Raman isosbestic points from liquid water

Walrafen, G. E.; Hokmabadi, M. S.; Yang, Wenshu

doi:10.1063/1.451383

Cited by 281 publications

(230 citation statements)

References 15 publications

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“…1, inside the T range inaccessible for bulk water, such a spectral contribution seems to play a determinant role in the water physics. With such an idea in mind, we have studied the OHS spectra by means of a spectral deconvolution with four Gaussian components: the V (3,120 cm Ϫ1 ) contribution and the three other I (3,220 cm Ϫ1 ), II (3,400 cm Ϫ1 ), and III (3,540 cm Ϫ1 ), coming from the well established studies of OHS vibrational spectra (30)(31)(32)(33) (Fig. 2).…”

Section: Resultsmentioning

confidence: 99%

Evidence of the existence of the low-density liquid phase in supercooled, confined water

Mallamace

Broccio

Corsaro

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

277

297

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By confining water in a nanoporous structure so narrow that the liquid could not freeze, it is possible to study properties of this previously undescribed system well below its homogeneous nucleation temperature T H ‫؍‬ 231 K. Using this trick, we were able to study, by means of a Fourier transform infrared spectroscopy, vibrational spectra (HOH bending and OH-stretching modes) of deeply supercooled water in the temperature range 183 < T < 273 K. We observed, upon decreasing temperature, the building up of a new population of hydrogen-bonded oscillators centered around 3,120 cm ؊1 , the contribution of which progressively dominates the spectra as one enters into the deeply supercooled regime. We determined that the fractional weight of this spectral component reaches 50% just at the temperature, T L Ϸ 225 K, where the confined water shows a fragile-to-strong dynamic cross-over phenomenon dynamic cross-over in water ͉ dynamic transitions in water ͉ Fourier transform infrared spectroscopy ͉ low-density liquid water ͉ Widom line in water W ater plays a fundamental and ubiquitous role on Earth and in all aspects of life phenomena. Understanding its properties is of paramount importance to mankind, and thus water is the most studied molecular system in science and technology. However, despite intense scrutiny over the years, scientists are still far from reaching a coherent understanding of all its unusual properties (1-3). Instead of behaving like other simple molecular liquids, many thermodynamic response functions of water, such as the isothermal compressibility, isobaric heat capacity, and thermal expansion coefficient, display counterintuitive trends as temperature is lowered. In particular, extrapolated from their values at moderately supercooled states, these functions all appear to diverge at a singular temperature around T S ϭ 228 K. Over the years, many plausible explanations for these strange behaviors have been proposed, starting from the two-state and the clathrate models (1-3). Three hypotheses are of active interest: (i) the stability limit (4), (ii) the percolation (5), and (iii) liquid-liquid (LL) critical point (6). The third approach has received support from various theoretical studies (7-9). However, in all three approaches, the main role is played by the local hydrogen-bond (HB) interaction pattern surrounding a typical water molecule in liquid state that governs the overall structure and dynamics (1) of water. Some of our recent experimental results (10, 11) on water confined in nanoporous structures as a function of temperature and pressure showed that the theoretical approach based on existence of the LL critical point is able to describe coherently many strange properties of water. By using the neutronscattering technique, we obtained evidence of the LL critical point (the second critical point predicted by the theory to be at T C ϳ 220 K and P C ϳ 1 kbar) located at T C ϭ 200 K and P C ϭ 1.5 kbar (10). This result was also subsequently confirmed qualitatively by an extensive molecular dynam...

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Section: Resultsmentioning

confidence: 99%

Evidence of the existence of the low-density liquid phase in supercooled, confined water

Mallamace

Broccio

Corsaro

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

277

297

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“…Between 18 and 120 THz (600-4000 cm À1 ), pure water exhibits two noticeable dispersions assigned to the H-O-H bending (49 THz) and O-H stretching (~100 THz) (99). Especially, the latter is strongly coupled with intermolecular HB dynamics (49)(50)(51)(52)(55)(56)(57)(58), and in general, the O-H stretching frequency red-shifts as the intermolecular HB becomes stronger (100)(101)(102)(103)(104). On the other hand, the complex dielectric constant of albumin crystal exhibits the several amide bands (66,105,106) between 30 and 50 THz, the C-H stretching (87 THz) (107), and N-H stretching (~100 THz) (66) in the MIR region.…”

Section: Derivation Of O-h Stretching Of Hydration Watermentioning

confidence: 99%

“…9, the three-Gaussian fitting can provide a good fit to the O-H stretching of bulk water and hydration water. Given that the O-H stretching frequency undergoes red-shift as the intermolecular HB strengthens (49,(100)(101)(102)(103)(104), the three Gaussian subbands were assigned to the three dominant populations of water molecules as follows: ''strong HB'' (~99 THz), ''intermediate HB'' (~102 THz), and ''weak HB'' (~107 THz) water species. From best-fitted parameters, the fractional band intensity (which equals a relative band area of a subband divided by the total band area) was determined as shown in Fig.…”

