Comparison of the structure and iron-binding properties of ELT and other chelators
| . | DFO . | DFP . | DFX . | ELT . |
|---|---|---|---|---|
| Molecular weight | 561 | 139 | 373 | 442 |
| Chelator/iron(III) ratio | 1:1 | 3:1 | 2:1 | 2:1 and 1:1 |
| Log stability constant for iron (III) | 30.6 | 37.2 | 36.5 | 34.9 |
| pFe (pmol/L) | 26.6 | 20.7 | 23.1* | 22.0 |
| Charge of free ligand at pH 7.4 | 1+ | 0 | 1− | 1− |
| Charge of iron complex at pH7.4 | 1+ | 0 | 3- | 3- (2:1); 0 (1:1) |
| Lipid solubility free ligand (log P) | −3 | −0.8 | 4.3 | 6.3 |
| . | DFO . | DFP . | DFX . | ELT . |
|---|---|---|---|---|
| Molecular weight | 561 | 139 | 373 | 442 |
| Chelator/iron(III) ratio | 1:1 | 3:1 | 2:1 | 2:1 and 1:1 |
| Log stability constant for iron (III) | 30.6 | 37.2 | 36.5 | 34.9 |
| pFe (pmol/L) | 26.6 | 20.7 | 23.1* | 22.0 |
| Charge of free ligand at pH 7.4 | 1+ | 0 | 1− | 1− |
| Charge of iron complex at pH7.4 | 1+ | 0 | 3- | 3- (2:1); 0 (1:1) |
| Lipid solubility free ligand (log P) | −3 | −0.8 | 4.3 | 6.3 |
Binding properties of ELT are not previously described and were determined specifically for this article. The relative stabilities of iron(III) binding are represented by the pFe, where the pFe of a given chelator for iron(III) is the negative log of the uncoordinated metal concentration under defined conditions.50 The higher the pFe values, the lower the concentration of uncoordinated iron(III), and hence the greater stability for the iron–chelate complex. ELT can form neutrally charged 1:1 complexes with iron(III) or 3− negatively charged 2:1 complexes. Properties of other chelators use published data,11,19 except for the pFe value of DFX, where 23.1 is used based on the properties of the molecule in 100% water; The widely adopted values of 22.4 or 22.5 are based on titrations run in 20% DMSO. When pairs of chelators are combined in solution, iron(III) will bind preferentially to the chelator with the higher pFe value. This is highest for DFO and lowest for DFP, with DFX having an intermediate value but greater than ELT.
Kpart, partition coefficient.51-53
Value determined for 100% aqueous system.