As Spring emerges, Nature is gently awakening. And insects will soon be engaged in all kinds of athletic and sonorous feats. Amongst which, the flea and its jump. Fleas can reach up to 30cm, which may not sound much yet such a performance represents 150 times their size – something no Olympic champion could achieve! And as the fleas make joyful leaps, cicadas sing songs and dragonfly beat their wings.

There is a protein – specific to insects – at the heart of all this seasonal leaping, singing and wing-beating: resilin. Resilin has exceptional properties. It is extremely elastic, so much so that it dethrones by far the best synthetic rubber known to date: polybutadiene. No matter how much it is stretched, resilin springs back to its initial shape and, what is more, without weakening its initial elasticity. The source of such a characteristic is to be found in the protein’s sequence, which is a succession of short amino-acid stretches that are almost identical. As a consequence, one particular amino acid is repeated: proline. Proline is elbow-shaped and eases each short amino-acid stretch into a U-shape. Scientists believe that a succession of such bends creates a spiral, which bows and stretches much in the way a spring would.

Resilin is not a loner but forms homopolymers, thus generating the ideal elastic substance. Resilin polymers are found in parts of the body where there are highly repetitive movements such as the back legs of jumping insects, the vibrating membrane of cicadas, or the wings of dragonflies. And it is thanks to resilin that a fly can beat its wings 500 million times in its life span, without causing any damage to them. What is more, resilin is not renewed! Adult insects still have the resilin of their youth – which only goes to show how resistant the protein is.

A number of human organs also have elastic properties: skin, ligaments, lungs or arteries. Yet there is no human resilin. However, we do own other kinds of so-called elastic proteins – though less effective – such as elastin. It is becoming a thin line between humans and flies. Recently, scientists managed to produce synthetic fly resilin. Characteristics such as those belonging to resilin are naturally of great interest in the industry of biomaterials and medical research. It could be used to elaborate new vascular implants, for example, which would restore suppleness to arteries, or be used to devise prostheses, which could replace defective discs between vertebrae. Nature – it seems – never ceases to be a great source of inspiration…

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