Intramolecular OH stretching analysis of hydrated lysozyme in presence of trehalose by IR spectroscopy

The present work reports the analysis of the intramolecular OH stretching band obtained by InfraRed spectroscopy measurements. In order to characterize the effect of trehalose on the hydration properties of lysozyme the so-called two-state model is adopted for the analysis of the intramolecular OH stretching band. This latter assumes that, provided that the trehalose OH stretching contribution is subtracted, water molecules can be partitioned into two different states of inter-molecular bonding: molecules with two OH groups both hydrogen-bonded within a tetrahedral network, and molecules with one or two dangling OH groups. What emerges from this study is that trehalose significantly influences the hydrogen bond network of water and its temperature behaviour. Such a result confirms that the trehalose induced strengthening of the hydrogen-bond network leads to a stabilization of the lysozyme structure. Moreover, the analysis of the spectra temperature dependence shows a trehalose-induced higher thermal restraint of the lysozyme-trehalose-water system in respect to the lysozyme-water mixture.