Synthetic Copper-Sulfide Complexes as Models for the Active Sites in Nitrous Oxide Reductase

Nitrous oxide (N2O) is one of the most harmful greenhouse gases inducing global warming, and also one of the leading causes towards the depletion of the Earth’s ozone layer. In the ecological nitrogen cycle, an enzyme called nitrous oxide reductase converts N2O into completely benign materials: nitrogen and water. There are two N2O-activating sites in this particular enzyme, denoted as CuZ* and CuZ. Both active sites contain 4 copper atoms adjoined to a single sulfur (µ4-S). Although nitrous oxide reductase has been the focus of several structural and electronic studies, very little is known about the precise interaction between N2O and the enzyme active sites. More specifically, no experimental evidence exists detailing the binding mode of N2O to the active sites during substrate activation; nor has the catalytic reduction mechanism been experimentally established. Our studies are aimed at constructing synthetic, small-molecule complexes that serve as structural and/or functional models to the catalytically relevant CuZ* active site. Development of biomimetic complexes, as a means for investigating the intimate dynamics of the metalloenzyme active sites, provides an additional scientific approach for divulging the reduction of N2O facilitated by CuZ*.