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

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, [Fe (NA)], and [Fe (NA)] in detail, from a theoretical standpoint. The chemical computations on the [Fe (NA)] and [Fe (NA)] complexes show that NA can bind with both Fe (+ 2) and Fe (+ 3) ions. The calculations confirm that the [Fe (NA)] is thermodynamically more stable in comparison with [Fe (NA)], while [Fe (NA)] is kinetically more stable than [Fe (NA)]. Under the physiological conditions prevailing in plant tissues, [Fe (NA)] can undergo reduction, but the auto-oxidation of [Fe (NA)] to [Fe (NA)] is prevented. In summary, NA can translocate Fe ions within plant tissues, wherever required, both as Fe (+ 2) and Fe (+ 3) complexes.