Figure 2From: Rigidity analysis of protein biological assemblies and periodic crystal structuresMethane (two left images) is rigid because all pair-wise distances between atoms are fixed. In ethane (center), a carbon atom (gray) and its bonded neighbor atoms form a rigid body. The two bodies share a hinge along the center C-C bond, shown as an abstract body-bar-hinge framework (second from right). A protein's peptide units are modeled as rigid bodies (far right).Back to article page