NMR Study of Water Structure in Supercritical States (INTERFACE SCIENCE-Solutions and Interfaces)

The proton chemical shift of water is measured at temperatures up to 400°C and densities of 0.19, 0.41, 0.49, and 0.60 g/cm3. The magnetic susceptibility correction is made in order to express the chemical shift relative to an isolated water molecule in the gas phase. Comparison of the observed chemical shift to that of a solitary water molecule in an organic solvent shows that the hydrogen bonding persists in the supercritical water. At each density, the strength of the hydrogen bonding is found to reach a plateau value at high temperatures

A multicenter prospective registry of Borden type I dural arteriovenous fistula: results of a 3-year follow-up study

PURPOSE: Although intracranial dural arteriovenous fistula (DAVF) without retrograde leptomeningeal venous drainage (Borden type I) is reported to have a benign nature, no study has prospectively determined its clinical course. Here, we report a 3-year prospective observational study of Borden type I DAVF. METHODS: From April 2013 to March 2016, consecutive patients with DAVF were screened at 13 study institutions. We collected data on baseline characteristics, clinical symptoms, angiography, and neuroimaging. Patients with Borden type I DAVF received conservative care while palliative intervention was considered when the neurological symptoms were intolerable, and were followed at 6, 12, 24, and 36 months after inclusion. RESULTS: During the study period, 110 patients with intracranial DAVF were screened and 28 patients with Borden type I DAVF were prospectively followed. None of the patients had conversion to higher type of Borden classification or intracranial hemorrhage during follow-up. Five patients showed spontaneous improvement or disappearance of neurological symptoms (5/28, 17.9%), and 5 patients showed a spontaneous decrease or disappearance of shunt flow on imaging during follow-up (5/28, 17.9%). Stenosis or occlusion of the draining sinuses on initial angiography was significantly associated with shunt flow reduction during follow-up (80.0% vs 21.7%, p = 0.02). CONCLUSION: In this 3-year prospective study, patients with Borden type I DAVF showed benign clinical course; none of these patients experienced conversion to higher type of Borden classification or intracranial hemorrhage. The restrictive changes of the draining sinuses at initial diagnosis might be an imaging biomarker for future shunt flow reduction

Anhydrobiosis-Associated Nuclear DNA Damage and Repair in the Sleeping Chironomid: Linkage with Radioresistance

Anhydrobiotic chironomid larvae can withstand prolonged complete desiccation as well as other external stresses including ionizing radiation. To understand the cross-tolerance mechanism, we have analyzed the structural changes in the nuclear DNA using transmission electron microscopy and DNA comet assays in relation to anhydrobiosis and radiation. We found that dehydration causes alterations in chromatin structure and a severe fragmentation of nuclear DNA in the cells of the larvae despite successful anhydrobiosis. Furthermore, while the larvae had restored physiological activity within an hour following rehydration, nuclear DNA restoration typically took 72 to 96 h. The DNA fragmentation level and the recovery of DNA integrity in the rehydrated larvae after anhydrobiosis were similar to those of hydrated larvae irradiated with 70 Gy of high-linear energy transfer (LET) ions (4He). In contrast, low-LET radiation (gamma-rays) of the same dose caused less initial damage to the larvae, and DNA was completely repaired within within 24 h. The expression of genes encoding the DNA repair enzymes occurred upon entering anhydrobiosis and exposure to high- and low-LET radiations, indicative of DNA damage that includes double-strand breaks and their subsequent repair. The expression of antioxidant enzymes-coding genes was also elevated in the anhydrobiotic and the gamma-ray-irradiated larvae that probably functions to reduce the negative effect of reactive oxygen species upon exposure to these stresses. Indeed the mature antioxidant proteins accumulated in the dry larvae and the total activity of antioxidants increased by a 3–4 fold in association with anhydrobiosis. We conclude that one of the factors explaining the relationship between radioresistance and the ability to undergo anhydrobiosis in the sleeping chironomid could be an adaptation to desiccation-inflicted nuclear DNA damage. There were also similarities in the molecular response of the larvae to damage caused by desiccation and ionizing radiation

Dynamics of Supercritical Water (INTERFACE SCIENCE-Solutions and Interfaces)

