Role of Solvent on Protein-Matrix Coupling in MbCO Embedded in Water-Saccharide Systems: A Fourier Transform Infrared Spectroscopy Study

Abstract

Embedding protein in sugar systems of low water content enables one to investigate the protein dynamic-structure function in matrixes whose rigidity is modulated by varying the content of residual water. Accordingly, studying the dynamics and structure thermal evolution of a protein in sugar systems of different hydration constitutes a tool for disentangling solvent rigidity from temperature effects. Furthermore, studies performed using different sugars may give information on how the detailed composition of the surrounding solvent affects the internal protein dynamics and structural evolution. In this work, we compare Fourier transform infrared spectroscopy measurements (300-20 K) on MbCO embedded in trehalose, sucrose, maltose, raffinose, and glucose matrixes of different water content. At all the water contents investigated, the protein-solvent coupling was tighter in trehalose than in the other sugars, thus suggesting a molecular basis for the trehalose peculiarity. These results are in line with the observation that protein-matrix phase separation takes place in lysozyme-lactose, whereas it is absent in lysozyme-trehalose systems; indeed, these behaviors may respectively be due to the lack or presence of suitable water-mediated hydrogen-bond networks, which match the protein surface to the surroundings. The above processes might be at the basis of pattern recognition in crowded living systems; indeed, hydration shells structural and dynamic matching is first needed for successful come together of interacting biomolecules.

Proteins in amorphous saccharide matrices: Structural and dynamical insights on bioprotection

“…While the protein interacts either with single or multiple hydrogen bonds with water, the few sugar OH groups bound to the protein are in large majority linked through a single (donor) hydrogen bond. These results are in agreement with previous [26], sucrose (dashed lines) [27,54], maltose (thin lines) [28].…”

“…Spectra distance, calculated for the WAB (SDWAB, upper panels) and the COB (SDCO, lower panels). Data refer to ternary dry (black symbols), ternary hydrated (grey symbols) and binary (open symbols, only in the upper panels), for samples of trehalose (left panels), sucrose (middle panels), maltose (right panels) [28,32].…”

“…The protein-matrix interaction, and its dependence on hydration, has been also studied by Infrared Spectroscopy (FTIR) on carboxy-myoglobin (MbCO) embedded in trehalose matrices at different water content [26][27][28]. The properties of the protein have been studied following the thermal evolution of the CO stretching band (COB, ∼ 1900-2000 cm −1 ), which is split into three different sub-bands (A substates) [29], each corresponding to a specific different environment experienced by the bound CO within the heme pocket [30].…”

“…Overall, FTIR and MD results suggested that the rigidity of the HB network increases on drying. This network is mainly responsible for coupling the internal dynamics of the protein to that of the low-water matrix [28]. Saccharides protect biomolecules not by simply preserving their native solvation, but rather by locking their surface either directly or through networks of water molecules, thus hindering internal motions.…”

Ligand recombination and a hierarchy of solvent slaved dynamics: The origin of kinetic phases in hemeproteins

“…In Fig. 7 the MEM derived kinetic populations are shown for the single H64L mutant in a trehalose glass as a function of increasing exposure to humidity (a→c) which "loosens" the strong hydrogen bonding network comprising the glassy matrix (Cordone et al, 1998;Librizzi et al, 1999;Cottone et al, 2001;Cordone et al, 2005;Giuffrida et al, 2006). Under these conditions, the onset of the D state is sufficiently slow that no D state kinetic populations are observed (vide infra).…”