On the complexity of Engh and Huber refinement restraints: the angle τ as example

The angle τ (backbone N—Cα—C) is the most contested Engh and Huber refinement target parameter. It is shown that this parameter is ‘correct’ as a PDB-wide average, but can be improved by taking into account residue types, secondary structures and many other aspects of our knowledge of the biophysical relations between residue type and protein structure.

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