Alfieri A, Malito E, Orru R, FraaijeMW, Mattevi A (2008) Proc Natl Acad Sci USA 105:6572

1. Investigating the oxygen reactivity in flavoenzymes: computational analysis of oxygen diffusion pathways Andrea Mattevi, University of Pavia (Italy) We are studying O2 diffusion in the monooxygenase component (C2) of p‑hydroxyphenylacetate hydroxylase from A. baumannii and alditol oxidase (AldO) from S. coelicolor using an integrated computational and experimental procedure. Enhanced-statistics MD simulations (total of 30-40 ns of simulation time) capture the spontaneous (unbiased) diffusion of O2, filling the gap between current sampling times with explicit solvent (~101 ns scale) and measured diffusion times (>102 ns scale). O2 diffusion is effectively guided by multiple-pathways which converge to defined dioxygen active site entry points. O2 is able to reach specifically the flavin C4a atom both in the monooxygenase and the oxidase active sites. This suggests that – independently of the detailed nature of the enzymatic reaction – O2 reacts with the flavin by direct contact with the cofactor C4a atom. • Alfieri A, Malito E, Orru R, FraaijeMW, Mattevi A (2008) Proc Natl Acad Sci USA 105:6572 • Baron R, Riley C, Chenprakhon P, Thotsaporn K, Winter RT, Alfieri A, Forneris F, van Berkel WJ, Chaiyen P, Fraaije MW, Mattevi A, McCammon JA (2009) Proc Natl Acad Sci USA, 106:10603 Time-dependent representation of the O2 pathways is displayed using volume isosurfaces colored depending on the simulation time from blue (entrance into the protein) to red (end of successful path).