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  • Analytical Chemistry and Spectroscopy  (9)
  • Amino Acid Sequence  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Dynamic NMR: A single operational parameter approach for evaluation of lifetime in an uncoupled, equally populated AB system (1974)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 6 (1974), S. 16-19 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two simple formulae involving only one variable are presented for the simple and rapid estimation of the mean lifetime (τ) of exchange in uncoupled, paripartite AB systems. These formulae are shown to provide τ values comparable to those obtained from total line-shape analysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270060106
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  • 2
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance studies of internal rotation: IVFor Part III, see Ref. 1. - rotational barriers and conformation of phthalic amides (1974)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 6 (1974), S. 20-22 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rotational barriers about the C—N bond of the N,N,N′,N′-tetramethyldiamides of phthalic, isophthalic and terephthalic acids have been determined by the iterative total line shape NMR method. Some evidence about the conformation of these compounds in solution has also been obtained by infrared and dipole moment studies.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270060107
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance studies of internal rotation. VFor Part IV, see Ref. 1. - Rotational barriers of acetylenic amides (1974)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 6 (1974), S. 508-509 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rotational barriers about the C—N bond of the N,N-dimethylamides of propiolic, methylpropiolic and phenylpropiolic acids have been determined by the iterative total line shape nuclear magnetic resonance method.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270060913
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamic NMR: A new intensity ratio for evaluation of lifetime in paripartite A ⇌ B systems (1976)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 8 (1976), S. 132-136 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple formula for evaluation of rates of exchange in paripartite A ⇌ B systems is introduced. It is concerned only with the intensity ratio in a two-site system in much the same way as that of Rogers and Woodbrey, but the new formula is also applicable above the coalescence point of the spectrum. The formula has been applied to the classical case of N,N-dimethyltrichloroacetamide. An error analysis demonstrates that the approximations inherent in the derivation of the new formula lead to smaller errors than do those of Rogers and Woodbrey.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270080306
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  • 5
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance studies of internal rotation - IIIFor Part II, see Ref. 1. Rotational barriers in META- and PARA-substituted N, N-dimethylcinnamamides (1971)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 3 (1971), S. 551-556 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rotational barriers about the C—N bond of eight m- and p-substituted N, N-dimethyl cinnamamides have been determined by the iterative total line shape NMR method. The ΔG298·2-≠ values have been correlated with the substituent constants σ, σn and σ+. By comparison of the results with literature data, some conclusions about the accuracy of the barrier determination as well as the transmittance of polar effects in conjugated amides have been drawn.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270030509
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamic NMR: Field dependence of the coalescence temperature and temperature dependence of T2 Relaxation times in N,N-dimethyltrichloroacetamide (1985)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 23 (1985), S. 529-532 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The field dependence of the 1H and 13C coalescence temperatures in N,N-dimethyltrichloroacetamide has been used to determine the most reliable activation parameters for internal rotation of the amide moiety. The results were found to be in excellent agreement with those obtained earlier by the double-fitting procedure and demonstrate its validity. Direct measurements of the T2 relaxation times of the methyl protons show that T2 depends exponentially on temperature.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260230709
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  • 7
    Electronic Resource
    Electronic Resource
    Diastereoisomers with three neighbouring phenyl groups. XIFor Part X, see Ref. 1. - Hindered phenyl and formylmethylamino group rotations in 3-(formylmethylamino)-1,2,3-triphenylpropyl chlorides (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 564-570 
    Details
    ISSN: 0749-1581
    Keywords: 1H NMR ; Hindered rotation ; Phenyl, formylmethylamino and formyl groups ; 3-Formylmethylamino-1,2,3-triphenylpropyl chlorides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Unusually high free energies of activation for the rotation of phenyl groups, 12.1 and 11.1 kcal mol-1, are observed in the (1R*, 2S*, 3S*) and (1R*, 2R*, 3S*) isomers of 3-(formylmethylamino)-1,2,3-triphenylpropyl chloride, and for the rotation of the formylmethylamino group (11.7 kcal mol-1) in the Z rotamer of the former isomer. These high barriers can be related to the interdependence of the rotation of such large planar groups in the strongly biased preferred conformations. The barriers for rotation of the formyl group are in the usual range (22.5 and 20.6 kcal mol-1) for (1R*, 2S*, 3S*) and (1R*, 2R*, 3S*) isomers, respectively.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260260707
