Shiyu Zhang , Marie M. Melzer , S. Nermin Sen , Nihan Çelebi-Ölçüm & Timothy H. Warren Nature Chemistry (2016), doi:10.1038/nchem.2502 1 Department of Chemistry, Georgetown University, Box 571227, Washington, DC 20057, USA. 2 Department of Chemical Engineering, Yeditepe University, Istanbul 34755, Turkey. 3 Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA. http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem.2502.html Abstract Nitric oxide ( NO ) participates in numerous biological processes, such as signalling in the respiratory system and vasodilation in the cardiovascular system. Many metal-mediated processes involve direct reaction of NO to form a metal–nitrosyl (M–NO), as occurs at the Fe 2+ centres of soluble guanylate cyclase or cytochrome c oxidase. However, some copper electron-transfer proteins that bear a type 1 Cu site (His 2 Cu–Cys) reversibly bind N...