Nature of biological water: a femtosecond study

Bhattacharyya, Kankan

doi:10.1039/b800278a

Cited by 202 publications

(255 citation statements)

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“…It does not necessarily mean that the same situation repeats itself for a hydrated protein, or applies equally well to the Mössbauer experiment with a much longer resolution time of t r ≃ 140 ns [4]. Some experimental data indeed claim the existence of independent relaxation processes of the protein hydration shells with significantly slower relaxation times [65,66]. The resolution of this claim, however, depends on the water mode probed by the observations.…”

Section: Discussion and Implications For The Protein Dynamical Trmentioning

confidence: 89%

Dynamical and orientational structural crossovers in low-temperature glycerol

2016

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Mean square displacements of hydrogen atoms in glass-forming materials and proteins, as reported by incoherent elastic neutron scattering, show kinks in their temperature dependence. This crossover, known as the dynamical transition, connects two approximately linear regimes. It is often assigned to the dynamical freezing of subsets of molecular modes at the point of equality between their corresponding relaxation times and the instrumental observation window. The origin of the dynamical transition in glass-forming glycerol is studied here by extensive molecular dynamics simulations. We find the dynamical transition to occur for both the center of mass translations and the molecular rotations at the same temperature, insensitive to changes of the observation window. Both the translational and rotational dynamics of glycerol show a dynamic crossover from the structural to a secondary relaxation at the temperature of the dynamical transition. A significant and discontinuous increase in the orientational Kirkwood factor and in the dielectric constant is observed in the same range of temperatures. We, however, do not find any indications of a true thermodynamic transition to an ordered low-temperature phase. We therefore suggest that all observed crossovers are dynamic in character. The increase in the dielectric constant is related to the dynamic freezing of dipolar domains on the time-scale of simulations.

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Section: Discussion and Implications For The Protein Dynamical Trmentioning

confidence: 89%

Dynamical and orientational structural crossovers in low-temperature glycerol

2016

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“…It also remains to be seen whether the liquid state of water exists during the HDA to LDA ice transition not only in the water confined to the interior spaces of a protein crystal but also in high-pressure cryocooled bulk water (27). Experiments with faster time resolution (37) and that directly probe the dynamic properties of liquid water (38,39) may provide more insight into the phase behavior of supercooled water.…”

Section: Discussionmentioning

confidence: 99%

Evidence for liquid water during the high-density to low-density amorphous ice transition

Kim

Barstow²,

Täte

et al. 2009

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

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Polymorphism of water has been extensively studied, but controversy still exists over the phase transition between high-density amorphous (HDA) and low-density amorphous (LDA) ice. We report the phase behavior of HDA ice inside high-pressure cryocooled protein crystals. Using X-ray diffraction, we demonstrate that the intermediate states in the temperature range from 80 to 170 K can be reconstructed as a linear combination of HDA and LDA ice, suggesting a first-order transition. We found evidence for a liquid state of water during the ice transition based on the protein crystallographic data. These observations open the possibility that the HDA ice induced by high-pressure cryocooling is a genuine glassy form of high-density liquid.liquid-liquid hypothesis ͉ supercooled water ͉ water phases ͉ high-density liquid S upercooled water shows anomalous thermodynamic behavior (1-3). Theories that account for these anomalous properties include the stability limit (4), the singularity-free (5, 6), and the liquid-liquid (LL) critical point (7) hypotheses. The latter 2 hypotheses propose the existence of 2 distinct forms of supercooled water: high-density liquid (HDL) and low-density liquid (LDL) water (8). In the singularity-free hypothesis, HDL transforms continuously to LDL. In the LL critical point theory, HDL undergoes a first-order phase transition to LDL (8). However, experimental study of the HDL-LDL phase transition is challenging as supercooled water spontaneously converts to crystalline forms below the homogeneous nucleation temperature (Ϸ235 K at 0.1 MPa). The transition between 2 glassy forms of water, high-density amorphous (HDA) and low-density amorphous (LDA) ice, has been extensively studied (9-18), as an analogue of the HDL-LDL transition. Controversy still exists as to whether the HDA-LDA ice transition is truly a first-order phase transition (10-13) or if it occurs because of a relaxation process of an unstable amorphous structure (15-18). More importantly, the connection between the HDA-LDA ice transition and the HDL-LDL phase transition, implied by thermodynamic and structural studies on water (19-22), remains challenging to prove experimentally (8).We used X-ray diffraction to study the transition of HDA to LDA ice in protein crystals. HDA ice was induced inside protein crystals by a high-pressure cryocooling method (23) originally developed for macromolecular crystallography (23-26). The Bragg diffraction from protein crystals mainly provides information on protein structure. The simultaneously recorded water diffuse diffraction (WDD) profile reports on the phase of the water in the protein crystal, which accounts for typically 40-60% of its volume. Fig. 1 shows diffraction images and the WDD profiles from a high-pressure cryocooled crystal of the globular protein thaumatin. As the crystal temperature is increased from 80 to 170 K, the primary WDD peak, corresponding to the mean distance between neighboring water molecule oxygen atoms, shifts to lower momentum transfer (Q) region [Q ϭ 4 sin( )/ , wh...

