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"Hu, Qi"
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Role of Auxin and Nitrate Signaling in the Development of Root System Architecture
The plant root is an important storage organ that stores indole-3-acetic acid (IAA) from the apical meristem, as well as nitrogen, which is obtained from the external environment. IAA and nitrogen act as signaling molecules that promote root growth to obtain further resources. Fluctuations in the distribution of nitrogen in the soil environment induce plants to develop a set of strategies that effectively improve nitrogen use efficiency. Auxin integrates the information regarding the nitrate status inside and outside the plant body to reasonably distribute resources and sustainably construct the plant root system. In this review, we focus on the main factors involved in the process of nitrate- and auxin-mediated regulation of root structure to better understand how the root system integrates the internal and external information and how this information is utilized to modify the root system architecture.
Journal Article
Subnanometric Ru clusters with upshifted D band center improve performance for alkaline hydrogen evolution reaction
Subnanometric metal clusters usually have unique electronic structures and may display electrocatalytic performance distinctive from single atoms (SAs) and larger nanoparticles (NPs). However, the electrocatalytic performance of clusters, especially the size-activity relationship at the sub-nanoscale, is largely unexplored. Here, we synthesize a series of Ru nanocrystals from single atoms, subnanometric clusters to larger nanoparticles, aiming at investigating the size-dependent activity of hydrogen evolution in alkaline media. It is found that the d band center of Ru downshifts in a nearly linear relationship with the increase of diameter, and the subnanometric Ru clusters with d band center closer to Femi level display a stronger water dissociation ability and thus superior hydrogen evolution activity than SAs and larger nanoparticles. Benefiting from the high metal utilization and strong water dissociation ability, the Ru clusters manifest an ultrahigh turnover frequency of 43.3 s
−1
at the overpotential of 100 mV, 36.1-fold larger than the commercial Pt/C.
Metal nanocluster properties undergo drastic activity alterations with slight size variations, although in-depth examinations of such changes are challenging to perform. Here, authors demonstrate Ru cluster size governs the d-band center position and electrocatalytic activity for H
2
evolution.
Journal Article
Ultrafast charge ordering by self-amplified exciton–phonon dynamics in TiSe2
The origin of charge density waves (CDWs) in TiSe
2
has long been debated, mainly due to the difficulties in identifying the timescales of the excitonic pairing and electron–phonon coupling (EPC). Without a time-resolved and microscopic mechanism, one has to assume simultaneous appearance of CDW and periodic lattice distortions (PLD). Here, we accomplish a complete separation of ultrafast exciton and PLD dynamics and unravel their interplay in our real-time time-dependent density functional theory simulations. We find that laser pulses knock off the exciton order and induce a homogeneous bonding–antibonding transition in the initial 20 fs, then the weakened electronic order triggers ionic movements antiparallel to the original PLD. The EPC comes into play after the initial 20 fs, and the two processes mutually amplify each other leading to a complete inversion of CDW ordering. The self-amplified dynamics reproduces the evolution of band structures in agreement with photoemission experiments. Hence we resolve the key processes in the initial dynamics of CDWs that help elucidate the underlying mechanism.
The physical origins of charge density waves in 1T-TiSe2 and their response to ultrafast excitation have long been a topic of theoretical and experimental debate. Here the authors present an ab initio theory that successfully captures the observed dynamics of charge density wave formation.
Journal Article
Genome-wide profiling in colorectal cancer identifies PHF19 and TBC1D16 as oncogenic super enhancers
Colorectal cancer is one of the most common cancers in the world. Although genomic mutations and single nucleotide polymorphisms have been extensively studied, the epigenomic status in colorectal cancer patient tissues remains elusive. Here, together with genomic and transcriptomic analysis, we use ChIP-Seq to profile active enhancers at the genome wide level in colorectal cancer paired patient tissues (tumor and adjacent tissues from the same patients). In total, we sequence 73 pairs of colorectal cancer tissues and generate 147 H3K27ac ChIP-Seq, 144 RNA-Seq, 147 whole genome sequencing and 86 H3K4me3 ChIP-Seq samples. Our analysis identifies 5590 gain and 1100 lost variant enhancer loci in colorectal cancer, and 334 gain and 121 lost variant super enhancer loci. Multiple key transcription factors in colorectal cancer are predicted with motif analysis and core regulatory circuitry analysis. Further experiments verify the function of the super enhancers governing
PHF19
and
TBC1D16
in regulating colorectal cancer tumorigenesis, and KLF3 is identified as an oncogenic transcription factor in colorectal cancer. Taken together, our work provides an important epigenomic resource and functional factors for epigenetic studies in colorectal cancer.
