An axial met ligand at a type 1 copper site is preferable for fast electron transfer

Rapid fire! The replacement of the axial oxygen ligand at the type 1 copper site of stellacyanin with a weakly interacting thioether sulfur results in a fivefold increase in the electron self-exchange rate constant. This provides the first example of a type 1 copper site variant that exhibits increased reactivity and demonstrates that a site with an axial Met ligand is preferable for fast electron transfer, as shown.