Abstract
We studied the pressureinduced unfolding and refolding of monomeric proteins, such as SNase, αchymotrypsin and ubiquitin, by using synchrotron Xray smallangle scattering and Fouriertransform infrared spectroscopy, which monitor changes in the tertiary and secondary structural properties of the proteins upon pressurization. Furthermore, by using the pressurejump relaxation technique in combination with timeresolved Xray diffraction and infrared spectroscopy, the kinetics of the unfolding/refolding of the proteins, was investigated. Significant differences in secondary structure and chain compactness in the folding/unfolding reactions of these proteins are observed. The results are compared with data obtained from other methods of denaturation, such as heat and pressure-assisted cold denaturation. The cold- and pressure-induced unfolding both yield a particularly unfolded state characterized by a persistent amount of secondary structure.