Active enhancers are still understudied in colorectal cancers (CRC). Here the authors analyse active enhancers in CRC patients using genomics, transcriptomics, and epigenomics, identifying and validating variant super-enhancer loci as well as KLF3 as a relevant transcription factor.
Journal Article
Mechanisms of BRCA1–BARD1 nucleosome recognition and ubiquitylation
The BRCA1–BARD1 tumour suppressor is an E3 ubiquitin ligase necessary for the repair of DNA double-strand breaks by homologous recombination
1
–
10
. The BRCA1–BARD1 complex localizes to damaged chromatin after DNA replication and catalyses the ubiquitylation of histone H2A and other cellular targets
11
–
14
. The molecular bases for the recruitment to double-strand breaks and target recognition of BRCA1–BARD1 remain unknown. Here we use cryo-electron microscopy to show that the ankyrin repeat and tandem BRCT domains in BARD1 adopt a compact fold and bind to nucleosomal histones, DNA and monoubiquitin attached to H2A amino-terminal K13 or K15, two signals known to be specific for double-strand breaks
15
,
16
. We further show that RING domains
17
in BRCA1–BARD1 orient an E2 ubiquitin-conjugating enzyme atop the nucleosome in a dynamic conformation, primed for ubiquitin transfer to the flexible carboxy-terminal tails of H2A and variant H2AX. Our work reveals a regulatory crosstalk in which recognition of monoubiquitin by BRCA1–BARD1 at the N terminus of H2A blocks the formation of polyubiquitin chains and cooperatively promotes ubiquitylation at the C terminus of H2A. These findings elucidate the mechanisms of BRCA1–BARD1 chromatin recruitment and ubiquitylation specificity, highlight key functions of BARD1 in both processes and explain how BRCA1–BARD1 promotes homologous recombination by opposing the DNA repair protein 53BP1 in post-replicative chromatin
18
–
22
. These data provide a structural framework to evaluate BARD1 variants and help to identify mutations that drive the development of cancer.
The authors elucidate the mechanisms for the ubiquitylation specificity and recruitment of the ubiquitin ligase complex BRCA1–BARD1 to damaged DNA within chromatin to facilitate homologous recombination.
Journal Article
Anti-inflammatory and Analgesic Effects of Polygonum orientale L. Extracts
L. (family: Polygonaceae), named Hongcao in China, is a Traditional Chinese Medicinal and has long been used for rheumatic arthralgia and rheumatoid arthritis. However, no pharmacological and mechanism study to confirm these clinic effects have been published. In this investigation, the anti-inflammatory, analgesic effects and representative active ingredient compounds of
have been studied.
Dried small pieces of the stems and leaves of
were decocted with water and partitioned successively to obtain ethyl acetate and ethyl ether extract of
(POEa and POEe). Chemical compositions of them were analyzed by UPLC-Q-Exactive HRMS. Anti-inflammatory and analgesic effects of POEa and POEe were evaluated using xylene induced ear edema, carrageenan induced paw edema, Freunds' complete adjuvant induced arthritis, and formaldehyde induced pain in rat. Their mechanisms of anti-inflammatory and analgesic effects were also studied via assays of TNF-α, IL-1β, IL-6, and PGE2 in serum.
UPLC-Q-Exactive HRMS analysis showed that POEa and POEe mainly contained flavonoids including orientin, isoorientin, vitexin, luteolin, and quercetin. Furthermore, anti-inflammatory effects of POEa and POEe were evident in xylene induced ear edema. The paw edema in Freund's complete adjuvant and carrageenan were significantly (
< 0.05, 0.01) inhibited by POEa (5, 7.5 g/kg). POEe (7.5 g/kg) was significantly (
< 0.05, 0.01) inhibited Freunds' complete adjuvant induced paw edema and cotton pellet induced granuloma formation. Similarly, POEe significantly (
< 0.05, 0.01) inhibited the pain sensation in acetic acid induced writhing test. POEa (5, 7.5 g/kg) significantly (
< 0.05, 0.01) inhibited formaldehyde induced pain in both phases. POEa (7.5 g/kg) markedly (
< 0.05) prolonged the latency period of hot plate test after 30 and 60 min. The concentrations of TNF-α, IL-1β, IL-6, and PGE2 were significantly (
< 0.01) decreased by POEa (3.75, 5 g/kg).
