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  • 1
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    Hyperuniformity in amorphous silicon [Applied Physical Sciences] (2013)
    National Academy of Sciences
    Details
    Publication Date: 2013-08-14
    Description: We report the results of highly sensitive transmission X-ray scattering measurements performed at the Advanced Photon Source, Argonne National Laboratory, on nearly fully dense high-purity amorphous-silicon (a-Si) samples for the purpose of determining their degree of hyperuniformity. A perfectly hyperuniform structure has complete suppression of infinite-wavelength density fluctuations, or, equivalently,...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 2
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    Biosynthesis of the immunosuppressants FK506, FK520, and rapamycin involves a previously undescribed family of enzymes acting on chorismate [Chemistry] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-03-23
    Description: The macrocyclic polyketides FK506, FK520, and rapamycin are potent immunosuppressants that prevent T-cell proliferation through initial binding to the immunophilin FKBP12. Analogs of these molecules are of considerable interest as therapeutics in both metastatic and inflammatory disease. For these polyketides the starter unit for chain assembly is (4R,5R)-4,5-dihydroxycyclohex-1-enecarboxylic acid derived from the shikimate pathway. We show here that the first committed step in its formation is hydrolysis of chorismate to form (4R,5R)-4,5-dihydroxycyclohexa-1,5-dienecarboxylic acid. This chorismatase activity is encoded by fkbO in the FK506 and FK520 biosynthetic gene clusters, and by rapK in the rapamycin gene cluster of Streptomyces hygroscopicus. Purified recombinant FkbO (from FK520) efficiently catalyzed the chorismatase reaction in vitro, as judged by HPLC-MS and NMR analysis. Complementation using fkbO from either the FK506 or the FK520 gene cluster of a strain of S. hygroscopicus specifically deleted in rapK (BIOT-4010) restored rapamycin production, as did supplementation with (4R,5R)-4,5-dihydroxycyclohexa-1,5-dienecarboxylic acid. Although BIOT-4010 produced no rapamycin, it did produce low levels of BC325, a rapamycin analog containing a 3-hydroxybenzoate starter unit. This led us to identify the rapK homolog hyg5 as encoding a chorismatase/3-hydroxybenzoate synthase. Similar enzymes in other bacteria include the product of the bra8 gene from the pathway to the terpenoid natural product brasilicardin. Expression of either hyg5 or bra8 in BIOT-4010 led to increased levels of BC325. Also, purified Hyg5 catalyzed the predicted conversion of chorismate into 3-hydroxybenzoate. FkbO, RapK, Hyg5, and Bra8 are thus founder members of a previously unrecognized family of enzymes acting on chorismate.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 3
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    Astrocytic purinergic signaling coordinates synaptic networks (2005)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2005-10-08
    Description: To investigate the role of astrocytes in regulating synaptic transmission, we generated inducible transgenic mice that express a dominant-negative SNARE domain selectively in astrocytes to block the release of transmitters from these glial cells. By releasing adenosine triphosphate, which accumulates as adenosine, astrocytes tonically suppressed synaptic transmission, thereby enhancing the dynamic range for long-term potentiation and mediated activity-dependent, heterosynaptic depression. These results indicate that astrocytes are intricately linked in the regulation of synaptic strength and plasticity and provide a pathway for synaptic cross-talk.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pascual, Olivier -- Casper, Kristen B -- Kubera, Cathryn -- Zhang, Jing -- Revilla-Sanchez, Raquel -- Sul, Jai-Yoon -- Takano, Hajime -- Moss, Stephen J -- McCarthy, Ken -- Haydon, Philip G -- New York, N.Y. -- Science. 