REVVING YOUR NANOSCALE ENGINE

Researchers in the SFU Physics department have discovered how “molecular machines,” found in the human body, can run so quickly.

Biological molecular machines are microscopic proteins that carry out biological tasks by converting between different forms of energy. Many molecular machines burn chemical fuel to produce movement, similar to a car engine, only 100 million times smaller. An example of this is the protein kinesin, which transports cargo along cellular filaments to specific destinations within cells, and supports critical functions such as cellular division.

Postdoctoral researcher Aidan Brown and Assistant Professor David Sivak’s research focused on highly evolved molecular machines to find out how they could make use of their fuel to run quickly.  Previous studies indicated that energy from their fuel should be spread evenly throughout the machine’s operating cycle. However, Brown and Sivak discovered that in general, higher operating speeds can be achieved through the uneven distribution of energy. “Directing energy to naturally slower stages, and less to the faster stages, results in optimal speed,” Sivak says.

“Living things care about doing things quickly, and evolution has had billions of years to tinker with designs to improve them, so existing biological molecular machines should show signs of such energy arrangements if they are indeed useful,” says Brown.  Indeed, in the few machines that have independently been measured, energy seems to be spread unevenly similar to Brown and Sivak’s theory. 

Brown and Sivak were partly driven by curiosity, trying to understand the basic physics of the effective and diverse molecular machines that are central to biological function in any living thing.  Sivak says, “Nanoscale objects effectively follow different rules than the human-sized objects we are familiar with. Through this work and other research in my group, we want to find out what the rules are and understand how biology has cleverly taken advantage of these rules.” He adds,  “We want to find out not just how life works, but why life works the way it does.”

Practically, how can this information be used? Brown points toward nanotechnology applications: “Engineers have begun to build synthetic molecular machines. Our work could help in the design of more efficient molecular machines, for example for fast and targeted drug delivery.”

The research was funded by NSERC, Canada Research Chairs, and SFU President’s Research Start-up Grant. The complete paper, published by Proceedings of the National Academy of Sciences of the United States of America (PNAS) can be found here.