Direct electrochemistry of iron(III)- and copper(II)-transferrins embedded in a bilayer membrane film composed of artifical cationic-type lipid

摘要

Fe(III)- and (Cu(II)-transferrins were embedded into a cast film composed of artificial cationic-type lipid, 2C_(16)N~+Br~-. However, for the lipid films composed of 2C_(16)N~+PSS~-, 2C_(12)SucSO_3~-Na~+ and 2C_(12)gluco, the incorporation of Fe(III)- and Cu(II)-transferrins into the lipid films was spectrochemically and electrochemically undetectable even at temperatures above the phase transition temperature of the lipids. The incorporation of transferrin into the 2C_(16)N~+Br~- film was completely inhibited under high electrolyte concentrations. These results indicate that the incorporation of transferrin into the cationic-type lipid film, 2C_(16)N~+Br~-, can be attributed to ion exchange between the bromide anion of the lipid and the negatively charged transferrin. The Fe(III)- and Cu(II)-transferrins embedded into the 2C_916)N~+Br~- film on a graphite electrode showed well-defined redox waves. The evaluated redox potentials of Fe(III)- and Cu(II)-transferrin were approximately 0.017 and 0.237 V(vs. NHE), respectively, in a phosphate buffer (pH 7, μ = 0.1) solution containing 0.1 mmol dm~(-3)K_2C_2O_4 at 30 ℃. The results obtained in the present study indicate that an electrode modified with a cast film of this cationic-type of lipid is useful as an electrochemical interface for not only Fe(III)-transferrin but also metal reconstituted transferrins such as Cu(II)-transferrin.