Immobilization of hemoglobin at the galleries of layered niobate HCa ₂Nb₃O₁₀

Hemoglobin (Hb) was intercalated at the galleries of layered niobate HCa₂Nb₃O₁₀ (HCNO). Two different kinds of layered phases of Hb-CNO composites Hb-CNO-1 and Hb-CNO-2 were obtained with the interlayer distances of 7.2 and 10.3 nm in correspondence with the monolayer and bilayer arrangements of proteins between the niobate layers, respectively, based on the powder XRD pattern, HRTEM, UV-vis spectra and CHN analyses. FTIR spectra of Hb-CNO composites show that amide I and amide II bands were actually the same as those of the native Hb, which indicates that there is almost no structural change after immobilization. Michaelis-Menten model methods were used to study the peroxidatic activity of the reaction of 2-methoxyphenol and H ₂O₂ for the entrapped Hb in the galleries of HCNO. Compared to that of free Hb, the kinetic parameters of Hb-CNO kcat, KM and kcat/KM were affected by the immobilization process. The immobilized Hb showed a higher relative activity than that of free Hb after incubated in phosphate buffer (pH=7) at 80°C for a period of time. The environments between the layers of HCNO are hydrophilic which will bind water tightly and help to stabilize the 'essential water' layer around the protein. So, immobilization of Hb between the layers of HCNO enhanced the activity of Hb in water-DMSO mixture.