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.
Who Sang That Song? Posted on October 17, 2016 by Deb in Music. People write to AskDeb.com all the time asking questions like this: Who sang that songâ¦? Who sang this songâ¦? Who singsâ¦? This page collects all of the âwho sang that songâ and âwho sings that songâ questions on one page, along with the answers to those questions. So if youâre wondering who sings (fill in the blank here), this is the place to find out.