Steven Large

David Sivak


November 09, 2018

Countless numbers of infinitesimally small motors, called molecular machines, carry out a vast array of tasks in the human body. From the targeted transportation of material to the production of cellular energy resources, these nanometer-sized machines are vital to our health. Modern experimental techniques have only recently begun to conduct detailed experimental study of these machines, and there remain large gaps in our understanding of these nanomachines.

In a paper published today in Europhysics Letters, SFU physics PhD candidate Steven Large, SFU physics professor David Sivak, and collaborator Raphael Chetrite of the University of Nice, propose a fundamental physical principle underlying their operation.

Large says, “While these microscopic machines behave quite regularly on average, at any given time a particular machine can act quite unpredictably.” He explains, “Molecules of water and proteins, for example, are constantly bumping into these machines, giving them energy; because the machines are so small and pretty soft, this energy is enough to really knock them around.  Since the jostled molecules move around randomly, this makes the behavior of any one of these microscopic machines unpredictable.”

Sivak’s team set out to decipher how efficient such machines can be. Scientists already knew that for a predictable machine, its efficiency always decreases with its speed. Sivak and co-workers discovered that unpredictable machines constantly dissipate heat during their operation. They concluded that an unpredictable machine is most efficient when it operates at an intermediate speed, balancing energy loss from ongoing operation and from going fast.

So how can this information be used?

Sivak says that a better understanding of these principles could help illuminate molecular-motor-related diseases, such as cardiomyopathy which can be caused by a mutation in a molecular machine called myosin, which makes muscles contract.  Malfunction of this mutated machine prevents heart muscle from contracting properly, so it doesn't pump blood as effectively.    

He adds, We’re also hopeful that artificial nanomachines can be used for nanotechnology and biomedical applications such as artificial photosynthesis or drug delivery. There’s a lot of basic science and engineering to be done before we get there, but these fundamental principles help point the way.”