Much Stronger than a Car

Photo: A natural pond

“These findings are twofold,” says Danielle France, a member of MIT’s Division of Biological Engineering. “First, they give us an idea of how a cell can manage to generate such enormous force; and second, they provide clues for how engineers might reconstruct these mechanisms for nano-scale devices.”

The spring in the unicellular Vorticella convallaria is a contractile fiber bundle, called the spasmoneme, which runs the length of the stalk. At rest, the stalk is elongated like a stretched telephone cord. When it contracts, the spasmoneme winds back in a flash, forming a tight coil. To find out how strongly Vorticella recoils, France and colleagues used a unique microscope to apply an extra load to the spring.

In the past, researchers have measured the Vorticella’s ability to recoil its spring at 40 nano newtons of force and at a speed of eight centimeters per second. These measurements, when scaled up to the size of a car engine, prove the Vorticella to be the more powerful of the two. However, when France used the centrifuge microscope, she discovered that the spring was able to recoil against as much as 300 nano newtons of force.

“This is the maximum amount of power we can currently test,” says France. “We suspect the coil is even more powerful.”

France and colleagues also made an important link between the engine’s fuel, calcium, and the major protein component centrin of the stalk. When the researchers introduced an antibody for the Vorticella centrin into the cell, the spring was no longer able to contract, indicating that the cell uses a powerful centrin-based mechanism, one that is unlike other known cellular engines.

“When it comes to creating nano devices, this is a great mechanism for movement,” says France. “Rather than requiring electricity, this is a way to generate movement simply from a change in the chemical environment. Here, a simple change in calcium would power this spring.”; Source: Whitehead Institute for Biomedical Research