Browse Articles

Material properties of biomolecular condensates emerge from nanoscale dynamics

Biomolecular condensates form by phase separation of biological polymers and have important functions in the cell—functions that are inherently linked to their physical properties at different scales. A notable aspect of such membraneless organelles is that their viscoelastic properties can vary by orders of magnitude, but it has remained unclear how these pronounced differences are rooted in the nanoscale dynamics at the molecular level. Here, we investigate a series of condensates formed by complex coacervation of highly charged disordered proteins and polypeptides that span about two orders of magnitude in bulk viscosity. We find that their viscosity is highly correlated with protein translational diffusion and nano- to microsecond chain dynamics. Remarkably, analytical relations from polymer physics can predict condensate viscosity from diffusivity and chain dynamics, and vice versa, even for more hydrophobic disordered proteins and for synthetic polyelectrolytes, indicating a mechanistic link across several decades of length- and timescales. Atomistic simulations reveal that the observed differences in friction—a key quantity underlying these relations—reflect differences in interresidue contact lifetimes as a function of arginine content and salt concentration, leading to the vastly different dynamics among condensates. The rapid exchange of interresidue contacts we observe may be a general mechanism for preventing dynamic arrest in compartments densely packed with polyelectrolytes, such as the cell nucleus.

Climate warming increases global oceanic dimethyl sulfide emissions

Oceanic dimethyl sulfide (DMS) is the largest natural source of atmospheric sulfur. DMS is biologically produced in seawater and emitted into the atmosphere, where its oxidation products contribute to aerosol formation with consequences for cloud albedo and the Earth’s radiative budget and climate. Climate model projections of how DMS emissions change with global warming are largely uncertain, even contradictory. Here, we use machine-learning models trained with biome-resolved global observations to simulate seawater DMS concentrations (1850 to 2100) using physico-chemical and biological predictors from eight CMIP6 models. The scatter in current projections is largely reduced, and globally averaged seawater DMS concentrations are predicted to decrease in the coming decades. However, global DMS emissions will increase due to rising surface wind speeds and sea surface temperatures which contradicts the current AR6 assessment that the DMS flux will reduce in the future. Concurrence of increasing DMS emissions and declining anthropogenic sulfur dioxide emissions suggests an increase in the relative importance of DMS to sulfate aerosol formation and its climate cooling impact.

MyD88 knockdown by RNAi prevents bacterial stimulation of tubeworm metamorphosis

Diverse animals across the tree of life undergo the life-history transition of metamorphosis in response to bacteria. Although immunity has been implicated in this metamorphosis in response to bacteria, no functional connection has yet been demonstrated between immunity and metamorphosis. We investigated a host–microbe interaction involving a marine tubeworm, Hydroides elegans , that undergoes metamorphosis in response to Pseudoalteromonas luteoviolacea , a metamorphosis-inducing marine bacterium. By creating a marine bacteria–mediated RNA interference approach, we show that myeloid differentiation factor 88 (MyD88), a critical immune adaptor for Toll-like receptor and interleukin pathways, is necessary for the stimulation of metamorphosis in response to bacteria. In addition to a developmental role, we show that MyD88 is necessary for survival during exposure to the bacterial pathogen Pseudomonas aeruginosa , showing that Hydroides utilizes MyD88 during both development and an immune response. These results provide a functional characterization of the innate immune system involved in an animal's metamorphosis.

Suborbital- and millennial-scale monsoon variability during Pleistocene interglacials

Observational and modeling results show that the frequency and amplitude of extreme climatic events have increased significantly in the context of global warming. However, whether abrupt climate changes intensified during past warm periods remains poorly constrained due to the lack of high-resolution geological records. Here, we report a 512-m predominantly lacustrine sedimentary record from the Weihe Basin (North China), revealing that lake levels fluctuated significantly on suborbital (half- and quarter-precession) and millennial timescales over the last 2 Ma. Grain-size results reveal that magnitudes of rapid lake level fluctuations increased dramatically during Pleistocene interglacials, differing from glacial amplification of abrupt climate events recorded in North Atlantic marine sediments. Model results indicate that summer insolation maxima in low-latitude region of both hemispheres can lead to intensified monsoon precipitation in East Asia. Our proxy-model comparison highlights the importance of low-latitude bihemispheric insolation maxima in driving millennial-scale hydroclimatic variability in a warming future.

