Question

Using an example, explain what an entatic state is

Answer 1

Entatic state

The word Entatic derived from a Greek word entasis, which literally meaning is “in a stretched state or under tension”.

The term was coined by Vallee and Williams.

According to IUPAC Gold Book, “A state of an atom or group which, due to its binding in a protein, has its geometric or electronic condition adopted for function”.

For example the Geometry around copper ion in blue copper protein.

Explanation:

In the blue copper protein, Cu ion is ligated by two nitrogen from histidine, one sulfur from methionine and one sulfur from cysteinate ligands.

Crystal structure of protein show very irregular (distorted) tetrahedral coordination geometry (a highly energetic transition state geometry) between reduced Cu(I)-d¹⁰ and oxidized Cu(II)-d⁹ configuration, whereas preferred geometry of Cu(I)-d¹⁰ is tetrahedral or trigonal and square planar or square pyramidal of Cu(II)-d⁹.

Strongly distorted geometry around the Cu ion is an example of entatic state.