Scattering fingerprints of two-state dynamics

Abstract Particle transport in complex environments such as the interior of living cells is often (transiently) non-Fickian or anomalous, that is, it deviates from laws Brownian motion. Such anomalies may be result small-scale spatio-temporal heterogeneities in, viscoelastic properties of, medium, molecular crowding, etc. Often observed dynamics displays multi-state characteristics, i.e. distinct modes dynamically interconverting between each other a stochastic manner. Reliably distinguishing single- and challenging requires combination approaches. To complement existing methods relying on analysis particle’s mean squared displacement, position- displacement-autocorrelation function, propagators, we here focus ‘scattering fingerprints’ dynamics. We develop theoretical framework for two-state scattering signatures—the intermediate function dynamic structure factor—and apply to simple model systems well particle-tracking experiments cells. consider inert tracer-particle motion with an internal Our results generally relevant interpretation state-of-the-art differential microscopy particulate systems, inelastic quasielastic neutron (incl. spin-echo) x-ray probing structural dynamical macromolecules, when underlying transport.