Discrete breathers in a realistic coarse-grained model of proteins

We report the results of molecular dynamics simulations of an off-lattice protein model featuring a physicalforce-field and amino-acid sequence. We show that localized modes of nonlinear origin, discrete breathers(DB), emerge naturally as continuations of a subset of high-frequency normal modes residing at specificsites dictated by the native fold. In the case of the small beta-barrel structure that we consider, DB-mediatedlocalization occurs on the turns connecting the strands. At high energies, discrete breathers stabilise thestructure by concentrating energy on few sites, while their collapse marks the onset of large-amplitudefluctuations of the protein. Furthermore, we show how breathers develop as energy-accumulating centresfollowing perturbations even at distant locations, thus mediating efficient and irreversible energytransfers. Remarkably, due to the presence of angular potentials, the breather induces a local staticdistortion of the native fold. Altogether, the combination of this two nonlinear effects may provide a readymeans for remotely controlling local conformational changes in proteins.