Chemical and biophysical studies of ionic protein fluids

When heated, many pure substances, for example metals, will melt and form liquids. One of the reasons that melting occurs is because the metal atoms are of a similar size to the distance over which the forces between them act. For large biological molecules like proteins however, heating the dry protein powder results in decomposition and the formation of a gas, i.e. there is no liquid phase. Polymers however, are also large molecules that do melt when heated (like melting plastic), and this is due in part to the greater distances over which the forces between the polymer molecules act. In the research proposed here, we wish to attach polymers to the surface of proteins so that proteins can form liquids with no water. The method for attaching the polymer to the protein involves the chemical modification of the protein surface to make it highly charged. The polymers are oppositely charged and as a result they bind electrostatically to the protein surface. Effectively, the polymers at the surface behave as a fluidization region and these molecules need to be selected carefully so that the modified proteins behave as a single entity and can be classified as true liquids. In recent studies we have achieved this by modifying the protein to give a highly positively charged surface, and then adding a negatively charged polymer surfactant. We then remove the unbound surfactant, freeze the sample, and carefully remove all the water by freeze-drying to produce a powder that melts at around 29 C, producing a liquid protein. We now wish to extend this method to produce a wide range of liquid proteins with different properties. We will study both the internal structure and the fluid properties of each protein liquid formed. The information gained about the internal structure will be used to help determine if the natural properties of the proteins are still present in the liquid state. After we understand the structure and how and why these liquid proteins form, we will use this information to develop new types of smart' materials using liquid proteins, e.g. for biosensors and for new types of wound dressing materials.

My proposed work is to alter the phase diagram of proteins to include a solvent-free ionic liquid state, and in doing so, show a significant advance in the properties and potential practical uses of proteins. The impact of such materials is expected to encompass a diverse range of fields including bionanotechnology, medicine, food and health care, biosensing, and the subsequent development of multifunctional bionanomaterials and devices, which would be of significant benefit for the UK's competitiveness and economic performance. As I expect that the methodology generated in this project will contribute largely to the generic preparation of a new class of substances (ionic protein fluids), I expect an impact in the broader economic marketplace via an increased capacity for the development of near-future technologies. As solvent-less liquid proteins have an effective protein concentration much greater than the aqueous solubility limit, they are perfect candidates for development in new medical technologies. As an example, the high viscosity of these materials would be appropriate for high-potency, low-cost external enzymatic treatments, and as pharmaceutical transport and storage materials. An obvious medical application would be the development of active wound dressing materials, where highly concentrated protein could be introduced to the wound by applying barrier films consisting of melts with tuneable properties. The function of these enzymes may be to deliver oxygen (e.g. in the case of glucose oxidase) or to promote the degradation of the necrotic debris associated with cell breakdown upon healing (e.g in the case of protease and lyase). In each case the physical properties of the ionic protein fluid allows effective fabrication, which is an important criterion for material design. As new ionic protein fluids are produced and tested, the potential impact will be assessed by Prof. Mann and other senior members of the Centre for Organized Matter (Bristol). If it is decided that a new material has promise, the University of Bristol Patent Office and Technology Transfer team will be contacted and asked to assess the potential for exploitation of any intellectual property as patentable technology.