Conformations and diffusion of flexibly linked colloidal chains

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.

Polymorphism and Perfection in Crystallization of Hard Sphere Polymers

“…Experiments on linear polymers of hard spheres are very challenging. In spite of the granular, colloidal, or droplet polymers being significantly less well explored than the “traditional” ones, over the years, there have been significant advances in their synthesis and characterization [ 61 , 62 , 63 , 64 , 65 ]. From the perspective of theory and simulation [ 66 , 67 ], emphasis is placed on the phase transition of semi-flexible [ 68 , 69 , 70 ] or flexible [ 71 , 72 ] chains of hard spheres, while recently, it was demonstrated that the use of block copolymers leads to HCP stable phases [ 73 , 74 , 75 ].…”

Self-Assembly Dynamics of Reconfigurable Colloidal Molecules

“… 37 The assembly of a single flexible tetrahedral cluster by holographic optical tweezers was demonstrated as a proof of principle. 28 However, while this method is very useful to study the dynamics of individual colloidal molecules with internal degrees of freedom, 20 , 28 , 38 the time-consuming particle-by-particle addition is not a viable approach for the production of more than a few individual flexible colloidal molecules.…”

“…The particles were mixed in a number ratio of 1:5 and 1:20 to obtain good statistics, and the growth of the colloidal molecules was observed for 1.2 days. At this number ratio, a few colloidal polymers ,, and other composite structures were produced besides the colloidal molecules, which were excluded from the total count to enable a comparison with the simulations. The population growth at different N ’s including and up to the expected maximum N max = 4 were recorded at fixed time intervals.…”

Non-Gaussian, transiently anomalous and ergodic self-diffusion of flexible dumbbells in crowded two-dimensional environments: coupled translational and rotational motions

“…Normal and anomalous diffusion in the crowded solutions of anisotropic and/or non-spherical-as well as of spherical but non-isotropically interacting 80,81 molecules was examined in a number of studies , including some recent experimental investigations 96,99,104 . The diffusive properties of molecules of dumbbell-, ellipsoid-, and rod-like shape 82,96,97,100,101,[104][105][106][107][108][109] , protein molecules 110,111 , active and passive dimers with anisotropic mobility 89,102,106,[112][113][114] , self-propelled massive particles with time-dependent mass 109 , colloidal dimers and flexible multimers 115,116 , stiff self-propelled filaments in crowded solutions 117 , trimer-like tracers in 2D 93,95 and tetrahedral patchy particles in 3D 81,118 , as well as the dynamics of elongated particles with fluctuating and oscillating shapes [119][120][121] were studied recently as well.…”