Effects of macromolecular crowding on the collapse of biopolymers

TL;DR

This paper investigates how macromolecular crowding influences biopolymer collapse, showing that crowding modestly shrinks IDPs but can induce DNA to transition from coil to globule, explained through scaling and simulation.

Contribution

The study introduces a combined scaling and simulation framework to quantitatively explain biopolymer behavior under crowding conditions, including the coil-to-globule transition.

Findings

IDPs are modestly reduced in size by crowding.

DNA undergoes coil-to-globule transition at small crowding volume fractions.

Theoretical model matches experimental observations.

Abstract

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