cover illustration Neighboring residues of K58 in the reduced DsbA protein (PDB ID: 1A23) determined by the sphere model (A) and the “full-atom” model (B), respectively. The distance between the Cα atoms of residues K58 and M153 is less than the 9.0 Å's cutoff as was used by previous studies. Therefore, M153 would be considered as a surrounding residue of K58 in the sphere model, although they are actually far apart and separated by other residues. To better describe protein structures, the “full-atom” model takes the size, shape and orientation of amino acids into consideration. Two residues would be defined as structural neighbors only if the minimal distance between the heavy atoms of them is less than 4.5 Å. For further details please see Kang et al., pp. 75-83.