Eletrochemical aspects of models of carbon-fixation for the emergence of life on early earth

Author(s)

Thiago Altair Ferreira

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2023-08-17

Examining board members

Douglas Galante; Iolanda Midea Cuccovia; Reuben Hoyt Hudson; Gustavo Frederico Porto de Mello; Elton Fabiano Sitta

• Advisor: Hamilton Brandão Varela de Albuquerque; Douglas Galante

Abstract

Living systems generally exhibit a certain kinetic and thermodynamic specificity in their vital processes. Universally, the driving force of natural chemiosmotic and electrochemical gradients in cells are coupled to diverse metabolic pathways by enzymatic systems. Considering this characteristic, there is the so-called alkaline hydrothermal vents model for the emergence of life on the early Earth. According to that hypothesis, the cited specificity may have analogues in geological systems, the alkaline hydrothermal vents (AHVs), whose arrangement of mineral components and physicochemical parameters may have been the requirement for the emergence of mechanisms of life on the prebiotic Earth. We, therefore, propose the electrochemical study of that model for the emergence of life. This work focuses on the concept of the interface between hydrothermal vent and the early ocean, and the CO2 reduction according to transduction models based on the acetyl-CoA (Wood-Ljungdahl, WL) pathway, which is universally present in the genome of known living things. For this study, we approached the use of iron minerals, similar in structure to enzyme active sites, under conditions of electrochemical, temperature, and pH gradients, typical condition of the aforementioned geological interface. We first conducted a literature review of the AHV model focusing on experimental work and on the main questions about emergence of life that the model currently seeks to answer. We then developed detailed and reproducible experimental protocols that served to obtain results and open for future work aimed at exploring new proposals that have been presented in the literature of the area. We obtained experimental results using techniques such as cyclic voltammetry and electrochemical impedance spectroscopy. From these, we had information about the stability and activity of different iron minerals, presented in the literature in the context of the AHV model, for the formation of intermediates of the WL pathway. The results also open for study of the electron transfer mechanism that may have taken place at that interface and may have involved different phases of iron minerals. (AU)

• FAPESP's process: 18/12491-2 - Thermodynamic and electrocatalitic aspects in free energy transfer models for the emergency of life on early earth
• Grantee: Thiago Altair Ferreira
• Support Opportunities: Scholarships in Brazil - Doctorate