title: An extended-X-ray-absorption-fine-structure investigation of diferric transferrins and their iron-binding fragments.
abstract: Iron K-edge extended-X-ray-absorption-fine-structure (e.x.a.f.s.) spectra were recorded for diferric human and rabbit serum transferrins and for diferric chicken ovotransferrin in aqueous solution; for ovotransferrin e.x.a.f.s. spectra from the N-terminal and C-terminal domain fragments were also measured. The overall spectral profiles closely resemble one another, indicating similar iron-binding sites. The simulation of the diferric ovotransferrin spectrum suggests a first co-ordination shell consisting of six low-Z ligands (nitrogen/oxygen), two ligands at a distance of approx. 0.185 nm (1.85 A) and four ligands at approx. 0.204 nm (2.04 A). The two shorter distances may correspond to Fe-O (tyrosine), whereas the longer distance is consistent with Fe-N (histidine) and Fe-O (water). Detailed analysis of the spectra of the N-terminal and C-terminal fragments indicates a difference in the short ligand distance.
mesh_terms: D001665:Binding Sites; D003207:Conalbumin; D007501:Iron / Q000032:analysis*; D008024:Ligands; D010446:Peptide Fragments / Q000032:analysis; D013057:Spectrum Analysis; D014168:Transferrin; D014965:X-Rays
chemical_list: D008024:Ligands; D010446:Peptide Fragments; D014168:Transferrin; C028283:diferric transferrin; D003207:Conalbumin; D007501:Iron