Nuclear Overhauser effect structural restraints

The structure determination of biopolymers using NMR spectroscopy usually involves interactions of protons[216,33. Typically, interactions of protons (nuclear Overhauser effect, NOE) that are close in space but separated by several subunits of the biopolymer are used to establish the folding of the backbone. Distance restraints are then used to compute a structure which is checked by back-calculation of the NOE spectra and comparison with experimental results 361. For large and highly flexible systems molecular dynamics is invaluable for scanning the conformational space. 

The elucidation of the scalar coupling network by the correlation experiments is, apart from small molecules, not sufficient for the unambiguous, sequential and stereo-specific assignment. The complementary information of spatially adjacent protons is obtained via cross-relaxation experiments, the laboratory-frame nuclear Overhauser enhancement spectroscopy (NOESY) and the rotating-frame nuclear Overhauser effect spectroscopy (ROESY). These experiments provide also the distance restraints for the structure determination and help to recognize exchange processes. 

L. Nilsson, G. M, Close, A, M. Gronenbom, A. T. Brunger, and M. Karplus,/. Mol. Biol., 188,455 (1986). Structure refinement of Oligonucleotides by Molecular Dynamics with Nuclear Overhauser Effect Interproton Distance Restraints Application to 5 d(CGTACG)2. 

Structure Refinement of Oligonucleotides by Molecular Dynamics with Nuclear Overhauser Effect Interproton Distance Restraints Application to 5 d(CGTACG). 

Basic data obtained from NMR studies consist of distance and torsion angle restraints. Once resonances have been assigned, nuclear Overhauser effect (NOE) contacts are selected and their intensities are used to calculate interproton distances. Information on torsion angles are based on the measurement of coupling constants and analysis of proton chemical shifts. Together, this information is used to formulate a nonlinear optimization problem, the solution of which should provide the correct protein structure. Typically, a hybrid energy function of the following form is employed ... 

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