We currently have five research projects underway in the Fudge Lab.
Biomechanics of the cytokeratin network in skin cells
Previous research from our lab has demonstrated that the cytoskeletal filaments known as 'intermediate filaments' (IFs) are far softer and more extensible than previously believed. These findings distinguish IFs from the other two cytoskeletal filaments, F-actin and microtubules, and suggest unique mechanical roles for the IF network in cells. Postdoc Dr. Oualid Haddad is currently investigating the effect that disease causing mutations in cytokeratin genes have on the mechanical behavior of intermediate filaments in human keratinocytes. The particular mutations he is looking at cause the skin-blistering disease Epidermolysis Bullosa Simplex. This project is made possible by a collaboration with Dr. Birgitte Lane and Dr. David Russell at the University of Dundee in Scotland.
Biomechanics of whale baleen alpha-keratin
Mammals produce two kinds of materials that are reinforced with intermediate filament proteins - soft keratins found in skin and hard keratins that make up structures such as hair, nail, claw, and horn. We have shown in previous work that the dramatic differences between the mechanical properties of soft and hard alpha keratins may be related to a critical dehydration step that occurs in the development of hard alpha keratins. During this process, air drying of the keratin makes it considerably stiffer and less extensible, and these properties are preserved via shrinkage and chemical crosslinking of the surrounding protein matrix. We are interested in whale baleen alpha keratin primarily because it develops without the benefit of an air-drying step and it allows us to test hypotheses about how important air drying is to the development of hard alpha keratins. In addition, there is little known about the structure of whale baleen and we are currently trying to understand how it develops as well as how it functions in life.
Biomimetics of high performance protein fibers
The inevitable shortage of petroleum will have implications for more than just energy production - it also means that we need to start thinking about finding renewable alternatives to petrochemical-based polymers that we now depend upon for making a vast array of industrial and consumer products. Artificial spider silk has been hailed as a renewable, protein-based high performance fibre, although spinning artificial spider silk has proven far more difficult and expensive than anyone could have originally imagined. For this reason, we are employing a biomimetics approach to explore other natural fibres that could serve as more viable models for spinning high performance renewable fibres. One such model is the protein fibres that are found within the defensive slime of hagfishes. These "slime threads" are similar to spider silk in their dimensions, but they differ in a couple of important ways that make them excellent candidates for such a biomimetic project. Slime threads are built within cells from intermediate filament proteins via a process of hierarchical self-assembly. This is quite different from the dynamic spinning process that transforms liquid crystalline spider silk proteins in the silk gland into an insoluble fibre. The other important difference is that the proteins that make up slime threads are relatively small and not very repetitive, which makes them amenable to production in high-throughput expression systems such as bacteria. Spider silk genes are relatively enormous, and extremely repetitive - two traits that make them difficult to maintain in bacteria. This project is led by postdoctoral fellow Dr. Atsuko Negishi and M.Sc. student Nicole Pinto.
Biophysics of hagfish slime
Hagfishes are bottom dwelling proto-vertebrates that are capable of producing startling amounts of defensive slime when they are provoked. We have investigated the composition and mechanical properties of the slime using a variety of techniques. We have also demonstrated that hagfish slime is especially good at clogging the gills of would-be fish predators, which may be one of its primary functions in life. The slime is composed of fine protein slime threads as well as a mucus component that comes packaged in tiny vesicles. When these components are ejected from the slime glands, they combine synergistically to form a slime mass in which a large volume of water is entrained. Recent work by Julia Herr has investigated the chemical composotion of the slime and the mechanisms of mucin vesicle stabilization an deployment. Tim Winegard recently published a paper on the mechanisms of thread skein deployment, which involves the unravelling of 15 cm long threads from subcellular structures. You can find pdfs of both of these papers by clicking on the Publications link to the left. Current research is focused on understanding the molecular mechanisms that govern the swelling and rupture of mucin vesicles as well as the cellular mechanisms by which slime threads are manufactured within the cytoplasm of gland thread cells.
Biophysics of the ocular lens
Fiber cells within the mammalian ocular lens contains cytoskeletal filaments known as "beaded filaments," which are heteropolymers of the proteins filensin and phakosin. In humans, mutations in beaded filament genes have been linked to autosomal-dominant congenital cataracts (ADCC). Because phakosin and filensin both belong to the intermediate filament gene family, we suspect that beaded filaments play a mechanical role in the lens. We recently published a paper with collaborators John Hess and Paul FitzGerald at UC Davis in which we showed that beaded filament knockout indeed changes the mechanical properties of the murine lens. For more information, see our publication in Investigative Ophthalmology and Vision Sciences in the Publications link on the left.