Transferrin, a mechanism for the holoprotein formation from nitrilotriacetato-Fe(III)-transferrin mixed complex

Holotransferrin formation from the mixed transferrin-nitrilotriacetatoFe(III) iron complex (THFeL) in the presence of carbonate has been investigated between pH 6.5 and 8.5. Both C- and N-sites seem equivalent towards the interaction with bicarbonate. Bicarbonate interacts with THFeL to yield a new mixed complex, T’H2FeL; apparent rate constant, 2.25 s-1. T’H2FeL, then, loses two protons and the nitrilotriacetate ligand to yield the holoprotein, T’Fe; the two protons dissociation constant, Ka = 4.35 X 10-15 M2. This is accompanied by a gain of about ten orders of magnitude in the stability of the iron-protein complex and can be of interest for a better understanding of iron-uptake by the protein in natural media

The interaction of salicylaldehydebenzoylhydrazone with Ca

This article reports a spectrophotometrical study of complex formation between Mg2+, Ca2+ and Salicylaldehydebenzoylhydrazone (SBH) with Mg2+ and Ca2+. At pH > 9.11, the unprotonated species of SBH, L forms a monocomplex with Mg2+ (affinity constant : 4.80 × 103 M-1) and with Ca2+ (affinity constant : 750 M-1). In neutral media, where the SBH ligand is present under the monoprotonated LH species, SBH does not possess any measurable affinity for Mg2+ or Ca2+ with for both metals a pM value of 5.0 for [Μ] = 1 × 10-5 M, [SBH] = 1 × 10-4 M and pH 7.4. These results are of interest for the iron-overload chelating therapy in which the chelating drug should be able to only form stable complexes with iron but not with the other metallic cations essential for the metabolism