VO4 refers to the vanadate ion, which is a polyatomic ion composed of one vanadium atom and four oxygen atoms. It carries a negative charge and is commonly found in various chemical compounds. Vanadate ions are often studied in the fields of chemistry and materials science due to their unique properties and potential applications. In biological systems, VO4 can play a role in enzyme activity and is sometimes used in biochemical research. It is also relevant in the production of certain catalysts and in the study of vanadium's effects on health and the environment.