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“…Fourth, the slow component of C(t), which has time constants of 8, 6, and 3 ps, respectively, in the TX-100, DTAB, and SDS micelles, shows reasonable agreement with results from previous studies, 54,60 which has been assigned to solvation of water molecules that are bound to the surface of the micelle by hydrogen bonding or the head group-water interactions. [40][41][42][43][44] Lastly, the constant offset observed in the C(t) of curcumin in the three micelles, which is expressed as a 3 in Table 2, indicates the presence of a decay component with a time constant that is vastly longer than the 10 ps time window of the solvation dynamics studies. Although this decay component of C(t) is too long to be resolved with our solvation dynamics investigations, it has been established in previous studies that C(t) has a long-lived component in micelles, with time constants ranging from 165 to 300 ps.…”

Section: Uv-vis Absorption and Emission Spectra Of Curcumin In Micellesmentioning

confidence: 99%

“…Solvation dynamics in micellar media is currently an intense area of research. [40][41][42][43][54][55][56][57][58][59][60][61][62] Surfactant micelles are excellent model systems for more complex biomembranes, and investigations on solvation dynamics in micelles provide critical insight into the behavior of small molecules in biomembranes. First of all, in our study, it is noteworthy that for each of the micelles, the value of the time constant τ 2 of C(t), as summarized in Table 2, is virtually identical within experimental error to that of the fast component of the fluorescence upconversion results shown in Figure 3 and Table 1.…”

Section: Uv-vis Absorption and Emission Spectra Of Curcumin In Micellesmentioning

confidence: 99%

Excited-State Intramolecular Hydrogen Atom Transfer of Curcumin in Surfactant Micelles

et al. 2010

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Femtosecond fluorescence upconversion experiments were performed on the naturally occurring medicinal pigment, curcumin, in anionic, cationic, and neutral micelles. In our studies, the micelles are composed of sodium dodecyl sulfate (SDS), dodecyl trimethyl ammonium bromide (DTAB), and triton X-100 (TX-100). We demonstrate that the excited-state kinetics of curcumin in micelles have a fast (3−8 ps) and slow (50−80 ps) component. While deuteration of curcumin has a negligible effect on the fast component, the slow component exhibits a pronounced isotope effect of ∼1.6, indicating that micelle-captured curcumin undergoes excited-state intramolecular hydrogen atom transfer. Studies of solvation dynamics of curcumin in a 10 ps time window reveal a fast component (≤300 fs) followed by a 8, 6, and 3 ps component in the solvation correlation function for the TX-100, DTAB, and SDS micelles, respectively. October 23, 2009; ReVised Manuscript ReceiVed: January 4, 2010 Femtosecond fluorescence upconversion experiments were performed on the naturally occurring medicinal pigment, curcumin, in anionic, cationic, and neutral micelles. In our studies, the micelles are composed of sodium dodecyl sulfate (SDS), dodecyl trimethyl ammonium bromide (DTAB), and triton X-100 (TX-100). We demonstrate that the excited-state kinetics of curcumin in micelles have a fast (3-8 ps) and slow (50-80 ps) component. While deuteration of curcumin has a negligible effect on the fast component, the slow component exhibits a pronounced isotope effect of ∼1.6, indicating that micelle-captured curcumin undergoes excited-state intramolecular hydrogen atom transfer. Studies of solvation dynamics of curcumin in a 10 ps time window reveal a fast component (e300 fs) followed by a 8, 6, and 3 ps component in the solvation correlation function for the TX-100, DTAB, and SDS micelles, respectively. Keywords

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Nature of biological water: a femtosecond study

Cited by 202 publications

References 124 publications

Dynamical and orientational structural crossovers in low-temperature glycerol

Dynamical and orientational structural crossovers in low-temperature glycerol

Evidence for liquid water during the high-density to low-density amorphous ice transition

Excited-State Intramolecular Hydrogen Atom Transfer of Curcumin in Surfactant Micelles

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