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  • 1
    Electronic Resource
    Electronic Resource
    [3 + 1] Cycloaddition: reaction of dichlorogermylene with hexafluoro-2-propanethione 1-adamantylimide (1992)
    s.l. : American Chemical Society
    Organometallics 11 (1992), S. 15-16 
    Details
    ISSN: 1520-6041
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/om00037a008
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  • 2
    Electronic Resource
    Electronic Resource
    Atomic resolution structure of biotin-free Tyr43Phe streptavidin: what is in the binding site? (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 1118-1126 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The streptavidin–biotin system is an example of a high-affinity protein–ligand pair (Ka ∼ 1013 mol−1). The thermodynamic and structural properties have been extensively studied as a model system for protein–ligand interactions. Here, the X-ray crystal structure of a streptavidin mutant of a residue hydrogen bonding to biotin [Tyr43Phe (Y43F)] is reported at atomic resolution (1.14 Å). The biotin-free structure was refined with anisotropic displacement parameters (using the SHELXL97 program package). The high-resolution data also allowed interpretation of side-chain and residue disorder in 41 residues where alternate conformations were refined. The Y43F mutation is unambiguously observed in difference maps, although only a single O atom per monomer is altered. The atomic resolution enabled the identification of 2-methyl-2,4-pentanediol (MPD) molecules in the biotin-binding pocket for the first time. Electron density for MPD was observed in all four subunit binding sites of the tetrameric protein. This was not possible with data at lower resolution (1.8–2.3 Å) for wild-type streptavidin or mutants in the same crystal form using MPD in the crystallization. The impact of MPD binding on these studies is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444999002322
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  • 3
    Electronic Resource
    Electronic Resource
    Relative occupancy, endemism, taxonomic distinctiveness and vulnerability: prioritizing regional conservation actions (1997)
    Springer
    Biodiversity and conservation 6 (1997), S. 211-232 
    Details
    ISSN: 1572-9710
    Keywords: species conservation priorities ; regional approach ; Transvaal mammals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method is presented whereby regional species are scored and ranked in order of regional conservation importance according to a number of different but complementary 'rarity' criteria. Approaches for determining regional occupancy (RO), relative taxonomic distinctiveness (RTD), relative endemism (RE) and relative vulnerability (RV) rankings for regional faunas are proposed. The continuous variable approach and resultant positively skewed 'rarity' scores suggest easy identification of regional priority species. These methods are collectively applied to a regional mammalian fauna in order to prioritize species for conservation action using a regional priority score (RPS). The proposed method is a comparative relational approach aimed at determining which species require the establishment of viable populations within a regional context. The two species afforded highest RPSs for the Transvaal region, South Africa, are Gunning's golden mole Amblysomus gunningi and Juliana's golden mole A. julianae. These two species are true endemics, with geographic ranges completely restricted to the region. Also of high regional conservation importance are the four-toed elephant shrew Petrodromus tetradactylus, pangolin Manis temminckii and aardvark Orycteropus afer. Although these species have low RE scores, they have high RTD and RV scores. The equal weightings given to the four components of 'rarity' ensures that species achieving a high score in any of these categories will be considered for regional priority listing. This approach is simple, explicit and repeatable, circumventing problems of scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018392019594
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  • 4
    Electronic Resource
    Electronic Resource
    Nature reserve selection in the Transvaal, South Africa: what data should we be using? (1996)
    Springer
    Biodiversity and conservation 5 (1996), S. 685-698 
    Details
    ISSN: 1572-9710