2005 Oct 7;310(5745):113-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neuroscience, Conte Center for Integration at the Tripartite Synapse, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16210541" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine/*metabolism ; Adenosine A1 Receptor Antagonists ; Adenosine Triphosphatases/antagonists & inhibitors ; Adenosine Triphosphate/analogs & derivatives/metabolism/pharmacology ; Animals ; Astrocytes/drug effects/*physiology ; Cells, Cultured ; Excitatory Postsynaptic Potentials ; Hippocampus/drug effects/physiology ; In Vitro Techniques ; Long-Term Potentiation/drug effects ; Mice ; Mice, Transgenic ; Neuronal Plasticity/drug effects ; Purinergic P1 Receptor Antagonists ; Purinergic P2 Receptor Antagonists ; Receptor, Adenosine A1/metabolism ; Receptors, N-Methyl-D-Aspartate/antagonists & inhibitors/metabolism ; Receptors, Purinergic P1/metabolism ; Receptors, Purinergic P2/metabolism ; Synapses/*physiology ; *Synaptic Transmission/drug effects ; Xanthines/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Functional modulation of GABAA receptors by cAMP-dependent protein phosphorylation (1992)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1992-07-31
    Description: gamma-Aminobutyric acidA (GABAA) receptors are ligand-gated ion channels that mediate inhibitory synaptic transmission in the central nervous system. The role of protein phosphorylation in the modulation of GABAA receptor function was examined with cells transiently transfected with GABAA receptor subunits. GABAA receptors consisting of the alpha 1 and beta 1 or the alpha 1, beta 1, and gamma 2 subunits were directly phosphorylated on the beta 1 subunit by adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase (PKA). The phosphorylation decreased the amplitude of the GABA response of both receptor types and the extent of rapid desensitization of the GABAA receptor that consisted of the alpha 1 and beta 1 subunits. Site-specific mutagenesis of the serine residue phosphorylated by PKA completely eliminated the PKA phosphorylation and modulation of the GABAA receptor. In primary embryonic rat neuronal cell cultures, a similar regulation of GABAA receptors by PKA was observed. These results demonstrate that the GABAA receptor is directly modulated by protein phosphorylation and suggest that neurotransmitters or neuropeptides that regulate intracellular cAMP levels may modulate the responses of neurons to GABA and consequently have profound effects on synaptic excitability.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Moss, S J -- Smart, T G -- Blackstone, C D -- Huganir, R L -- Wellcome Trust/United Kingdom -- New York, N.Y. -- Science. 1992 Jul 31;257(5070):661-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neuroscience, 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/1323140" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Line ; Cells, Cultured ; Colforsin/pharmacology ; Cyclic AMP/*pharmacology ; Electric Conductivity ; Immunosorbent Techniques ; Kinetics ; Mice ; Mutagenesis, Site-Directed ; Neurons/drug effects/physiology ; Peptide Mapping ; Phosphorylation ; Protein Kinases/*metabolism ; Rats ; Receptors, GABA-A/genetics/*physiology ; Recombinant Proteins/physiology ; Transfection ; Zinc/pharmacology ; gamma-Aminobutyric Acid/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
    Electronic Resource
    Electronic Resource
    Intra-oral lactic acid production during clearance of different foods containing various carbohydrates (1997)
    Springer
    European journal of nutrition 36 (1997), S. 191-197 
    Details
    ISSN: 1436-6215
