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  • NMR
  • Springer  (12)
  • Elsevier
  • Institute of Physics
  • Wiley
  • 1975-1979  (12)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Molecular motion and interactions in aqueous carbohydrate solutions. III. A combined nuclear magnetic and dielectric-relaxation strategy (1976)
    Springer
    Journal of solution chemistry 5 (1976), S. 33-46 
    Details
    ISSN: 1572-8927
    Keywords: Aqueous ; hydration ; sugar ; carbohydrate ; nuclear magnetic relaxation ; NMR ; dielectric relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A strategy is developed for the complementary use of dielectric and nuclear magnetic relaxation methods to elucidate the molecular dynamics in aqueous solutions of small hydrophilic molecules, and hence determine extents of hydration. The nuclear magnetic relaxation data, as well as characterizing the motional properties of various carbohydrate solutes, is used here to test alternative models for the resolution of the dielectric spectra into their component relaxation processes. This approach results in a much more confident analysis of solvent relaxation properties than has in the past been usual, to yield information relating to the extents of hydration of small sugars and the possible orientation-specific nature of this hydration. It is demonstrated that the dielectric relaxation of the sugar molecules themselves is unequivocally not due to the reorientation of the whole molecule and most likely is dominated by the rotation of hydrate side chain groups (hydroxyls and hydroxymethyl). In proton magnetic relaxation studies of glucose in D2O it is observed that one particular proton (H-1 in the α-form only) is extremely susceptible to inter-molecular proton-proton interactions while the remaining protons are very effectively shielded. This observation is shown to be fully consistent with the conformational and hydration properties of glucose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647179
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular motion and interactions in aqueous carbohydrate solutions. II. Nuclear-magnetic-relaxation studies (1976)
    Springer
    Journal of solution chemistry 5 (1976), S. 17-31 
    Details
    ISSN: 1572-8927
    Keywords: Aqueous ; hydration ; sugar ; carbohydrate ; nuclear-magnetic relaxation ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Nuclear-magnetic-relaxation studies of a range of aqueous mono- and disaccharide solutions are reported. These include17O relaxation of solvent and1H,2H,13C, and17O relaxation of various solutes. The limitations of nuclear-magnetic relaxation for providing direct indications of solvent motions or extents of hydration of these sugars are outlined. In contrast to the solvent studies, the motional properties of the solutes themselves have been reasonably well defined, with1H,2H, and13C studies of the sugar ring C−H groups all indicating very similar rotational correlation times. Shorter correlation times estimated for the −CH2OH and −OH side chains, implying that internal motions make a significant contribution to the relaxation of these groups. Differences in reorientation rates of pentose monosaccharides, hexose monosaccharides, and disaccharides are discussed in terms of molecular size and solvent interactions. In every case examined, the solute NMR rotational correlation time is in serious disagreement with that expected from previous dielectric-relaxation studies. Some of the implications of this discrepancy are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647178
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  • 3
    Electronic Resource
    Electronic Resource
    Self-diffusion and electron spin exchange of hydrophobic probes in dilute solution (1975)
    Springer
    Journal of solution chemistry 4 (1975), S. 797-807 
    Details
    ISSN: 1572-8927
    Keywords: NMR ; ESR ; spin exchange ; self-diffusion ; hydrophobic interaction ; nitroxide ; spin probe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electron spin exchange rate constants have been measured by ESR spectroscopy for a nitroxide spin probe in a number of solvents, including water. The apparent collision rate constants (k c ′ ) calculated from the spin exchange rate constants showed marked deviations from the Smoluchowsky equation (k c ′ η=const), which were greatest in solvents of lowest viscosity. These effects are attributed to inefficiency of the spin exchange process. Self-diffusion coefficients (D) were measured for diamagnetic analogs of the nitroxide spin probe in similar solvent systems by pulsed field gradient NMR spectroscopy. TheD values gave reasonable agreement when corrected for viscosity (Dη=const). Collision rate constants calculated fromD were in good agreement with those measured by ESR in solvents of high viscosity. Thek c ′ value for the spin probe in water was significantly lower than that in isoviscous organic solvents. This effect is discussed in terms of a hydrophobic hydration shell for the spin probe which acts as an additional barrier to collision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00650536
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of pressure and temperature of self-diffusion coefficients in several concentrated deuterium oxide diamagnetic electrolyte solutions (1976)
    Springer
    Journal of solution chemistry 5 (1976), S. 563-574 
    Details
    ISSN: 1572-8927
    Keywords: Self-diffusion ; concentrated electrolyte solutions ; high pressure ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pressure dependences of the self-diffusion coefficients of deuterium oxide in 4.5m solutions of LiCl−D2O and CsCl−D2O (also 7m) and 3.06m CaCl2−D2O have been measured by the NMR spin-echo method at 30°C, 60°C, and 90°C. Shear viscosities and densities of these solutions have also been determined over the same range of experimental conditions. The experimental data show that the diffusion constantD decreases with the increasing structure-making ability of the electrolyte cation Ca+2〉Li+. In contrast, the diffusion coefficient for D2O in the 4.5 and 7m CsCl solutions is equal to that for pure D2O at 30°C but lower at 60°C and 90°C. It has been found that the Stokes-Einstein equation relates well the diffusion coefficients to shear viscosity in these concentrated electrolyte solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647378
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  • 5
    Electronic Resource
    Electronic Resource
    Structural characterization of thermal prebiotic polypeptides (1976)
