You can search an up-to-date database of nonredundant protein chains while selecting chains based on the R value and resolution and filtering residues based on their average B factor. You can select structural motifs up to 10 residues long with either broad secondary-structure types or fine-grained ranges of the F and ? dihedral angles. You can additionally restrict your query by amino acid type, by backbone covalent geometry and/or side chain conformatonal angles.