Magnetic Quantum Dots Steer and Detach Microtubules From Kinesin‐Coated Surfaces

Abstract

The microtubule (MT)-kinesin system has been extensively studied because of its role in cellular processes, as well as its potential use for controllably transporting objects at the nanoscale. Thus, there is substantial interest in methods to evaluate MT properties, including bending radius and the binding energy of kinesin motor proteins to MT tracks. Current methods to identify these properties include optical tweezers, microfluidic devices, and magnetic fields. Here, the use of magnetic quantum dots (i.e., MagDots) is evaluated as a method to study MT-kinesin interactions via applied magnetic forces. Magnetic fields are generated using a magnetic needle whose field gradient is quantified by finite element modeling (FEM). Magnetic force is applied to MagDot-labeled MTs and demonstrated sufficient to steer and detach MTs from kinesin-coated surfaces. Taking advantage of the dual-functionality of MagDots, the magnetic force experienced by a single MagDot and the number of MagDots on MTs are determined. The total force exerted on MTs by MagDots is estimated to be %0.94-2.47 pN. This approach could potentially be used to interrogate MT properties and MT-kinesin interactions, enhancing our biological understanding of this system and enabling further development of MT shuttles for nanotransport.

Structural interactions in polymer-stabilized magnetic nanocomposites

“…Previously, we have shown that magnetic forces on the order of 0.1-0.2 pN are required to capture similar nanocomposites 33,34 and that neodymium magnets can capture particles within B2 mm of their surfaces. 35 The absence of significant size change in the pellet or supernatant can be explained by structure stabilization engendered by strong van der Waals forces, dipole-dipole interactions between SPIONs, and entropic stabilization provided by the BCPs. These results indicate that magnetic forces applied after composite formation were not sufficient to break BCP entropic barriers to change composite size, at least at the strengths investigated here.…”

Synthetic Systems Powered by Biological Molecular Motors

“…The gliding velocity is governed by the ATP concentration and temperature, , and the direction of the filament movement follows a persistent random walk driven by thermal fluctuations of the tip of the moving filaments . This persistent random walk, as well as the interaction of the filament with obstacles, can be simulated using Brownian dynamics methods. − Gliding filaments can be confined by guiding structures to prescribed paths, ,− directed by obstacles, controlled by light, ,− or other stimuli, ,− and can capture analytes and carry cargo. ,− The natural arrangement of stationary filaments supporting the movement of biomolecular motors is also employed, but the transport distance is largely limited to the length of the filament or filament assembly in this geometry. These discoveries led to more advanced applications including sensors, − computation, screens, and switches .…”