Investigating the influence of water in lysozyme structure and dynamics using FT-IR and XRD

Abstract: Water is “the matrix of life” for its fascinating properties. The well-known simple water molecule consists of one oxygen atom and two hydrogen atoms, covering most of planet earth’ssurface. It is the most studied element in science; however, its properties are still not fully understood. Another essential building block of life is proteins, which manifest naturally in aqueous environments. The protein activity is controlled by the protein folding process that is dependent on the surrounding environment. It is hypothesized that the hydrogen bond network of water plays an important role in the folding process. Here, we investigate the protein lysozyme in liquid water as well as in the crystalline state ice Ih, exploring various temperatures, using FT-IR and XRD. Our main finding is that a transition occurs at approximately T=210 K, indicative of the hypothesised protein dynamic “glass” transitionobserved by previous studies in supercooled water at similar temperatures.