [M - H2O]- and [M - CH3OH]-. It is shown, however, that the methyl ester methyl is not lost in this last fragmentation. Two other significant ions contain the side chain and the ring of methyl abscisate, respectively. In contrast, the NICI mass spectrum of methyl 2E abscisate differs principally in showing an abundant loss of a hydrogen atom.
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    Biological Mass Spectrometry 15 (1988), S. 459-460 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Biological Mass Spectrometry 14 (1987), S. 535-541 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A moving belt interface was used to identify budesonide metabolites, obtained from rat and mouse liver incubations, by liquid chromatography/mass spectrometry (LC/MS). The metabolites were separated on a small-bore C18 column with an ethanol/water gradient as mobile phase at a flow rate of 0.2 ml min-1. A spray device was used for deposition of the aqueous solvent on to the belt. Chemical ionization mass spectra were obtained with methane as the reagent gas. Deuterium-labelled budesonide, which was used to facilitate metabolite identification by the isotope cluster technqiue, was found to be slightly separated from the unlabelled analogue on the LC column. Incubations were also performed under 18O2 to elucidate the mechanism of a new metabolic pathway (16α, 17α-acetal splitting) and to confirm the oxidative nature of reactions leading to hydroxylated metabolites. The moving belt LC/MS technique afforded higher sensitivity, and gave more abundant MH+ ions of the compounds studied, than previously found by direct probe mass spectrometry. Phthalate ester background, partly from the polymide belt, complicated the identification of minor metabolites.
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    Biological Mass Spectrometry 15 (1988), S. 99-104 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dehydroepiandrosterone sulphate (DHAS) has been quantified in human blood serum by fast atom bombardment (FAB)/tandem mass spectrometry of immunoadsorption extracts. FAB of DHAS yielded abundant ions corresponding to the intact steroid sulphate; these were selected by a double-focusing mass spectrometer prior to collisionally activated decomposition in a quadrupole collision cell and mass analysis by a quadrupole mass filter. [HSO4]- (m/z 97) was the sole prominent daughter ion. For quantitative analyses the quadrupole mass filter was set to transmit m/z 97 and a narrow-range magnet scan yielded a spectrum of parents, including m/z 367 and 369, corresponding to DHAS and the (2H2)-analogue (used as internal standard), respectively. Serum concentrations by this procedure were in good agreement with data obtained by gas chromatographic/mass spectrometric analyses of DHA heptafluorobutyrate, formed by direct derivatization of the steroid sulphate.
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    Biological Mass Spectrometry 14 (1987), S. 587-588 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Biological Mass Spectrometry 14 (1987), S. 599-602 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the quantification in plasma of CP-55,940, a new non-opiate oral analgetic agent, using capillary gas chromatography/mass spectrometry. After extraction, derivation of the drug and a structural analog internal standard is carried out with trifluoracetyl imidazole. The derivative exhibited excellent gas chrornatographic properties. Electron impact yielded an abundant high mass ion whose monitoring permitted the sensitive and specific determination of CP-55,940 down to 0.5 ng ml-1.
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    Biological Mass Spectrometry 14 (1987), S. 613-616 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the quantification of tulobuterol in human plasma, based upon selective extraction and high resolution capillary gas chromatography-mass spectrometry. The mass spectrometric determination is based on selected ion monitoring of two fragment ions derived from the N,O-heptafluorobutyryl derivatives of tulobuterol and its internal standard, deschlorotulobuterol. The plasma work-up procedure consists of extraction of 1.0 ml alkalinised plasma with dichloromethane, back-extraction into an acidified aqueous phase, followed by a final extraction with dichloromethane after realkalinisation. The method gave interference-free and linear results. The between-assay variability is 4.7% CV at the 3.0 μg l-1 plasma concentration level. The assay permitted quantitative measurements down to 170 ng tulobuterol per litre of plasma and hence provided sufficient sensitivity for quantification of plasma levels after therapeutic doses.
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    Biological Mass Spectrometry 14 (1987), S. 627-632 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In phytochemical and chemotaxonomic research work mass spectrometry plays an outstandingly important role. Using gas chromatography/mass spectrometry (GC/MS) we established the chemotaxa of Tanacetum vulgare L. Chemotypes with essential oils countaining 60-90% of artemisia ketone, carveol, dihydrocarvone, myrtenol, umbellulone, terpinen-4-ol, davanone, and Tagetes species containing various essential oils can be clearly distinguished by their spectra; we examined many variations of Tagetes erecta, T. lucida, T. minuta, T. patula and T. tenuifolia. We have identified α-β-pinene-, 1,8-cineol-, linalool-, camphor-, nerol-, geraniol- and γ-gurjonene as components of Achillea distans L. Injecting the essential oil direct from the oil-secreting organs of T. minuta plants we identified using GC/MS 6-10 and 16% eugenol from the involucral bract and hypsophyll, respectively, as well as β-ocimene, dihydrotagetone, tagetone, Z- and E-ocimenones. In the course of studies on essential fatty acids Borago officinalis and Lappula squarrosa were selected from 70 species of the family Boraginaceae to obtain seed oil as a source of γ-linolenic acid, and for the PG synthesis we isolated several grams of γ-linolenic acid, as well as C18:4, i e. octadecatetraenic acid, from L. squarrosa on the basis of the mass spectra. From the seed oil of Aquilegia vulgaris C18:3 (5) from the oil of Limnanthes dougloasii C20:1 (5) and from the seed oils of Delphinium consolida and of Tropaeolum species (T. majus, T. minus, T. peregrinum) C20:1 (11) fatty acids were identified on the basis of spectra.
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    Biological Mass Spectrometry 15 (1988), S. 659-667 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problem of reproducing electron capture negative ion mass spectra has been addressed by studying parameters that affect negative ion abundance on a Hewlett Packard 5985B mass spectrometer. Parameters affecting negative ion formation in the ion source, such as ion source temperature, pressure, sample concentration and electron energy, were studied in conjunction with the effect of lenses used to extract and transmit ions to the quadruples. From these experiments, it was found that, in addition to ion source temperature, the ion focus potential has the most dramatic effect on the abundance of molecular ions relative to fragment ions like Cl-. With proper control, it was found that the relative abundance of ions from decafluorotriphenylphosphine could be reproduced over a period of one year.
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    Biological Mass Spectrometry 15 (1988), S. 677-679 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Biological Mass Spectrometry 15 (1988), S. 243-247 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 9-hydroxy-2-(U-2H3) methylellipticinium acetate (elliptinium) was synthesized with an isotopic purity of at least 96%. The structure was confirmed by proton nuclear magnetic resonance and direct probe fast atom bombardment mass spectrometry. A mixture of elliptinium and its deuterated analogue was administered intravenously to rats. In urine, after analysis by liquid chromatography/mass spectrometry (LC/MS), unchanged drug and N-acetylcysteinylelliptinium were found. In bile, after ion-pair extraction and LC/MS, the glutathionyl-elliptinium was found in addition to the parent drug and the N-acetylcysteine adduct.
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