The air-water interface stabilizes α-helical conformations of the insulin B-chain

Abstract

Adsorption of proteins onto liquid interfaces, such as the air-water interface, often leads to changes in the protein conformation. This can lead to changes in protein assembly behaviour, with aggregation and fibrillation often enhanced. To understand the relationship between protein conformation and aggregation, knowledge of protein structure at interfaces, on the single molecular level, is necessary. Using molecular dynamics simulations the effect of the air-water interface on conformation of the insulin B-chain is investigated. At the air-water interface the protein adopts an α-helical conformation, whereas in bulk solution it adopts disordered structures. The α-helical conformation is templated by the partitioning of hydrophobic side chains into the air, leading to the formation of an amphipathic helix. This structure presents a hydrophobic face which may lead to further aggregation, which helps explain the enhancement of insulin fibrillation at interfaces. This knowledge of the molecular conformation gives new insight into the contribution of protein structural change on the interfacial aggregation of proteins.