Rotary Motor Research Articles

Quantum‐Classical Simulations Reveal the Photoisomerization Mechanism of a Prototypical First‐Generation Molecular Motor

Light‐driven molecular rotary motors convert the energy of absorbed light into unidirectional rotational motion and are key components in the design of molecular machines. The archetypal class of light‐driven rotary motors is chiral overcrowded alkenes, where the rotational movement is achieved through consecutive cis‐trans photoisomerization reactions and thermal helix inversion steps. While the thermal steps have been rather well understood by now, our understanding of the photoisomerization reactions of overcrowded alkene‐based motors still misses key points that would explain the striking differences in operation efficiency of the known systems. Here, we employ quantum‐chemical calculations and nonadiabatic molecular dynamics simulations to investigate the excited‐state decay and photoisomerization mechanism in a prototypical alkene‐based first‐generation rotary motor. We show that the initially excited bright state undergoes an ultrafast relaxation to multiple excited‐ state minima separated by low energy barriers and reveal a slow picosecond‐timescale decay to the ground state, which only occurs from a largely twisted dark excited‐state minimum, far from any conical‐intersection point. Additionally, we attribute the origin of the high yields of forward photoisomerization in our investigated motor to the favorable topography of the ground‐state potential energy surface, which is controlled by the conformation of the central cyclopentene rings.

A Chemically Powered Rotary Molecular Motor Based on Reversible Oxazepine Formation.

While biological machines are powered mainly by chemical transformations, chemically driven artificial rotary motor systems are very limited. Here, we report an aniline-phenol-based rotary molecular motor that operates via an information ratchet mechanism. The 360° directional rotation about a single covalent bond can be chemically driven by reversible oxazepine formation. Both the oxazepine formation and hydrolysis steps are kinetically gated via dynamic kinetic resolution, arising from the kinetic bias of chiral catalysts for enantiomers. Given the 95 % ee (97.5 : 2.5) and 88 % ee (94 : 6) of the individual gating steps of motor analogues, the overall directionality ratio could be calculated to be 91.7 : 8.3 (97.5 %×94 %≈91.7 %), which means that the motor will make one mistake (backward rotation) approximately every 11 to 12 turns.

ЕЛЕКТРОМЕХАНІЧНІ ХАРАКТЕРИСТИКИ БЕЗКОНТАКТНОГО ДВИГУНА З ПОСТІЙНИМИ МАГНІТАМИ ПРИ ШИРОТНО-ІМПУЛЬСНОМУ ЖИВЛЕННІ

The paper is devoted to the study of the characteristics and operating modes of a brushless permanent magnet motor in the structure of an electric drive with a two-wire external power supply from a voltage source with pulse-width regulation. The dependences of the motor rotation frequency, the stator current effective value and the average value of the current in the DC link of the voltage inverter, as well as the dependences of the torque coefficient on the average value of the motor torque are given. The influence of the frequency of the pulse supply voltage on the operating modes of the motor is studied. The current and torque limitation modes of the motor in a system with a single-position relay controller and a fixed transistor shutdown interval former are studied. Ref. 12, fig. 16.

Combined vibration control of flexible cantilever beam driven by MFC actuators and rotary motor

Combined vibration control of flexible cantilever beam driven by MFC actuators and rotary motor

Visualizing Single V-ATPase Rotation Using Janus Nanoparticles.

Understanding the function of rotary molecular motors, such as rotary ATPases, relies on our ability to visualize single-molecule rotation. Traditional imaging methods often involve tagging those motors with nanoparticles (NPs) and inferring their rotation from the translational motion of NPs. Here, we report an approach using "two-faced" Janus NPs to directly image the rotation of a single V-ATPase from Enterococcus hirae, an ATP-driven rotary ion pump. By employing a 500 nm silica/gold Janus NP, we exploit its asymmetric optical contrast, a silica core with a gold cap on one hemisphere, to achieve precise imaging of the unidirectional counterclockwise rotation of single V-ATPase motors immobilized on surfaces. Despite the added viscous load from the relatively large Janus NP probe, our approach provides accurate torque measurements of a single V-ATPase. This study underscores the advantages of Janus NPs over conventional probes, establishing them as powerful tools for the single-molecule analysis of rotary molecular motors.