Section: Hydrogen-bond Strengthmentioning

confidence: 99%

Hydrogen Bond Network of Water around Protein Investigated with Terahertz and Infrared Spectroscopy

Shiraga

Ogawa

Kondo

2016

Biophysical Journal

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The dynamical and structural properties of water at protein interfaces were characterized on the basis of the broadband complex dielectric constant (0.25 to 400 THz) of albumin aqueous solutions. Our analysis of the dielectric responses between 0.25 and 12 THz first revealed hydration water with retarded reorientational dynamics extending~8.5 Å (corresponding to three to four layers) out from the albumin surface. Second, the number of nonhydrogen-bonded water was decreased in the presence of the albumin solute, indicating protein inhibits the fragmentation of the water hydrogen-bond network. Finally, water molecules at the albumin interface were found to form a distorted hydrogen-bond structure due to topological and energetic disorder of the protein surface. In addition, the intramolecular O-H stretching vibration of water (~100 THz), which is sensitive to hydrogen-bond environment, pointed to a trend that hydration water has a larger population of strongly hydrogen-bonded water molecules compared with that of bulk water. From these experimental results, we concluded that the ''strengthened'' water hydrogen bonds at the protein interface dynamically slow down the reorientational motion of water and form the less-defective hydrogen-bond network by inhibiting the fragmentation of water-water hydrogen bonds. Nevertheless, such a strengthened water hydrogen-bond network is composed of heterogeneous hydrogen-bond distances and angles, and thus characterized as structurally ''distorted.''

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“…Both of these observations have been interpreted as evidencing two distinct types of structures (18). In fact, the existence of an isosbestic point has commonly been considered a fingerprint of two-state behavior (9,18).…”

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confidence: 99%

Unified description of temperature-dependent hydrogen-bond rearrangements in liquid water

Smith

Cappa

Wilson

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

395

387

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The unique chemical and physical properties of liquid water are a direct result of its highly directional hydrogen-bond (HB) network structure and associated dynamics. However, despite intense experimental and theoretical scrutiny spanning more than four decades, a coherent description of this HB network remains elusive. The essential question of whether continuum or multicomponent (''intact,'' ''broken bond,'' etc.) models best describe the HB interactions in liquid water has engendered particularly intense discussion. Most notably, the temperature dependence of water's Raman spectrum has long been considered to be among the strongest evidence for a multicomponent distribution. Using a combined experimental and theoretical approach, we show here that many of the features of the Raman spectrum that are considered to be hallmarks of a multistate system, including the asymmetric band profile, the isosbestic (temperature invariant) point, and van't Hoff behavior, actually result from a continuous distribution. Furthermore, the excellent agreement between our newly remeasured Raman spectra and our model system further supports the locally tetrahedral description of liquid water, which has recently been called into question continuous distribution ͉ hydrogen-bond structure ͉ isosbestic points I n a continuum model, liquid water comprises a random, three-dimensional network of hydrogen bonds (HBs) encompassing a broad distribution of O-H⅐⅐⅐O HB angles and distances. Therefore, the concept of a ''broken'' HB is an arbitrary one. This ambiguity is often evident in molecular dynamics (MD) simulations of water, where, to define an ''intact'' or "broken" HB, an arbitrary energetic (1-4) or geometric (5-7) definition is used. However, the temperature dependence of the Raman (8) and IR (9, 10) spectra and, more recently, the x-ray absorption spectrum (11,12) seem to indicate the existence of spectrally distinguishable HB configurations. Such results have typically been interpreted as indicating that liquid water comprises two classes of HB domains: intact (or ''ice-like'') and broken. Furthermore, recent ultrafast HB dynamics measurements have attributed distinct relaxation times to specific substructures (13,14) or have ascribed the slow relaxation component (Ͼ1 ps) to HB ''breakage'' (15). These claims have been supported by molecular dynamics (MD) simulations, which have been interpreted as indicating that the time and temperature dependence of the IR spectrum results from the breaking and reforming of HBs (16,17 The Raman OH stretching region (3,200-3800 cm Ϫ1 ) of liquid water is characterized by a highly asymmetric band structure and an isosbestic point between 3°C and 85°C. Both of these observations have been interpreted as evidencing two distinct types of structures (18). In fact, the existence of an isosbestic point has commonly been considered a fingerprint of two-state behavior (9, 18). Such a point can arise from distinct spectral components corresponding to interconverting chemical species that vary in intensit...

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Raman isosbestic points from liquid water

Cited by 281 publications

References 15 publications

Evidence of the existence of the low-density liquid phase in supercooled, confined water

Evidence of the existence of the low-density liquid phase in supercooled, confined water

Hydrogen Bond Network of Water around Protein Investigated with Terahertz and Infrared Spectroscopy

Unified description of temperature-dependent hydrogen-bond rearrangements in liquid water

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