Deriving and visualizing macromolecular structures, X-ray crystallography, NMR spectroscopy, electron microscopy, structure visualization, examining and interpreting structural data, Protein Data Bank (PDB), structures classification schemes (CATH, SCOP), structure validation software, secondary structure assignment, structure comparison and alignment, domain assignment, functional assignment from structure, protein docking, comparative assessment of protein structure prediction (CASP), comparative modeling, fold recognition, ab-initio structure prediction