The fourth ligand on the Zn(II) ion is a water molecule. The zinc coordination is tetrahedral. The three histidine residues are sometimes referred to as first coordination sphere ligands. This set of ligands is appropriate to give the water ligand the pKa of 6.5, a value where catalysis is most efficient.
Behind Closed Doors  is a country song written by Kenny O'Dell. It was first recorded by Charlie Rich for his 1973 album Behind Closed Doors. The single was Rich's first number-one hit on the country charts, spent 20 weeks on this chart, and was also a crossover hit on the pop charts. Background vocals were provided by The Nashville Edition.
Cartman sings the song Come Sail Away in the South Park episode Cartman's Mom is Still a Dirty ***. The episode belongs to the second season of the South Park cartoon.Edit.he lead singer is a person who sings the most in a song. Here are some examples of Lead singers: Nadine (Girls Aloud) Vanessa (The Saturdays) Brad Delp (Boston). This person â¦ is usually also the leader of the musical group. 7 people found this useful.