By employing single particle tracking on the basis of fast video microscopy, we directly measure the equilibrium short and long time diffusion coefficients of blank and DNA-grafted (molecular weight of 250, 1000 and 4000 base pairs (bp)) tracer colloids in dilute lambda-DNA solutions. We compare these results to recently reported microfluidic mobilities under non-equilibrium steady state flow and to the predictions of quantitative theoretical models. A pronounced discrepancy between the measured equilibrium and non-equilibrium mobilities is observed for colloids grafted with 4000 bp DNA molecules, revealing the inapplicability of the Stokes-Einstein relation under these conditions. We demonstrate that this deviation may be interpreted as a strong micro-shear-thinning effect that is caused by the formation of entanglements between the grafted DNA brush and lambda-DNA coils from the suspension. (C) 2012 Elsevier Ltd. All rights reserved.