Mueller, P.P.MuellerKopke, S.S.KopkeSheldrick, George M.George M.Sheldrick2018-11-072018-11-072003https://resolver.sub.uni-goettingen.de/purl?gro-2/46619The proper assignment of metal ions in X-ray structures of proteins is not always easy, but in many cases this knowledge can be important, e.g. for an understanding of enzyme mechanism. In this publication, the bond-valence approach is assessed critically. A simplified version, the calcium bond-valence sum (CBVS), is proposed for the convenient analysis of the geometric environment of potential sites with a view to metal-ion assignment. The bond-valence approach is found to be more reliable for structures determined from high-resolution data (1.5 Angstrom or better).journal_article10.1107/S090744490201800012499536000179955400005