Fragile-to-strong dynamic crossover

Liu L, Mon CY, Chen SH. The fragile-to strong dynamic crossover transition in confined water nuclear magnetic reso- 57. nance results. J. Chem. Phys. 2006 124 161102. 

Chen SH, Liu L, Fratini E, Baglioni P, Faraone A, Mamontov E. Observation of fragile-to-strong dynamic crossover in protein hy- 95. dration water. Proc. Nat. Acad. Sci. U.S.A. 2006 103 9012-9016. 

S.-H. Chen, L. Liu, X. Chu, Y. Zhang, E. Fratini, P. Baglioni, A. Faraone, E. Mamontov, Experimental evidence of fragile-to-strong dynamic crossover in DNA hydration water, J. Chem. Phys. 125 (2006) 171103. 

Figure 23 shows the results of a recent TMSC experiment in MGM-41-S confined water with (p = 2.4 and 1.8 nm. Note that there is a close similarity between these data and the data obtained from adiabatic calorimetry. Their interpretation, however, is completely different. Taking into account the results obtained for the water transport coefficients, represented by the NMR and neutron data, the results obtained for the dynamic fragile-to-strong glass crossover (Fig. 9), and the violation of the Stokes-Einstein relation (Fig. 10) we can assume that these maxima in Cp at about 225K are related to the crossover phenomenon and not a GT process. 

Faraone A, Mamontov E. Experimental evidence of fragile-to- 96. strong dynamic crossover in DNA hydration water. J. Chem. 

For m>30 and Dj-kIO liquids are considered fragile whereas m<30 and Oj > 10 there are encountered to strong glass formers, with d5mamics closer to the Arrhenius pattern. In supercooled liquids at least two dynamical domains with the crossover at r(jg)< are considered. ... 

Of paramount importance are the two crossover phenomena observed in protein hydration water, which, on the basis of the many results we have described, can be considered responsible for the biological activity of macromolecules, including RNA and DNA. Neutron measurements of the MSD indicate, surprisingly, that the crossover temperature of biopolymer and its hydration water are closely synchronized. More precisely, FTIR experiments indicate that when a biosystem restores its dynamics, the solvent crosses from a strong to a fragile liquid, that is, the HB networking changes from a thermal state in which LDL dominates to one in which HDL dominates. At the same time, irreversible denaturation takes place when the HB numbers decrease to the point at which only a few water molecules are bonded. 

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