First-Principles Modeling of Nitazoxanide Analogues as Prospective PFOR-Targeted Antibacterials

Pyruvate:ferredoxin oxidoreductase (PFOR) is a key Achilles' heel in anaerobic pathogens. We integrate electronic-structure calculations (DFT), cheminformatic QSAR metrics, and residue-resolved docking to distill a concise "recognition code" and translate it into practical design rules. Using nitazoxanide (Nita; ΔG_(bind) ≈ -10.0 kcal·mol^-1) as a well-established reference, productive binding requires a conserved triad: a hydrogen-bond donor addressing Thr-997 and Cys-840, a π-π stack with Phe-869, and a recurrent π-σ contact to Thr-997 that orients the scaffold. Deacetylation to tizoxanide unmasks the phenolic donor and raises local electrophilicity, yet it also slightly loosens pocket packing (-9.6 kcal·mol^-1). Strategic halogenation introduces a σ-hole interaction near Pro-29, tightening pose geometry without disrupting the donor network; the lead analogue yields -10.1 kcal·mol^-1, and two others match the reference by preserving the triad and hydrophobic belt. The result is a minimal, testable recipe-retain the phenolic donor, enforce Thr-997/Cys-840 and Phe-869, and add a calibrated halogen σ-hole-offering falsifiable predictions to surpass nitazoxanide and guiding synthesis and biophysical validation in targeted PFOR inhibition.