Model approach of artificial muscle and leg movements

In this work, two flexible ropes are winded to an electronic motor in opposite directions and the other terminal ends are pinned to two jointed points for mimicking the artificial muscles. Electrical signals from a neural circuit are used to control the rotation of electronic motor(s), and the pulling forces along the flexible ropes control the rotation angles of the jointed pendulums as legs. The leg gaits are investigated in dynamics by changing the channel current shunted from the neural circuit, and the electronic motor-controlled flexible ropes behave as artificial muscles. A single neural circuit and two coupled neural circuits are used to control the electromechanical legs by adjusting the forcing current. The neural circuit drives the electronic motor and then jointed pendulums are controlled. The circuit equations, rotation equations and energy description are presented. It provides possible guidance to design artificial muscles for aiding disabled legs and arms.

A high-response-frequency bimodal network polyacrylate elastomer with ultrahigh power density under low electric field

Dielectric elastomers, used as driver modules, require high power density to enable fast movement and efficient work of soft robots. Polyacrylate elastomers usually suffer from low power density under low electric fields due to limited response frequency. Here, we propose a bimodal network polyacrylate dielectric elastomer which breaks the intrinsic coupling relationship between dielectric and mechanical properties, featuring relatively high dielectric constant, low Young’s modulus, and wide driving frequency bandwidth (~200 Hz) like silicones. Therefore, an ultrahigh power density (154 W kg−1@20 MV m−1, 200 Hz) is realized at low electric field and high resonance frequency, 75 times greater than at 10 Hz. Further, a rotary motor is developed, reaching an impressive speed of 1245 rpm at 19.6 MV m−1 and 125 Hz, surpassing previous acrylate-based motors and entering the high-speed domain of silicone-based motors. These findings offer a versatile strategy to fabricate high-power-density dielectric elastomers for low-electric-field soft actuators.

Design and experimental evaluation of a non-contact ultrasonic motor using acoustic phase holography

Abstract Non-contact ultrasonic motors address certain limitations of conventional ultrasonic motors. However, they continue to have intricate designs and electronics. Acoustic holography has emerged as a technique for its flexibility and dynamicity in manipulating acoustic phase and amplitude patterns in the nearfield, offering a reduction in mentioned complexities. Therefore, this technique may find utility in the development of non-contact ultrasonic motors. This paper discusses a novel design for non-contact rotary ultrasonic motor using acoustic holography. Acoustic holographic technique modulates the acoustic phase to create a phase gradient, resulting in a rotary flow that drives the rotor in the interface of aqueous media and air. The motor’s performance is influenced by factors such as the acoustic pressure amplitude, the number of 0 to 2 π pitches, and the rotor’s geometry. An empirical study using the Response Surface Method (RSM) identified an optimal number of pitches for maximum rotational speed at a constant voltage. The motor torque was measured by calculating the drag forces applied to the rotor blades. It was found that the minimum output torque occurs when the stator phase pitches match the rotor blades. The ideal motor performance is achieved with eight rotor blades and six phase pitches. The motor’s top speed reached 40 rpm, and the output torque varied around 0.1 μN.m, depending on the phase pitches and rotor blades. In summary, the research highlights the potential of acoustic holography in designing a non-contact ultrasonic motor, with specific configurations yielding optimal speed and torque.

Coupling Rotary Motion to Helicene Inversion within a Molecular Motor.

Towards complex coupled molecular motions, the remote handedness inversion of a helicene moiety was achieved by a rotary molecular motor. The use of a specifically engineered dynamic helicene stator in a novel overcrowded-alkene second-generation molecular motor based on a fluorinated dibenzofluorene fragment allows for an unprecedented control over helicity inversion. This is achieved by the mechanical coupling of the rotation of the rotor to the helicene inversion of the stator half via a remote chirality transmission process. Thus, the unidirectional rotary motion generated upon irradiation is used to invert the dynamic stereochemistry of a helicene, leading to a 6-steps cycle with eight intermediates. In this cycle, both alternation between P and M configurations of the helicene stator and dynamic thermal interconversion (paddling motion) can be achieved. In-depth computational and spectroscopic studies were performed to support the associated mechanism. The control over coupled motion and dynamic helicity offers prospects for the development of complex responsive systems.

