title: Direct electrochemistry of hemoglobin adsorbed on self-assembled monolayers with different head groups or chain length.
abstract: The electrochemical behaviors of hemoglobin (Hb) were studied by adsorbing Hb on the gold electrodes modified with self-assembled monolayers (SAMs) of different terminal groups and alkyl chain length. Specifically, through adsorbing the Hb molecules onto the SAMs of 3-mercaptopropanoic acid (MPA), 1-propanethiol (PT) and cysteamine hydrochloride (cys), the influences of the terminal groups of alkanethiols on the electron transfer of Hb were examined. A quasi-reversible redox process was observed when Hb was adsorbed on the MPA-modified electrode. However, an irreversible reduction process and no redox response were shown when Hb molecules were adsorbed on the SAMs of PT and cys-modified electrodes, respectively. The dependence of the direct electrochemical response of Hb on the alkyl chain length of alkanethiols (n) was further investigated on the SAMs of HS(CH(2))(n)COOH (n=1, 2, 5 and 10). When n was 1, Hb showed a weak current response. When n were 2 and 5, quasi-reversible redox processes with nearly similar electron transfer rate constants (k(s)) of 0.49 and 0.47 s(-1) were obtained, respectively. Increasing the number of methylene groups within carboxyl alkanethiol to 10 resulted in a significant decrease of the electron transfer rate and current response of Hb. The observations indicated that the SAM of MPA can provide suitable properties to keep Hb in a favorable adsorption state for direct electron transfer (DET). Furthermore, the direct electrochemistry of the Hb adsorbed on the SAM of MPA was studied in detail.
authors.affiliation: School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, PR China. maizhb@mail2.sysu.edu.cn
authors.forename: Zhibin
authors.initials: Z
authors.lastname: Mai
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Zhao
authors.forename: Zong
authors.initials: Z
authors.lastname: Dai
authors.forename: Xiaoyong
authors.initials: X
authors.lastname: Zou
mesh_terms: D015097:3-Mercaptopropionic Acid / Q000737:chemistry; D000327:Adsorption; D000818:Animals; D002384:Catalysis; D002417:Cattle; D004563:Electrochemistry; D004566:Electrodes; D004579:Electron Transport; D006046:Gold / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013499:Surface Properties
chemical_list: D006454:Hemoglobins; D013438:Sulfhydryl Compounds; D006046:Gold; D015097:3-Mercaptopropionic Acid; D006861:Hydrogen Peroxide