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"W Lu"
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Structural basis of how stress-induced MDMX phosphorylation activates p53
The tumor-suppressor protein p53 is tightly controlled in normal cells by its two negative regulators—the E3 ubiquitin ligase MDM2 and its homolog MDMX. Under stressed conditions such as DNA damage, p53 escapes MDM2- and MDMX-mediated functional inhibition and degradation, acting to prevent damaged cells from proliferating through induction of cell cycle arrest, DNA repair, senescence or apoptosis. Ample evidence suggests that stress signals induce phosphorylation of MDM2 and MDMX, leading to p53 activation. However, the structural basis of stress-induced p53 activation remains poorly understood because of the paucity of technical means to produce site-specifically phosphorylated MDM2 and MDMX proteins for biochemical and biophysical studies. Herein, we report total chemical synthesis, via native chemical ligation, and functional characterization of (24–108)MDMX and its Tyr99-phosphorylated analog with respect to their ability to interact with a panel of p53-derived peptide ligands and PMI, a p53-mimicking but more potent peptide antagonist of MDMX, using FP and surface plasmon resonance techniques. Phosphorylation of MDMX at Tyr99 weakens peptide binding by approximately two orders of magnitude. Comparative X-ray crystallographic analyses of MDMX and of pTyr99 MDMX in complex with PMI as well as modeling studies reveal that the phosphate group of pTyr99 imposes extensive steric clashes with the C-terminus of PMI or p53 peptide and induces a significant lateral shift of the peptide ligand, contributing to the dramatic decrease in the binding affinity of MDMX for p53. Because DNA damage activates c-Abl tyrosine kinase that phosphorylates MDMX at Tyr99, our findings afford a rare glimpse at the structural level of how stress-induced MDMX phosphorylation dislodges p53 from the inhibitory complex and activates it in response to DNA damage.
Journal Article
Lattice distortion enabling enhanced strength and plasticity in high entropy intermetallic alloy
Intermetallic alloys have traditionally been characterized by their inherent brittleness due to their lack of sufficient slip systems and absence of strain hardening. However, here we developed a single-phase B2 high-entropy intermetallic alloy that is both strong and plastic. Unlike conventional intermetallics, this high-entropy alloy features a highly distorted crystalline lattice with complex chemical order, leading to multiple slip systems and high flow stress. In addition, the alloy exhibits a dynamic hardening mechanism triggered by dislocation gliding that preserves its strength across a wide range of temperatures. As a result, this high-entropy intermetallic circumvents precipitous thermal softening, with extensive plastic flows even at high homologous temperatures, outperforming a variety of both body-centered cubic and B2 alloys. These findings reveal a promising direction for the development of intermetallic alloys with broad engineering applications.
Intermetallics are traditionally characterised by their inherent brittleness due to a lack of sufficient slip systems and the absence of strain hardening. Here authors show that a single-phase distorted high entropy B2 intermetallic alloy displays notable strength and plasticity at room temperature, along with stable plastic flow at high homologous temperatures.
Journal Article
A sustainable ultra-high strength Fe18Mn3Ti maraging steel through controlled solute segregation and α-Mn nanoprecipitation
The enormous magnitude of 2 billion tons of alloys produced per year demands a change in design philosophy to make materials environmentally, economically, and socially more sustainable. This disqualifies the use of critical elements that are rare or have questionable origin. Amongst the major alloy strengthening mechanisms, a high-dispersion of second-phase precipitates with sizes in the nanometre range is particularly effective for achieving ultra-high strength. Here, we propose an alternative segregation-based strategy for sustainable steels, free of critical elements, which are rendered ultrastrong by second-phase nano-precipitation. We increase the Mn-content in a supersaturated, metastable Fe-Mn solid solution to trigger compositional fluctuations and nano-segregation in the bulk. These fluctuations act as precursors for the nucleation of an unexpected α-Mn phase, which impedes dislocation motion, thus enabling precipitation strengthening. Our steel outperforms most common commercial alloys, yet it is free of critical elements, making it a new platform for sustainable alloy design.
