The trehalose coating effect on the internal protein dynamics

15N and 13C NMR experiments were applied to conduct a comparative study of a cold shock protein (Csp) in two states—lyophilized powder and a protein embedded in a glassy trehalose matrix. Both samples were studied at various levels of rehydration. The experiments used (measuring relaxation rates R1 and R1ρ, motionally averaged dipolar couplings and solid state exchange method detecting reorientation of the chemical shift anisotropy tensor) allow obtaining abundant information on the protein structural features and internal motions in a range of correlation times from nanoseconds to seconds. The main results are: (a) the trehalose coating makes the protein structure more native in comparison with the dehydrated lyophilized powder, however, trehalose still cannot remove all non-native hydrogen bonds which are present in a dehydrated protein; (b) trehalose has an appreciable effect on the internal dynamics: the motion of the backbone N–H groups in the nanosecond and microsecond time scales becomes slower while the motional amplitude remains constant; (c) upon adding water to the Csp–trehalose mixture, water molecules accumulate around proteins forming a layer between the protein surface and the trehalose matrix. The protein dynamics become faster, however, not as fast as in the fully hydrated state; (d) the hydration response of dynamics of the NH and CH(CH2) groups in a protein is qualitatively different: upon increasing protein hydration, the correlation times of the N–H motions become shorter and the amplitude remains stable, and for CH(CH2) groups the motional amplitude increases and the correlation times do not change. This can be explained by a different ability of the NH and CH(CH2) groups to form hydrogen bonds.