Perturbations of chemical shifts

Fig. 3.53 Stereo plot of the membrane-bound conformation of (a) SK. F96079 (11) and (b) SK. F 96464 (12), consistent with the intermol-ecular NOEs and ring current perturbation of chemical shifts, (c) A hypothetical complex between a DMPC molecule and SK. F 96464 (12),...

Solvent accessibility of native and mutant HiPIPs has been determined by multinuclear NMR methods, in particular, by use of the H/ exchange rates of backbone amide protons, evaluated by HSQC experiments, and from the isotopic perturbation of chemical shifts of labeled native and mutant HiPIPs (43, 149). 

Fig. 2 Chemical shift perturbation and chemical shift mapping, (a) Portions of the [15N, 1H]-HSQC spectra of Bcf-xL recorded in absence (black) and in presence of each of the four molecules (in colors). Resonance assignments for amino acid residues that exhibit large shifts are reported, (b) Structure of Bc1-Xl in complex with the BH3 peptide from Bak (PDB code 1BXL) showing the chemical shift changes in Bcl-xL upon ligand binding (blue, large shits yellow, no shifts the Bak peptide is reported in cyan). Adapted from [48]...

The deuterium isotope effects on chemical shift consists of intrinsic isotope effect (direct perturbation of the shielding of X atom) and equilibrium isotope effect (perturbation of the equilibrium caused by the isotopic substitution). The values of deuterium isotope effects are to some extent independent of chemical shifts and allow determination of the mole fraction of the forms in equilibrium. 

The coupling of the GPC spin column/ESI-MS screening results with NMR (2D HSQC) is a powerful method for confirming that the non-covalent binders identified by the MS experiments truly bind at the predicted active site by observing NMR chemical shift perturbations in the vicinity of the protein active site [1, 15]. In contrast, the absence of chemical shift perturbations or a random distribution of chemical shift changes on the protein surface would imply a lack of an interaction of the compound with the protein or potentially the existence of non-specific binding. The development of the GPC spin column/MS/NMR assay... 

XYZ systems of 260 and 261 and found that the introduction of a methyl group perturbs the chemical shifts of the benzene ring protons some distance away. The transmission of this effect through many bonds led to the conclusion that these systems possessed aromatic character.341 The analysis of the ABCD system of 254b has also been performed by Hall.452... 

The signal exhibited by a particular nucleus in an NMR experiment is dependent upon two perturbations the chemical shift, and the effects of spin-spin coupling. 

McCoy, M. A. and Wyss, D. F. (2000). Alignment of weakly interacting molecules to protein surfaces using simulations of chemical shift perturbations. J. Biomol. NMR 18, 189-198. 

Fig. 15. Schematic illustration of the design of SAR by NMR. The HSQC spectra yield a single peak for each backbone amide proton in the target protein. Ligands that bind to the protein perturb the chemical shifts of localized regions of the protein, thus identifying the binding site. When two proximate binding ligands are identified, they are chemically linked to produce a tight-binding lead molecule.

Chemical-Shift Perturbation. Chemical shift is a function of the chemical (and hence magnetic) environment that individual nuclei experience. Perturbations of chemical... 

Analysis of Chemical Shift Perturbations in Protein-DNA Complexes... 

Assuming then that the chemical shifts also represent the relative populations of the Bj and Bn states in the HP-0 complexes, we can calculate the fractional populations by assuming a simple two-state model. A plot of chemical shifts (and Bij Bn) populations vs. sequence for several of the operator complexes is shown in Figure 3. Note as expected for the very similar perturbation in P chemical shifts in the 01 wild type and Y7I mutant headpiece complexes, the pattern of sequence-specific variation of P chemical shifts in the two complexes is very similar (Figure 3A). However, in the lac 02 mutant operator-headpiece complex several of the phosphates are significantly perturbed from the phosphate ester populations in the 01-HP complex. Phosphates such as p6, p8 and pll in the 02 complex are apparently constrained to a Bj conformation (Figure 3B pi5 is also shifted to a more B/-type state). 

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