Recent demands to design alloys in a more sustainable way have discouraged the use of critical elements that are rare. Here the authors demonstrate a segregation-based strategy to produce a sustainable steel, Fe18Mn3Ti, without critical elements while achieving ultrahigh-strength.
Journal Article
Potential ecological risk assessment and prediction of soil heavy-metal pollution around coal gangue dump
The aim of the present study is to evaluate the potential ecological risk and trend of soil heavy-metal pollution around a coal gangue dump in Jilin Province (Northeast China). The concentrations of Cd, Pb, Cu, Cr and Zn were monitored by inductively coupled plasma mass spectrometry (ICP-MS). The potential ecological risk index method developed by Hakanson (1980) was employed to assess the potential risk of heavy-metal pollution. The potential ecological risk in the order of ER(Cd) > ER(Pb) > ER(Cu) > ER(Cr) > ER(Zn) have been obtained, which showed that Cd was the most important factor leading to risk. Based on the Cd pollution history, the cumulative acceleration and cumulative rate of Cd were estimated, then the fixed number of years exceeding the standard prediction model was established, which was used to predict the pollution trend of Cd under the accelerated accumulation mode and the uniform mode. Pearson correlation analysis and correspondence analysis are employed to identify the sources of heavy metals and the relationship between sampling points and variables. These findings provided some useful insights for making appropriate management strategies to prevent or decrease heavy-metal pollution around a coal gangue dump in the Yangcaogou coal mine and other similar areas elsewhere.
Journal Article
4D printed hydrogel scaffold with swelling-stiffening properties and programmable deformation for minimally invasive implantation
The power of three-dimensional printing in designing personalized scaffolds with precise dimensions and properties is well-known. However, minimally invasive implantation of complex scaffolds is still challenging. Here, we develop amphiphilic dynamic thermoset polyurethanes catering for multi-material four-dimensional printing to fabricate supportive scaffolds with body temperature-triggered shape memory and water-triggered programmable deformation. Shape memory effect enables the two-dimensional printed pattern to be fixed into temporary one-dimensional shape, facilitating transcatheter delivery. Upon implantation, the body temperature triggers shape recovery of the one-dimensional shape to its original two-dimensional pattern. After swelling, the hydrated pattern undergoes programmable morphing into the desired three-dimensional structure because of swelling mismatch. The structure exhibits unusual soft-to-stiff transition due to the water-driven microphase separation formed between hydrophilic and hydrophobic chain segments. The integration of shape memory, programmable deformability, and swelling-stiffening properties makes the developed dynamic thermoset polyurethanes promising supportive void-filling scaffold materials for minimally invasive implantation.
3D printing has potential in designing personalised scaffolds, but minimally invasive implantation is still challenging. Here, the authors report the development of a polyurethane material with temperature triggered shape memory and water triggered deformation that allows for transcatheter delivery.
Journal Article
Cooperative polariton dynamics in feedback-coupled cavities
The emerging field of cavity spintronics utilizes the cavity magnon polariton (CMP) induced by magnon Rabi oscillations. In contrast to a single-spin quantum system, such a cooperative spin dynamics in the linear regime is governed by the classical physics of harmonic oscillators. It makes the magnon Rabi frequency independent of the photon Fock state occupation, and thereby restricts the quantum application of CMP. Here we show that a feedback cavity architecture breaks the harmonic-oscillator restriction. By increasing the feedback photon number, we observe an increase in the Rabi frequency, accompanied with the evolution of CMP to a cavity magnon triplet and a cavity magnon quintuplet. We present a theory that explains these features. Our results reveal the physics of cooperative polariton dynamics in feedback-coupled cavities, and open up new avenues for exploiting the light–matter interactions.
Rabi oscillations of magnons typically do not have few photon control of single spin quantum systems. Here, the authors use a feedback cavity architecture to increase magnon-photon cooperativity, enabling increased control of light-matter interactions in magnonic systems via cooperative polariton dynamics.