Coupling Rotary Motion to Helicene Inversion within a Molecular Motor

Towards complex coupled molecular motions, the remote handedness inversion of a helicene moiety was achieved by a rotary molecular motor. The use of a specifically engineered dynamic helicene stator in a novel overcrowded‐alkene second‐generation molecular motor based on a fluorinated dibenzofluorene fragment allows for an unprecedented control over helicity inversion. This is achieved by the mechanical coupling of the rotation of the rotor to the helicene inversion of the stator half via a remote chirality transmission process. Thus, the unidirectional rotary motion generated upon irradiation is used to invert the dynamic stereochemistry of a helicene, leading to a 6‐steps cycle with eight intermediates. In this cycle, both alternation between P and M configurations of the helicene stator and dynamic thermal interconversion (paddling motion) can be achieved. In‐depth computational and spectroscopic studies were performed to support the associated mechanism. The control over coupled motion and dynamic helicity offers prospects for the development of complex responsive systems.

Characterization of Stepper Motor Rotation for Automatic Self-Cleaning Litter Box Using IOT Technology

Characterization of Stepper Motor Rotation for Automatic Self-Cleaning Litter Box Using IOT Technology

Development of a Multi-Motor Asynchronous Electric Drive with Changes in the Coordinated Rotation of the Supply Voltages of the Motors

This study considered the issue of increasing the synchronizing capacity of a system for the coordinated rotation of asynchronous motors. Electromechanical relationships were obtained for changes in the value of the supply voltage of individual motors, the total rotor resistance (Ra), and the angular positions of the rotors (φ1, φ2, and φ3), with possible changes in angular misalignment. Additionally, we created an algorithm for calculating the currents and torques of the system’s motors within 0 and 90° and constructed the relevant mechanical characteristics. Ultimately, we developed various versions of multi-motor asynchronous electric drives with regulation and supply voltages (Un = 0.7 ÷ 1.0), featuring increasing and equalizing torques (Mn = 1.0 ÷ 1.4) in the system as a whole, along with the preliminary synchronization and synchronous braking of all motors.

A supervised machine learning model to select a cost-effective directional drilling tool

With the increased directional drilling activities in the oil and gas industry, combined with the digital revolution amongst all industry aspects, the need became high to optimize all planning and operational drilling activities. One important step in planning a directional well is to select a directional tool that can deliver the well in a cost-effective manner. Rotary steerable systems (RSS) and positive displacement mud motors (PDM) are the two widely used tools, each with distinct advantages: RSS excels in hole cleaning, sticking avoidance and hole quality in general, while PDM offers versatility and lower operating costs. This paper presents a series of machine learning (ML) models to automate the selection of the optimal directional tool based on offset well data. By processing lithology, directional, drilling performance, tripping and casing running data, the model predicts section time and cost for upcoming wells. Historical data from offset wells were split into training and testing sets and different ML algorithms were tested to choose the most accurate one. The XGBoost algorithm provided the most accurate predictions during testing, outperforming other algorithms. The beauty of the model is that it successfully accounted for variations in formation thicknesses and drilling environment and adjusts tool recommendations accordingly. Results show that no universal rule favors either RSS or PDM; rather, tool selection is highly dependent on well-specific factors. This data-driven approach reduces human bias, enhances decision-making, and could significantly lower field development costs, particularly in aggressive drilling campaigns.

Photoreceptor-Like Signal Transduction Between Polymer-Based Protocells.

