α-Selective glycosidation of d-tagatofuranose with a 3,4-O-isopropylidene protection

An α-selective glycosidation reaction of D-tagatofuranose was successfully achieved using 3,4-O-isopropylidene-protected D-tagatofuranose as a glycosyl donor. A variety of glycosyl acceptors, including primary, secondary, and β-amino alcohols, and carbohydrates, can be used for this D-tagatofuranosidation reaction with complete α-selectivities and good yields (57-83%). The stereochemistries at the anomeric positions were determined by nuclear Overhauser effect spectroscopic correlations, as well as comparison of the chemical shifts in the 13C NMR spectra

The ubiquitination-deubiquitination cycle on the ribosomal protein eS7A is crucial for efficient translation

Ubiquitination is a major post-translational modification of ribosomal proteins. The role of ubiquitination in the regulation of ribosome functions is still being elucidated. However, the importance of ribosome deubiquitination remains unclear. Here, we show that the cycle of ubiquitination and deubiquitination of the 40S ribosome subunit eS7 is important for efficient translation. eS7 ubiquitination at lysine 83 is required for efficient protein translation. We identified Otu2 and Ubp3 as the deubiquitinating enzymes for eS7. An otu2Δubp3Δ mutation caused a defect in protein synthesis. Ubp3 inhibited polyubiquitination of eS7 in polysomes to keep eS7 in a mono-ubiquitinated form, whereas Otu2 was specifically bound to the free 40S ribosome and promoted the dissociation of mRNAs from 40S ribosomes in the recycling step. Our results provide clues for understanding the molecular mechanism of the translation system via a ubiquitination-deubiquitination cycle

Evidence and mechanism of efficient thermally activated delayed fluorescence promoted by delocalized excited states

The design of organic compounds with nearly no gap between the first excited singlet (S1) and triplet (T1) states has been demonstrated to result in an efficient spin-flip transition from the T1 to S1 state, that is, reverse intersystem crossing (RISC), and facilitate light emission as thermally activated delayed fluorescence (TADF). However, many TADF molecules have shown that a relatively appreciable energy difference between the S1 and T1 states (~0.2 eV) could also result in a high RISC rate. We revealed from a comprehensive study of optical properties of TADF molecules that the formation of delocalized states is the key to efficient RISC and identified a chemical template for these materials. In addition, simple structural confinement further enhances RISC by suppressing structural relaxation in the triplet states. Our findings aid in designing advanced organic molecules with a high rate of RISC and, thus, achieving the maximum theoretical electroluminescence efficiency in organic light-emitting diodes

Body weight reduction by exercise increases the urinary 3-methylhistidine excretion level with relatively positive nitrogen, sodium, and potassium balances when compared to dietary restriction

Background: Regarding changes in muscle mass, differences due to types of exercise and/or nutritional interventions, and associations with nutrient balances are still unclear. Methods: To estimate changes in muscle mass during a body weight loss program using either a diet or exercise regimen, we investigated levels of muscle mass-related indices, and body contents of nitrogen, sodium, and potassium as measured by the balance method. Six healthy young adult male volunteers participated in two 10-day crossover experiments (20 days total). The first 5 days comprised an adjustment period (energy intake, 2656 ± 367 kcal/day (mean ± standard deviation)). During the second 5-day period, the participants either reduced their energy intake to 1770 ± 244 kcal/day (diet regimen) or exercised on a bicycle ergometer to expend 886 ± 122 kcal/day (exercise regimen). Results: The nitrogen, sodium, and potassium balances were significantly more positive during the exercise regimen than during the diet regimen. The urinary excretion levels of creatinine, 3-methylhistidine (3-MH), aldosterone, and catecholamines, and the 3-MH/creatinine ratio were significantly increased only during the exercise regimen. Conclusions: The exercise regimen suppresses the decrease in muscle mass-related indices during body weight loss compared to the diet regimen with a relatively positive state of whole-body protein, sodium, and potassium balances, accompanied by an increase in sympathetic/adrenal cortical functions

Effect of copper addition on the cluster formation behavior of Al-Mg-Si, Al-Zn-Mg, and Al-Mg-Ge in the natural aging

The time-dependent resistivity of Al-Mg-Si(-Cu), Al-Zn-Mg(-Cu), and Al-Mg-Ge(-Cu) alloys are studied over a range of constant temperatures between 255 K and 320 K. The resistivity vs time curves for the samples show three temperature stages associated with solute element–vacancy clustering. Cu addition was found to make the stage transition time longer for the studied samples. Arrhenius plots of the transition time vs temperature provide the activation energy (Q) of clustering from stage I to II and II to III. While the Cu addition increased the Q(I to II) values of Al-1.0 pct Mg2Si-0.20 pct Cu and Al-2.68 pct Zn-3.20 pct Mg-0.20 pct Cu, it was found that the added Cu decreased the Q(I to II) value of Al-0.44 pct Mg-0.19Ge-0.18 pct Cu. The Q(II to III) values of Al-1.0 pct Mg2Si and Al-2.68 pct Zn-3.20 pct Mg were slightly decreased by the Cu addition. The different effect of added Cu on the Q values is discussed in terms of diffusivity and binding energy between vacancies and solute elements.acceptedVersio