Full text
| |
| Author(s): |
Lucyano Jefferson Alves de Macêdo
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT) |
| Defense date: | 2022-01-21 |
| Examining board members: |
Frank Nelson Crespilho;
Adalgisa Rodrigues de Andrade;
Daniel Rodrigues Cardoso;
Edson Roberto Leite;
Jacqueline Ferreira Leite Santos
|
| Advisor: | Frank Nelson Crespilho |
| Abstract | |
Redox enzymes are biological catalysts with a complex structure which possess electron donors/acceptors unities and/or ions that lead charge transfer reactions. In redox biology, the reactions catalyzed by redox enzymes are associated to life, its origin, to evolution, and genomics; in industry, redox enzymes are used to accelerate reactions for producing medicines, beverages, and foods; in biotechnology and medicine, they are used in clinical diagnosis and biosensors; in the field of clean and sustainable energy, redox enzymes are employed in the production of biofuels, besides serving as models for the synthesis of biomimetic catalysts for fuel cells and aqueous non-toxic batteries. Therefore, understanding how bioelectrochemical mechanisms work in redox enzymes and their kinetic and thermodynamic properties allow to obtain simpler and biomimetic molecules, granting the advancement of the scientific and technological state-of-the-art. In this sense, this Doctoral Thesis presents a proposal to investigate influence of transition metals present in the catalytic pocket of redox enzymes and also in biomimetic catalysts through in situ and operando spectroscopic and spectrometric techniques coupled to electrochemistry focusing on the electron transfer processes and the mechanisms involved. This Thesis is divided into three parts. In the first, we present a study in the far infrared region for the redox reactions with Prussian blue, ferrocene, and nickel phthalocyanine. The electron transfer reaction with these three compounds was monitored through the changes in the absorption of radiation by the metal- ligand moiety. We have overcome the experimental difficulties in working with aqueous medium, being possible to successfully propose a novel setup to probe the effect of the oxidation state of metallic centers on the vibrational modes of the first coordination sphere. In the second part of this Thesis, we present a new instrumental strategy for Raman spectroelectrochemistry and differential electrochemical mass spectrometry aiming to investigate the important reaction of the conversion of the nitrite ion to ammonia. Here, we propose to utilize the biomimetic catalyst iron phthalocyanine in aqueous phase, that is, dissolved in the electrolyte. Strategically, this configuration allows the observation of an unprecedent catalytic route, with the formation of nitric oxide, nitrous oxide, and hydroxylamine as intermediates, which have never been observed experimentally to this date. The third and last part of this Thesis consists of using synchrotron radiation, for the first time, in a bioelectrochemical study. Here, we propose an entrapment approach for the redox enzyme bilirubin oxidase in a carbon mesoporous matrix, used as bioelectrodes with operando X-ray absorption spectroscopy. The bioelectrocatalyzed oxygen reduction reaction to water was investigated in detail, being possible to propose a new mechanism of tridimensional catalysis, where the copper (II) sites present in the structure of bilirubin oxidase participate, step-by-step, in the electron transfer reaction playing the role of electronic bridges. Therefore, in the Thesis, we present three distinct ways of using in situ and operando spectroscopic and spectrometric techniques, contributing to the area of bioelectrochemistry with the direct visualization of how the centers containing transition metals work. Consequently, the instrumental strategies presented here contribute to promote the elucidation of complex mechanisms involving enzymes and biomimetic compounds. (AU) | |
| FAPESP's process: | 17/20493-2 - Study of metalloenzymes through electrochemistry coupled to vibrational spectroscopy |
| Grantee: | Lucyano Jefferson Alves de Macêdo |
| Support Opportunities: | Scholarships in Brazil - Doctorate |