Localized Control of the Swarming of Kinesin-Driven Microtubules Using Light.

The swarming of self-propelled cytoskeletal filaments has emerged as a new aspect in the field of molecular machines or robotics, as it has overcome one of the major challenges of controlling the mutual interaction of a large number of individuals at a time. Recently, we reported on the photoregulated swarming of kinesin-driven cytoskeletal microtubule filaments in which visible (VIS) and ultraviolet (UV) light triggered the association and dissociation of the swarm, respectively. However, systematic control of this potential system has yet to be achieved to optimize swarming for further applications in molecular machines or robotics.

Autonomous assembly and disassembly of gliding molecular robots regulated by a DNA-based molecular controller.

In recent years, there has been a growing interest in engineering dynamic and autonomous systems with robotic functionalities using biomolecules. Specifically, the ability of molecular motors to convert chemical energy to mechanical forces and the programmability of DNA are regarded as promising components for these systems. However, current systems rely on the manual addition of external stimuli, limiting the potential for autonomous molecular systems.

Role of tubulin C-terminal tail on mechanical properties of microtubule.

Tubulin C-terminal tail (CTT) is a disordered segment extended from each tubulin monomer of αβ tubulin heterodimers, the building blocks of microtubules. The tubulin CTT contributes to the cellular function of microtubules such as intracellular transportation by regulating their interaction with other proteins and cell shape regulation by controlling microtubule polymerization dynamics. Although the mechanical integrity of microtubules is crucial for their functions, the role of tubulin CTT on microtubule mechanical properties has remained elusive.

Effects of three microtubule-associated proteins (MAP2, MAP4, and Tau) on microtubules' physical properties and neurite morphology.

The physical properties of cytoskeletal microtubules have a multifaceted effect on the expression of their cellular functions. A superfamily of microtubule-associated proteins, MAP2, MAP4, and tau, promote the polymerization of microtubules, stabilize the formed microtubules, and affect the physical properties of microtubules. Here, we show differences in the effects of these three MAPs on the physical properties of microtubules.

Reversible Photocontrol of Microtubule Stability by Spiropyran-Conjugated Tau-Derived Peptides.

Spatiotemporal modulation of microtubules by light has become an important aspect of the biological and nanotechnological applications of microtubules. We previously developed a Tau-derived peptide as a binding unit to the inside of microtubules. Here, we conjugated the Tau-derived peptide to spiropyran, which is reversibly converted to merocyanine by light, as a reversible photocontrol system to stabilize microtubules.

Collision-induced torque mediates the transition of chiral dynamic patterns formed by active particles.

Controlling the patterns formed by self-propelled particles through dynamic self-organization is a challenging task. Although varieties of patterns associated with chiral self-propelled particles have been reported, essential factors that determine the morphology of the patterns have remained unclear. Here, we explore theoretically how torque formed upon collision of the particles affects the dynamic self-organization of the particles and determine the patterns.

Generation of stable microtubule superstructures by binding of peptide-fused tetrameric proteins to inside and outside.

Microtubules play important roles in biological functions by forming superstructures, such as doublets and branched structures, in vivo. Despite the importance, it is challenging to construct these superstructures in vitro. Here, we designed a tetrameric fluorescent protein Azami-Green (AG) fused with His-tag and Tau-derived peptide (TP), TP-AG, to generate the superstructures.

Light-induced stabilization of microtubules by photo-crosslinking of a Tau-derived peptide.

For light-induced stabilization of microtubules (MTs) to manipulate cells, a photo-reactive diazirine group was conjugated to a Tau-derived peptide, a motif binding on the inside of MTs. Ultraviolet (UV) light irradiation induced significant stabilization of MTs the formation of a covalent bond of the peptide and showed toxicity.

Fluctuation in the Sliding Movement of Kinesin-Driven Microtubules Is Regulated Using the Deep-Sea Osmolyte Trimethylamine -Oxide.

Nowadays, biomolecular motor-based miniaturized lab-on-a-chip devices have been attracting much attention for their wide range of nanotechnological applications. Most of the applications are dependent on the motor-driven active transportation of their associated filamentous proteins as shuttles. Fluctuation in the movement of the shuttles is a major contributor to the dispersion in motor-driven active transportation, which limits the efficiency of the miniaturized devices.

Mechanical Deformation of Microtubules on a Two-Dimensional Elastic Medium.

Microtubule, the most rigid filamentous protein in cytoskeleton, plays significant roles in cellular mechano-transduction and mechano-regulation of cellular functions. In cells, the mechanical stress serves as a prevalent stimulus to frequently cause deformation of the microtubules participating in various cellular events. While the experimental and simulation-based approaches have confirmed the role of mechanical stress to tune mechanical properties of microtubule.

Cargo Transport by Microtubule-Associated Motor Protein Along Mechanically Deformed Microtubules.

Mechanical forces play pivotal roles in regulating various cellular functions. Biomolecular motor protein-driven intracellular transportation is one example which is affected by mechanical forces, although the mechanism at molecular level is unknown. In this chapter, we describe deformation of microtubules under compressive stress and we show that such deformation of microtubules affects the kinetics of dynein-driven cargo transportation along the microtubules.

Fabrication of Artificial Muscle from Microtubules, Kinesins, and DNA Origami Nanostructures.

Fabrication of molecular devices using biomolecules through biomimetic approaches has witnessed a surge in interest in recent years. DNA a versatile programmable material offers an opportunity to realize complicated operations through the designing of various nanostructures such as DNA origami. Here we describe the methods to use DNA origami for the self-assembly of the biomolecular motor system, microtubule (MT)-kinesin.

