Science Bulletin最新文献

DHX36 plays a crucial role in regulating transcriptional and post-transcriptional processes through its interaction with G-quadruplexes (G4s). The mechanisms by which DHX36 regulates G4s vary across different cell types and physiological conditions. Oocyte-specific conditional knockout (CKO) mice were utilized to study the impact of DHX36 deficiency on female fertility. The results show that the CKO mice exhibit severely impaired hormone response, ovulation, and complete infertility. The CKO germinal vesicle (GV) oocytes display large nucleoli, aberrant chromatin configuration, decreased chromatin accessibility, disturbed transcriptome, and inhibited meiosis progression. Following fertilization, the embryos derived from the CKO oocytes arrest at the zygote or 2-cell stage. Notably, we observed inadequate rRNA transcription in growing GV oocytes, as well as insufficient pre-rRNA processing and translation activity in fully-grown GV oocytes. Using a G4 probe and antibody, we found increased G4s formation at the chromatin and cytoplasm of CKO GV oocytes; these G4s mainly originate from the rDNA and pre-rRNA. Furthermore, the distribution of DHX36 was found to be spatiotemporally synchronized with that of pre-rRNA and G4s in early mouse embryos. In vitro experiments confirmed that DHX36 directly binds with pre-rRNA through the RHAU-specific motif (RSM). Overexpression of DHX36 could partially alleviate the pre-rRNA accumulation in fully-grown CKO oocytes. In conclusion, this study highlights the physiological significance of DHX36 in maintaining female fertility, underscoring its critical role in rRNA homeostasis and chromatin configuration through G4-unwinding mechanism in mouse oocytes.

Recently, a signature of high-temperature superconductivity above the liquid nitrogen temperature (77 K) was reported for La₃Ni₂O_7-δ under pressure. This finding immediately stimulated intense interest in the possible mechanism of high-T_c superconductivity in double-layer nickelates. Notably, the pressure-dependent phase diagram inferred from transport measurements indicates that the superconductivity under high pressure emerges from the suppression of density-wave-like order at ambient pressure, which is similar to high-temperature superconductors. Therefore, clarifying the exact nature of the density-wave-like transition is important for determining the superconducting mechanism in double-layer nickelates. Here, nuclear magnetic resonance (NMR) spectroscopy of ¹³⁹La nuclei was performed to study the density-wave-like transition in a single crystal of La₃Ni₂O_7-δ. At high temperatures, two sets of sharp ¹³⁹La NMR peaks are clearly distinguishable from a broad background signals, which are ascribed to La(1) sites from two bilayer Ruddlesden-Popper phases with different oxygen vacancy δ. As the temperature decreases, the temperature-dependent ¹³⁹La NMR spectra and nuclear spin-lattice relaxation rate (1/T₁) for both La(1) sites provide evidence of spin-density-wave (SDW) ordering below the transition temperature (T_SDW), which is approximately 150 K. The anisotropic splitting in the NMR spectra suggests the formation of a possible double spin stripe with magnetic moments aligned along the c-axis. Furthermore, we studied the pressure-dependent SDW transition up to ∼ 2.7 GPa. Surprisingly, the T_SDW inferred from NMR measurements of both La(1) sites increases with increasing pressure, which is opposite to the results from previous transport measurements under pressure and suggests an intriguing phase diagram between superconductivity and SDW. In contrast, the present ¹³⁹La NMR is insensitive to the possible charge-density-wave (CDW) order in the Ni-O planes. All these results will be helpful for building a connection between superconductivity and magnetic interactions in double-layer nickelates.

The introduction of foreign metals with a higher oxophilicity represents a promising strategy to promote water dissociation and in turn kinetics of alkaline hydrogen evolution reaction (HER). However, the further improvement of HER activity is limited by the unfavorable interaction of hydroxyl generated by the dissociation of water with active sites. Herein, we propose a strategy of alkaline earth metal cations-driven electron delocalization to elaborately tailor the binding of hydroxyl with the active sites. Taking FeNiMg-layered double hydroxides (FeNiMg-LDH) as a prototypical example, the combined operando spectroscopy analysis and theoretical calculations show that the introduction of Mg cations in solid- solution phase can create a local electronic field and delocalize the electron between Fe and adsorbed hydroxyl, resulting in an optimization of hydroxyl binding strength. Accordingly, FeNiMg-LDH lowers the overpotentials to deliver 10 mA cm^-2 in alkaline electrolyte by 39 and 64 mV, compared to FeNi-LDH and Ni-LDH catalysts, respectively. This work sheds new light on the rational design of advanced HER electrocatalyst for alkaline water electrolysis.