ETD

• computational chemistry
• fatty acid photodecarboxylase
• photoenzymes
• QM/MM

Photoenzymes constitute a rare class of biocatalysts that utilize light to trigger chemical transformations under mild conditions. Among them, the fatty acid photodecarboxylase from Chlorella variabilis (CvFAP) has emerged as a paradigm of light-driven, redox-neutral decarboxylation of free fatty acids into C1-shortened alkanes and alkenes. This reaction proceeds with high efficiency through radical intermediates, following visible-light excitation of the flavin adenine dinucleotide (FAD) cofactor. Beyond its native role in hydrocarbon formation, recent experimental advances have demonstrated that engineered variants of CvFAP can be repurposed into radical photocyclases (RAPs), enabling stereoselective C–C bond formation via intramolecular radical cyclization.

This thesis investigates the mechanism behind radical cyclization catalyzed by an engineered CvFAP variant. The main goals are: i) to characterize substrate conformational flexibility in the active site, ii) to identify geometries enabling productive cyclization, iii) to map the electronic energy landscape of the radical intermediate, and iv) to estimate forward electron transfer rates. To achieve these goals, a multiscale computational strategy was applied, combining extensive molecular dynamics (MD) simulations with quantum mechanics/molecular mechanics (QM/MM) calculations.