In collaboration with Prof. Cecilia Tommos (Stockholm University), we have designed, biochemically expressed and purified a single molecule four helix bundle maquette scaffold. This scaffold is being elaborated with cysteine residues to mimic the Mo-S coordination found in natural enzymes containing molybdopterins. The biochemical synthesis of this bundle provides not only for the generation of a (Cys)4 site to mimic xanthine oxidase (model shown to right), but also for asymmetric (Cys)3 and (Cys)2 sites to model sulfite oxidase and sulfite reductase, respectively.