Effects of macromolecular crowding on the collapse of biopolymers

Abstract

Experiments show that macromolecular crowding modestly reduces the size of intrinsically disordered proteins (IDPs) even at volume fraction ($\varphi$) similar to that in the cytosol whereas DNA undergoes a coil-to-globule transition at very small $\varphi$. We show using a combination of scaling arguments and simulations that the polymer size ${\overline{R}}_g(\varphi )$ depends on $x={\overline{R}}_g(0)/D$ where $D$ is the $\varphi$-dependent distance between the crowders. If $x\lesssim \mathcal{O}(1)$, there is only a small decrease in ${\overline{R}}_g(\varphi )$ as $\varphi$ increases. When $x\gg \mathcal{O}(1)$, a cooperative coil-to-globule transition is induced. Our theory quantitatively explains a number of experiments.

7 pages 5 figures, accepted in Phys. Rev. Lett