Local Dense Structural Heterogeneities in Liquid Water from Ambient to 300 MPa Pressure: Evidence for Multiple Liquid–Liquid Transitions

Abstract

Difference and double-difference near-infrared DO-D and HO-H stretching overtone (2nuOD and 2nuOH) spectroscopy and a rigorous (physically substantiated) band deconvolution technique were applied to reveal three different kinds of inherent (interstitial) structures of liquid water, which determine its high density (compared to ice lh under ambient conditions), its compressibility (under hydrostatic pressure, up to 300MPa), and its high fragility (manifested under temperature variation). Our data processing allowed the rigorous discrimination of up to six vibrational components. On the basis of an extensive comparative analysis combined with available structural data (X-ray and neutron scattering) and molecular dynamics (MD) simulations for liquid water, as well as with experimental and computed data for small non-tetrahedrally arranged water clusters, the major four components could be ascribed to: i) The basic lh icelike substructure; ii) the temperature-dependent remote interstitial "defects" due to tetrahedral displacements (primarily responsible for transport properties); iii) the interstitial "defects" most probably arranged in quasiplanar noncyclic tetramers (totally absent in the ice structure); and iv) the interstitial "defects" formed with increasing pressure, probably arranged in cubic water octamers and composed of two pairs of noncyclic and cyclic tetramer fragments. The latter structures include, essentially, bent hydrogen bonds stabilized by resonance effects.

A nature of conformational changes of yeast tRNAPhe

“…The existence of water octamers having oxygen atoms situated in eight corners of the cube with internal hydrogen bond lengths of about 2.75Å was confirmed by crystallographic data [45]. Interestingly, cubic water has been also detected under the pressure of 3 kbar [46]. The difference in FTIR spectra of water measured at pressure are much smaller than those due to temperature increase.…”

“…This was interpreted rather as an essential reorientation of hydrogen bonds than variation in density [46]. The calculated energy of "bent" hydrogen bonds in cubic water amounts to 4 versus 5.5 kcal mol −1 for "normal" bonds in hexagonal structure [46]. The formation of octamer (cube) from two tetramers results in reducing the volume by 1.3 cm 3 mol −1 [46].…”

“…The difference in FTIR spectra of water measured at pressure are much smaller than those due to temperature increase. This was interpreted rather as an essential reorientation of hydrogen bonds than variation in density [46]. The calculated energy of "bent" hydrogen bonds in cubic water amounts to 4 versus 5.5 kcal mol −1 for "normal" bonds in hexagonal structure [46].…”

“…The calculated energy of "bent" hydrogen bonds in cubic water amounts to 4 versus 5.5 kcal mol −1 for "normal" bonds in hexagonal structure [46]. The formation of octamer (cube) from two tetramers results in reducing the volume by 1.3 cm 3 mol −1 [46]. As it was proposed earlier, water in such a form fits very well to the major groove of Z-DNA, so the changes in water structure followed by reorganisation of hydrogen bonds net induce the switching from B to Z conformation [47].…”

High hydrostatic pressure approach proves RNA catalytic activity without magnesium

“…At normal conditions, water occurs mostly in tetrahedral conformation (tetramer), while under high pressure it is changed into cubes (octamers), which results in reducing the volume by 1.3 cm 3 mol −1 [46][47][48][49][50][51]. Such changes in the water structure were followed by reorganisation of its binding network and effect on nucleic acid conformation.…”