Deciphering inter- and intracellular signaling pathways is pivotal for understanding the intricate communication networks that orchestrate life's dynamics. Communication models involving bottom-up construction of protocells are emerging but often lack specialized compartments sufficiently robust and hierarchically organized to perform spatiotemporally defined signaling. Here, the modular construction of communicating polymer-based protocells designed to mimic the transduction of information in retinal photoreceptors is presented. Microfluidics is used to generate polymeric protocells subcompartmentalized by specialized artificial organelles. In one protocell population, light triggers artificial organelles with membrane-embedded photoresponsive rotary molecular motors to set off a sequence of reactions starting with the release of encapsulated signaling molecules into the lumen. Intercellular communication is mediated by signal transfer across membranes to protocells containing catalytic artificial organelles as subcompartments, whose signal conversion can be modulated by environmental calcium. Signal propagation also requires selective permeability of the diverse compartments. By segregating artificial organelles in distinct protocells, a sequential chain of reactions mediating intercellular communication is created that is further modulated by adding extracellular messengers. This connective behavior offers the potential for a deeper understanding of signaling pathways and faster integration of proto- and living cells, with the unique advantage of controlling each step by bio-relevant signals.

Bidirectional Molecular Motors by Controlling Threading and Dethreading Pathways of a Linked Rotaxane.

Artificial molecular motors have been presented as models for biological molecular motors. In contrast to the conventional artificial molecular motors that rely on covalent bond rotation, molecular motors with mechanically interlocked molecules (MIM) have attracted considerable attention owing to their ability to generate significant rotational motion by dynamically shuttling macrocyclic components. The topology of MIM-type rotational molecular motors is currently limited to catenane structures, which require intricate synthetic procedures that typically produce a low synthetic yield. In this study, we develop a novel class of MIM-type molecular motors with a rotaxane-type topology. The switching of the threading/dethreading pathways of the linked rotaxane by protecting/deprotecting the bulky stopper group and changing the solvent polarity enables a net unidirectional rotation of the molecular motor. The threading/dethreading reaction rates were quantitatively evaluated through detailed spectroscopic investigations. Repeated net unidirectional rotation and switching of the direction of rotation were also achieved. Our findings demonstrate that linked rotaxanes can serve as MIM-type molecular motors with reversible rotational direction controlled by threading/dethreading reactions. These motors hold potential as components of molecular machinery.

Bidirectional Molecular Motors by Controlling Threading and Dethreading Pathways of a Linked Rotaxane

AbstractArtificial molecular motors have been presented as models for biological molecular motors. In contrast to the conventional artificial molecular motors that rely on covalent bond rotation, molecular motors with mechanically interlocked molecules (MIMs) have attracted considerable attention owing to their ability to generate significant rotational motion by dynamically shuttling macrocyclic components. The topology of MIM‐type rotational molecular motors is currently limited to catenane structures, which require intricate synthetic procedures that typically produce a low synthetic yield. In this study, we develop a novel class of MIM‐type molecular motors with a rotaxane‐type topology. The switching of the threading/dethreading pathways of the linked rotaxane by protecting/deprotecting the bulky stopper group and changing the solvent polarity enables a net unidirectional rotation of the molecular motor. The threading/dethreading reaction rates were quantitatively evaluated through detailed spectroscopic investigations. Repeated net unidirectional rotation and switching of the direction of rotation were also achieved. Our findings demonstrate that linked rotaxanes can serve as MIM‐type molecular motors with reversible rotational direction controlled by threading/dethreading reactions. These motors hold potential as components of molecular machinery.

Molecular mechanism of flagellar motor rotation arrest in bacterial zoospores of Actinoplanes missouriensis before germination

Zoospores of the filamentous actinomycete Actinoplanes missouriensis swim vigorously using flagella and stop swimming to initiate germination in response to nutrient exposure. However, the molecular mechanisms underlying swimming cessation remain unknown. A protein (FtgA) of unknown function encoded by a chemotaxis gene cluster (che cluster-1) was found to be required for flagellar rotation arrest; the zoospores of ftgA-knockout mutants kept swimming awkwardly after germination. An ftgA-overexpressing strain exhibited a non-flagellated phenotype. Isolation of a suppressor strain from this strain and further in vivo experiments revealed that the extended N-terminal region of FliN, a component of the C-ring of the flagellar basal body, was involved in the function of FtgA; FliN-P101S canceled the flagellar rotation arrest by FtgA, as well as the negative effect of ftgA-overexpression on flagellation. Furthermore, bacterial two-hybrid assays suggested that FtgA interacted not only with the C-terminal core region of FliN but also with chemotaxis regulatory proteins CheA1 and CheW1-2, which are encoded by che cluster-1. We propose the following working model of motility regulation in A. missouriensis zoospores: the chemotaxis sensory complex initially captures FtgA to allow zoospores to swim and then releases FtgA to stop flagellar rotation (i.e., swimming) in response to external nutrient signals.