Construction of Molecular Robots from Microtubules for Programmable Swarming.

Swarm robotics has been attracting much attention in recent years in the field of robotics. This chapter describes a methodology for the construction of molecular swarm robots through precise control of active self-assembly of microtubules (MTs). Detailed protocols are presented for the construction of molecular robots through conjugation of DNA to MTs and demonstration of swarming of the MTs.

Dynamic Pattern Formation of Active Matters Triggered by Mechanical Stimuli.

In vitro gliding assay of the filamentous protein microtubule (MT) on a kinesin motor protein coated surface has appeared as a classic platform for studying active matters. At high densities, the gliding MTs spontaneously align and self-organize into fascinating large-scale patterns. Application of mechanical stimuli e.

Functionalization of Tubulin: Approaches to Modify Tubulin with Biotin and DNA.

The filamentous cytoskeletal protein microtubule, a polymer of α and β heterodimers of tubulin, plays major roles in intracellular transport as well as in vitro molecular actuation and transportation. Functionalization of tubulin dimers through covalent linkage facilitates utilization of microtubule in the nanobioengineering. Here we present a detailed description of the methodologies used to modify tubulin dimers with DNA strand and biotin through covalent interaction.

Controlling the Rigidity of Kinesin-Propelled Microtubules in an Gliding Assay Using the Deep-Sea Osmolyte Trimethylamine -Oxide.

The biomolecular motor protein kinesin and its associated filamentous protein microtubule have been finding important nanotechnological applications in the recent years. Rigidity of the microtubules, which are propelled by kinesin motors in an gliding assay, is an important metric that determines the success of utilization of microtubules and kinesins in various applications, such as transportation, sensing, sorting, molecular robotics, etc. Therefore, regulating the rigidity of kinesin-propelled microtubules has been critical.

Controlling Collective Motion of Kinesin-Driven Microtubules via Patterning of Topographic Landscapes.

Biomolecular motor proteins that generate forces by consuming chemical energy obtained from ATP hydrolysis play pivotal roles in organizing cytoskeletal structures in living cells. An ability to control cytoskeletal structures would benefit programmable protein patterning; however, our current knowledge is limited because of the underdevelopment of engineering approaches for controlling pattern formation. Here, we demonstrate the controlling of self-assembled patterns of microtubules (MTs) driven by kinesin motors by designing the boundary shape in fabricated microwells.

Deformation of microtubules regulates translocation dynamics of kinesin.

Microtubules, the most rigid components of the cytoskeleton, can be key transduction elements between external forces and the cellular environment. Mechanical forces induce microtubule deformation, which is presumed to be critical for the mechanoregulation of cellular events. However, concrete evidence is lacking.

Monopolar flocking of microtubules in collective motion.

Flocking is a fascinating coordinated behavior of living organisms or self-propelled particles (SPPs). Particularly, monopolar flocking has been attractive due to its potential applications in various fields. However, the underlying mechanism behind flocking and emergence of monopolar motion in flocking of SPPs has remained obscured.

Controlling the length of self-assembled microtubes through mechanical stress-induced scission.

We demonstrate that mechanical stress-induced scission is an effective strategy to control the length of self-assembled microtubes. By applying mechanical stress with variable magnitude and mode, the length of microtubes can be tightly regulated. We have succeeded in reducing the average length of microtubes ∼twenty-fold through stretching and compression.

Molecular swarm robots: recent progress and future challenges.

Recent advancements in molecular robotics have been greatly contributed by the progress in various fields of science and technology, particularly in supramolecular chemistry, bio- and nanotechnology, and informatics. Yet one of the biggest challenges in molecular robotics has been controlling a large number of robots at a time and employing the robots for any specific task as flocks in order to harness emergent functions. Swarming of molecular robots has emerged as a new paradigm with potentials to overcome this hurdle in molecular robotics.

Photo-regulated trajectories of gliding microtubules conjugated with DNA.

We regulate the persistency in motion of kinesin-driven microtubules (MTs) simply using a photoresponsive DNA (pDNA) and ultraviolet (UV)-visible light. The path persistence length of MTs, which is a measure of the persistency in their motion, increases and decreases upon illuminating the MTs with UV and visible light respectively. Moreover, pDNA is found to work as a shield for MTs against damage under UV irradiation.

Magnetic Force-Induced Alignment of Microtubules by Encapsulation of CoPt Nanoparticles Using a Tau-Derived Peptide.

Construction of magnetotactic materials is a significant challenge in nanotechnology applications such as nanodevices and nanotransportation. Artificial magnetotactic materials can be designed from magnetotactic bacteria because these bacteria use magnetic nanoparticles for aligning with and moving within magnetic fields. Microtubules are attractive scaffolds to construct magnetotactic materials because of their intrinsic motility.

Regulation of Biomolecular-Motor-Driven Cargo Transport by Microtubules under Mechanical Stress.

Mechanical stress on cells has profound influences on biological processes, such as cell shape regulation, the formation of tissue patterns, and development. Recently, mechanosensing properties of the microtubule, an important cytoskeletal component, have drawn attention. In this work, we studied cargo transport by dynein, a microtubule-associated motor protein, along microtubules deformed under mechanical stress.

Radial alignment of microtubules through tubulin polymerization in an evaporating droplet.

We report the formation of spherulites from droplets of highly concentrated tubulin solution via nucleation and subsequent polymerization to microtubules (MTs) under water evaporation by heating. Radial alignment of MTs in the spherulites was confirmed by the optical properties of the spherulites observed using polarized optical microscopy and fluorescence microscopy. Temperature and concentration of tubulins were found as important parameters to control the spherulite pattern formation of MTs where evaporation plays a significant role.