Surface-Controlled Properties of Myosin Studied by Electric Field Modulation

Abstract

The efficiency of dynamic nanodevices using surface-immobilized protein molecular motors, which have been proposed for diagnostics, drug discovery, and biocomputation, critically depends on the ability to precisely control the motion of motor-propelled, individual cytoskeletal filaments transporting cargo to designated locations. The efficiency of these devices also critically depends on the proper function of the propelling motors, which is controlled by their interaction with the surfaces they are immobilized on. Here we use a microfluidic device to study how the motion of the motile elements, i.e., actin filaments propelled by heavy mero-myosin (HMM) motor fragments immobilized on various surfaces, is altered by the application of electrical loads generated by an external electric field with strengths ranging from 0 to 8 kVm(-1). Because the motility is intimately linked to the function of surface-immobilized motors, the study also showed how the adsorption properties of HMM on various surfaces, such as nitrocellulose (NC), trimethylclorosilane (TMCS), poly(methyl methacrylate) (PMMA), poly(tert-butyl methacrylate) (PtBMA), and poly(butyl methacrylate) (PBMA), can be characterized using an external field. It was found that at an electric field of 5 kVm(-1) the force exerted on the filaments is sufficient to overcome the frictionlike resistive force of the inactive motors. It was also found that the effect of assisting electric fields on the relative increase in the sliding velocity was markedly higher for the TMCS-derivatized surface than for all other polymer-based surfaces. An explanation of this behavior, based on the molecular rigidity of the TMCS-on-glass surfaces as opposed to the flexibility of the polymer-based ones, is considered. To this end, the proposed microfluidic device could be used to select appropriate surfaces for future lab-on-a-chip applications as illustrated here for the almost ideal TMCS surface. Furthermore, the proposed methodology can be used to gain fundamental insights into the functioning of protein molecular motors, such as the force exerted by the motors under different operational conditions.

Controlled Surface Silanization for Actin-Myosin Based Nanodevices and Biocompatibility of New Polymer Resists

“…Thus, Sundberg et al 24 proposed that a rougher surface may cause a decrease in the sliding velocity due to friction or a nonuniform HMM surface density. Furthermore, van Zalinge et al 47 suggested that chemical interactions of the forceproducing HMM motor domains with protruding parts of the surface may cause a decrease in sliding velocity with increased surface roughness. However, Albet-Torres et al 22 did not detect clear differences in motility quality between surfaces with different roughnesses.…”

“…On the other hand, the differences in velocity between TU7 and CSAR 62 and the similarities between TMCS and TU7 support the view that also other factors than the contact angle and surface roughness are important. 14,21,22,47 More detailed studies in the future as previously performed for other polymer materials 21,48 would be of value, e.g., analyzing the difference in water uptake and polymer mechanical properties at the macromolecular chain level. In this connection it is of interest 21 to investigate if there are differences in total HMM density as well as in the fraction of active HMM molecules on the different polymers.…”

Do Actomyosin Single-Molecule Mechanics Data Predict Mechanics of Contracting Muscle?

“…The choice of surface in single-molecule optical tweezers studies is thus important. In addition to surface hydrophobicity also surface charge [ 98 , 99 ] and nanomechanical properties of the surface may be of relevance [ 100 , 101 , 102 ].…”

Switching of actin-myosin motors by voltage-induced pH bias in vitro

“…It is known that the movement of filaments is not restricted to a certain direction when HMM molecules are randomly fixed on glass slides without orientation [1]. At the same time, alignment of the movement of filaments was observed when an external electric field was applied to the motility system [5,6]. Therefore, the filament velocity in our system with voltage application may also have been affected by electrophoresis, which can attract actin filaments toward an anode.…”

“…In addition to their importance for muscular physiology, the ability of these complexes to generate force and transport vesicles in vivo can potentially drive micro-devices [3,4]. In the context of motility control, the movement of actin filaments interacting with myosin motors fixed on a glass slide, which is referred to as "in vitro motility assay", can be aligned when a direct or alternating current electric field is applied to the system [5,6]. In addition, the velocity can be enhanced using micro-heater, conductive polymers, or conductive glass [7e9], although these methods are lacking in terms of active switching off of the motility.…”