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  • Nucleic acids  (3)
  • Activation  (2)
  • Heterocycles
  • Wiley-Blackwell  (7)
  • Blackwell Publishing Ltd
  • 1965-1969  (7)
  • 1969  (7)
Collection
Publisher
  • Wiley-Blackwell  (7)
  • Blackwell Publishing Ltd
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  • 1965-1969  (7)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 8 (1969), S. 478-482 
    ISSN: 0570-0833
    Keywords: Sesquifulvalenes ; Fulvalene ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heterosesquifulvalenes containing sulfur or oxygen as hetero atom may be prepared, e.g., by condensation of cyclopentadienes with thiopyrones or pyrones in acetic anhydride. Heterosesquifulvalenes containing nitrogen can be obtained from the oxygen compounds by O,N-exchange. The ground state of all these compounds is determined mainly by the nonpolar resonance formula.
    Additional Material: 1 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 8 (1969), S. 711-727 
    ISSN: 0570-0833
    Keywords: tRNA ; Nucleic acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transfer ribonucleic acids (tRNAs)Abbreviations used according to IUPAC-IUB convention: tRNA = transfer ribonucleic acid; tRNAyeast = mixture of tRNAs from yeast; tRNAPhe = phenylalanine specific tRNA; Phe-tRNA = tRNA esterified (“charged”) with Phe; mRNA = messenger RNA; DNA = deoxyribonucleic acid; U = uridine; A = adenosine; C = cytidine; G = guanosine; pA = 5′-adenylic acid; Ap or A- = 3′-adenylic acid; m2′G = 2′-O-methyl guanosine; m7G = 7-methyl guanosine; m22G = N(2)-dimethyl guanosine; other methylated nucleosides are abbreviated analogously; abbreviations of other odd nucleosides are given with Fig. 2; p or - signifies phosphate; RNase = ribonuclease; DEAE = diethylaminoethyl; fMet = N-formayl methionine. occur in all living organisms. In biological protein synthesis they accept activated amino acids which are then transferred to growing peptide chains. With molecular weights lying between 25000 and 30000, tRNAs are easily within the reach of today's physical, chemical, and biochemical methods. The primary structures of several tRNAs as well as some relationships between structure and function have been elucidated. Three-dimensional structure, specificity, and mechanism of action are the subjects of present research efforts.
    Additional Material: 7 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 8 (1969), S. 578-593 
    ISSN: 0570-0833
    Keywords: DNA damage ; Nucleic acids ; Uracil dimers ; Thymine dimers ; Pyrimidines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radiation damage observed when UV and ionizing radiations react on biological objects is caused in many cases by changes in the nucleic acids. Exposure of these compounds to UV radiation in vitro and in vivo leads, inter alia, to dimerization of the pyrimidine bases with formation of cyclobutane derivatives, and to addition of water to the 5,6-double bond of the pyrimidine bases to form derivatives of the 6-hydroxyhydropyrimidine system. The structure of the irradiation products has been established. The dimerization prevents the reduplication of the DNA, and the addition of water appears to be the cause of UV mutations. Ionizing radiation in aqueous solution results e.g. in addition of H and/or HO radicals to the 5,6-double bond of the pyrimidine bases and cleavage of the imidazole ring of the purine bases. The mutations caused by ionizing radiation are probably also due, in part, to the formation of 6-hydroxydihydropyrimidine derivatives.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 8 (1969), S. 962-974 
    ISSN: 0570-0833
    Keywords: Heterocycles ; Aziridinium salts ; Azetidinium salts ; Cycloaddition ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and important reactions of stable aziridinium salts are described in this article. The more stable azetidinium salts, which undergo similar reactions, have also been studied. Polar and dipolar cycloadditions produce heterocycles by ring expansions that can be represented as .
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 8 (1969), S. 438-444 
    ISSN: 0570-0833
    Keywords: Activation ; Activation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nature of the Arrhenius activation energy and frequency factor is reexamined in terms of information now becoming available on the microscopic aspects of collisional reactions. It is pointed out that the activation energy is not generally equal to the threshold for reaction, and its correct conceptual meaning is discussed. The temperature dependence of this quantity and its relation to the threshold energy is developed for a number of representative forms of the energy dependence of the reaction cross-section (excitation function). The uses and limitations of the activation energy as a means of evaluating thresholds, excitation functions, and the presence of tunneling processes are discussed.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 8 (1969), S. 650-659 
    ISSN: 0570-0833
    Keywords: Activation ; Nitrogen fixation ; Nitrogen fixation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several transition metal complexes that can absorb nitrogen from the gas phase are now known. Some of the N2-metal complexes are stable enough to be isolated and their structure elucidated, the N2 molecule remaining chemically inert. In other cases reduction to N3- is possible, but the structure of the reactive intermediate N2-metal complex can be approached only by mechanistic studies. In the stable complexes the nitrogen is bound via a lone pair of electrons in the direction of the molecular axis (“end-on”), in the reducible complexes possibly “edge-on”.
    Additional Material: 12 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 8 (1969), S. 12-20 
    ISSN: 0570-0833
    Keywords: Hereditary DNA alterations ; Mutations ; Chromosomes ; Nucleic acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mutations and recombinations are hereditary alterations of DNA, which is found mainly in the chromosomes of cells. They can occur spontaneously and they can be induced by high energy radiation or by chemicals. This article considers the developments following the discovery of the DNA structure that have led to a molecular explanation of point mutations, of large chromosome alterations, and of recombination. In conclusion, consequences for human society are drawn from the knowledge gained.
    Additional Material: 17 Ill.
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