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  • Inorganic Chemistry  (5)
  • Life Sciences (General)  (5)
  • Lunar and Planetary Science and Exploration  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 107-126 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigations on BenzothiireneThermolysis and photolysis of 1,2,3-benzothiadiazole 10c furnish the products 11c - 15c. 13C-labelling experiments demonstrate that an intermediate benzothiirene 1c is not formed. Isotopomeric reaction products are due to H-shifts. Electron withdrawing ester groups in 6-position enable the ring closure to the substituted benzothiirenes 1d, e on the photochemical but not on the thermal route. A proof is given by an extensive study of the disulfides 14d, e, 14d′, e′, and 14d˝, e˝, generated in the thermolysis, photolysis and by an independent procedure. The results are based on 13C and 1H NMR measurements. Unequivocal signal correlations were made by deuterations and heteronuclear double resonances.
    Notes: Thermolyse und Photolyse von 1,2,3-Benzothiadiazol 10c, liefern die Produkte 11c - 15c. Mit Hilfe der 13C-Markierungstechnik wird gezeigt, daß dabei kein intermediäres Benzothiiren 1c gebildet wird. Isotopomere Reaktionsprodukte gehen auf H-Verschiebungen zurück. Durch elektronenziehende Estergruppen in 6-Position wird der Ringschluß zu den substituierten Benzothiirenen 1d, e zwar nicht bei der Thermolyse, wohl aber bei der photochemischen Reaktionsführung ermöglicht. Zum Nachweis dient eine eingehende Untersuchung der bei Thermolyse, Photolyse und auf einem unabhängigen Weg erhaltenen Disulfide 14d, e, bzw. 14d′, e′ und 14d˝, e˝. Die vorliegenden Ergebnisse basieren auf 13C- und 1H-NMR-Messungen. Zur eindeutigen Signalzuordnung wurden Deuterierungen und heteronucleare Doppelresonanzen herangezogen.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 608 (1992), S. 17-22 
    ISSN: 0044-2313
    Keywords: Barium-crownether complex ; octaselenido cadmate ; synthesis ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Crystal Structure of [Ba(18-Crown-6)(DMF)4][Cd(Se4)2]The title compound has been prepared by the reaction of a DMF-solution of lithium polyselenide with BaSe2 and cadmium acetate in the presence of 18-crown-6, forming black crystals. The compound was characterized by IR spectroscopy and by an X-ray structure determination. Space group P2/a, Z = 4, 5392 observed unique reflections, R = 0.048. Lattice dimensions at -90°C: a = 2021.9(12); b = 1019.8(6); c= 2270.8(14)pm, ß = 106.98(4)°. The structure consists of [Ba(18-crown-6)(DMF)4]2+ ions, in which the barium ions are coordinated by the six oxygen atoms of the crown ether molecule and by four oxygen atoms of the DMF molecules, and of [Cd(Se4)2]2- ions. The cadmium atoms are coordinated by two tetraselenide ions in a chelating fashion.
    Notes: Die Titelverbindung entsteht in Form schwarzer Kristalle bei der Einwirkung einer Lithiumpolyselenidlösung auf Bariumdiselenid und Cadmiumacetat in Dimethylformamid in Gegenwart von 18-Krone-6. Die Verbindung wurde durch das IR-Spektrum und eine röntgenographische Strukturanalyse charakterisiert. Raumgruppe P2/a, Z = 4, 5392 beobachtete unabhängige Reflexe, R = 4,8%. Gitterabmessungen bei -90°C: a = 2021,9(12); b = 1019,8(6); c = 2270,8(14) pm, ß = 106,98(4)°. Die Struktur ist aufgebaut aus [Ba(18-Krone-6)(DMF)4]2+-Ionen, in denen die Bariumionen von den sechs Sauerstoffatomen des Kronenethers und von vier O-Atomen der DMF-Moleküle koordiniert sind, und [Cd(Se4)2]2- -Anionen. In diesen sind die Cadmiumatome von zwei Tetraselenidionen chelatartig umgeben.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 608 (1992), S. 173-183 
    ISSN: 0044-2313
    Keywords: Titanium ; zirconium ; hafnium ; cobalt carbonyl derivatives ; preparation ; i.r. ; 1H n.m.r.spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Titanium-, Zirconium- und Hafniumderivate von CobaltcarbonylenBimetallische und trimetallische Verbindungen mit M-Co-Bindungen (M = Ti, Zr, Hf) werden erhalten durch Reaktionen von R41-Derivaten (R1 = PhCH2; R22N; R2 = Me, Et) mit HCo(CO)4 (A) bzw. durch Umsetzung von R31MX-Derivaten (X = CI, Br; R1 = PhCH2, R22N und R3O; R3 = i-Pr, n-Bu) mit Na[Co(CO)4] (B). Dabei wurden Verbindungen des Typs R31MCo(CO)4 mit R1 = PhCH2, R2)2N und solche des typs R21M[Co(CO)4]2 mit R1 = PhCH2 nach den Methoden A und B gewonnen während (R3O)4-n Ti[Co(Co)4]n-Derivate (n = 1,2) nur gemäß Methode B zugängig waren.Phosphan- und Phosphitderivate der angeführten Verbindungen wurden erhalten bei Substitution von jeweils einer CO-Gruppe durch PR34-Liganden bzw. durch Reaktion von HCo(CO)3(PR34 mit R41M Verbindungen. Der Einfluß der Substituenten R1 und PR34 auf die Stabilität der Verbindungen wird diskutiert.
