Presence Of Nitrilotriacetate Research Articles

Formation of monoferric ovotransferrins in the presence of chelates

1. When ovotransferrin is partially saturated with iron, endotherms for apo-ovotransferrin, two monoferric ovotransferrins and Fe2-ovotransferrin are observed by differential scanning calorimetry. The relative sizes of the endotherms are changed in the presence of the iron-chelating agents nitrilotriacetic acid and ATP. 2. When iron is added as Fe(III)-nitrilotriacetate, at Fe-nitrilotriacetate: ovotransferrin ratios less than unity, the endotherm for Fe2-ovotransferrin is essentially absent. At Fe-nitrilotriacetate: ovotransferrin ratios of unity the only species present in solution in appreciable concentration as evidenced by their differential-scanning-calorimetry endotherms, are two monoferric ovotransferrins in approximately equal amounts. At Fe-nitrilotriacetate: ovotransferrin ratios greater than unity, the apo-ovotransferrin endotherm is absent, and the endotherms for the two monoferric ovotransferrins decrease in size as the endotherm for Fe2-ovotransferrin increases. 3. In the presence of nitrilotriacetate, binding of iron to the two sites of ovotransferrin is highly anti-co-operative, but essentially indiscriminate. When monoferric ovotransferrin is formed from apo-ovotransferrin, binding at one site is slightly favoured compared with binding at the other site, but once iron has been bound at either site, the binding affinity for iron at the unoccupied site is much decreased.

The inducible citrate-dependent iron transport system in Escherichia coli K12

A citrate-dependent system of iron uptake was found in wild-type cells of Escherichia coli K12, and in mutants which were unable, for a variety of reasons, to make use of the enterochelin system of iron transport. A mutant strain which did not show a growth response to citrate, was shown to lack the citrate-dependent iron uptake system. Identification of this citrate-dependent system was facilitated in the presence of nitrilotriacetate, which abolished a low-affinity iron uptake observed in the absence of added chelators. In growing cells, induction of the citrate-dependent system occurred within 20 min of exposure to citrate, and required new protein synthesis. The citrate-dependent system has a lower initial rate of iron uptake and a slightly lower affinity for iron ( K m 0.2 μM) that the enterochelin-mediated system ( K m 0.1 μM). In cells with both systems operating optimally, the overall initial rate of iron uptake was equal to the sum of the uptakes contributed by the two individual system. The inducible citrate-dependent system is thus entirely separate from the respressible enterochelin-mediated system, and the two systems can operate simultaneously in wild-type cells.

Removal of metals by chemical treatment of municipal waste water

The reduction of the metal content of waste water by chemical treatment with aluminium sulfate or calcium hydroxide has been studied. p] Pb(II), Cu(II), Cr(III), Hg(II), Cd(II) and As(V) are reduced to low levels by both precipitants. Zn(II), Ni(II) and Co(II) are precipitated only at pH-values ≤ 9·5. The precipitation of Cu(II) and Pb(II) is greatly inhibited by the presence of nitrilotriacetate at pH ≤9.