title: Structural electrochemical study of hemoglobin by in situ circular dichroism thin layer spectroelectrochemistry.
abstract: Secondary and tertiary or quaternary structural changes in hemoglobin (HB) during an electroreduction process were studied by in situ circular dichroism (CD) spectroelectrochemistry with a long optical path thin-layer cell. By means of singular value decomposition least-squares analysis, CD spectra in the far-UV region give two similar alpha components with different CD intensity, indicating slight denaturation in the secondary structures due to the electric field effect. CD spectra in the Soret band show a R-->T transition of two quaternary structural components induced by electroreduction of the heme, which changes the redox states of the center ion from Fe3+ to Fe2+ and the co-ordination number from 6 to 5. The double logarithmic analysis shows that electroreduction of hemoglobin follows a chemical reaction with R-->T transition. Some parameters in the electrochemical process were obtained: formal potential, E0'=-0.167 V; electrochemical kinetic overpotential, deltaE0=-0.32 V; standard electrochemical reaction rate constant, k0=1.79 x 10(-5) cm s(-1); product of electron transfer coefficient and electron number, alphan=0.14; and the equilibrium constant of R-->T transition, Kc=9.0.
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, PR China.
authors.forename: Yongchun
authors.initials: Y
authors.lastname: Zhu
authors.forename: Guangjin
authors.initials: G
authors.lastname: Cheng
authors.forename: Shaojun
authors.initials: S
authors.lastname: Dong
mesh_terms: D002942:Circular Dichroism; D004563:Electrochemistry; D006454:Hemoglobins / Q000737:chemistry*; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet
chemical_list: D006454:Hemoglobins