Ortega Núñez, Mario E.

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    Electrochemistry of Hemoglobin I from Lucina pectinata immobilized on a modified gold electrode with cysteine or 3-mercaptopropionic acid: Electrochemical activity for hydrogen sulfide
    (2012) Ortega Núñez, Mario E.; Vega Olivencia, Carmen A.; College of Arts and Sciences - Sciences; Cádiz, Mayra E.; Tremont, Rolando; López Garriga, Juan; Department of Chemistry; Aponte, Nilda E.
    The extraordinary affinity of recombinant hemoglobin I from Lucina pectinata (rHbI) for hydrogen sulfide (H2S) allow to postulate it as substrate for the preparation of the hydrogen sulfide sensors. The modification of a gold surface with recombinant hemoglobin I, electrochemical characterization of H2S and electrochemical kinetics parameters were reported. The first sensor model was prepared using cysteine. This system allowed studying how the protein was immobilized on the gold surface and its response to H2S. The second sensor model, using 3-MPA, was an exploration of another linker to try to improve the robustness of the sensor signal in the quantification of H2S. This model provided information about the electrokinetic and electrochemical parameters of the hemoglobin, as well as their response to H2S. Cyclic Voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the electrodes modification process, while FTIR was used to verify the presence of hemoglobin on the surface. In CV a pair of well-defined redox peaks for rHbIFe(III)–rHbIFe(II) at 0.213 V (with Cys) and 0.190 V (with 3-MPA) vs. Ag/AgCl were obtained. Electrochemical parameters of immobilized hemoglobin I as formal potential (Eo’), charge transfer coefficient (!) and apparent heterogeneous electron transfer rate constant (ks) were estimated by cyclic voltammetry data. The high-resolution XPS from S2p and C1s regions provide further evidence that cysteine and 3-mercaptopropionic acid are adsorbed to gold surface. Also, it confirms the presence of nickel ion in the Ni2p region when the monolayer Lnk/Au is treated with the solution of NiCl2. The electrochemical response of rHbI-electrode in presence of hydrogen sulfide (H2S) was studied, obtaining changes in oxidation and reduction current peaks from the voltammograms. The amperometric response of the rHbI-(Cys)-electrode to H2S was linear in the range from 90 to 400 nM (n = 7, r2 = 0.993), while rHbI-(3-MPA)-electrode was linear from 40 to 600 nM with a correlation coefficient of 0.998 (n = 16). This method provides an alternative procedure of surface modification for immobilization of histidinetag proteins or enzymes for sensors preparation.