Dissociation and Nucleation of Tetra-n-butyl Ammonium Bromide Semi-Clathrate Hydrates at High Pressures

The equilibrium pressure-temperature relations of the tetra-n-butyl ammonium bromide (TBAB) semiclathrate hydrate were measured at pressures of up to 80 MPa by high-pressure differential scanning calorimetry. As a pressurizing medium, tetrafluoromethane (CF4), which cannot occupy any hydrate cages in the TBAB semiclathrate hydrate at the present experimental pressures, was used. The dissociation temperature of tetragonal TBAB semiclathrate hydrate (TBAB·26H2O) increases with the increase in pressure, whereas the dissociation enthalpy is (192 ± 3) J·g-1 and almost constant at pressures of up to 80 MPa. The temperature difference between formation and dissociation at the same pressure, that is, the maximum allowable degree of supercooling, is (17.7 ± 0.7) K and independent of the pressure.Takeshi Sugahara and Hironobu Machida. Dissociation and Nucleation of Tetra-n-butyl Ammonium Bromide Semi-Clathrate Hydrates at High Pressures. Journal of Chemical & Engineering Data, 62 (9), 2721–2725, September 14, © 2017 American Chemical Society. https://doi.org/10.1021/acs.jced.7b0011

Intracrine activity involving NAD-dependent circadian steroidogenic activity governs age-associated meibomian gland dysfunction

新たなイントラクライン機構を用いた加齢性眼疾患治療へ --眼局所のホルモンの加齢変化とサーカディアンリズムが鍵--. 京都大学プレスリリース. 2022-02-14.Canonically, hormones are produced in the endocrine organs and delivered to target tissues. However, for steroids, the concept of tissue intracrinology, whereby hormones are produced in the tissues where they exert their effect without release into circulation, has been proposed, but its role in physiology/disease remains unclear. The meibomian glands in the eyelids produce oil to prevent tear evaporation, which reduces with aging. Here, we demonstrate that (re)activation of local intracrine activity through nicotinamide adenine dinucleotide (NAD+)-dependent circadian 3β-hydroxyl-steroid dehydrogenase (3β-HSD) activity ameliorates age-associated meibomian gland dysfunction and accompanying evaporative dry eye disease. Genetic ablation of 3β-HSD nullified local steroidogenesis and led to atrophy of the meibomian gland. Conversely, reactivation of 3β-HSD activity by boosting its coenzyme NAD+ availability improved glandular cell proliferation and alleviated the dry eye disease phenotype. Both women and men express 3β-HSD in the meibomian gland. Enhancing local steroidogenesis may help combat age-associated meibomian gland dysfunction

Dissociation and Nucleation of Tetra‑<i>n</i>‑butyl Ammonium Bromide Semi-Clathrate Hydrates at High Pressures

The equilibrium pressure–temperature relations of the tetra-<i>n</i>-butyl ammonium bromide (TBAB) semiclathrate hydrate were measured at pressures of up to 80 MPa by high-pressure differential scanning calorimetry. As a pressurizing medium, tetrafluoromethane (CF₄), which cannot occupy any hydrate cages in the TBAB semiclathrate hydrate at the present experimental pressures, was used. The dissociation temperature of tetragonal TBAB semiclathrate hydrate (TBAB·26H₂O) increases with the increase in pressure, whereas the dissociation enthalpy is (192 ± 3) J·g^–1 and almost constant at pressures of up to 80 MPa. The temperature difference between formation and dissociation at the same pressure, that is, the maximum allowable degree of supercooling, is (17.7 ± 0.7) K and independent of the pressure

Gas sorption of nano-porous supramolecules formed by multi-hydrogen bonded coordination capsules

[{Re-I(CO)(3)(Hbim)}(3)(tpta)](2) (1, Hbim(-) = 2,2'-biimidazolate monoanion, tpta = 2,4,6-tripyridyl-1,3,5-triazine) was prepared as a nano-space supramolecule by using a new group of H-bonded coordination capsules. The hamburger bun-shaped half unit [{Re-I(CO)(3)(Hbim)}(3)(tpta)] contains six intermolecular H-bonds of Hbim(-) ligands with complementary dual NH center dot center dot center dot N types, and three [Re-I(CO)(3)(Hbim)] are coordinated by bridging tridentate tpta. Interestingly, mechanical grinding easily would convert single crystals of 1 to an amorphous state with minor crystallinity while maintaining the nano-space pores. The ground sample can reversibly uptake and release small molecules such as CO2 and (CH2Cl)(2)