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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature structural & molecular biology 13 (2006), S. 594-602 
    ISSN: 1545-9985
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] SecA is a helicase-like motor that couples ATP hydrolysis with the translocation of extracytoplasmic protein substrates. As in most helicases, this process is thought to occur through nucleotide-regulated rigid-body movement of the motor domains. NMR, thermodynamic and biochemical data show that ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature structural & molecular biology 13 (2006), S. 831-838 
    ISSN: 1545-9985
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Allosteric interactions are typically considered to proceed through a series of discrete changes in bonding interactions that alter the protein conformation. Here we show that allostery can be mediated exclusively by transmitted changes in protein motions. We have characterized the negatively ...
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature structural biology 9 (2002), S. 193-197 
    ISSN: 1072-8368
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Signal propagation in biological systems occurs through a series of inter- and intramolecular events, the precise pathways of which remain elusive in most cases. With respect to protein–DNA interactions in particular, little is known about the association and dissociation reaction pathways. ...
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biomolecular NMR 11 (1998), S. 423-435 
    ISSN: 1573-5001
    Keywords: 13C shieldings ; hemoproteins ; isotope effects ; model compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract 13C NMR spectra of several carbon monoxide (99.7% 13C and 11.8% 18O enriched) hemoprotein models with varying polar and steric effects of the distal organic superstructure and constraints of the proximal side are reported. This enables the 57Fe-13C(O) coupling constants ( $$^{\text{1}} {\text{J}}_{{\text{57}}_{{\text{Fe}}} \_13_{\text{C}} }$$ ), 13C shieldings (δ(13C)), and 18O isotope effects on13 C shieldings (1Δ13C(18O/16O)) to be measured and hence comparisons with hemoproteins, C-O vibrational frequencies and X-ray structural data to be made. Negative polar interactions in the binding pocket and inhibition of Fe/→/CO back-donation or positive distal polar interactions with amide NH groups appear to have little direct effect on $$^{\text{1}} {\text{J}}_{{\text{57}}_{{\text{Fe}}} \_13_{\text{C}} }$$ couplings. Similarly, the axial hindered base 1,2-dimethylimidazole has a minor effect on the $$^{\text{1}} {\text{J}}_{{\text{57}}_{{\text{Fe}}} \_13_{\text{C}} }$$ values despite higher rates of CO desorption being observed for such complexes. On the contrary,13 C shieldings vary widely and an excellent correlation was found between the infrared C-O vibrational frequencies (ν(C-O)) and13 C shieldings and a reasonable correlation with18 O isotope effects on 13C shieldings. This suggests that δ(13C), ν(C-O) and1 Δ13 C(18O/16O) are accurate monitors of the multiple mechanisms by which steric and electronic interactions are released in superstructured heme model compounds. The 13C shieldings of heme models cover a 4.0 ppm range which is extended to 7.0 ppm when several HbCO and MbCO species at different pH values are included. The latter were found to obey a similar linear δ(13 (13C) versus ν(C-O) relationship, which proves that both heme models and heme proteins are homogeneous from the structural and electronic viewpoint. Our results suggest that ν(C-O), δ(13C) and 1Δ13C(18O/16O) measurements reflect similar interaction which is primarily the modulation of π back-bonding from the Fe dπ to the CO π* orbital by the distal pocket polar interactions. The lack of correlation between1 Δ13 C(18O/16O) and crystallographic CO bond lengths (r(C-O)) reflects significant uncertainties in the X-ray determination of the carbon and oxygen positions.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. S57 
    ISSN: 1075-4261
    Keywords: 13C-NMR ; 57Fe-NMR ; ν(C—O) stretching vibration ; ν(Fe—C) stretching vibration ; heme proteins ; heme models ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: 13C- and 57Fe-NMR spectra of several carbon monoxide hemoprotein models with varying polar and steric effects of the distal organic superstructure, constraints of the proximal side, and solvent polarity are reported. The 13C shieldings of heme models cover a 4.0 ppm range that is extended to 7.0 ppm when several hemoglobin CO and myoglobin CO species at different pHs are included. Both heme models and heme proteins obey a similar excellent linear δ(13C) versus ν(C—O) relationship that is primarily due to modulation of π backbonding from Fe dπ to the CO π* orbital by the distal pocket polar interactions. There is no direct correlation between δ(13C) and Fe—C—O geometry. The poor monotonic relation between δ(13C) and ν(Fe—C) indicates that the iron-carbon π bonding is not a primary factor influencing δ(13C) and δ(57Fe). The δ(57Fe) was found to be extremely sensitive to deformation of the porphyrin geometry, and increased shielding by more than 600 ppm with increased ruffling was observed for various heme models of known X-ray structures. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: S57-S69, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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