Biomolecular Motor‐Powered Self‐Assembly of Dissipative Nanocomposite Rings

Abstract

Thermodynamic relaxation can generate complex nanostructured materials via self-assembly; these structures, however, are ultimately limited by chemical equilibria and diffusional transport processes. [1] In contrast, living systems use a concerted combination of thermodynamic and energydissipating processes to remove these functional limitations, and generate complex, structured materials with a wide range of adaptive and emergent behaviors. An underlying principle of such systems involves the dynamic self-assembly of materials, which occurs outside of thermodynamic equilibrium, requires a source of energy, and bridges multiple length scales. [2][3][4] Analogous principles have been applied to assemble a broad range of artificial ''dissipative'' structures [5] through electrorheological, [6] magnetohydrodynamic, [7] electrohydrodynamic, [8] and magnetorheological, [9] interactions that induce spatiotemporal ordering. Efforts to understand these effects have led to significant insights into fundamental nonequilibrium physics.[10] While these approaches expand the practical range of materials, they rely on programmed or user-defined stimuli to drive the assemblies out of equilibrium. The next major step in developing materials assemblies will involve selfregulating systems that define the dynamic assembly and adaptive behavior of materials. Such feedback-regulated systems will extend the functional nature of nanostructured materials to include revolutionary behaviors (e.g., adaptive reconfiguration and self-healing), currently unattainable by conventional self-assembly methods.There are few examples of dynamic self-assembly in which the energy component is intrinsic to the system, as opposed to externally applied (e.g., electromagnetic fields). One system involves the dynamic assembly of nanospools [11,12] and nanocomposite rings [13] wherein assembly is achieved through a stochastic interaction of energy-dissipation and thermodynamic processes. One remarkable characteristic of both structures is the significant energy (i.e., >10 5 kT) that is required for their formation, which is based on the relatively high bending rigidity of the microtubules. [11] This energy input is cooperatively supplied through the hydrolysis of ATP by kinesin (energy dissipation) and the formation of multiple biotin-streptavidin bonds (thermodynamic). In addition, the nanospools display a highly nonequilibrium existence in which the unzipping of biotin-streptavidin bonds by kinesin motor leads to the spontaneous unspooling for the structures.[11] A unique aspect of the nanocomposite rings concerns the ability to assemble quantum dots across multiple length scales. The microtubules in these structures serve as a nanoscale scaffold for assembling the quantum dots; the quantum dot-laden microtubules subsequently self-organize into microscale, optically active structures. [13] While the properties of these nonequilibrium structures have been described, the mechanism of their formation is unknown and may provide valuable insight with respect t...

Understanding the role of transport velocity in biomotor-powered microtubule spool assembly

“…Such relaxation would highlight the dynamic nature of microtubule assembly, as suggested by the presence of a metastable stage at the fastest transport velocity (~15 min in Fig. 2b, iii; reported previously 26 ). However, we did not detect any substantial difference in spool circumference over the same time course (~15 min vs. >60 min, Fig.…”

Loop formation of microtubules during gliding at high density

“…Previous studies have observed the formation of microtubule 'spools' created using microtubule-gliding assays and cross-linked microtubules that bundle together (Liu et al 2008, Hess et al 2005, Kawamura et al 2008, 2010b, 2010a. The likely mechanism of spool formation appears to be pinning of a bundle on a dead kinesin in the gliding chamber that allows for high curvature and then cross-linking of the bundle to itself (Hess et al 2005).…”

Effect of length and rigidity of microtubules on the size of ring-shaped assemblies obtained through active self-organization

“…10,11 Among them, the ring-shaped assembly have been attracting considerable attention and appears to be a promising candidate for application in nanotechnology as this non-equilibrium structure is capable of storing a huge amount of bending energy 8 and can provide continuous work without changing the position of the mass center. [12][13][14][15][16] Therefore, it is important to understand how different factors affect the formation and properties of ring-shaped MT assemblies such as rotational direction, thickness (subtraction of inner diameter from outer diameter), size etc.. So far, we have successfully controlled the rotational direction 17 and thickness 18 of the ring-shaped MT assembly by tuning helical structure of MTs and by feeding MTs in a stepwise manner in the AcSO respectively.…”