Theoretical studies on the coordination chemistry of phytosiderophores with special reference to Fe-nicotianamine complexes in graminaceous plants.

Abstract

Nicotianamine (NA) is one of the metal-chelating molecules found in higher plants in abundance. Synthesized by the enzyme nicotianamine synthase, NA has a major role in the transport of iron in plant tissues. This research paper deals with the coordination chemistry of the possible complexes of NA, [FeII (NA)]-, and [FeIII (NA)] in detail, from a theoretical standpoint. The chemical computations on the [FeII (NA)]- and [FeIII (NA)] complexes show that NA can bind with both Fe (+ 2) and Fe (+ 3) ions. The calculations confirm that the [FeIII (NA)] is thermodynamically more stable in comparison with [FeII (NA)]-, while [FeII (NA)]- is kinetically more stable than [FeIII (NA)]. Under the physiological conditions prevailing in plant tissues, [FeIII (NA)] can undergo reduction, but the auto-oxidation of [FeII (NA)]- to [FeIII (NA)] is prevented. In summary, NA can translocate Fe ions within plant tissues, wherever required, both as Fe (+ 2) and Fe (+ 3) complexes.