    Keywords: Cooked starch ; diet ; oral breakdown ; glucose ; HPLC analysis ; lactic acid ; oral fluid ; organic acids ; sugars ; saliva ; gekochte Stärke ; Nahrung ; oraler Abbau ; Glukose ; HPLC-Analyse ; Milchsäure ; Mundflüssigkeit ; organische Säuren ; Zucker ; Speichel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Nach dem Genuß von sechs zucker- und/oder stärkehaltigen Nahrungsmitteln (Schokoladenriegel, Kartoffelchips, gefüllter Keks, Würfelzucker, Rosinen und Geleebohnen) wurde der Kohlenhydratabbau und die Säureproduktion im Mund über zwei Stunden verfolgt und analysiert. Jedes Nahrungsmittel wurde an acht Probanden in Zeitintervallen von 30 min untersucht. Die Freisetzung von Glukose und die Bildung von Milchsäure im Mund wurden mittels HPLC-Analyse qualitativ und quantitativ über zwei Stunden verfolgt und statistisch ausgewertet. Innerhalb der ersten 30 Minuten wurde Milchsäure in folgender Rangordnung produziert: (höchster Wert) Rosinen 〉 Schokoladenriegel 〉 Würfelzucker 〉 Geleebohnen 〉 gefüllter Keks 〉 Kartoffelchips (niedrigster Wert); nach 120 Minuten änderte sich diese Rangordnung wie folgt: Kartoffelchips 〉 Geleebohnen 〉 Würfelzucker 〉 Schokoladenriegel 〉 gefüllter Keks 〉 Rosinen. Die Menge der produzierten Milchsäure war linear abhängig von der Menge der von den Speisen freigesetzten Glukose. Gekochte Stärke wurde im Mund über Maltotriose und Maltose zu Glukose abgebaut. Klebrige (zuckerhaltige) Nahrungsmittel (Schokoladenriegel) verlassen die Mundhöhle schneller als Nahrungsmittel, die gekochte Stärke enthalten (Kartoffelchips); letztere produzieren daher über einen längeren Zeitraum (2 h) im Munde mehr Milchsäure.
    Notes: Summary Oral carbohydrate clearance and acid production were monitored over a two hour time period following the ingestion of six foods (chocolate bar, potato chip, oreo cookie, sugar cube, raisin and jelly bean). Each food was evaluated intra-orally in eight volunteers. Oral fluid samples were obtained from each volunteer at 30 min intervals at five different tooth sites using absorbent paper points. The oral fluid samples were analyzed qualitatively and quantitatively for carbohydrates and organic acids using high performance liquid chromatography. Data obtained for each food were averaged and subjected to statistical analysis. The quantity of lactic acid produced 30 min after ingestion was found to be in the following order: (highest) raisin 〉 chocolate bar 〉 sugar cube 〉 jelly bean 〉 oreo cookie 〉 potato chip (least). Two hours after food intake the order had changed significantly: potato chip 〉 jelly bean 〉 sugar cube 〉 chocolate bar 〉 oreo cookie 〉 raisin. A direct linear relationship existed between lactic acid production and the presence of glucose. In foods containing cooked starch prolonged clearance occurs via the intermediate metabolites maltotriose, maltose and glucose. Results indicated that the term ‘stickiness’, when used to label certain foods such as jelly bean and chocolate bar, should be used cautiously. Foods containing only cooked starch or cooked starch and sugars can be considered as ‘sticky’, since glucose arising from their intra-oral degradation contributed to acid production over prolonged periods of time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01611399
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  • 6
    Electronic Resource
    Electronic Resource
    Quantitation of carbohydrate sweeteners and organic acids in human oral fluid using HPLC analysis (1992)
    Springer
    European journal of nutrition 31 (1992), S. 147-154 
    Details
    ISSN: 1436-6215
    Keywords: Sugars ; carbohydrates ; lacticacid ; oralfluid ; HPLC ; glucose ; sucrose ; Zucker ; Kohlenhydrate ; Milchsäure ; Speichel ; HPLC-Analyse ; Glukose ; Saccharose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Eine empfindliche HPLC-Methode wurde für die qualitative und quantitative Analyse von Kohlehydraten und organischen Säuren in Mundflüssigkeiten (Speichel und Zahnplaque) entwickelt. Für die Trennung dieser Verbindungen wurde eine Aminex HPX-87H (Bio-Rad) Chromatographie-Säule verwendet. Alle Komponenten des HPLC-Systems waren mit Edelstahl-Kapillaren verbunden. Die isokratische Elution beider Verbindungs-Klassen erfolgte mit 0,01 n Schwefelsäure. Alle Verbindungen wurden mit einem RI-(Refraktion-Index-) Detektor gemessen. Die Ergebnisse wurden mit einem PC-gestütztem Auswertesystem automatisch gesammelt und integriert. Die zeitbedingte Abnahme der Konzentration von Kohlehydraten im Munde einerseits und die Produktion von organischen Säuren durch Bakterien der Mundhöhle andererseits können mit dieser empfindlichen HPLC-Methode bis zu einer Genauigkeit von 0,1 µg Substanz per Analyse (80 µl) bestimmt werden.
