Increasing Contact-Ion Pairing as a Supercooled Water Anomaly. Estimation of the Fictive Temperature of Hyperquenched Glassy Water

Abstract

In "dilute" aqueous D 2 O solution of calcium nitrate, contact-ion pairing increases on cooling from 300 to 240 K, despite simultaneous increase of water's dielectric permittivity. This increase in contact-ion pairing was quantified by FT-IR spectroscopic evaluation of nitrate's ν 2 band region. The bound/free nitrate area ratios strongly increase on supercooling in a nonlinear way, in a similar manner as the anomalous molar volume of supercooled water does, which suggests that both anomalies have a common origin in the structural changes of supercooled water. By extrapolation of bound/free nitrate area ratios, we conclude that water and the solute become, on hyperquenching into the glassy state, immobilized between 230 and 200 K. This is important for analysis of the thermodynamic path liquid water takes on quenching into the glassy state, and it gives a low-temperature limit where conformational changes can occur in a biomolecule during quenching of its aqueous solution into the glassy state.

Unexpected B II Conformer Substate Population in Unoriented Hydrated Films of the d(CGCGAATTCGCG) 2 Dodecamer and of Native B-DNA from Salmon Testes

“…Seshadri and Jones (1963) argue that on solutesolvent interaction, "one might expect that the bands associated with such systems would be more pronouncedly of Gauss form because the number of participating species will be very large." In our previous curve resolution studies of contact ion pairing in glassy aqueous solution, the band shapes were nearly pure Gaussian (Fleissner et al, 1996(Fleissner et al, , 1998.…”

Prediction of entropy and dynamic properties of water below the homogeneous nucleation temperature

“…These measurements can be carried out at temperatures down to the quench rate dependent ÿctive temperature, which has been estimated by Fleissner et al [54] to be 200 -230 K for hyperquenched water. If this is the case then during the quench, the liquid maintains its internally equilibrated condition from 5 -35 K below the usual homogeneous nucleation temperature.…”

Dielectric and Calorimetric Studies of Hydrated Purple Membrane

“…the difficult-to-probe region below 235 K, the temperature region between 200 and 230 K (27,36) may be physically the most interesting to study. In this study, it is possible that the changed dynamics occurs when the local b-relaxation is merged with a weak or invisible a-relaxation of the confined water (37), together with the change in character mentioned above.…”