    Notes: Bimetallic and trimetallic compounds containing unsupported bonds of subgroup 4 metals (M = Ti, Zr, Hf) and Co were prepared by hydride elimination (A) from R41M derivatives (R1 = PhCH2; R22N; R2 = Me, Et)) and by salt elimination (B) from R31MX (X = Cl, Br; R.1 = PhCH2, R22N and R3O; R3= i-Pr, n-Bu)) by reaction with HCo(CO)4 and Na[Co(CO)4], respectively. Compounds R31MCo(CO)4 with R1 = PhCH2, R21M[Co(CO)4]2 R.1 = PhCH2, were prepared both by methods A and B, while (R3O)4-n Ti[Co(Co)4]n (n = 1, 2) compounds were obtained by reaction B. Several tertiary phosphine and phosphite derivatives of the former two types were obtained by substitution of a carbonyl group by PR34 ligand or by A type reaction of HCo(CO)3(PR34 with R41M compounds.
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  • 4
    ISSN: 0044-2313
    Keywords: Mixed polyselenido complexes of zinc/tungsten, Mercury/tungsten ; crystal structures ; FIR spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Syntheses and Crystal Structures of the Polyselenido Complexes (PPh4)6[M(Se4)2]2[WSe4] · DMF with M = Zinc and MercuryThe title compounds have been prepared by the reactions of the acetates of zinc and mercury, respectively, with excess (PPh4)2 WSe4 in boiling dimethylformamide, forming black-red single crystals. According to the X-ray structure determinations both compounds crystallize isotypically in the space group 12/a with four formula units per unit cell. (PPh4)6[Zn(Se4)2]2[WSe4] · DMF: a = 2888.1(6), b = 1740.3(2), c = 2893.9(4) pm, β = 90.47(1)°. 3230 observed unique reflections, R = 0.009.(PPh4)6[Hg(Se4)2]2[WSe4] · DMF: a = 2891.8(5), b = 1738.0(4), c = 2920.1(5) pm, β = 90.29(2)°. 2978 observed unique reflections, R = 0.115%.The compounds consist of PPh4+ ions, spirocyclic octaseleno metallates [M(Se4)2]2-, tetrahedral WSe42-ions, and disordered DMF Molecules.
    Notes: Die Titelverbindungen entstehen in Form schwarz-roter Einkristalle beim Erhitzen der Acetate von Zink und Quecksilber mit überschüssigem (PPh4)2 WSe4 in Dimethylformamid-Lösungen. Nach den Röntgenstrukturanalysen kristallisieren die Verbindungen isotyp in der Raumgruppe I2/a mit vier Formeleinheiten pro Elementarzelle. (PPh4)6[Zn(Se4)2]2[WSe4]· DMF: a = 2888,1(6), b = 1740,3(2), c = 2893,9(4) pm, β = 90,47(1)°. 3230 beobachtete unabhängige Reflexe, R = 9,9%.(PPh4)6[Hg(Se4)2]2[WSe4] · DMF: a = 2891,8(5), b = 1738,0(4), c = 2920,1(5) pm, β = 90,29(2)°. 2978 beobachtete unabhängige Reflexe, R = 11,5%.Die Verbindungen bestehen aus PPh4 +-Ionen, spirocyclischen Octaselenometallaten [M(Se4)2]2-, tetraedrischen WSe42- Ionen und eingelagerten, fehlgeordneten DMf-Molekülen.
