Role of the solvent in the dynamical transitions of proteins: The case of the lysozyme-water system

Abstract

We study the dynamics of hydration water in the protein lysozyme in the temperature range 180 K<T<360 K using Fourier-transform-infrared and nuclear magnetic resonance (NMR) spectroscopies. By analyzing the thermal evolution of spectra of the OH-stretching vibration modes and the NMR self-diffusion (DS) and spin-lattice relaxation time (T1), we demonstrate the existence of two dynamical transitions in the protein hydration water. Below the first transition, at about 220 K, the hydration water displays an unambiguous fragile-to-strong dynamic crossover, resulting in the loss of the protein conformational flexibility. Above the second transition, at about 346 K, where the protein unfolds, the dynamics of the hydration water appears to be dominated by the non-hydrogen-bonded fraction of water molecules.

Hydrogen Bond Network of Water around Protein Investigated with Terahertz and Infrared Spectroscopy

“…This fast relaxationc fast ðuÞ coupled with changes in the slow relaxationc slow ðuÞ can be used to define the population of the NHB water molecules, i.e., the fragmentation of HBs in the presence of albumin. It has been pointed out the population of this NHB water is coupled with protein thermal unfolding (85), prompting the need for quantification of NHB water adjacent to the protein molecule but little has been done to date.…”

The puzzling unsolved mysteries of liquid water: Some recent progress

“…This work, supported by the NSF Chemistry Division, has been carried out with many collaborators and has been heavily influenced by a number of experimentalists including S.-H. Chen [44,50,77,82], L. Liu [39,40], F. Mallamace [85,86], O. Mishima [13,87,88], J. Teixeira [89][90][91], M.-C. Bellissent [92][93][94][95], and H. Reichert [96].…”

Dynamical changes in hydration water accompanying lysozyme thermal denaturation

“…We used NMR (a 700-MHz Bruker Avance spectrometer) at one atmosphere to measure the proton selfdiffusion coefficient of lysozyme hydration water [14,28]. We performed the measurements using the pulsed field gradient stimulated echo (PGSTE) technique [50] with a field gradient value of 1200 Gauss/cm [14].…”

“…Many studies have probed the thermal limit of the biological activity of protein and have linked its onset at low temperatures to the occurrence of a dynamical crossover in the hydration water at approximately 225 K [10][11][12][13][14][15][16][17][18][19][20]. Although this precise value of temperature has been debated, given the possibility of inadequate instrumental resolutions, there is a consensus that the crossover occurs and that it is important [21][22][23][24][25][26][27][28][29][30][31].…”

“…The thermal denaturation of the lysozyme has been studied using such techniques as calorimetry, nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy [13,14,43,44]. The process is kinetic and moves through three states: the native state ↔ the reversible unfolding state → the irreversible denatured state.…”