Protein topologyProtein topology is a property of protein molecule that does not change under deformation.FrameworksTwo main topology frameworks have been developed and applied to protein molecules.Knot Theorywhich categorises chain entanglements. The usage of knot theory is limited to a small percentage of proteins as most of them are unknot.Circuit topologycategorises intra-chain contacts based on their arrangements. Circuit topology is a determinant of protein folding kinetics and stability.Other usesIn biology literature, the term topology is also used to refer to mutual orientation of regular Protein [secondary structure|secondary structures], such as alpha-helices and beta strands in protein structure . For example, two adjacent interacting alpha-helices or beta-strands can go in the same or in opposite directions. Topology diagrams of different proteins with known three-dimensional structure are provided by PDBsum.