Interface-packing analysis of F1-ATPase using integral equation theory and manifold learning

It has been shown that the translational entropy of water plays a key role in biological processes such as protein folding and ligand binding. Under the physiological condition, tightly packed protein conformations like native structures are achieved so that the translational entropy of water is maximized. In this study, we investigate the rotation mechanism of a rotary protein motor, F1-ATPase, by analyzing the packing at the interfaces between the subunits. The packing at the interface between a subunit pair is analyzed using the change in the solvent entropy upon forming subunit pair, ∆S. It is found that as the γ subunit rotates, the ∆S value of a α-β subunit pair decrease because the interface packing becomes loose. However, because the interface packing of another α-β subunit pair becomes tighter upon the rotation, ∆S of this α-β subunit pair increases, leading to a compensation of the decrease in ∆S. Such compensation would be necessary to maximize the solvent entropy of F1-ATPase. In this study, packing at the interfaces between the subunits is also analyzed using a manifold-learning technique, and it is suggested a possibility that a qualitative estimation of the ∆S values of some α-β subunit pairs can be predicted using a manifold-learning technique.

Effect of load-resisting force on photoisomerization mechanism of a single second generation light-driven molecular rotary motor.

A pivotal aspect of molecular motors is their capability to generate load capacity from a single entity. However, few studies have directly characterized the load-resisting force of a single light-driven molecular motor. This research provides a simulation analysis of the load-resisting force for a highly efficient, second-generation molecular motor developed by Feringa et al. We investigate the M-to-P photoinduced nonadiabatic molecular dynamics of 9-(2,3-dihydro-2-methyl-1H-benz[e]inden-1-ylidene)-9H-fluorene utilizing Tully's surface hopping method at the semi-empirical OM2/MRCI level under varying load-resisting forces. The findings indicate that the quantum yield remains relatively stable under forces up to 0.003a.u., with the photoisomerization mechanism functioning typically. Beyond this threshold, the quantum yield declines, and an alternative photoisomerization mechanism emerges, characterized by an inversion of the central double bond's twisting direction. The photoisomerization process stalls when the force attains a critical value of 0.012a.u. Moreover, the average lifetime of the excited state oscillates around that of the unperturbed system. The quantum yield and mean lifetime of the S1 excited state in the absence of external force are recorded at 0.54 and 877.9fs, respectively. In addition, we analyze a time-dependent fluorescence radiation spectrum, confirming the presence of a dark state and significant vibrations, as previously observed experimentally by Conyard et al.

Chromatin Buffers Torsional Stress During Transcription.

Transcription through chromatin under torsion represents a fundamental problem in biology. Pol II must overcome nucleosome obstacles and, because of the DNA helical structure, must also rotate relative to the DNA, generating torsional stress. However, there is a limited understanding of how Pol II transcribes through nucleosomes while supercoiling DNA. In this work, we developed methods to visualize Pol II rotation of DNA during transcription and determine how torsion slows down the transcription rate. We found that Pol II stalls at ± 9 pN·nm torque, nearly sufficient to melt DNA. The stalling is due to extensive backtracking, and the presence of TFIIS increases the stall torque to + 13 pN·nm, making Pol II a powerful rotary motor. This increased torsional capacity greatly enhances Pol II's ability to transcribe through a nucleosome. Intriguingly, when Pol II encounters a nucleosome, nucleosome passage becomes more efficient on a chromatin substrate than on a single-nucleosome substrate, demonstrating that chromatin efficiently buffers torsional stress via its torsional mechanical properties. Furthermore, topoisomerase II relaxation of torsional stress significantly enhances transcription, allowing Pol II to elongate through multiple nucleosomes. Our results demonstrate that chromatin greatly reduces torsional stress on transcription, revealing a novel role of chromatin beyond the more conventional view of it being just a roadblock to transcription.