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  • 1
    Electronic Resource
    Electronic Resource
    Water Exchange Filter (WEX Filter) for Nuclear Magnetic Resonance Studies of Macromolecules (1994)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 116 (1994), S. 11982-11984 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00105a044
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Separation of intramolecular NOE and exchange peaks in water exchange spectroscopy using spin-echo filters (1996)
    Springer
    Journal of biomolecular NMR 7 (1996), S. 77-82 
    Details
    ISSN: 1573-5001
    Keywords: Water exchange ; NOE ; Pulsed field gradients ; Macromolecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A technique for separating intramolecular NOE and solvent-proton exchange peaks in exchange spectroscopy is demonstrated. This method utilizes the large differences in relaxation and coupling properties of water and macromolecules to separate the two effects. The spin-echo filter consists of a water-frequency selective 90° pulse followed by a spin-echo sequence. If the echo time is sufficiently long, protein resonances (e.g. CαH protons) excited by the selective pulse are removed due to their much shorter T2 values and J-coupling evolution. By combining the filter with exchange spectroscopy (EXSY) or water exchange (WEX) filter experiments, exchange peaks can be selectively observed. In this paper the filter is combined with a modified version of the WEX filter (WEX II filter) with 1D and 2D detection and applied to a zinc finger peptide and to staphylococcal nuclease, allowing estimation of the contribution of intramolecular NOEs to the exchange spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190459
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  • 3
    Electronic Resource
    Electronic Resource
    Accurate Quantitation of Water-amide Proton Exchange Rates Using the Phase-Modulated CLEAN Chemical EXchange (CLEANEX-PM) Approach with a Fast-HSQC (FHSQC) Detection Scheme (1998)
    Springer
    Journal of biomolecular NMR 11 (1998), S. 221-226 
    Details
    ISSN: 1573-5001
    Keywords: CLEANEX-PM ; hydrogen exchange ; NOE ; protein ; pulsed field gradients ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Measurement of exchange rates between water and NH protons by magnetization transfer methods is often complicated by artifacts, such as intramolecular NOEs, and/or TOCSY transfer from Cα protons coincident with the water frequency, or exchange-relayed NOEs from fast exchanging hydroxyl or amine protons. By applying the Phase-Modulated CLEAN chemical EXchange (CLEANEX-PM) spin-locking sequence, 135°(x) 120°(-x) 110°(x) 110°(-x) 120°(x) 135°(-x) during the mixing period, these artifacts can be eliminated, revealing an unambiguous water-NH exchange spectrum. In this paper, the CLEANEX-PM mixing scheme is combined with Fast-HSQC (FHSQC) detection and used to obtain accurate chemical exchange rates from the initial slope analysis for a sample of 15N labeled staphylococcal nuclease. The results are compared to rates obtained using Water EXchange filter (WEX) II-FHSQC, and spin-echo-filtered WEX II-FHSQC measurements, and clearly identify the spurious NOE contributions in the exchange system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008276004875
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  • 4
    Electronic Resource
    Electronic Resource
    Measurement of water-amide proton exchange rates in the denatured state of staphylococcal nuclease by a magnetization transfer technique (1997)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 28 (1997), S. 325-332 
    Details
    ISSN: 0887-3585
    Keywords: hydrogen exchange ; denatured state ; staphylococcal nuclease ; NMR ; magnetization transfer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The rates of hydrogen exchange were measured in a “physiological” denatured state of staphylococcal nuclease using a NMR magnetization transfer experiment suitable for the measurement of exchange rates faster than 0.5 s-1. The results are compared with predicted exchange rates (kex) for the random coil state (Bai et al., Proteins 17:75-86, 1993). No protection factors (· predicted rate/measured rate) larger than 2.4 were observed, consistent with other NMR data which strongly suggest only small amounts of residual secondary structure in this denatured state. Systematically low protection factors (0.51 · 0.23) were found for Asp and Glu residues, while high protection factors were observed for Gly (1.60 · 0.60). We conclude that the predicted exchange rates (kex) may have an uncertainty of 2- to 3-fold. Thus, for denatured proteins only protection factors with a value of 5 or larger can be assigned structural significance. These results also demonstrate that multidimensional magnetization transfer NMR techniques are powerful tools in this research field due to its ability to measure rapidly exchanging protons (·05 s-1) with high accuracy. Proteins 28:325-332, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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