Active liquid crystals powered by force-sensing DNA-motor clusters

Abstract

Cytoskeletal active nematics exhibit striking nonequilibrium dynamics that are powered by energy-consuming molecular motors. To gain insight into the structure and mechanics of these materials, we design programmable clusters in which kinesin motors are linked by a double-stranded DNA linker. The efficiency by which DNA-based clusters power active nematics depends on both the stepping dynamics of the kinesin motors and the chemical structure of the polymeric linker. Fluorescence anisotropy measurements reveal that the motor clusters, like filamentous microtubules, exhibit local nematic order. The properties of the DNA linker enable the design of force-sensing clusters. When the load across the linker exceeds a critical threshold, the clusters fall apart, ceasing to generate active stresses and slowing the system dynamics. Fluorescence readout reveals the fraction of bound clusters that generate interfilament sliding. In turn, this yields the average load experienced by the kinesin motors as they step along the microtubules. DNA-motor clusters provide a foundation for understanding the molecular mechanism by which nanoscale molecular motors collectively generate mesoscopic active stresses, which in turn power macroscale nonequilibrium dynamics of active nematics.

Engineering stability, longevity, and miscibility of microtubule-based active fluids

“…Indeed, experiments suggested that kinesin-1 motors in active nematics are under a significant loads that are directed along the direction of MT alignment. 59…”

“…Importantly, K560-SNAP like K401 and to lesser extend K365 can spontaneously oligomerize and thus could power the active fluid even in the absence of any BG-labeled MTs. 53 This non-specific activity was eliminated using the dissociation buffer and the centrifugation steps in this protocol which removes the K560-SNAP that are not attached to the BG-MT via SNAP-BG reaction.…”

Learning without neurons in physical systems

“…self-propelled particles) can expend energy and perform actions on microscopic scales. Such systems are potentially capable of learning either by combining synthetic active matter with DNA-based elements (67) and through rearrangement of nematic or polar filaments as in natural systems such as the cytoskeleton (68,69). Related ideas have been explored through simulations (70,71,72), though truly autonomous learning has yet to be demonstrated on the molecular scale.…”

DNA-Controlled Spatiotemporal Patterning of a Cytoskeletal Active Gel

“…25−29 Whereas the former have the advantage of greater programmability, they lack the self-organization properties of cytoskeletal active gels. 30−33 Despite progress in using DNA to tune the rheology of active gels 29,34 or to trigger its activity on the microscale, 25,26,35 we lack methods to control the spatiotemporal self-organization of cytoskeletal active gels on the macroscale, as we demonstrate in the following.…”

“…A promising route relies on DNA hybridization reactions triggering forces that change the shape of hydrogels. Indeed, DNA reactions can be exquisitely controlled − and coupled to a great variety of materials. − The mechanical amplification of a DNA signal can be performed by either DNA reactions, such as in DNA-responsive hydrogels, , or motor proteins, such as in DNA-based cytoskeletal active gels. − Whereas the former have the advantage of greater programmability, they lack the self-organization properties of cytoskeletal active gels. − Despite progress in using DNA to tune the rheology of active gels , or to trigger its activity on the microscale, ,, we lack methods to control the spatiotemporal self-organization of cytoskeletal active gels on the macroscale, as we demonstrate in the following.…”