Using electrical and optical tweezers to facilitate
studies of molecular motors.
Phys Chem Chem Phys. 11:4834-4839. 2009.
Dielectrophoresis was used to stretch and
suspend actin filaments across a trench etched between two
electrodes patterned on a glass slide. Optical tweezers were
used to bring a motor protein-coated bead into close proximity
to a pre-selected, suspended actin filament, facilitating
the attachment of the myosin-coated bead to the filament.
The clearance beneath the filament allowed the bead to move
freely along and around its filamentous track, unhindered
by solid surfaces. Using defocused images, the three-dimensional
position of the bead was tracked as a function of time to
obtain its trajectory. Experiments were carried out with myosin
V and myosin X. Both motor proteins followed left-handed helical
paths with the myosin X motor exhibiting a shorter pitch than
the myosin V. The combined use of electrostatic and optical
tweezers facilitates the preparation of motility assays with
suspended tracks. Variants of this technique will enable higher
complexity experiments in vitro to better understand the behavior
of motors in cells.