Quantitative Analysis of \textit{Dictyostelium Discoideum} Chemotaxis*

We used microfluidic tools to expose \textit{Dictyostelium discoideum} to stationary spatial gradients of the chemoattractant cyclic adenosine 3',5' monophosphate (cAMP). At a cAMP gradient of $10^{-2}$ ${\rm nM}/\mu{\rm m}$, the chemotactic velocity reached a plateau, which continued for gradients up to 1 ${\rm nM}/\mu{\rm m}$. Our measurements agree with [Song at al, Eur. J. Cell Biol., 85(10):981]. We also found that the chemotactic velocity was highly correlated with the cell's polarization. We present a model based on a generalized Langevin equation that provides good agreement with the measured data.