    Springer
    Journal of molecular evolution 7 (1976), S. 105-110 
    Details
    ISSN: 1432-1432
    Keywords: NMR ; Prebiotic Polypeptides ; Proteinoids ; Polypeptide Thermal Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Thermal polycondensation of amino-acids as a possible prebiotic path of chemical evolution of life has been critically examined. The polymeric materials studied by nmr methods have scarce resemblance to natural peptidic material because β, γ and ε peptide bonds largely predominate over $$\tilde \alpha $$ -peptide bonds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01732469
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  • 6
    Electronic Resource
    Electronic Resource
    Stacking Interactions of nucleobases: NMR-Investigations I. Selfassociation of N6,N9-Dimethyladenine and N6-Dimethyl-N9-Ethyladenine (1975)
    Springer
    European biophysics journal 1 (1975), S. 113-120 
    Details
    ISSN: 1432-1017
    Keywords: Stacking ; selfassociation ; NMR ; Isodesmic Model ; Enthalpy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The selfassociation of N6,N9-dimethyladenine and N6-dimethyl-N9-ethyladenine has been studied by means of NMR technique. The thermodynamic quantities have been calculated using an isodesmic NMR model with three NMR parameters (the monomer shift δM and two complex shifts δ 2 and δ 3). The dependence of the thermodynamic quantities on the NMR parameters is discussed. Special attention is given to the determination of δ M and its temperature dependence. Calculations with δ 3=2·δ 2 and δ M taken independently of temperature result in an average entropy δ S =−17.9±1.8 e.u. for N6,N9-dimethyladenine and δ S =−16.7±1.7 e.u. for N6-dimethyl-N9-ethyladenine and in an average enthalpy δH=−7.2±0.6 kcal· mol−1 for both substances investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00539773
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  • 7
    Electronic Resource
    Electronic Resource
    Stacking interactions of nucleobases: NMR-Investigations II. Selfassociation of purine- and pyrimidine-derivatives (1975)
    Springer
    European biophysics journal 1 (1975), S. 311-318 
    Details
    ISSN: 1432-1017
    Keywords: Stacking ; Selfassociation ; NMR ; Nucleobases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The selfassociation of various purine- and pyrimidine-derivatives in D2O has been studied by means of NMR technique. The thermodynamic quantities have been calculated using an isodesmic NMR model. Among the nucleobases investigated, the adenine-derivatives were found to be most suitable for quantitative determination. A comparison of methylated adenine-derivatives and the pH-dependence of the selfassociation lead to the conclusion, that the stacking associates are stabilized by special van der Waals interactions based, essentially, on the polarizability of the π-electron-system of the associated molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00537644
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  • 8
    Electronic Resource
    Electronic Resource
    1H NMR studies at 360 Mhz of the methyl groups in native and chemically modified basic pancreatic trypsin inhibitor (BPTI) (1977)
    Springer
    European biophysics journal 3 (1977), S. 303-315 
    Details
    ISSN: 1432-1017
    Keywords: NMR ; Proteinase inhibitor ; Protein modification ; Protein structure ; Basic pancreatic trypsin inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract In the 1H NMR spectra obtained at 360 MHz after digital resolution enhancement, the multiplet resonances of the methyl groups in the basic pancreatic trypsin inhibitor (BPTI) were resolved. With suitable double irradiation techniques the individual methyl resonances were assigned to the different types of aliphatic amino acid residues. Furthermore, from pH titration and comparison of the native protein with chemically modified BPTI, the resonance lines of Ala 16 in the active site and Ala 58 at the C-terminus were identified. Potential applications of the resolved methyl resonances as natural NMR probes for studies of the molecular conformations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00535703
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  • 9
    Electronic Resource
    Electronic Resource
    Dynamics of the aromatic amino acid residues in the globular conformation of the basic pancreatic trypsin inhibitor (BPTI) (1976)
    Springer
    European biophysics journal 2 (1976), S. 139-158 
    Details
    ISSN: 1432-1017
    Keywords: NMR ; Protein conformation ; Molecular dynamics ; Proteinase inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary The basic pancreatic trypsin inhibitor (BPTI) was investigated by high resolution1H NMR techniques at 360 MHz. Observation of the amide proton resonances of the polypeptide backbone showed that the globular conformation of BPTI determined by X-ray studies in single crystals is maintained in aqueous solution over the temperature range from 4
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00863706
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  • 10
    Electronic Resource
    Electronic Resource
    Association of sexual hormones with nucleobases in water: NMR-Investigations (1975)
    Springer
    European biophysics journal 1 (1975), S. 319-328 
    Details
    ISSN: 1432-1017
    Keywords: Sexual Hormones ; Nucleobases ; NMR ; Stacking ; Enthalpies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The mixed association of testosterone-sulfate and estradiol-sulfate with several derivatives of nucleobases in D2O has been investigated by means of nuclear magnetic resonance spectroscopy. From, the differences among the chemical shifts of the hormone-protons it is concluded, that the nucleobases in the complexes are located above the center of the steroid molecule. The Β-side of the steroid which is characterized by the axial methyl-groups is directed towards the bases. The enthalpies of mixed association of the hormones with a certain nucleobase are of the same order of magnitude as the enthalpy of selfassociation of this nucleobase (Schimmack et al., to be published). It is suggested that the complexes are stabilized by van-der-Waals forces. This stacking-like interaction is not specific for the male or female sex hormones: no qualitative or quantitative differences have been observed among the complexes of the two hormone-sulfates with the nucleobases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00537645
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