This is the metabolic network of the roundworm Caenorhabditis elegans. Nodes are metabolites (e.g., proteins), and edges are interactions between them. Since a metabolite can iteract with itself, the network contains loops. The interactions are undirected. There may be multiple interactions between any two metabolites.
arenas_metaigraph object
Jerome Kunegis. KONECT - The Koblenz Network Collection. In Proc. Int. Web Observatory Workshop, pages 1343-1350, 2013.
Jordi Duch and Alex Arenas. Community detection in complex networks using extremal optimization. Phys. Rev. E, 72(2):027104, 2005.