Protein molecules are highly dynamic, continually changing shape in response to changes in external conditions. Scientists have long sought to mimic this behaviour in artificial materials, and now a team at the City University of New York (CUNY) in the US has done just that, constructing a crystalline solid that switches between several distinct architectures as the ambient humidity changes. Their work could make it easier to fabricate adaptive materials on a large scale for applications such as humidity-responsive coatings. Proteins owe their shape-shifting character to a series of complex interactions that take place between two or more molecules. These supramolecular interactions, as they are known, allow proteins to adapt their properties – and therefore their functions – as needed. Water plays an important role in such interactions because it stabilizes certain structures while weakening others.…