NCBI, the National Center for Biotechnology Information, provides this seachable database, consisting of "experimentally determined three-dimensional biomolecular structures" of macromolecules obtained from the Brookhaven Protein DataBank (PDB). The PDB currently contains more than 7600 proteins, 600 nucleic acids, and 12 carbohydrates, and adds new entries weekly. Designed "to facilitate comparative analysis involving 3-D structures," MMDB may be queried directly using author name(s) or descriptive text terms. Structures may be viewed using Cn3D, RasMol or MAGE; see instructions for viewing and downloading in the FAQ section on site.