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Abstract DNA motors that consume chemical energy to generate processive mechanical motion mimic natural motor proteins and have garnered interest due to their potential applications in dynamic nanotechnology, biosensing, and drug delivery. Such motors translocate by a catalytic cycle of binding, cleavage, and rebinding between DNA “legs” on the motor body and RNA “footholds” on a track. Herein, we address the well‐documented trade‐off between motor speed and processivity and investigate how these parameters are controlled by the affinity between DNA legs and their complementary footholds. Specifically, we explore the role of DNA leg length and GC content in tuning motor performance by dictating the rate of leg‐foothold dissociation. Our investigations reveal that motors with 0 % GC content exhibit increased instantaneous velocities of up to 150 nm/sec, three‐fold greater than previously reported DNA motors and comparable to the speeds of biological motor proteins. We also demonstrate that the faster speed and weaker forces generated by 0 % GC motors can be leveraged for enhanced capabilities in sensing. We observe single‐molecule sensitivity when programming the motors to stall in response to the binding of nucleic acid targets. These findings offer insights for the design of high‐performance DNA motors with promising real‐world biosensing applications. 

Molecular motors, such as myosin and kinesin, perform diverse tasks ranging from vesical transport to bulk muscle contraction. Synthetic molecular motors may eventually be harnessed to perform similar tasks in versatile synthetic systems. The most promising type of synthetic molecular motor, the DNA walker, can undergo processive motion but generally exhibits low speeds and virtually no capacity for force generation. However, we recently showed that highly polyvalent DNA motors (HPDMs) can rival biological motors by translocating at micrometer per minute speeds and generating 100+ pN of force. Accordingly, DNA nanotechnology-based designs may hold promise for the creation of synthetic, force-generating nanomotors. However, the dependencies of HPDM speed and force on tunable design parameters are poorly understood and difficult to characterize experimentally. To overcome this challenge, we present RoloSim, an adhesive dynamics software package for fine-grained simulations of HPDM translocation. RoloSim uses biophysical models for DNA duplex formation and dissociation kinetics to explicitly model tens of thousands of molecular scale interactions. These molecular interactions are then used to calculate the nano-and microscale motions of the motor. We use RoloSim to uncover how motor force and speed scale with several tunable motor properties such as motor size and DNA duplex length. Our results support our previously defined hypothesis that force scales linearly with polyvalency. We also demonstrate that HPDMs can be steered with external force, and we provide design parameters for novel HPDM-based molecular sensor and nanomachine designs. 

Reactivity trends for molecular solids cannot be explained exclusively through the topochemical phenomenon ( i.e. diffusivity, reaction cavities) or electronic structure of the molecules. As an example of this class, Diels–Alder reactions of small molecules with pentacene thin films are examined to elucidate the importance of surface phenomena to reactivity. Polarization modulation-infrared reflection–absorption spectroscopy (PM-IRRAS) has revealed that vapors from the small molecules condense on the surface, in a non-covalent manner, to form a coating 2–3 molecules thick. The phase of this layer can provide increased surface diffusion (both reactant and product) which rapidly accelerates the reaction rate. Kinetic studies of pentacene thin film reactions demonstrate the importance of this condensed state to trends in reactivity, with layers in a quasi-liquid state showing a rate acceleration of 13–30 times compared to those in a quasi-solid state. Scanning electron microscopy provides further evidence of this phase behavior, while solid-state UV-vis confirms the kinetic results. 

Abstract Inspired by biological motor proteins, that efficiently convert chemical fuel to unidirectional motion, there has been considerable interest in developing synthetic analogues. Among the synthetic motors created thus far, DNA motors that undertake discrete steps on RNA tracks have shown the greatest promise. Nonetheless, DNA nanomotors lack intrinsic directionality, are low speed and take a limited number of steps prior to stalling or dissociation. Herein, we report the first example of a highly tunable DNA origami motor that moves linearly over micron distances at an average speed of 40 nm/min. Importantly, nanomotors move unidirectionally without intervention through an external force field or a patterned track. Because DNA origami enables precise testing of nanoscale structure‐function relationships, we were able to experimentally study the role of motor shape, chassis flexibility, leg distribution, and total number of legs in tuning performance. An anisotropic rigid chassis coupled with a high density of legs maximizes nanomotor speed and endurance.