You have a sculpture, an intricate piece of modern art, covered in bulges and blisters. Your task is to weave a cover for it. The fit must be exact. You have to fill in every dent and wrap around every lump. Here’s the catch: you have to make this faultless shroud from a single piece of string that must automatically weave itself into the right three-dimensional shape.

This is the challenge that Sarel Fleishman, Timothy Whitehead and Damian Ekiert from the University of Washington have just overcome. Their “sculpture” is a protein called haemagglutinin, or HA, which sits on the surface of flu viruses. Their “shroud” is another protein designed to perfectly fit onto the contours of HA and neutralise it. They have found a way of fashioning these designer proteins on a computer – a feat that could make it easier to create the next generation of anti-flu drugs.

Under the microscope, flu viruses look like spherical pincushions. The “pins” consist of two proteins: haemagglutinin, which allows the virus to stick to a host cell, and neuraminidase, which allows it to eventually escape. The different versions of these ...