    Notes: Summary A sensitive high performance liquid chromatography (HPLC) assay was developed for the qualitative and quantitative determination of carbohydrate sweeteners and organic acids in oral fluid. To separate these compounds, an ion-moderated partition resin HPLC column (Aminex HPX-87H) was used. All components of the HPLC system were interconnected using stainless steel capillary tubing. Isocratic elution with 0.01 N sulfuric acid provided the profile of both compound classes. The compounds were detected using a refractive index detector. The method employed computerized data collection and integration (Omega-2 system) with a detection sensitivity of 0.1 µg compound per HPLC assay (80 µl). This method is useful in caries research, because it detects minute amounts of sugars and organic acids in oral fluid during clearance studies of various foods in the mouth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01623073
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  • 7
    Electronic Resource
    Electronic Resource
    Plasma oxidation of polymers (1986)
    Springer
    Plasma chemistry and plasma processing 6 (1986), S. 401-416 
    Details
    ISSN: 1572-8986
    Keywords: Plasma oxidation ; polymers ; copolymers ; mechanism ; plasma-developable resists
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The rates of plasma oxidation have been measured for homopolymers of several monomers and for copolymers of methyl methacrylate with styrene and vinyl naphthalene. Our results show that relatively small amounts of the aromatic component in the copolymer convey substantially increased resistance to plasma oxidation. Current knowledge of the mechanisms of plasma oxidation is reviewed and new mechanistic explanations are suggested. The implications for improved design of plasma-developable resists systems are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00565552
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  • 8
    Electronic Resource
    Electronic Resource
    Arrhenius parameters for reactions of oxygen atoms with the fluorinated ethylenesThis paper was presented at the Seventh International Symposium on Fluorine Chemistry at Santa Cruz, California, July 1973. (1974)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 443-452 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Competitive studies of the reactions of ground-state oxygen atoms, generated by mercury-photosensitized decomposition of nitrous oxide, have been carried out with ethylene and all the fluoroethylenes using 2-(trifluoromethyl)-propene as reference compound. From measurements at 25°C and 150°C relative rate constants have been determined and used to calculate the Arrhenius parameters shown in the following table: TextOlefin\documentclass{article}\pagestyle{empty}\begin{document}$$\frac{{A_{{\rm olefin}} }}{{A_{{\rm 2TFMP}} }}$$\end{document}ΔERef\documentclass{article}\pagestyle{empty}\begin{document}$$\frac{{A_{{\rm olefin}} }}{{A_{{\rm C}_{\rm 2} {\rm H}_{\rm 4} } }}$$\end{document}ΔEC2H4CH2—CH21.10-1.18(1.0)(0)CH2—CHF1.030.840.942.02CH2—CF20.711.490.652.67CHF—CHF (cis-)1.231.921.123.10CHF—CHF (trans-)1.400.791.271.97CF2—CHF1.060.000.961.22CF2—CF20.86-3.220.78-2.04ΔERef = Eolefin - E2TFMP and ΔEC2H4 = Eolefin - EC2H4. Units are kJ/mole.The results are compared with corresponding data for other atoms and radicals, and discussed in terms of the electronic changes produced in the double bond by fluorine substitution, and in relation to the nature of the transition state.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550060314
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  • 9
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    Huntingtin-associated protein 1 regulates inhibitory synaptic transmission by modulating  -aminobutyric acid type A receptor membrane trafficking (2004)
    National Academy of Sciences
    Details
    Publication Date: 2004-08-13
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    The biosynthetic gene cluster of the maytansinoid antitumor agent ansamitocin from Actinosynnema pretiosum (2002)
    National Academy of Sciences
    Details
    Publication Date: 2002-06-11
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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