Open AccessPlacement of molecules in (not out of) the cell
Author(s) -
Dauter Zbigniew
Publication year - 2013
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444912044794
Subject(s) - protein data bank (rcsb pdb) , protein data bank , symmetry operation , crystallography , unit (ring theory) , symmetry (geometry) , crystal structure , macromolecule , crystal (programming language) , group (periodic table) , space (punctuation) , computer science , chemistry , mathematics , physics , protein structure , stereochemistry , geometry , quantum mechanics , nuclear magnetic resonance , biochemistry , mathematics education , programming language , operating system
To uniquely describe a crystal structure, it is sufficient to specify the crystal unit cell and symmetry, and describe the unique structural motif which is repeated by the space‐group symmetry throughout the whole crystal. It is somewhat arbitrary how such a unique motif can be defined and positioned with respect to the unit‐cell origin. As a result of such freedom, some isomorphous structures are presented in the Protein Data Bank in different locations and appear as if they have different atomic coordinates, despite being completely equivalent structurally. This may easily confuse those users of the PDB who are less familiar with crystallographic symmetry transformations. It would therefore be beneficial for the community of PDB users to introduce standard rules for locating crystal structures of macromolecules in the unit cells of various space groups.