Bioinorganic Chemistry and Applications

Research Article

Niobium Uptake and Release by Bacterial Ferric Ion Binding Protein

Table 2

Species detected by ESI-MS assay of products from the reaction of [Nb(NTA)2]− or [Cp2Nb(OH)Cl2]with apo-Fbp.
Calcd/Da Obsd/Da
Recombinant apo-Fbp with [Cp2Nb(OH)Cl2]
(33640)33648
aFbp + 4Cp2NbCl2 (34816)34813
aFbp + 4Cp2NbCl2+OH− (34833)34829
aFbp + 4Cp2NbCl2+2OH− (34850)34842
aFbp + 4Cp2NbCl2+3OH− (33867)34871
aFbp + 4Cp2Nb(OH)Cl2 (34884)34890
Recombinant apo-Fbp with [Nb(NTA)2]−
aFbp + NH4+ (33657)33655
aFbp + 2Nb(NTA)2 + NTA + CH3COO− (34835)34837
aFbp + 3Nb(NTA)2 + NTA (34966)34965
The formulations are merely those which give reasonable fits to the observed masses and cannot be interpreted as giving structural information about the nature of the bound complexes. For example some sites could be on the exposed surface of the protein as well as in the interdomain cleft.