"Understanding, engineering and exploiting protein self-assembly."

Fibre formation by proteins is required in many biological situations. Despite this fact, the way that proteins reproducibly form fibres with specific size, shape and chemical features remains elusive. It is likely, in fact, that nature has evolved a number of different approaches to answer this problem. This Discovery Grant will build understanding of the transformation from isolated proteins soluble in water to fibrillar forms with dramatically different properties. By doing so, fundamental insight into these critical biological entities will be developed and we will be able to tweak and optimize protein fibrils for new purposes. Two specific types of protein fibre are targeted in this Discovery Grant. The first of these is spider silk, a material with strength and toughness not found in current synthetic materials. We are using bacteria to produce the type of silk that spiders use to wrap their prey, with the dual advantage of allowing us to modify individual amino acids at will and to incorporate forms of atoms allowing use of nuclear magnetic resonance (NMR) spectroscopy. The second class of protein we are studying is collagen. In this case, we are using computational methods to engineer collagen-like proteins that are made partially in bacteria and partially by chemical methods. Because parts of the protein are made chemically, we can incorporate a much wider variety of chemical functionality into these proteins.In both cases, we use NMR spectroscopy to pinpoint the locations of each individual atom within the protein both in solution and in fibre form. We can also monitor specific changes to atomic positions and motions during the transition from soluble to fibrous. As we do so, we monitor the types and properties of fibres that are formed using atomic force microscopy (AFM). This allows visualization of the fibre surface alongside measurement of strength and elasticity. Comparison of the atomic positioning to mechanical properties as a function of changes in amino acid sequence allows us to engineer new forms of fibre based on spider silk or collagen but with specific, engineered properties.