Model for the Architecture of Claudin-Based Paracellular Ion Channels through Tight Junctions

AbstractClaudins are main cell–cell adhesion molecules of tight junctions (TJs) between cells in epithelial sheets that form tight barriers that separate the apical from the basolateral space but also contain paracellular channels that regulate the flow of ions and solutes in between these intercellular spaces. Recently, the first crystal structure of a claudin was determined, that of claudin-15, which indicated the parts of the large extracellular domains that likely form the pore-lining surfaces of the paracellular channels. However, the crystal structure did not show how claudin molecules are arranged in the cell membrane to form the backbone of TJ strands and to mediate interactions between adjacent cells, information that is essential to understand how the paracellular channels in TJs function. Here, we propose that TJ strands consist of claudin protomers that assemble into antiparallel double rows. This model is based on cysteine crosslinking experiments that show claudin-15 to dimerize face to face through interactions between the edges of the extracellular β-sheets. Strands observed by freeze-fracture electron microscopy of TJs also show that their width is consistent with the dimensions of a claudin dimer. Furthermore, we propose that extracellular variable regions are responsible for head-to-head interactions of TJ strands in adjoining cells, thus resulting in the formation of paracellular channels. Our model of the TJ architecture provides a basis to discuss structural mechanisms underlying the selective ion permeability and barrier properties of TJs

Esr and radiocarbon dating of gut strings from early plucked instruments

Early European plucked instruments have recently experienced a great revival, but a few aspects remain unknown (e.g., the gauge of gut strings). Here we report, for the first time, that the electron spin resonance (ESR) signal intensity of oxidized iron, Fe(III), from gut strings at g = 2 increases linearly with age within a few hundred years. The signal increase in the remaining old strings on early instruments can be used to judge if they are as old as or younger than the instrument. Obtaining the authenticity information of gut strings contributes to the revival of the old instruments and the music. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

A new method for the estimation of cooling and denudation rates using paramagnetic centers in quartz: a case study on the Eldzhurtinskiy Granite, Caucasus

We present a new method for the assessment of the most recent cooling and denudation rates using paramagnetic centers in quartz measured by electron spin resonance (ESR) spectroscopy. These centers have a relatively low thermal stability. For cooling rates of 40° and 1000°C Myr−1, effective closure temperatures vary between 55° and 82°C (Ti center) and 49° and 64°C (Al center), respectively. Samples were collected from two cores that were drilled into the Eldzhurtinskiy Granite, which has an emplacement age of ∼2 Ma as measured by U/Pb analyses of zircons. One 1500 m core was taken from a drill hole into the dome of the granite, a second core of 4000 m from a drill hole at the base of the Baksan Valley. Our results yield cooling rates of between 160 and 250°C Myr−1 for the upper core and between 570° and 600°C Myr−1 for the lower core; the corresponding denudation rates are ∼2.5 (upper core) and 5.5mm a−1 (lower core). The shape of the temperature profile of the lower core indicates recent erosion. When fitting the temperature data with a two-dimensional heat-transfer model, we obtain a net denudation rate of ∼10 mm a−1 and cooling rates in the range of 500°C Myr−1, thus confirming the cooling rates estimated by ESR. However, the ESR denudation rates underestimate the erosion rate of the Baksan Valley because the geothermal gradient is not equilibrated between the surface and the depth of the annihilation temperatures, 950 and 1800 m for the Al and Ti centers, respectively. We conclude that ESR measurements of paramagnetic centers in quartz will allow the reconstruction of landscape dynamics for the past 10–1000 kyr and that in conjunction with U/Pb, fission track, and Ar/Ar analyses it will be possible to develop dynamic models for Quaternary tectonic movements

飲水指導は夜間頻尿患者の頻尿症状を有効に改善する

OBJECTIVES: To evaluate how guidance on water-intake impacts the degree of nocturia. METHODS: A total of 67 male patients were enrolled in the present study. Patients were asked to adjust their water and food intakes so that their 24-h urine production/bodyweight would be equal or lower than 30 mL/kg. One month after the treatment, the therapeutic gain from and adverse effects of fluid restriction were examined by comparing the pretreatment and post-treatment value of various parameters. RESULTS: Overall, 65 eligible patients were evaluated. In 44 patients (67%), the frequency of nocturia was improved to one or more times. The change in frequency of nocturia showed a positive correlation with the change in nocturnal urine volume. The change in nocturnal urine volume showed a positive correlation with the changes in 24-h urine production/bodyweight, 24-h drinking volume and daytime drinking volume. The changes in 24-h urine production/bodyweight and daytime drinking volume were independent factors influencing therapeutic effect. None of the participants reported any adverse event. CONCLUSIONS: In patients with a 24-h urine production/bodyweight equal or higher than 30 mL/kg, guidance on water intake might be considered effective and safe as a lifestyle therapy. Water restriction should be carried out not only in the evening, but also during daytime.博士（医学）・乙第1348号・平成26年12月3日© 2014 The Japanese Urological Associatio

Quasi-elastic neutron scattering studies on fast dynamics of water molecules in tetra-n-butylammonium bromide semiclathrate hydrate

