Tridentate chelate ligands of 2,6-bis[hydroxy(methyl)amino]-1,3,5-triazine family rapidly release iron from human recombinant ferritin in the presence of oxygen. The reaction is inhibited by superoxide dismutase, catalase, mannitol and urea. Suggested reaction mechanism involves reduction of the ferritin iron core by superoxide anion, diffusion of iron(II) cations outside the ferritin shell, and regeneration of superoxide anions through oxidation of iron(II) chelate complexes with molecular oxygen.

Alkylation of one of the imidazole rings of hexahistidine with Baylis-Hillman esters tethered to nitrilotriacetate residue was achieved in aqueous solutions at neutral pH and at micromolar concentrations in the presence of Ni(2+), Cu(2+), or Zn(2+) cations. The utility of the approach for selective functionalization of His-tagged recombinant proteins was demonstrated by attachment of a fluorescent label to recombinant protein A with an alkynyl group followed by a "click" 1,3-dipolar cycloaddition reaction.

The thermodynamics of Cu 2+-and Ni 2+-NTA binding to polypeptides containing 2-6 histidine residues in neutral buffered aqueous solutions were characterized by isothermal titration calorimetry (ITC). The apparent dissociation constants of ternary complexes of N-acetylhexahistidine-Ni 2+-NTA and N-acetylhexahistidine-Cu 2+-NTA were 69.5 M and 27.1 M, respectively. Decreased number of histidine residues in the oligohistidine fragment caused gradual decrease in the stability of the mixed metal complexes and a change in the binding stoichiometry from ~ 1:1 for N-acetylhexahistidine and N-acetylpentahistidine to ~ 0.5:1 for Nacetyltetrahistidine and ~ 0.3:1 for N-acetyltrihistidine, N-acetyldihistidine and N-acetylhistidine ligands. In all Ac(His) 1-6 COO-NTA-M 2+-Ac(His) 1-6 COO

Formation of labile 1 : 1 : 1 ternary mononuclear complexes of iron(iii) cation with η3-terdentate meridional binders was studied using electrospray ionisation mass spectrometry (ESI-MS) titration and UV-Vis titration in solution phase. Low selectivities towards formation of ternary heteroleptic complexes in the solution phase vs. symmetric 2 : 1 complexes were obtained with combinations of dianionic 2,6-bis[hydroxy(methyl)amino]-1,3,5-triazine (BHT) ligands with monoanionic terdentate ligands such as 2-[(2-pyridinylmethylene)amino]phenol. Moderate selectivities were observed in formation of ternary iron(iii) complexes of iron(iii) between BHT ligands and neutral terdentate ligands such as pyridin-2-ylmethylpyridin-2-ylmethyleneamine. Results obtained by MS titrations were in a reasonable agreement with UV titration data indicating that quantitative ESI MS spectrometry can be applied to these labile iron(iii) complexes.