Cbl-b Ubiquitin ligase in complex with Ubiquitin 32 (PDB: 2OOB); the solution complex of Barnase-Barstar 33 from B. amyloliquefaciens (PDB: 1BRS); the transmembrane homodimer of outer membrane phospholipase A (OMPLA) from E. coli (PDB: 1QD6); and the homodimer of a E. coli homolog of transmembrane ClC chloride channels (PDB: 1OTS). The test systems will in the remainder be denoted by the following names: UBA domain/Ubiquitin, Barnase/Barstar, OMPLA homodimer, and ClC homodimer.