    Keywords: reserve selection ; databases ; mammals ; South Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Iterative reserve selection algorithms were applied to two mammal databases, generalized to sixteenth degree grid squares, for the Transvaal region of South Africa. Based on primary point data, 24 grid squares are required to represent all species at least once, while only 13 grid squares are required when based on distribution map data; only two of these grid squares are common to both analyses. As the number of representations per species is increased from one to five, the number of selected grid squares increased to 86 and 71 or 72 respectively, with only 17 of these common to both analyses. These differences in the selection of sites are further reflected in the degree of congruence between selected grid squares and existing conservation areas which is on average 63.3% for grid squares selected from the primary database and only 42.5% for those selected from the distribution map database. These results emphasize the importance of quality data input when evaluating regional reserve networks. Highly generalized distribution map data sets, on the one hand, are extrapolations of limited data sets and contain non-quantifiable levels of false-positives which could have significant implications if used for establishing regional reserve networks. On the other hand, although there are problems associated with the establishment of primary diversity databases, namely data currency and uneven and non-random sampling (leading to false negatives), they remain our most reliable option for assigning conservation value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00051781
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of the New Silanediyldiphosphinite tBu2Si(OPPh2)2 and its Reactions with the Norbornadiene Complexes C7H8M(CO)4 (M = Cr, Mo, W). Crystal Structures of cis-M(CO)4[tBu2Si(OPPh2)2] (M = Cr, Mo) (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 694-698 
    Details
    ISSN: 0044-2313
    Keywords: Silanediyldiphosphinite ; chelate complexes ; synthesis ; structure, multinuclear NMR spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese eines neuen Silandiyldiphosphinits tBu2Si(OPPh2)2 und seine Reaktionen mit den Norbornadien-Komplexen C7H8M(CO)4 (M = Cr, Mo, W). Kristallstrukturen von cis-M(CO)4[tBu2Si(OPPh2)2] (M = Cr, Mo)Silandiyldiphosphinit tBu2Si(OPPh2)2 1 wurde dargestellt. 1 reagiert mit den Norbornadienkomplexen C7H8M(CO)4 (M = Cr, Mo, W) zu sechsgliedrigen Chelaten des Typs cis-M(CO)4[tBu2Si(OPPh2)2] 2-4. Die Kristallstrukturen des Chromkomplexes Cr(CO)4[tBuSi(OPPh2)2] 2 und des Molybdänkomplexes Mo(CO)4[tBuSi(OPPh2)2] 3 wurden bestimmt. Beide kristallisieren triklin (Raumgruppe P1) mit den Zellkonstanten: (2) a = 1 093(3) pm, b = 1 477(5) pm und c = 1 542(5) pm; α = 108.4(2)°, b̃ = 103.87(11)° und b̃ = 104.57(10)°; U = 2.143(12) nm3; Z = 2; (3) a = 1097.8(2) pm, b = 1 483.7(2) pm und c = 1 554.3(2) pm; α = 108.10(1)°, b̃ = 103.956(6)° und γ = 104.213(7)°; U = 2.1899(6) nm3; Z = 2. Beide Komplexe bestehen aus diskreten, leicht verdrillten oktaedrischen Monomeren mit annähernd planaren Chelatringen. Im Gegensatz hierzu wurde bei den Röntgenstrukturanalysen verwandter Komplexe Konformationen ermittelt, die von Twistboot zu „Chaiselongue“ variieren.
    Notes: Silanediyldiphosphinite tBu2Si(OPPh2)2 1 has been synthesised. 1 reacts with the norbornadiene complexes C7H8M(CO)4 (M = Cr, Mo, W) to give six-membered chelate rings of the type cis-M(CO)4[tBu2Si(OPPh2)2] 2-4. The crystal structures of the chromium and molybdenum complexes cis-Cr(CO)4[tBu2Si(OPPh2)2] 2 and cis-Mo(CO)4[tBu2Si(OPPh2)2] 3 have been determined. Both complexes crystallise in the triclinic system (space group P1) with unit cell parameters: (2) a = 1 093(3) pm, b = 1 477(5) pm and c = 1 542(5) pm; α = 108.4(2)°, b̃ = 103.87(11)° and b̃ = 104.57(10)°; U = 2.143(12) nm3; Z = 2; (3) a = 1 097.8(2) pm, b = 1 483.7(2) pm and c = 1 554.3(2) pm; α = 108.10(1)°, b̃ = 103.956(6)° and γ = 104.213(7)°; U = 2.1899(6) nm3; Z = 2. Both 2 and 3 consist of discrete, slightly distorted, octahedral monomers in which the six-membered chelate rings are essentially planar. In contrast, the conformations of the chelate rings found in crystal structures of analogous complexes vary from twist-boat to “chaise longue”.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19956210433
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  • 6
    Electronic Resource
    Electronic Resource
    Dilithium-N,N′-bis(trimethylsilyl)hydrazid und ein Hydrolyseprodukt side-on und end-on an N2-2- und O2-2-gebundene Li-Kationen (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 845-847 
    Details
    ISSN: 0009-2940