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  • 5
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Reaction of Tin Tetrachloride with Hexakis(trimethylsilyl)-1,4-benzdiamidine. Crystal Structures of C6H4[C(NSiMe3)2SnCl3 · CH3CN]2 and [Na-benzo-15-crown-5]2SnCl6The bis-amidinato complex C6H4[C(NSiMe3)2SnCl3 · CH3CN]2 (1) has been prepared by the reaction of tin tetrachloride with hexakis(trimethylsilyl)-1,4-benzdiamidine in the presence of acetonitrile, forming colourless, moisture sensitive crystals, which easily release the coordinated acetonitrile in vacuo. With sodium fluoride 1 reacts in acetonitrile solution in the presence of benzo-15-crown-5 forming [Na-benzo-15-crown-5]2SnCl6 (2). 1 and 2 are characterized by IR spectroscopy as well as by X-ray structure determinations.C6H4[C(NSiMe3)2SnCl3 · CH3CN]2 (1). Space group P21/c, Z = 2, 1700 observed unique reflexions, R = 0.045. Lattice dimensions at 19°C: a = 818.6, b = 1 838.2, c = 1 484.1 pm, β = 96.58°. 1 forms monomeric centrosymmetric molecules with the amidinato groups in 1,4-position of the C6H4 ring. The tin atoms are sixfold coordinated by two nitrogen atoms of the Amidinato chelate (Sn—N 217.2, 215.9 pm), by three chlorine atoms and by the nitrogen atom of the Acetonitrile molecule (Sn—N 244.0 pm).[Na-Benzo-15-Krone-5]2SnCl6 (2): Space group P21/C, Z = 2, 2585 observed unique reflexions, R = .032. Lattice dimensions at 19°C: a = 963.1; b = 946.6; c = 2082.6 pm; β = 101,79°. 2 centrosymmetric Ion triple with the tin atom of the SnCl62- unit in the symmetry center. The sodium ions are sevenfold coordinated by five oxygen atoms of the crown ether molecule, as well as by two chlorine atoms of the SnCl62- ions with Na…Cl bond length of 300.4 and 304.6 pm, respectively.
    Notes: Der Amidinatokomplex C6H4[C(NSiMe3)2SnCl3 · CH3CN]2 (1) wurde durch Reaktion von Zinntetrachlorid mit Hexakis(trimethylsilyl)-1,4-benzdiamidin in Gegenwart von Acetonitril hergestellt. 1 bildet farblose, feuchtigkeitsempfindliche Kristalle, die im Vakuum das koordinierte Acetonitril leicht abgeben. Mit Natriumflorid reagiert 1 in Acetonitrillösung in Gegenwart von Benzo-15-Krone-5 unter Bildung von [Na-Benzo-15-Krone-5]2SnCl6 (2). 1 und 2 werden durch ihre IR-Spektren und durch röntgenographische Kristallstrukturanalysen charakterisiert.C6H4[C(NSiMe3)2SnCl3 · CH3CN]2 (1): Raumgruppe P21/c, Z = 2, 1700 beobachtete unabhängige Reflexe, R = 4,5%. Die Gitterkonstanten bei 19 °C: a = 818,6; b = 1 838,2; c = 1 484,1 pm; β = 96,58°. 1 bildet monomere, zentrosymmetrische Moleküle mit den Amidinatogruppen in 1,4-Stellung des C6H4-Ringes. Die Zinnatome sind sechsfach koordiniert durch die beiden N-Atome des Amidinatochelats (Sn—N 217,2; 215,9 pm), durch drei Chloratome und durch das N-Atom des Acetonitrilmoleküls (Sn—N 244,0 pm).[Na-Benzo-15-Krone-5]2SnCl6 (2): Raumgruppe P21/c, Z = 2, 2585 beobachtete unabhängige Reflexe, R = 3,2%. Die Gitterkonstanten bei 19°C: a = 963,1; b = 946,6; c = 2082,6 pm; ° = 101,79°. 2 bildet zentrosymmetrische Ionentripel mit dem Zinnatom des SnCl62--Ions auf dem Symmetriezentrum. Die Natriumionen sind siebenfach koordiniert durch die fünf O-Atome der Kronenethermoleküle und durch zwei Cl-Atome des SnCl62--Anions mit Na…Cl-Abständen von 300,4 bzw. 304,6 pm.
