Structural information of biological macromolecules is readily available in the Protein Data Bank (PDB) http://www.pdb.org. Considering the high number of non redundant amino acid sequence entries, there is a huge gap between known annotated sequences and available 3 D structures. Developments in genomics have also spurred the developments in X-ray crystallography and NMR techniques to solve the new protein structure, which in turn has widened their use in drug discovery. In the absence of experimental structures, computational methods are used to predict 3 D protein models to provide insight into the structure and function of these proteins.