Ring closure dynamics for a chemically active polymer

Abstract

The principles that underlie the motion of colloidal particles in concentration gradients and the propulsion of chemically-powered synthetic nanomotors are used to design active polymer chains. The active chains contain catalytic and noncatalytic monomers, or beads, at the ends or elsewhere along the polymer chain. A chemical reaction at the catalytic bead produces a self-generated concentration gradient and the noncatalytic bead responds to this gradient by a diffusiophoretic mechanism that causes these two beads to move towards each other. Because of this chemotactic response, the dynamical properties of these active polymer chains are very different from their inactive counterparts. In particular, we show that ring closure and loop formation are much more rapid than those for inactive chains, which rely primarily on diffusion to bring distant portions of the chain in close proximity. The mechanism presented in this paper can be extended to other chemical systems which rely on diffusion to bring reagents into contact for reactions to occur. This study suggests the possibility that synthetic systems could make use of chemically-powered active motion or chemotaxis to effectively carry out complex transport tasks in reaction dynamics, much like those that molecular motors perform in biological systems.

Anomalous, non-Gaussian tracer diffusion in crowded two-dimensional environments

“…In the present study we neglected hydrodynamic interactions between the tracer and the crowders. In threedimensional systems this may affect the long time diffusion [2,50,[124][125][126]. The slow, 1/r decay of this hydrodynamic coupling implies that a diffusing particle is impacted by crowders from a finite distance that helps avoiding to collide with the crowders.…”

Brownian microhydrodynamics of active filaments

“…Activity, in the forms envisaged in this work, introduces an additional drift in the Fokker-Planck equation, destroying the balance between fluctuation and dissipation. This will lead to non-Gibbsian distributions in the stationary state, and, likely change well-known equilibrium properties like statics of the coil-globule transition [43] and the distribution of loop closure times [30]. We urge that some of these problems be addressed both experimentally and through theory and simulations.…”

“…While activity can be expressed through a variety of boundary conditions on both the fluid velocity and on the fluid stress , we assume here an active slip at the surface of the particle [24]. This encompasses a wide variety of active phenomena, including electrophoresis, diffusiophoresis [29], self-phoresis due to chemical catalysis [30], and even swimming of microorganisms [31,32]. We chose the fluid to be at rest at infinity.…”

Dynamics of flexible active Brownian dumbbells in the absence and the presence of shear flow

“…66 and, e.g., a novel time dependent power-law regime for the shear modulus is obtained. Other aspects, such as activity-induced ring closer, 67 emerging beat patterns, 68 and collective phenomena, 63 have been studied. The intramolecular dynamics has been addressed, 64 and activity induced aggregation of individual polymers in two dimensions.…”