Intracelluar Transport: Understanding Force Dependent Stepping

Within cells, small molecules such as glucose rely on diffusion to reach needed destinations.  Larger structures, like vesicles and organelles, need directed transport to navigate the crowded cytoplasm.  Molecular motor proteins provide the means for such transport, binding to intracellular cargo and stepping along in a hand-over-hand fashion on cytoskeletal railroads such as microtubules or actin filaments.  Molecular motor properties, such as the unburdened velocity and stepping rates, have a rich history of estimation through experiment.  In this talk, we will examine two experimental methods in an effort to understand force-dependent stepping and detachment rates for molecular motor proteins. Specifically, we will showcase three distinct models: 1) a mathematical model which qualitatively captures experimental observation; 2) a model for statistical inference and uncertainty quantification; and 3) a simplified model for rigorous analysis.  Through these models, we explore the consequences of model misspecification, the expected experimental behavior under different regimes, and develop guidelines for future experimentation.