The urge for a possible explanation of the emergence of life has led me to the project on electron bifurcation. After a more theoretical and computational endeavor during my masters, I now like to contribute additional experimental evidence for the understanding of this important energy-conserving mechanism in bioenergetics. In addition, my interest in the origin of metalloenzymes from minerals piques my attention from time to time.

Title of PhD-thesis: Assessment of the molecular parameters enabling flavin-based electron bifurcation
Sujet de la these: Etude des paramètres moléculaires à l’origine de la bifurcations des électrons

Abstract: Electron Bifurcation involves the coupling of two individual electron transfers from an intermediate-potential two-electron donor towards two energetically and spatially different pathways inside one enzyme. This pivotal process thereby couples a strongly favorable electron transfer to an unfavored one allowing for the generation of low-potential compounds.

The molecular basis of this coupling reaction is still highly debated. Two mutually non-exclusive hypotheses were formulated to explain electron bifurcation. These hypotheses favor either the electrostatic effect by the protein environment around the bifurcating center or the involvement of a conformationally driven gating of electrons. The inability to pinpoint specific aminoacids and molecular structures that enable this mechanism in the recently discovered flavin-based electron bifurcation have precluded an unambiguous determination concerning their relative importance.

This thesis aims to determine the electrochemical effects of hydrogen-bonding networks influencing the redox potentials of the functional sites. This will be tested by using optically and EPR-monitored chemical redox titration as well as cyclic voltametry at various pH values. Furthermore, stopped-flow experiments will be employed to follow the pH-dependent bifurcating activity.
The same techniques could also determine the contribution of global conformational changes in the enzymes to their bifurcating ability. These parameters will be assessed and compared in three flavoproteins (Nfn, Hnd, Hdr) which have only recently been demonstrated to perform electron bifurcation.

keywords: Electron bifurcation, flavoenzymes, bioenergetics, proton-coupled electron transfer, emergence of life, metalloenzymes