Editing ValidatorDB:Terminology (section)

=Non-standard residue=
With respect to the building blocks of biomacromolecules, '''ValidatorDB''' denotes as ''standard residues'' the 5 standard nucleotides (A, C, G, T, U) together with their 5 common deoxy forms (DA, DC, DG, DT, DU), and the 20 standard amino acids. Validation results for these standard building blocks of biomacromolecules are not included in our database because many tools already cover these.  Additionally, Selenomethionine (MSE) is also considered a ''standard residue'' here due to its extremely high occurrence in the Protein Data Bank (markedly higher than other ligands and non-standard residues), and high incidence of circumstantial inclusion in biomacromolecules (to aid X-ray crystallography experiments). Therefore, '''ValidatorDB''' covers only ''non-standard residues'', i.e., residues which cannot be denoted as ''standard'' by the above definition.