Also in collaboration with the Zaki lab, we have developed a data structure for protein surfaces, capable of identifying the correct complementary interaction surfaces in a known protein-protein interaction -- i.e. the protein docking problem. A boolean data structure has been defined with an eye towards developing a heiarchical search engine for protein surfaces. Ongoing research involves adding flexibility into these surface structures. This follows on previous development of a protein surface calculator, MASKER, which also uses Boolean masks.