Quantification of solvent water and hydration dynamic of thermo‐sensitive microgel by dielectric spectroscopy

The hydration of natural or synthetic macromolecules is of fundamental importance in our understanding of their structure and stability. Quantification of hydration water can promote the understanding to many complex biological mechanisms such as protein folding, as well as the dynamics and conformation of polymers. An approach to quantification of solvent water was developed by dielectric spectroscopy. Dielectric behaviors of PNIPAM microgels with different crosslink density distribution were measured in the range of 0.5–40 GHz and 15–50. An obvious relaxation process caused by free and bound water was found. Dielectric parameters of free and bound water show that the crosslink density distribution does not affect the volume phase transition temperature of microgels, but significantly influence the orientation dynamics of the solvent water. We found that the three kinds of microgel can be distinguished by the dielectric parameters of the bound water. In addition, the number of water in and outside microgel during the volume phase transition process was quantitatively calculated for the first time. This study provides the possibility for the quantification of water in complex biological process. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1859–1864     

Crystal structures of hydrates of simple inorganic salts. III. Water‐rich aluminium halide hydrates: AlCl3·15H2O,AlBr3·15H2O,AlI3·15H2O,AlI3·17H2O and AlBr3·9H2O

Water‐rich aluminium halide hydrate structures are not known in the literature. The highest known water content per Al atom is nine for the perchlorate and fluoride. The nonahydrate of aluminium bromide, stable pentadecahydrates of aluminium chloride, bromide and iodide, and a metastable heptadecahydrate of the iodide have now been crystallized from low‐temperature solutions. The structures of these hydrates were determined and are discussed in terms of the development of cation hydration spheres. The pentadecahydrate of the chloride and bromide are isostructural. In AlI₃·15H₂O, half of the Al³⁺ cations are surrounded by two complete hydration spheres, with six H₂O in the primary and 12 in the secondary. For the heptadecahydrate of aluminium iodide, this hydration was found for every Al³⁺.     

Efficient Mo(VI)-Catalyzed Hydration of Nitrile with Acetaldoxime

A method for the selective hydration of nitrile to amide by employing commercially available acetaldoxime and inexpensive oxometallate such as molybdate, vanadate, and tungstate in environmentally friendly water is described. Under this protocol, nitriles including aromatic nitriles, heterocyclic nitriles, and aliphatic nitriles were converted into the corresponding amides in good to excellent yields.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Stabilisation of the water permeability of mineral ultrafiltration membranes: An empirical modelling of surface and pore hydration

This work focuses on the study of the hydration phenomenon operating in Na–mordenite membranes during the conditioning step (stabilisation of filtration properties). First, experimental (filtration of pure water) tests are carried out immediately after putting the membrane in its casing and until the stabilization of the membrane permeation flux. The evolution of the hydraulic permeability shows that there are two separate steps during the conditioning of the membrane. A numerical approximation of the hydraulic permeability during the conditioning step was carried out. The first part of the equation expresses a fast decrease in the membrane's permeability during the beginning of the conditioning step (several hours). This behaviour is attributed to a surface hydration of the membrane and also to a modification of the crystalline framework. The second one is a slower phenomenon that takes place until the end of the conditioning step. It is attributed to the (intra-crystalline) hydration of micropores.     

Raman comparison of skin dermis of different ages: focus on spectral markers of collagen hydration

Skin aging is the most visible sign of aging of the body. This complex process involves molecular and structural alterations of the main skin constituents. The major cutaneous constituent is type I collagen that gives strength and resilience to the skin. This macromolecule possesses a particular triple helix structure and is arranged in the form of a fibrous network. Water plays a crucial role for maintaining this molecular assembly which is altered during intrinsic chronological aging. To investigate some of these structural alterations, Raman microspectroscopy was employed since this biophotonic approach permits to probe the biomolecular composition of the skin in a non‐destructive manner. In addition, type I collagen gives specific Raman vibrations; some of which being sensitive to the molecule conformation and to the water environment. In this purpose, Raman spectra of four skin samples of different ages (two samples of 40 year old and two samples of 70 year old) were collected by varying the relative environmental humidity. Our experiments highlighted spectral differences between the four samples. The analysis of the Raman data permitted to suggest a model for the interactions between collagen and water molecules and a decrease in collagen fibers compactness with chronological aging. Our study demonstrates that Raman spectroscopy can be a useful tool to investigate skin aging, with innovative applications in dermatology as well as in cosmetics. Copyright © 2013 John Wiley & Sons, Ltd.     

Reactivity of Ions of Actinides Towards Inorganic Free Radicals in Irradiated Aqueous Solutions

The paper is a short review of experimental data obtained during the study of reactivity of ions of actinides towards inorganic free radicals in irradiated aqueous solutions by pulse radiolysis method. The values of rate constants of reactions of these ions with primary products of water radiolysis (e_aq ^?, H, OH, O^?) and secondary radicals formed via reactions of these products with solutes and/or as a result of direct action of ionizing radiation on solutes (SO₄ ^?, NO₃, Cl₂ ^?, CO₃ ^?, O₂ ^? etc.) are listed. The peculiarities of the reactivity are discussed. The examples of application of the obtained data for the simulation of radiolytical transformations of ions of actinides are presented.     

Temperature effects on ion association and hydration in MgSO4 by dielectric spectroscopy.

A detailed investigation of aqueous solutions of magnesium sulfate has been made by dielectric relaxation spectroscopy (DRS) over a wide range of frequencies (0.2 MgSO(4) (0)(aq) is in good agreement with literature data at lower temperatures but is overestimated at higher temperatures due to processing difficulties. Despite the limited precision of the spectra, analysis of the individual steps in the ion-association process is possible for the first time. The 2SIPs are formed with little disturbance to their hydration shells, the (partial) destruction of which appears to occur mostly during the formation of SIPs. Effective hydration numbers derived from the DRS spectra indicate that both Mg(2+) and SO(4) (2-) influence solvent water molecules beyond their first hydration spheres but that MgSO(4)(aq) is less strongly hydrated than the previously studied CuSO(4)(aq).     

Effects of a Vocally Fatiguing Task and Systemic Hydration on Men''s Voices

Voice disorders, specifically vocal fatigue, are more commonly reported by women than by men. Previously, 4 women with normal untrained voices read loudly for 2 hours in an attempt to fatigue the voice. Vocal function deteriorated, as indicated by increases in phonation threshold pressure (PTP) and self-perceived phonatory effort. The increase in PTP was delayed or attenuated to some degree in 3 of the women when they drank ample amounts of water before the experiment. The current study examined the same vocal-loading task and water-drinking condition in 4 vocally normal men. PTP increased after the loud-reading task. Although 2 of the men appeared to benefit from increased systemic hydration (PTP increased more when they were underhydrated than well-hydrated), the other 2 men's data changed in the opposite direction. Phonatory effort correlated well with PTP; this varied across subject and pitch. Laryngeal endoscopy revealed an anterior glottal gap in two men after the loud-reading task. Amplitude of vocal fold vibration was judged to be reduced after the loud-reading task in three subjects when underhydrated and one subject when well hydrated. The high between-subject variability prohibits a conclusion that drinking water is beneficial to vocal function in men, but all subjects studied to date demonstrated detrimental vocal effects of prolonged loud talking.