title: Direct electron transfer for hemoglobin in biomembrane-like dimyristoyl phosphatidylcholine films on pyrolytic graphite electrodes.
abstract: Stable thin films made from dimyristoyl phosphatidylcholine (DMPC) with incorporated hemoglobin (Hb) on pyrolytic graphite (PG) electrodes were characterized by electrochemical and other techniques. Cyclic voltammetry (CV) of Hb-DMPC films showed a pair of well-defined and nearly reversible peaks at about -0.27 V vs. saturated calomel electrode (SCE) at pH 5.5, characteristic of Hb heme Fe(III)/Fe(II) redox couple. The electron transfer between Hb and PG electrodes was greatly facilitated in DMPC films. Apparent heterogeneous rate constants (ks) were estimated by fitting square wave voltammograms of Hb-DMPC films to a model featuring thin layer behavior and dispersion of formal potentials for redox center. The formal potential of Hb heme Fe(III)/Fe(II) couple in DMPC films shifted linearly between pH 4.5 to 11 with a slope of -48 mV pH-1, suggesting that one proton is coupled to each electron transfer in the electrochemical reaction. Soret absorption band positions suggest that Hb retains a near native conformation in DMPC films at medium pH. Differential scanning calorimetry (DSC) showed the phase transition for DMPC and Hb-DMPC films, suggesting DMPC has an ordered multibilayer structure. Trichloroacetic acid (TCA) was catalytically reduced by Hb-DMPC films with significant decreases in the electrode potential required.
authors.affiliation: Department of Chemistry, Beijing Normal University, China.
authors.forename: J
authors.initials: J
authors.lastname: Yang
authors.forename: N
authors.initials: N
authors.lastname: Hu
mesh_terms: D000465:Algorithms; D002152:Calorimetry, Differential Scanning; D002384:Catalysis; D004134:Dimyristoylphosphatidylcholine; D004563:Electrochemistry; D004566:Electrodes; D004579:Electron Transport; D006108:Graphite; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D008567:Membranes, Artificial; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet; D014238:Trichloroacetic Acid / Q000737:chemistry
chemical_list: D006454:Hemoglobins; D008567:Membranes, Artificial; D014238:Trichloroacetic Acid; D006108:Graphite; D007501:Iron; D004134:Dimyristoylphosphatidylcholine