In January 2003, we participated in a week long workshop on the Geometry of Protein Folding organized by Ileana Streinu. With Leslie Kuhn and Walter Whitely, we defined models of allosteric interactions based on the theory of combinatorial rigidity. Mantler has implemented a version of the pebble game for rigidity analysis that Jacobs and Thorpe call FIRST, and is developing the proofs that the heuristics used in FIRST are indeed correct. At Hellinga's suggestion, she has begun investigating flexibility of phosphofructokinase (PFK), to see if combinatorial rigidity could explain some of the allosteric nature of this classic protein. This implementation also helps analyze backbones for flexibility that can be exploited in doing protein design.

The examination of folding and linkages has revealed polyhedra that cannot be unfolded using edge cuts and a catalog of linkages that are interlocked.