Solvent-free liquid proteins

Abstract

The work presented in this thesis represents the first investigation into the structure, function, and material properties of solvent-free liquids of globular proteins. Using myoglobin as an archetypal system, it has been shown that solvent-free liquid proteins can be synthesized through the engineering of protein surfaces with an organic corona made from polymer surfactants. These novel materials have been shown to be stoichiometric constructs of protein and surfactant, with respect to charge, that once lyophilized form liquid-like materials with unique thermal properties and very low water contents. The generality of the synthetic procedure was tested with the formation of solvent-free liquid proteins with a variety of surfactants. The result of which was that for myoglobin, there was a surfactant molecular weight limit of c. 700 mg.mL-1 with respect to the constructs that possessed liquid phases. The suggestion of which was that the corona had to extended from the surface of the protein enough to satisfy the interparticle interactions required to yield an accessible liquid state. Spectroscopic measurements were used to assess the secondary structure of proteins in the solvent-free liquid state. UV/Vis spectroscopy showed that the prosthetic heme of myoglobin (and hemoglobin) was retained in a structurally conserved environment, and CD spectroscopy showed the retention of a significant amount of secondary structure. These studies were extended to show that in the absence of water, proteins retained the ability to thermally denature and subsequently refold. This proceeded with extraordinary thermal stability, with solvent-free liquid myoglobin exhibiting a half denaturation temperature of c. 160 QC. With the persistence of secondary structure in solvent-free liquid proteins, the function of myoglobin was also investigated. It has been shown that in the absence of water, oxygen binding was achievable up to 125 QC.EThOS - Electronic Theses Online ServiceGBUnited Kingdo