Journal Article
Outward foreign direct investment by emerging market firms: A resource dependence logic
This study examines and extends the resource dependence logic of diversification for a better understanding of outward foreign direct investment (OFDI) activities by emerging market firms. We contend that the diversification logic is bounded by state ownership, an important but less considered component of interdependence. Our empirical results, based on panel data analysis of Chinese listed firms, suggest that the level of interdependence between Chinese and foreign firms in China in multiple forms, including symbiotic, competitive, and partner interdependencies, is positively associated with the level of the Chinese firms' OFDI activities. However, Chinese firms with higher levels of state ownership are less susceptible to the pressures imposed by foreign firms to invest abroad.
Journal Article
A GABAergic neural circuit in the ventromedial hypothalamus mediates chronic stress–induced bone loss
Homeostasis of bone metabolism is regulated by the central nervous system, and mood disorders such as anxiety are associated with bone metabolism abnormalities, yet our understanding of the central neural circuits regulating bone metabolism is limited. Here, we demonstrate that chronic stress in crewmembers resulted in decreased bone density and elevated anxiety in an isolated habitat mimicking a space station. We then used a mouse model to demonstrate that GABAergic neural circuitry in the ventromedial hypothalamus (VMH) mediates chronic stress-induced bone loss. We show that GABAergic inputs in the dorsomedial VMH arise from a specific group of somatostatin neurons in the posterior region of the bed nucleus of the stria terminalis, which is indispensable for stress-induced bone loss and is able to trigger bone loss in the absence of stressors. In addition, the sympathetic system and glutamatergic neurons in the nucleus tractus solitarius were employed to regulate stress-induced bone loss. Our study has therefore identified the central neural mechanism by which chronic stress-induced mood disorders, such as anxiety, influence bone metabolism.
Journal Article
Intrinsic Capacity Impairment Patterns and their Associations with Unfavorable Medication Utilization: A Nationwide Population-Based Study of 37,993 Community-Dwelling Older Adults
Our aim was to explore the patterns of intrinsic capacity (IC) impairments among community-dwelling older adults and the associations of these different patterns with excessive polypharmacy, potentially inappropriate medications, and adverse drug reactions in a nationwide population-based study.
A cross-sectional study included older adults from the Taiwan Integrated Care for Older People (ICOPE) program in 2020.
The study subjects comprised 38,308 adults aged 65 years and older who participated in the ICOPE Step 1 screening and assessed six domains of IC following the World Health Organization (WHO) ICOPE approach.
Latent class analysis was adopted to identify distinct subgroups with different IC impairments patterns. The associations between different IC impairments patterns and unfavorable medication utilization, including excess polypharmacy (EPP), potentially inappropriate medications (PIMs), and adverse drug reactions (ADRs), were assessed by multivariate logistic regression models.
Latent class analysis identified five distinct subgroups with different IC impairment patterns: robust (latent class prevalence: 59.4%), visual impairment (17.7%), physio-cognitive decline (PCD) with sensory impairment (12.3%), depression with cognitive impairment (7.7%), and impairments in all domains (2.9%). Compared to the robust group, all other groups were at higher odds for unfavorable medication utilization. The “depression with cognitive impairment” group (EPP: aOR=4.35, 95% CI 3.52–5.39, p<0.01; PIMs: aOR=2.73, 95% CI 2.46–3.02, p<0.01) and the “impairment in all domains” group (EPP: aOR=9.02, 95% CI 7.16–11.37, p<0.01; PIMs: aOR=3.75, 95% CI 3.24–4.34, p<0.01) remained at higher odds for EPP and PIMs after adjustment.
We identified five distinct impairment patterns of IC, and each impairment pattern, particularly the “depression with cognitive impairment” and “impairment in all domains”, was associated with higher odds of EPP and PIMs. Further longitudinal and intervention studies are needed to explore long-term outcomes of different impairment pattern and their reversibility.
Journal Article