Super-rubber. Researchers have made their own resilin, the elastic protein that gives insects their jumping and flying abilities.

Nature's Super-Rubber Made in Lab

Forget flubber. Using a gene from fruit flies, scientists have produced the most resilient and stretchy rubber known. The material could be the starting point for a wide variety of applications, from industry to medicine.

The living world puts human engineering to shame. Take the rubbery material known as resilin, the protein that gives fleas their superhero jumping ability and cicadas their deafening chirp. First discovered 4 decades ago in dragonfly wings, resilin out-stretches and out-bounces every known human-made material. And because insects don't replace their resilin after pupating from larvae, the stuff has to last a lifetime.

Soon after the resilin gene was found within the fruit fly genome in 2001, scientists got to work trying to produce this super-rubber in the lab. A team led by Chris Elvin, a molecular biologist at CSIRO Livestock Industries in St. Lucia, Australia, started by moving the functional part of the gene into Escherichia coli bacteria. The researchers then grew large batches of the bacteria while spurring them to express the gene.

Harvesting the raw protein was easy. To become a super-rubber, however, individual resilin proteins must form a series of specific molecular bonds with each other. After many unsuccessful attempts with expensive industrial tricks, the researchers hit pay dirt with a simple and cheap method. They added a ruthenium metal catalyst and exposed the mix to bright white light, causing the resilin proteins to bond together in the correct conformation.

The homegrown resilin is impressive. Not only can the material stretch to three times its unstressed length without breaking, but its resilience--a measure of bounciness--is as high as that of natural resilin, the team reports 13 October in Nature. The synthetic resilin is "almost perfectly elastic," say the researchers, meaning that very little energy is lost as heat when it stretches. By comparison, polybutadiene "superballs" lose 20% of their energy with each bounce. The team aims to decipher the molecular mechanism that gives the material its characteristics to make novel materials for "tailor-made applications." One possible area is medical implantation, such as stents for holding arteries open after surgery or spinal disc replacements that can last a lifetime.

The study is "a real feat," says Sven Andersen, a molecular biologist at the University of Copenhagen, Denmark, and part of the team that first found the resilin gene. But designers will have to work with the fact that the material is biodegradable, he cautions, making outdoor applications vulnerable to hungry bacteria.

Related sites
Elvin's site
A 2002 Science report on stretchy proteins