The rotational dynamics of water in super- and subcritical conditions is investigated by measuring the spin-lattice relaxation time 1 of heavy water (D2O). The experimentally determined 1 is shown to be governed by the quadrupolar relaxation mechanism even in the supercritical conditions and to provide the second-order reorientational correlation time 2R of the O-D axis of a single water molecule. It is then found that while 2R decreases rapidly with the temperature on the liquid branch of the saturation curve, it remains on the order of several tens of femtoseconds when the density is varied up to twice the critical at a fixed supercritical temperature of 400 oC. The comparison of 2R with the angular momentum correlation time shows that the rotational dynamics is not diffusive in supercritical water. The dependence of 2R on the hydrogen bonding state is also examined in combination with molecular dynamics simulations, and the effect of the hydrogen bonding on the rotational dynamics in supercritical water is found to be weaker than but to be on the same order of magnitude as that in ambient water on the relative scale

Nuclear magnetic resonance study on rotational dynamics of water and benzene in a series of ionic liquids: Anion and cation effects.

The rotational correlation times (τ(2R)) for polar water (D(2)O) molecule and apolar benzene (C(6)D(6)) molecule were determined in ionic liquids (ILs) by means of the (2)H (D) NMR spin-lattice relaxation time (T(1)) measurements. The solvent IL was systematically varied to elucidate the anion and cation effects separately. Five species, bis(trifluoromethylsulfonyl)imide (TFSI(-)), trifluoromethylsulfonate (TfO(-)), hexafluorophosphate (PF(6) (-)), chloride (Cl(-)), and formate (HCOO(-)), were examined for the anion effect against a fixed cation species of 1-butyl-3-methyl-imidazolium (bmim(+)). Four species, bmim(+), N-methyl-N-butylpyrrolidinium (bmpy(+)), N,N,N-trimethyl-N-propylammonium (N(1,1,1,3) (+)), and P,P,P-trihexyl-P-tetradecylphosphonium (P(6,6,6,14) (+)), were employed for the cation effect against a fixed anion species of TFSI(-). The τ(2R) ratio of water to benzene, expressed as τ(W∕B), was used as a probe to characterize the strength of Coulombic solute-solvent interaction in ILs beyond the hydrodynamic limit based on the excluded-volume effect. The τ(W∕B) value was found to strongly depend on the anion species, and the solute dynamics are sensitive not only to the size but also to the chemical structure of the component anion. The cation effect was rather weak, in contrast. The largest and most hydrophobic P(6,6,6,14) (+) cation was exceptional and a large τ(W∕B) was observed, indicating a unique solvation structure in [P(6,6,6,14) (+)]-based ILs

In-situ NMR Study of Hydrothermal Reactions of Hazardous Chlorinated Organic Compounds: CH2Cl2 (INTERFACE SCIENCE-Solutions and Interfaces)

Hydrothermal decomposition of a hazardous chlorinated organic compound, dichloromethane, has been investigated using in-situ NMR spectroscopy. It is found that the hydrolysis of dichloromethane yields methanediol as an intermediate. Methanediol is a hydrated form of formaldehyde and easily transformed into methanol and formic acid under basic conditions. In the temperature range of 70-140 °C, the Cannizzaro-type reaction occurs: methanediol produces the reduced form, methanol and the oxydized form, formic acid. At higher temperatures between 200 and 250 °C, on the other hand, two methanediol molecules form glycolic acid which has a new C-C bond. The reaction rate constants and activation energies for the dechlorination and the Cannizzaro-type reactions have been obtained

14N NMR Spectra Sensitive to Membrane Curvature and Segmental Motions of Phospholipid Headgroup (INTERFACE SCIENCE-Solutions and Interfaces)

Surface curvature dependence of the dynamical structure of the headgroups of phospholipids was studied by 14N NMR on liposomes and micelles. When the diameter was increased from 55 to 100 nm in unilamellar vesicles, 14N NMR signals, for the first time observed for the micelles and unilamellar vesicles with high surface curvatures, suddenly vanished

Noncatalytic Cannizzaro-type Reaction of Formaldehyde in Hot Water (INTERFACE SCIENCE-Solutions and Interfaces)

In water at 250 °C and 4 MPa, methanol and formic acid are produced from the disproportionation reaction of formaldehyde without a catalyst, although at mild conditions, this reaction usually occurs in the presence of a large amount of base catalyst. Formic acid further undergoes the hydride transfer reaction with formaldehyde, and the final yield of methanol exceeds 50%