a b s t r a c t a r t i c l e i n f oDSC analysis has been used to quantify the reversibility of unfolding following thermal denaturation of lysozyme. Since the temperature at which protein unfolding occurs, T m , varies with different solution conditions, the effect on the melting temperature and the degree of refolding after thermal denaturation in low ionic strength sodium phosphate buffers (5-1000 mM) over a range of pH (5-9) in the presence/absence of disaccharides is examined. This study compares the enthalpies of unfolding during successive heating cycles to quantify reversibility following thermal denaturation. The disaccharides, trehalose and maltose were used to assess if the disaccharide induced increase in T m is reflected in the reversibility of thermally induced denaturation. There was extensive overlap between the T m values where non-reversible and reversible thermal denaturation occurred. Indeed, for pH 6, at the highest and lowest T m , no refolding was observed whereas refolding was observed for intermediate values, but with similar T m values having different proportions of refolded protein. We established a method to measure the degree of reversible unfolding following thermal denaturation and hence indirectly, the degree to which protein is lost to irreversible aggregation, and show that solution conditions which increase melt transition temperatures do not automatically confer an increase in reversibility. This type of analysis may prove useful in assessing the stability of proteins in both the biopharmaceutical and food industries.

The overall physical properties of tissues emerge in a complex manner from the properties of the component cells and other constituent materials from which the tissue is formed, across multiple length scales ranging from nanometres to millimetres. Recent studies have suggested that interfacial tension between cells contributes significantly to the mechanical properties of tissues and that the overall surface tension is determined by the ratio of adhesion tension to cortical tension. Using cavitation rheology (CR), we have measured the interfacial properties and the elastic modulus of spheroids formed from HEK cells. By comparing the work of bubble formation with deformation of the cell spheroid at different length scales, we have estimated the cortical tension for HEK cells. This innovative approach to understanding the fundamental physical properties associated with tissue mechanics may guide new approaches for the generation of materials to replace or regenerate damaged or diseased tissues.

Bigels (or double network gels) are an emerging class of tuneable soft materials characterized by two discrete but interpenetrating gel networks in which both networks contribute to the physical and mechanical properties of the material. We describe, for the first time, the formation of a bigel network from two different proteins. By careful control of solution conditions, kinetics and specific protein chemistry the inter-species interactions in the two protein system are weak compared with the intra-protein attraction, which leads to bigel formation. The resulting protein bigel has an elastic modulus four times greater than the combined elastic moduli of the parent gels, has an elastic response over several deformation cycles and is both thermo-and chemo-responsive. These gels have the potential to be used as biomimetics in tissue culture, in drug delivery or for biomedical applications such as wound healing.

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