Speaker
Description
The role of macromolecular excluded-volume effects in living systems (``macromolecular crowding'') is widely appreciated, but model crowders used in these studies are inadequately characterized. In this work, we examine viscosity, polymer self-diffusion and water diffusion in solutions crowded by dextran polymer of three different molecular weights. Solution viscosity and the reduced dextran self-diffusion follow size-dependent trends. The concentration dependence of the viscosity is well accounted for by power laws that signal a crossover from dilute to semi-dilute behaviors, with the latter scaling yielding a Flory exponent of 0.44 consistent with the branched nature of dextran. Dextran self-diffusion, on the other hand, has an exponential concentration dependence, which is consistent with an excess entropy scaling hypothesis. Finally, water diffusion decreases with polymer concentration but is independent of polymer molecular weight, and can be used to obtain the true excluded volume including hydration. In summary, well-characterized polymeric crowders are likely a good minimal option to mimic macromolecular crowding in cells.
| Keyword-1 | macromolecular crowding |
|---|---|
| Keyword-2 | branched polymers |
| Keyword-3 | self-diffusion |