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  • 1
    Electronic Resource
    Electronic Resource
    31P NMR relaxation measurements of the phosphate backbone of a double stranded hexadeoxynucleotide in solution: determination of the chemical shift anisotropy (1990)
    Springer
    European biophysics journal 18 (1990), S. 347-355 
    Details
    ISSN: 1432-1017
    Keywords: Chemical shift anisotropy ; 31P relaxation ; DNA dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The five phosphates of the deoxynucleotide d(CpGpTpApCpG)2 have been assigned by two-dimensional heteronuclear NMR spectroscopy. The chemical shift anisotropy and correlation time of each phosphate group has been determined from measurements of the spin-lattice, spin-spin relaxation rate constants and the 31P-{1H} nuclear Overhauser enhancement (NOE) at three magnetic field strengths (4.7 T, 9.4 T, and 11.75 T) and two temperatures (288 K and 298 K). As expected, the relaxation data require two mechanisms to account for the observed rate constants, i.e. dipole-dipole and chemical shift anisotropy. At 9.4 T and 11.75 T, the latter mechanism dominates the relaxation, leading to insignificant NOE intensities. The correlation time, chemical shift anisotropy and effective P-H distance were obtained from least-squares fitting to the data. Comparison of the fitted value for the correlation time with that obtained from 1H measurements shows that the molecule behaves essentially as rigid rotor on the nanosecond timescale. Large amplitude motions observed in long segments of DNA are due to bending motions that do not contribute significantly to relaxation in short oligonucleotides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196925
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of internal dynamics of deoxyriboses in the DNA hexamer d(CGTACG)2 by 1H NMR (1989)
    Springer
    European biophysics journal 17 (1989), S. 221-232 
    Details
    ISSN: 1432-1017
    Keywords: Cross relaxation ; DNA dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The conformations and internal dynamics of the deoxyriboses of d(CGTACG)2 have been determined by NMR measurements at 15°C. The conformations of the sugars were determined using coupling constants and time-dependent NOE measurements. The J-splitting patterns of the H1′, H2′ and H2″ resonances show that the sugars exist as mixtures of conformations near C2′ endo (south) and C3′ endo (north). The population of the south conformation was larger for the purines than for the pyrimidines. The overall tumbling time of the molecule in 2H2O was determined from measurements of the cross relaxation rate constant for the H6-H5 vectors of the two cytosine residues. Order parameters were determined for the H1′-H2″, H2′-H2″ and H2′-H3′ vectors from measurements of cross relaxation rate constants, making use of multi-spin analysis of the NOE build up rates. These order parameters are weakly dependent of the base sequence, and except for the terminal Cyt 1 residue, the H2′-H2″ and H2′-H3′ vectors are near unity, indicating the absence of rapid pseudorotation on the nanosecond time scale. However, the order parameter for the H1′-H2″ vector is significantly smaller than expected for rapid pseudorotation indicating the presence of other motions of the sugars. This motion must be about an effective axis parallel to the H2′-H″ vector, and to occur with an angular fluctuation of about 30°. The results show that to obtain highly refined structures for nucleic acids by NMR the effects of spin diffusion and motional averaging cannot be ignored.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00284729
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