POEa and POEe have anti-inflammatory and analgesic effects, which was mainly relevant to the presence of flavonoids, including orientin, isoorientin, vitexin, luteolin, and quercetin. The mechanism of anti-inflammatory and analgesic effects of POEa may be to decrease the concentrations of TNF-α, IL-1β, IL-6, and PGE2 in serum.
Journal Article
AdS/BCFT and Island for curvature-squared gravity
A
bstract
In this paper, we investigate AdS/BCFT for curvature-squared gravity. To warm up, we start with Gauss-Bonnet gravity. We derive the one point function of stress tensor and show that the central charge related to the norm of displacement operator is positive for the couplings obeying causality constraints. Furthermore, by imposing the null energy condition on the end-of-the-world brane, we prove the holographic g-theorem for Gauss-Bonnet gravity. This corrects a wrong point of view in the literature, which claims that the holographic g-theorem is violated for Gauss-Bonnet gravity. As a by-product, we obtain the boundary entropy and A-type boundary central charges in general dimensions. We also study AdS/BCFT for general curvature-squared gravity. We find that it is too restrictive for the shape of the brane and the dual BCFT is trivial if one imposes Neumann boundary conditions for all of the gravitational modes. Instead, we propose to impose Dirichlet boundary condition for the massive graviton, while imposing Neumann boundary condition for the massless graviton. In this way, we obtain non-trivial shape dependence of stress tensor and well-defined central charges. In particular, the holographic g-theorem is satisfied by general curvature-squared gravity. Finally, we discuss the island and show that the Page curve can be recovered for Gauss-Bonnet gravity. Interestingly, there are zeroth-order phase transitions for the Page curve within one range of couplings obeying causality constraints. Generalizing the discussions to holographic entanglement entropy and holographic complexity in AdS/CFT, we get new constraints for the Gauss-Bonnet coupling, which is stronger than the causality constraint.
Journal Article
Rational molecular passivation for high-performance perovskite light-emitting diodes
A major efficiency limit for solution-processed perovskite optoelectronic devices, for example light-emitting diodes, is trap-mediated non-radiative losses. Defect passivation using organic molecules has been identified as an attractive approach to tackle this issue. However, implementation of this approach has been hindered by a lack of deep understanding of how the molecular structures influence the effectiveness of passivation. We show that the so far largely ignored hydrogen bonds play a critical role in affecting the passivation. By weakening the hydrogen bonding between the passivating functional moieties and the organic cation featuring in the perovskite, we significantly enhance the interaction with defect sites and minimize non-radiative recombination losses. Consequently, we achieve exceptionally high-performance near-infrared perovskite light-emitting diodes with a record external quantum efficiency of 21.6%. In addition, our passivated perovskite light-emitting diodes maintain a high external quantum efficiency of 20.1% and a wall-plug efficiency of 11.0% at a high current density of 200 mA cm−2, making them more attractive than the most efficient organic and quantum-dot light-emitting diodes at high excitations.Improved understanding of passivation leads to near-infrared perovskite light-emitting diodes with 21.6% external quantum efficiency.
Journal Article
A dynamic modeling approach for six-degree-of-freedom control of maglev planar motors with reference trajectory tracking
Magnetic levitation planar motors (MLPMs) exhibit significant potential in high-precision positioning applications, however the 6-degree-of-freedom (6-DOF) control performance is inherently limited by complex nonlinear dynamics. This paper proposes a 6-DOF dynamic modeling methodology for maglev planar motors based on reference trajectory tracking. The proposed approach synergistically combines magnetic flux analytical linearization with electromagnetic coupling field decoupling, establishing a unified control framework that comprehensively addresses kinematic nonlinearities and full-DOF coupling effects. By employing harmonic spectral analysis and a dual-reference coordinate transformation architecture, the method enables precise analytical derivation of electromagnetic force/torque distributions within the operational workspace. Numerical simulations validate the improved modeling accuracy, demonstrating a 5.3-fold reduction in wrench prediction errors under large yaw rotations compared to conventional methods. Finally, an experimental rig of the planar motor is manufactured to validate the theoretical trajectory tracking method. The experimental results confirm the robustness of the methodology in achieving high-precision motion control and long-stroke trajectory tracking, offering valuable insights for bridging theoretical modeling and industrial implementation of maglev planar motor systems.
Journal Article