Nanotech_Roadmap_2007_main
<p>Jan 30, 2008 5:39 PM
 
1.3 Motors and Actuators  page 69
For motors and actuators, there are a number of function-specific
metrics of interest:
• Maximum load
− Stall force (for a linear motor)
− Stall torque (for a rotary motor)
• Maximum speed (unloaded linear and angular velocities,
respectively)
• Energy efficiency
1.3.1 Biological
All cellular organisms contain both linear and rotary molecular motors
(MM). An additional example is a bacteriophage that uses an ATPfueled
corkscrew motor to fill and pressurize a capsule with DNA.
While fluorescence labeling can be used to characterize the structure
and motion of MM, their localization remains a synthetic challenge.
One option for a positioning template is the bacterial S-layer; another is
a DNA origami based framework (see Topic 2 Systems and Frameworks),
an approach that promises great control in building complex,
functional structures.
Existing biological motors have diverse properties:
• Flagella
− Contain all of the components of conventional motors
(bearings, rotators, shafts, stators, fuel requirement, etc.)
− Powered by the flow of protons across a membrane
− Self assemble from 40 proteins
• Myosin (a muscle protein)
− Uses ATP fuel
− Drives linear motion of fibers, causing muscle
contraction
• Kinesin
− Uses ATP fuel, 100 steps/second, 5-7 pN force
− Transports large cargo objects (cell organelles) along
microtubules.
• ATP Synthase
− Rotary motor, 44 pN force
− Powered by the flow of protons across a membrane, the
resulting mechanical energy is used to sythesize ATP
• DNA Translocase
− Acts like a fishing rod reel: pulls in DNA like a line
− Bidirectional translocation
− When attached to a surface: directional, provides useful
work, pulls in DNA</p>