Protein motors are enzymes that naturally generate force and move along tracks of protein polymers (actin filaments or microtubules), using energy from the hydrolysis of adenosinetriphosphate (ATP). To harness these protein motors to power nanometer-scale devices, we have investigated effective and non-destructive methods for immobilizing protein motors on surfaces and to arrange the output of these motors, e.g. force and movement, to be in a defined direction. We found polymethylmethacrylate (PMMA) and NEB-22 to be useful for immobilizing protein motors while retaining their abilities to support the movement of protein polymers. We fabricated various patterns of tracks of PMMA or NEB22 on coverslips and protein motors were introduced and immobilized on the patterns. The trajectories of protein polymers were confined to these tracks. Simple patterns readily biased polymer movement confining it to be unidirectional. Applications of motor proteins in nanometric fine-movement microactuators are now stepping closer to reality.
Two examples of the use of biological materials in micrometer-size applications are discussed. The first concerns the control of motor protein movement, which is oriented toward actuator application. Two kinds of polymers, PTFE (poly-tetrafluoroethylene) and PMMA (poly-methylmethacrylate), are show to be useful in the control of the trajectories of actin filament movement through adsorption of myosin molecules. The second is a magnetic sensor that uses bacterial magnetic particles. Magnetic particle chains extracted through a magnetic trapping extraction method were immobilized on a cantilever for an atomic force microscope. This magnetic particle probe was sensitive enough to measure a standard magnetic force microscope (MFM) sample when used in an MFM system.
The fluorescence of fluorescently tagged proteins on functionalized polymer surfaces shifts towards higher wavelengths. Two types of polymers for light-assisted surface manipulation have been used, namely diazo-naphto- quionone/novolak (DNQ/N) resist and poly)tert-butyl- methacrylate). The proteins were either hydrophobicity- attached; covalently linked; or specific protein-protein recognition. We observed that on hydrophilic surfaces the fluorescence is shifted towards lower wavelengths. This parasitic effect has to be taken into account when 'reading' biochips but it can be also used for the 'alignment' of the fluorescence of the fluorescently tagged proteins on the same wavelengths via the manipulation of the properties of the substrate polymer.
This study attempts to assess the feasibility of building purposefully designed molecular motor arrays, the proteins responsible for the movements of the living organisms and cells. The 'building' process used high-resolution e-beam patterning, originating in semiconductor technology, upgraded to make biomicrolithography compatible with the patterning of bioactive molecules. The material used as a scaffold for the array [a copolymer of poly(tert-butyl-methacrylate/methyl- methacrylate)] was tailored to exhibit large difference in hydrophobicity when exposed to e-beam exposure. The e-beam patterning exposure-induced difference in hydrophobicity is responsible for the selective attachment of the myosin molecules on the patterned deep-submicron 'tracks,' and the higher concentration of 'guiding' molecules selectively confines the movement of the actin filaments.
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