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The temperature dependence of the density of pure H2O and D2O determined in the range of 20–45 °C. The relationships obtained by us (solid lines) are compared with the literature data for H2O⁵⁹ (black diamonds) and D2O 60,61 (black circles). The values estimated from binary H2O/D2O solvents are denoted in magenta.
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Normal and heavy water are solvents most commonly used to study the isotope effect. The isotope effect of a solvent significantly influences the behavior of a single molecule in a solution, especially when there are interactions between the solvent and the solute. The influence of the isotope effect becomes more significant in D2O/H2O since the hyd...
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Interest in deuterated de novo active pharmaceutical ingredients (APIs) is increasing due to the release of the first FDA approved deuterated drug, deutetrabenazine. Deuteration also holds promise for kinetic isotope effect (KIE) regulated fine-tuning of active pharmaceutical ingredient performance. As such, methods for highly selective deuteration...
Citations
... The pH of liquid H 2 O water increases from 7.0 to pD = 7.4 in D 2 O and pT = 7.6 in T 2 O at 25 ○ C, indicating the presence of small concentrations of H + /D + /T + and OH − /OD − /OT − in these liquids, which allow for isotope exchange. 8,9,45,46 It is well known that D 2 O and H 2 O water undergo a hydrogen isotope exchange reaction, [47][48][49][50] ...
To study the effect of hydrogen isotope substitution on the uptake of water during formation of clathrate hydrates, the harmonic intermolecular librational modes of selected water clusters (X2O)n with n = 2–6 and hydrogen isotopes X = H, D, and T are studied. The effects of the
quantum mechanical zero-point energy (ZPE) in each cluster on the binding energies of the H2O, D2O, and T2O clusters are determined, with
ZPE leading to the smallest binding energies in the H2O clusters and the largest binding energies in the T2O clusters. Corrections for anharmonicity of the librational modes are considered, and these bring the frequency ranges of the calculated intermolecular librational modes in
the clusters to the experimental ranges of the librational modes in the infrared spectra of H2O and D2O solid ice and clathrate hydrate phases,
and liquid H2O water. These calculations show the expected ranges of the binding energy of tritiated water onto a solid ice and clathrate
hydrate surface and can help quantify the isotopic enrichment on a growing clathrate hydrate phase from the solution.
... Currently, although studies report a clear solvent isotope effect in D 2 O compared to H 2 O that stiffens the protein [62][63][64], the effect of the protein's perdeuteration on its dynamics is still unclear and is reported to depend on proteins or regions inside the proteins [65], as well as timescales under study [66,67]. Indeed, even in a light system such as water, isotopic exchange induces only a D D 2 O /D H 2 O ≈ 1.2 ratio for the translational diffusion coefficient D at 310 K [68][69][70], and remains below 1.15 in many liquids for both rotational and translational diffusion [71], while we get τ inc,pGFP /τ inc,dGFP ≈ 3. ...
Within the last decades, it was often assumed that in hydrogen-rich disordered samples, such as proteins in solution or hydrated powder form, incoherent neutron scattering from hydrogen nuclei dominated the scattering signal to an extent that allowed all other contributions to be neglected. As incoherent scattering arises solely from self-correlations, it further justified such a choice. Consequently, heavy water was often used as a contrast tool to highlight molecular motions in live samples. Coherent scattering, which implies the scattering from many nuclei and therefore collective processes, is another non-negligible contribution to neutron scattering where cross sections of other nuclei than hydrogen are significant. The recent advent of instrumentation based on polarization of neutron beams and the analysis of their polarization state after scattering for dynamical studies allows us to separate and shed light on the two contributions. In the present study we reveal that, unexpectedly, the isotopic exchange of water in the hydration shell of proteins arises on a much faster timescale than assumed so far. Moreover, the collective and local D-bond network relaxation of hydration water contributes to a high extent to the coherent scattering signal, at odds with usual "static" approaches used to estimate the relative impacts of dynamics in the sample. Hence, hydration water necessarily contaminates nonpolarized standard experiments. The findings are of paramount importance for all neutron scattering experiments where partial or full deuteration is used.
... Isotopic effects indicate the difference in the outcome or magnitude of a given property of a material by substituting the isotope of a certain atom within the molecule, for instance, changing the hydrogen (H) atoms of water by deuterium (D) atoms to obtain heavy water. This small difference at the atomic level is generally reflected in the bulk, transport and surface properties [21,22]. Isotopic effects are very interesting because the magnitude of these effects can shed some light on the nature of the intermolecular interactions and structures in liquids and liquid mixtures [23]. ...
In this work, we report the CO 2 hydrate phase equilibria in water (H 2 O), heavy water (D 2 O), and their binary mixtures following the isochoric pressure search method using a rocking cell apparatus. The phase behaviour was mapped within the temperature and pressure range of 276.32 – 284.80 K and 1.59 – 3.78 MPa, respectively. It was found that there is a difference of ~2K in the equilibrium line of CO 2 hydrates formed in H 2 O and in D 2 O, respectively. The hydrate dissociation enthalpies obtained using the Clausius-Clapeyron equation indicate almost similar values formed either in D 2 O, H 2 O or their mixtures. These shifts in this equilibrium temperature were compared with the triphasic equilibrium temperature variation
estimation obtained using Molecular Dynamics Simulations and a very good agreement with the experimentally obtained values was observed. Further, a constant cooling method was used to obtain the onset temperature of hydrate nucleation for these systems at 3.5 MPa. It has been found that during the cooling ramps, the nucleation always occurred in the vicinity of the temperature of maximum density (TMD) of the systems where water still retains some structuredness. The nucleation experiments also give information about the metastable zone width (MSZW) of the studied systems. The results reported in this work indicate the magnitude of the isotopic effect on CO 2 hydrate formation and dissociation that may have implications towards the application of hydrate technology for separation and purification
processes.
... A slight variation was used for gels in H 2 O where SSF and SGF were prepared in 'air-contrast matched water' (ACMW, 8% D 2 O) resulting in a scattering length density of zero, thereby avoiding scattering from any air bubbles generated during the water flow. This common approach in neutron scattering has proven to have a negligible effect on structure when significant excess of H 2 O is used in mixtures of normal and heavy water (Stefaniuk et al., 2022). It was necessary to reduce the gel particle size to ensure the particles flowed continuously through the sample cell of the in situ flow system. ...