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  • 8
    Electronic Resource
    Electronic Resource
    Dynamic NMR: A new procedure for the estimation of mixing times in the 2D EXSY experiments. A four-site exchange system studied by 1D and 2D EXSY spectroscopy (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 739-744 
    Details
    ISSN: 0749-1581
    Keywords: 1H NMR ; 2D EXSY NMR ; mixing time ; complete lineshape analysis ; double-fit method ; barriers to restricted rotation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure for the estimation of the mixing time between the last two 90° pulses in the classic three-pulse sequence NOESY/EXSY is proposed and tested and some considerations for the treatment of the two-dimensional (2D) 1H NMR exchange spectra are given. The rate constants are thus obtained with reasonable precision. This procedure was followed to obtain the 2D spectra of the model compound α-[bis(dimethylamino)methylene]-4-nitrophenylacetonitrile, which represents a four-site exchange system. The barriers to restricted rotations found in this compound were also determined from one-dimensional (1D) 1H NMR spectra, which were processed with the iterative complete lineshape analysis (CLSA) method. The double-fit approach was incorporated in the CLSA method. It is shown that the results from the 2D dynamic NMR spectral studies corroborate those obtained by the CLSA double-fit method.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330909
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  • 9
    Electronic Resource
    Electronic Resource
    Restricted rotation of the phenyl group in β-hydroxyphosphonates: Dynamic NMR and semiempirical studies (1994)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 639-645 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; 13CNMR ; Dynamic NMR ; β-Hydroxyphosphonates ; Restricted rotation ; Steric effects ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Free energies of activation, ΔG298≠, for the rotation of the phenyl group in the range of 46.06-63.25 kJ mol-1 were observed in some model β-hydroxyphosphonates. These barriers were found to depend on the type of substituents at the phosphorus atom and on the substituents at the β-position with respect to the phenyl ring. The steric origin of this observation is discussed. Dynamic NMR studies were performed in order to determine the activation parameters for the exchange process. For that purpose, variable-temperature 1H and 13C NMR spectra were treated by non-iterative, iterative and iterative double-fit procedures. MNDO, AM1 and PM3 theoretical calculations of the barriers for three of the compounds studied are reported and results are compared with the experiments. It is found that the PM3 results are very close to the experimental data.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260321102
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  • 10
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    Structure of a V3-containing HIV-1 gp120 core (2005)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2005-11-15
    Description: The third variable region (V3) of the HIV-1 gp120 envelope glycoprotein is immunodominant and contains features essential for coreceptor binding. We determined the structure of V3 in the context of an HIV-1 gp120 core complexed to the CD4 receptor and to the X5 antibody at 3.5 angstrom resolution. Binding of gp120 to cell-surface CD4 would position V3 so that its coreceptor-binding tip protrudes 30 angstroms from the core toward the target cell membrane. The extended nature and antibody accessibility of V3 explain its immunodominance. Together, the results provide a structural rationale for the role of V3 in HIV entry and neutralization.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2408531/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2408531/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huang, Chih-chin -- Tang, Min -- Zhang, Mei-Yun -- Majeed, Shahzad -- Montabana, Elizabeth -- Stanfield, Robyn L -- Dimitrov, Dimiter S -- Korber, Bette -- Sodroski, Joseph -- Wilson, Ian A -- Wyatt, Richard -- Kwong, Peter D -- AI24755/AI/NIAID NIH HHS/ -- AI31783/AI/NIAID NIH HHS/ -- AI39429/AI/NIAID NIH HHS/ -- AI40895/AI/NIAID NIH HHS/ -- GM46192/GM/NIGMS NIH HHS/ -- Z99 AI999999/Intramural NIH HHS/ -- New York, N.Y. -- Science. 2005 Nov 11;310(5750):1025-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Vaccine Research Center, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16284180" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Antigens, CD4/chemistry/*metabolism ; Binding Sites ; Crystallization ; Crystallography, X-Ray ; HIV Antibodies/immunology ; HIV Envelope Protein gp120/*chemistry/immunology/metabolism ; HIV-1/*chemistry/immunology/metabolism ; Humans ; Hydrogen Bonding ; Immunodominant Epitopes ; Models, Molecular ; Molecular Sequence Data ; Peptide Fragments/*chemistry/immunology/metabolism ; Protein Binding ; Protein Conformation ; Protein Structure, Tertiary ; Receptors, CCR5/chemistry/metabolism ; Receptors, CXCR4/chemistry/metabolism
    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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