Protein Structure Determination

Even with modern supercomputers it is impossible to predict the absolute thermodynamic minimum of an unknown folded protein chain. If the

Fig. B.8.2. Double-stranded antiparallel 0-sheet with intermodular hydrogen bonds (dotted lines) [4].

structures of related proteins with similar sequences are known, homology modeling will produce very good estimates. In recent years conventional structure determination by X-ray crystallography has been complemented by the new NMR NOESY technique used for elucidation of solution structures (K. Wuthrich, Nobel Prize 2002). Although the results from both techniques are often perfectly superimposable, sometimes the structures differ substantially; in addition, flexible tails and protein dynamics can only be seen by NMR. This technique has hitherto been limited to a protein size of <200 kD, but progress is being made swiftly [8].

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