Richard Superfine and Russell Taylor head the UNC Chapel Hill Center for Computer Integrated Systems for Microscopy and Manipulation. The center is a resource for investigating the physical properties of biomolecules through microscopic manipulation.  I like the justification for looking at molecular motors…

As nanotechnologists we are interested in the design and construction of nanoscale electrical and mechanical devices that provide unprecedented functionality. In developing these systems, we are inevitably faced with the problem of actuation and transport, as well as the need to power these systems and couple them to electronic circuitry. Nature has already provided remarkable solutions to parts of this problem, supplying us with molecular motors powered chemically by individual ATP molecules.

The fuel is easy to deliver, stable and dense, the motors are tiny, strong and configurable.  This is a technology that really has potential

Web Page

Kinesins are molecular motors that carry ‘packages’ along the microtubles of the cytoskeleton. They are among the smallest protein motors with just 800 or so amino acids arranged as two structures tied together. The beauty of kinesin is that since the structure is well understood it can be attached to a tiny bead that it will then drag around.  By stabilizing the bead with laser ‘tweezers’ the little ’steps’ of kinesin transport can be seen through a conventional microscope.  The kinesin molecule drags itself, and teh attached bead, along a microtubule until it hits the end. This is a discovery phase project that is ripe for transition into the realm of biomimetics. Here is a working nano-engine that will run on a defined track. All the project needs is a clear application and a way to deposit the track (microtubule) in a specific place.

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The Molecular Motors Group at the has a really nice site (that includes the GIF above) with explanations of techniques and motivations in the world of molecular motors. The image above is remarkable because it shows single actin molecules, carrying a fluorescent tag, as they are pulled across a mat of myosin. Actin and myosin are the two molecules that interact to power muscular contraction. Actin is the passive player, being a polymeric protein with regularly spaced spots that myosin can get a grip. Myosin, which looks like a double headed golf club, grabs onto actin then changes conformation by acutely bending. Myosin then releases actin and grabs it at a site further along. It all looks rather like a frantic hand over hand tug of war. The whole reaction is powered by ATP the basic energy unit of life.

In this experiment myosin is attached to a plate and bathed in ATP rich fluid. Fluorescently labeled actin is then added and it is promptly yanked across the surface of the plate by the myosin. By measuring the speed of actin movement it is possible to learn the characteristics of different forms of myosin. When we find a few practical, interesting things to attach to these tiny motors it will be a great example of biomimetics.

Lab Website. 

While micro-electro-mechanical systems (MEMs) certainly claim some tiny motors, the really small stuff is all biological.  Motor molecules like dynein and kinesin shuttle material (proteins, vacuoles, organelles) from one place to another in the cell. At a slightly larger scale and longer distance scale actin and myosin interact to shorten muscle. I recently ran across a colleague’s website with wonderful images and explanations of some of these ‘molecular’ motors.  It is clear that this biomimetic technology in very close to paying off with product.

Steve Gross Lab Website