Tools to assist determination and validation of carbohydrate 3D structure data.

The frequency of glycosylated protein 3D structures in the Protein Data Bank (PDB) is significantly lower than the proportion of glycoproteins in nature, and if glycan 3D structures are present, then they often exhibit a large degree of errors. There are various reasons for this, one of which is a comparably low support of carbohydrates in software tools for 3D structure determination and validation. This chapter illustrates the current features that assist crystallographers with handling glycans during 3D structure determination in Coot and CNS and with validation of the results.