Conformations and diffusion of flexibly linked colloidal chains

TL;DR

This study investigates the conformations and diffusion behaviors of flexible colloidal chains, revealing how their shape and flexibility influence their motion, with implications for biological macromolecules and synthetic polymers.

Contribution

It provides experimental and simulation insights into the conformational statistics and diffusion properties of short, flexible colloidal chains, linking these behaviors to theoretical models.

Findings

Conformational statistics follow 2D Flory theory.

Diffusivity scales with Kirkwood-Riseman model.

Flexibility is determined by individual sphere diffusion.

Abstract

For biologically relevant macromolecules such as intrinsically disordered proteins, internal degrees of freedom that allow for shape changes have a large influence on both the motion and function of the compound. A detailed understanding of the effect of flexibility is needed in order to explain their behavior. Here, we study a model system of freely-jointed chains of three to six colloidal spheres, using both simulations and experiments. We find that in spite of their short lengths, their conformational statistics are well described by two-dimensional Flory theory, while their average translational and rotational diffusivity follow the Kirkwood-Riseman scaling. Their maximum flexibility does not depend on the length of the chain, but is determined by the near-wall in-plane translational diffusion coefficient of an individual sphere. Furthermore, we uncover shape-dependent effects in the short-time diffusivity of colloidal tetramer chains, as well as non-zero couplings between the different diffusive modes. Our findings may have implications for understanding both the diffusive behavior and the most likely conformations of macromolecular systems in biology and industry, such as proteins, polymers, single-stranded DNA and other chain-like molecules.