    Keywords: Lithium compounds ; Hydrazines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dilithium N,N′-Bis(trimethylsilyl)hydrazide and a Hydrolysis Product: Side-On- and End-On-Coordinated Li Cations to N2-2 and O2-2N,N′-Bis(trimethylsilyl)hydrazine is converted into the dilithium derivative [(Me3Si)2N2Li2] · 2 thf (1) by nBuLi. Compound 1 forms a tetramer which lies on a crystallographic inversion centre. The Li+ ions are found to be end-on to the N—N units and also coordinated by thf, but three Li+ ions are also positioned symmetrically above the N—N bonds. The hydrolysis of 1 in air leads to the formation of [(Me3SiOLi)4 · Li2O2 · LiN(SiMe3)2] · 2 thf (2) which contains four oxide and one peroxide ions. The O2-2 unit is side-on-coordinated by three Li+.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270510
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  • 7
    Electronic Resource
    Electronic Resource
    Reaktionen eines freien Stannaimins und von Basen-stabilisierten Stannylenen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2247-2253 
    Details
    ISSN: 0009-2940
    Keywords: Stannaimine ; Stannylenes ; 1,2-Additions ; [2 + 2] Cycloadditions ; [2 + 3] Cycloaddition ; [2 + 4] Cycloaddition ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of a Free Stannaimine and of Base-Stabilized StannylenesThe free stannaimine A reacts with methyllithium, 2,6-diisopropylaniline, and methyl vinyl ketone to give the corresponding 1,2-addition products (to the Sn—N bond) 2, 3, and 10. With 2,6-diisopropylphenyl isocyanate and benzaldehyde [2 + 2] cycloadditions to the C=O bonds lead to 4 and 5, while with benzonitrile oxide and acroleine [2 + 3] and [2 + 4] cyclo-additions produce 8 and 9. The pyridine adducts bis-[bis(trimethylsilyl)amino]stannylene and -germylene react with aryl azides to give the corresponding derivatives of tri-amino-2-pyridylstannane 11 and -germane 12. Bis[2-pyridyl-bis(trimethylsilyl)methyl]stannylene upon treatment with aryl azides form the 1-aza-8-stannabicyclo[3.2.0]octa-2,4,6-triene systems 13 and 14 via stannaimine intermediates. X-ray structure analyses are presented for 3, 11, and 13.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261013
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  • 8
    Electronic Resource
    Electronic Resource
    Synthese und Kristallstruktur der Spiro-Verbindung [(i-Pr)2P(S)NSiMe3]2SnCl2 (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 951-953 
    Details
    ISSN: 0044-2313
    Keywords: Four-membered Sn—N—P—S-spirocycle ; 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 the Spirocycle [(i-Pr)2P(S)NSiMe3]2SnCl2The reaction of (i-Pr)2P(S)N(SiMe3)2 (1) with SnCl4 in 2:1 ratio yields under elimination of ClSiMe3 the four-membered spirocycle [(i-Pr)2P(S)NSiMe3]2SnCl2 (2). The molecular structure of 2 was investigated by an X-ray structure analysis. Compound 2 crystallises in the monoclinic space group P21, Z = 2, a = 938.1(1), b = 1 424.1(2), c = 1 207.2(1) pm, β = 110.59(1)°, R = 2.05% for 4 102 reflexions.Compound 2 is a spirocycle with two Sn—N—P—S-rings joined at tin. The two rings are in cis-position.
    Notes: Die Reaktion von (i-Pr)2P(S)N(SiMe3)2 (1) mit SnCl4 im Molverhältnis 2:1 ergibt unter Eliminierung von ClSiMe3 die viergliedrige Spiro-Verbindung [(i-Pr)2P(S)NSiMe3]2SnCl2 (2). Die Molekülstruktur von 2 wurde mit Hilfe einer Röntgenstrukturanalyse aufgeklärt. Verbindung 2 kristallsiert in der monoklinen Raumgruppe P21, Z = 2, a = 938,1(1), b = 1 424,1(2), c = 1 207,2(1) pm, β = 110,59(1)°, R = 2,05% für 4 102 Reflexe.Bei Verbindung 2 handelt es sich um eine Spiro-Verbindung mit zwei Sn—N—P—S-Ringen, die über das Zinnatom verknüpft sind. Dabei stehen die Ringe in cis-Stellung zueinander.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19936190524
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  • 9
    Electronic Resource
    Electronic Resource
    Untersuchungen zur Struktur und Reaktivität eines StannaketeniminsProfessor Hans-Friedrich Grützmacher zum 60. Geburtstag gewidmetDiese Arbeit wurde von der Dr.-Otto-Röhm-Gedächtnisstiftung, dem Fonds der Chemischen Industrie und der Deutschen Forschungsgemeinschaft (SFB 247) gefördert. (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 104 (1992), S. 459-461 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19921040419
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  • 10
    Electronic Resource
    Electronic Resource
    [S(NtBu)3]2- - ein zum Sulfit-Ion isoelektronisches, zum Radikalanion oxidierbares, kappenförmiges DianionDiese Arbeit wurde von der Deutschen Forschungsgemeinschaft und dem Fonds der Chemischen Industrie gefördert. Herrn Dr. D. Marsh, Max-Planck-Institut für Biophysikalische Chemie, Göttingen, danken wir für die Aufnahme der ESR-Spektren.Professor Herbert W. Roesky zum 60. Geburtstag gewidmet (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 108 (1996), S. 208-211 
    Details
    ISSN: 0044-8249
    Keywords: Schwefelverbindungen ; Stickstoffverbindungen ; Strukturaufklärung ; Triazasulfit ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19961080219
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