The dynamics of the water molecules in tetra-n-butyl-d36-ammonium bromide semiclathrate hydrate were investigated by quasi-elastic neutron scattering (QENS). The QENS results clearly revealed afast reorientation motion of water molecules in the temperature range of 212–278 K. The mean jumpdistance of hydrogen atoms was within 1.5‒2.0 Å. The relaxation time of water reorientation wasestimated to be 100‒410 ps with activation energy of 10.2±5.8 kJ·mol-1. The activation energy wasin good agreement with the cleavage energy of hydrogen bonds. Such a short relaxation time ofwater reorientation is possibly due to strong interaction between a bromide anion and its surroundingwater molecules (similar to so-called negative hydration), which suggests a unique strategy fordesigning efficient, safe, and inexpensive proton conductors having the framework of semiclathratehydrates.Shimada Jin, Tani Atsushi, Yamada Takeshi, et al. "Quasi-elastic neutron scattering studies on fast dynamics of water molecules in tetra-n-butylammonium bromide semiclathrate hydrate", Applied Physics Letters 123, 50 (2023) https://doi.org/10.1063/5.0157560

Phase equilibrium temperature and dissociation enthalpy in the tri-n-butylalkylphosphonium bromide semiclathrate hydrate systems

Semiclathrate hydrate (SCH) is one of the phase change materials suitable for cold storage. The thermodynamic properties of SCHs, such as an equilibrium temperature and a dissociation enthalpy, depend on the size and shape of guest substances. In this study, to reveal the effect of cation size and shape on the thermodynamic properties, tri-n-butylalkylphosphonium bromide (P444R-Br) SCHs, where the alkyl group was n-propyl (R = 3), n-butyl (R = 4), n-pentyl (R = 5), i-butyl (R = i-4), i-pentyl (R = i-5), or allyl (R = Al)), were investigated. The branched alkyl groups (R = i-4 or i-5) raised the equilibrium temperature, whereas the shorter alkyl groups (R = 3 or Al) lowered one. Except for P4445-Br and P444(Al)-Br SCHs, the other P444R-Br SCHs had the same orthorhombic structure. Among the orthorhombic systems in the present study, the semiclathrate hydrate with a higher equilibrium temperature had a larger dissociation enthalpy

Phase Equilibrium Relations of Semiclathrate Hydrates Based on Tetra- n-butylphosphonium Formate, Acetate, and Lactate

Phase equilibrium (temperature-composition) relations of tetra-n-butylphosphonium formate (TBP-For), acetate (TBP-Ace), and lactate (TBP-Lac) semiclathrate hydrate systems have been measured. The highest equilibrium temperatures of TBP-For, TBP-Ace, and TBP-Lac semiclathrate hydrates were 280.9, 284.6, and 283.8 K at the atmospheric pressure, respectively, where the composition of tetra-n-butylphosphonium carboxylate was approximately 0.035 ± 0.001 (mole fraction) in every system. The dissociation enthalpies of tetra-n-butylphosphonium carboxylate semiclathrate hydrates were measured by differential scanning calorimetry. The dissociation enthalpies of TBP-For, TBP-Ace, and TBP-Lac semiclathrate hydrates were (187 ± 3), (193 ± 3), and (177 ± 3) J·g-1, respectively.Jin Shimada, Masami Shimada, Takeshi Sugahara, et al. Phase Equilibrium Relations of Semiclathrate Hydrates Based on Tetra-n-butylphosphonium Formate, Acetate, and Lactate. Journal of Chemical & Engineering Data, 63 (9), 3615-3620, September 13, © 2018 American Chemical Society. https://doi.org/10.1021/acs.jced.8b0048

Thermodynamic Properties of Tetra-n-butylphosphonium Dicarboxylate Semiclathrate Hydrates

Semiclathrate hydrate (SCH) is one of the phase change materials suitable for cold energy storage. Thermodynamic properties of SCHs, such as an equilibrium temperature and the dissociation enthalpy, depend on the size and shape of the guest substances. In the present study, to reveal the effects of steric conformations of the guest anions on the thermodynamic properties of SCHs, tetra-n-butylphosphonium dicarboxylate (TBP-DC) SCHs, where the anion was oxalate (TBP-Oxa), malonate (TBP-Mal), succinate (TBP-Suc), glutarate (TBP-Glu), maleate (TBP-Male), or fumarate (TBP-Fum), were investigated. TBP-Oxa, -Mal, -Suc, and -Fum SCHs had similar equilibrium temperatures, whereas the equilibrium temperatures of TBP-Glu and -Male SCHs were higher. This suggests that the size and conformation of glutarate and maleate anions are appropriate for the cage structures of SCHs. Moreover, we compared the equilibrium temperatures of TBP-Suc, -Male, and -Fum SCHs because TBP-Suc, -Male, and -Fum have similar anion structures. The equilibrium temperature of TBP-Suc SCH was similar to that of TBP-Fum SCH, whereas TBP-Male SCH showed a higher equilibrium temperature. This result implies that the succinate anion is accommodated in the trans conformation, similar to the fumarate anion, in the hydrate cages.Jin Shimada, Moe Yamada, Atsushi Tani et al. Thermodynamic Properties of Tetra-n-butylphosphonium Dicarboxylate Semiclathrate Hydrates. Journal of Chemical & Engineering Data, 67 (1), 67-73, January 13, © 2022 American Chemical Society. https://doi.org/10.1021/acs.jced.1c0074