Observation of a dynamic crossover in RNA hydration water which triggers a dynamic transition in the biopolymer

Abstract

High-resolution quasielastic neutron scattering spectroscopy was used to measure H2O and D2O hydrated RNA samples. The contribution of scattering from RNA was subtracted out by taking the difference of the signals between the two samples. The measurements were made at a series of temperatures from 270 K down to 180 K. The relaxing-cage model was used to analyze the difference quasielastic spectra. We observed clear evidence of a fragile-to-strong dynamic crossover (FSC) at TL=220 K in RNA hydration water. We further show that the mean-square displacements of the hydrogen atoms in both RNA and its hydration water exhibit a sharp change in slope at approximately the same temperature 220 K. This latter fact suggests that the dynamic transition in RNA is triggered by the abrupt change of mobility of the hydration water at its FSC temperature.

Slowdown of Interhelical Motions Induces a Glass Transition in RNA

“…(An additional difference is that NMR can also measure individual bond motions before averaging over all the molecules, therefore enabling detection at virtually any molecular site). Remarkably, the temperature extrapolation for the average of 1 -S 2 as described above for TAR strongly resembled the temperature dependence of the mean-square fluctuations h(Dx) 2 i measured in the inelastic neutron scattering studies of tRNA (16,17) and yeast RNA (18). In these INS experiments, the typical signature of the glass transition (as seen in RNA, as well as in proteins and in DNA) is marked by a biphasic change at T g in the slope of two roughly linear T-dependences as the mean-square fluctuations h(Dx) 2 i in the atomic displacements.…”

“…Fig. 2 b shows this T dependence of 1 -S 2 for TAR-RNA, together with the mean-square deviation fluctuations for tRNA and yeast RNA from INS measurements with data from Caliskan et al (16) and Chu et al (17,18) and with our simulated TAR-RNA inelastic neutron scattering data, i.e., with the TAR-RNA mean-square deviation fluctuations of hydrogens from our MD simulations (see below). A remarkable similarity in the values of T g and a universality in the overall shape of normalized fluctuation descriptors across various RNA systems and experimental methods was observed when scaling all INS and NMR and simulation data (see Fig.…”

Mean-squared atomic displacements in hydrated lysozyme, native and denatured

“…Thus, the first signs of the transition in hydrated biomolecules may coincide with the entrance of this component to the resolution window. At 220-230 K, the hydration water experiences a dynamical transition [20][21][22][23] that further increases anharmonicity. Finally, the onset of long-range translational motions of hydration water leads to an even faster increase in anharmonicity at temperatures above 240 K [47][48][49].…”

Cause of the fragile-to-strong transition observed in water confined in C-S-H gel

“…From quasi-elastic neutron scattering (QENS) studies it has been observed that the relaxation time of confined water exhibit an abrupt crossover from a non-Arrhenius to an Arrhenius dependence as the temperature decreases, which has been associated with the appearance of the fragile-to-strong transition (FST) expected for bulk water. The sharp change in temperature behavior has been observed for water in a variety of confining systems such as MCM-41, 4 carbon nanotubes, 5 white cement 6 as well as in aqueous solution of DNA, 7 RNA, 8 and lysozyme. 9 Some of these, or similar confining systems, have also been studied by using other different experimental techniques, such as broadband dielectric spectroscopy (BDS), [10][11][12][13][14][15] nuclear magnetic resonance (NMR), 16 or a combination of different techniques.…”