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  • 6
    Publication Date: 2011-08-24
    Description: Periplasmic binding proteins from E. coli undergo large conformational changes upon binding their respective ligands. By attaching a fluorescent probe at rationally selected unique sites on the protein, these conformational changes in the protein can be monitored by measuring the changes in fluorescence intensity of the probe which allow the development of reagentless sensing systems for their corresponding ligands. In this work, we evaluated several sites on bacterial periplasmic sulfate-binding protein (SBP) for attachment of a fluorescent probe and rationally designed a reagentless sensing system for sulfate. Eight different mutants of SBP were prepared by employing the polymerase chain reaction (PCR) to introduce a unique cysteine residue at a specific location on the protein. The sites Gly55, Ser90, Ser129, Ala140, Leu145, Ser171, Val181, and Gly186 were chosen for mutagenesis by studying the three-dimensional X-ray crystal structure of SBP. An environment-sensitive fluorescent probe (MDCC) was then attached site-specifically to the protein through the sulfhydryl group of the unique cysteine residue introduced. Each fluorescent probe-conjugated SBP mutant was characterized in terms of its fluorescence properties and Ser171 was determined to be the best site for the attachment of the fluorescent probe that would allow for the development of a reagentless sensing system for sulfate. Three different environment-sensitive fluorescent probes (1,5-IAEDANS, MDCC, and acylodan) were studied with the SBP171 mutant protein. A calibration curve for sulfate was constructed using the labeled protein and relating the change in the fluorescence intensity with the amount of sulfate present in the sample. The detection limit for sulfate was found to be in the submicromolar range using this system. The selectivity of the sensing system was demonstrated by evaluating its response to other anions. A fast and selective sensing system with detection limits for sulfate in the submicromolar range was developed. Copyright 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 517-526, 2002.
    Keywords: Life Sciences (General)
    Type: Biotechnology and bioengineering (ISSN 0006-3592); Volume 78; 5; 517-26
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  • 7
    Publication Date: 2011-08-24
    Description: With recent advances in plant biotechnology, transgenic plants have been targeted as an inexpensive means for the mass production of proteins for biopharmaceutical and industrial uses. However, the current plant purification techniques lack a generally applicable, economic, large-scale strategy. In this study, we demonstrate the purification of a model protein, beta-glucuronidase (GUS), by employing the protein calmodulin (CaM) as an affinity tag. In the proposed system, CaM is fused to GUS. In the presence of calcium, the calmodulin fusion protein binds specifically to a phenothiazine-modified surface of an affinity column. When calcium is removed with a complexing agent, e.g., EDTA, calmodulin undergoes a conformational change allowing the dissociation of the calmodulin-phenothiazine complex and, therefore, permitting the elution of the GUS-CaM fusion protein. The advantages of this approach are the fast, efficient, and economical isolation of the target protein under mild elution conditions, thus preserving the activity of the target protein. Two types of transformation methods were used in this study, namely, the Agrobacterium-mediated system and the viral-vector-mediated transformation system. Copyright 2002 Elsevier Science (USA).
    Keywords: Life Sciences (General)
    Type: Protein expression and purification (ISSN 1046-5928); Volume 25; 1; 195-202
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  • 8
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The architecture of NASA's program of robotic Mars exploration missions received an intense scrutiny during the summer months of 1998. We present here the results of that scrutiny, and describe a list of Mars exploration missions which are now being proposed by the nation's space agency. The heart of the new program architecture consists of missions which will return samples of Martian rocks and soil back to Earth for analysis. A primary scientific goal for these missions is to understand Mars as a possible abode of past or present life. The current level of sophistication for detecting markers of biological processes and fossil or extant life forms is much higher in Earth-based laboratories than possible with remotely deployed instrumentation, and will remain so for at least the next decade. Hence, bringing Martian samples back to Earth is considered the best way to search for the desired evidence. A Mars sample return mission takes approximately three years to complete. Transit from Earth to Mars requires almost a single year. After a lapse of time of almost a year at Mars, during which orbital and surface operations can take place, and the correct return launch energy constraints are met, a Mars-to-Earth return flight can be initiated. This return leg also takes approximately one year. Opportunities to launch these 3-year sample return missions occur about every 2 years. The figure depicts schedules for flights to and from Mars for Earth launches in 2003, 2005, 2007 and 2009. Transits for less than 180 deg flight angle, measured from the sun, and more than 180 deg are both shown.
    Keywords: Lunar and Planetary Science and Exploration
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  • 9
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    In:  Other Sources
    Publication Date: 2018-06-08
    Keywords: Lunar and Planetary Science and Exploration
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  • 10
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    Publication Date: 2018-06-08
    Description: NASA's Mars Surveyor Program (MSP) will launch two mission to the red planet about every 26 months (determined by energy considerations) from 1996 through 2005 at an annual cost of $100 million dollars per year (excluding the launch vehicles). Mars Global Survey (1996) and Mars Surveyor 98 are described in other papers. This paper will focus on the planning that is under way for the MSP missions to be launched in 2001 and beyond.
    Keywords: Lunar and Planetary Science and Exploration
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