Multiple sources of atmospheric CO ₂ activated by AMOC recovery at the onset of interglacial MIS 9

Using high-precision ice core measurements of CO 2 , δ 13 C–CO 2 , CH 4 , and N 2 O, this study provides carbon isotope constraints on a sizeable, centennial-scale CO 2 jump at the onset of Marine Isotope Stage 9 (MIS 9). The very end of the Heinrich stadial (HS) characterizing Termination IV (T-IV, ca. 343 to 333 ka ago) shows a 250-y-long jump in greenhouse gas concentrations, followed by a 1.3 ka gradual decline back to the initial concentration. During this so-called overshoot, CO 2 and CH 4 reach their highest levels (about 303 ppm and 800 ppb, respectively) over the past 800 ka prior to industrialization. The jump in CO 2 is not accompanied by a change in δ 13 C–CO 2, suggesting that multiple mechanisms contributed to the exceptionally elevated CO 2 values. Following the jump, a slow 0.2‰ enrichment in δ 13 C–CO 2 occurs. We propose that during the jump, the sudden resumption of deepwater formation in the North Atlantic (NA) triggered an amplified release of CO 2 from the Southern Ocean (SO) by a northward shift of the Intertropical Convergence Zone (ITCZ) and the SO westerlies, potentially in combination with a rapid land carbon release. The latter is expected from temporally enhanced wildfire activity related to higher fuel load and regionally changing weather conditions in connection to the ITCZ shift. A combination of marine proxy records and box model simulation suggests that the δ 13 C–CO 2 decrease expected from these processes is compensated by a net temperature increase in global sea surface temperature (SST) at the time of the AMOC resumption.

Anthropogenic iron alters the spring phytoplankton bloom in the North Pacific transition zone

Industrial activities have increased the supply of iron to the ocean, but the magnitude of anthropogenic input and its ecological consequences are not well-constrained by observations. Across four expeditions to the North Pacific transition zone, we document a repeated supply of isotopically light iron from an atmospheric source in spring, reflecting an estimated 39 ± 9 % anthropogenic contribution to the surface ocean iron budget. Expression of iron-stress genes in metatranscriptomes, and evidence for colimitation of ecosystem productivity by iron and nitrogen, indicates that enhanced iron supply should spur spring phytoplankton blooms, accelerating the seasonal drawdown of nitrate delivered by winter mixing. This effect is consistent with regional trends in satellite ocean color, which show a shorter, more intense spring bloom period, followed by an earlier arrival of oligotrophic conditions in summer. Continued iron emissions may contribute to poleward shifts in transitional marine ecosystems, compounding the anticipated impacts from ocean warming and stratification.

Location, location, location: Cholesterol in lipid droplets as a driver of MASH progression

Early dynamics of chromatin decompaction drive nuclear stiffening

Summer solstice optimizes the thermal growing season

Multiple studies have recently proposed the summer solstice as a universal cue for major plant physiological processes. While this would have strong implications for fundamental plant biology and climate change forecasting, we currently have no clear mechanisms to explain the emergence and importance of solstice as a cue. Here, we analyze temperature accumulation patterns in relation to the summer solstice across Europe and North America—in past, historical, and projected future climates. We show that, on average, the summer solstice coincides with a thermal optimum during the growing season. However, we also find significant local variation in the timing of this optimum across different climates—suggesting the potential of alternative cues.

Sensitivity of simulations of Plio–Pleistocene climate with the CLIMBER-2 Earth System Model to details of the global carbon cycle

The Earth system model CLIMBER-2 has been used in past work to successfully reproduce the glacial/interglacial cycles of the Plio–Pleistocene and the Mid-Pleistocene Transition (MPT) from predominantly 40 to 100 ky timescale oscillatory behavior as a function of declining volcanic outgassing and regolith removal. In this study, we further examine the sensitivity of this previous work to varying prescribed levels of volcanic outgassing and regolith extent and the long-term dynamics of the global carbon cycle, affecting the exchange and partitioning of carbon between different Earth system reservoirs and therefore global atmospheric CO 2 concentrations. As volcanic outgassing decreases, CO 2 and land carbon storage decrease, while ocean carbon storage, including CaCO 3 sediment, increases. At volcanic outgassing levels below a threshold value of roughly 5.7 Tmol C yr −1 , sea level decreases due to land ice formation, leading to increased carbon accumulation in the ocean and decreased carbon in the CaCO 3 sediment reservoir. Our previous finding of strong hysteresis and path dependence in the glacial/interglacial alternation history [J. Carrillo et al. , Proc. Natl. Acad. Sci. 121, e2322926121 (2024)] appears to be a tenuous climate feature, dependent on the precise representation of carbon cycle processes and, specifically, the numerical precision used in the calculation of certain key state variables in the model’s carbon cycle.

Updated fossil analyses reveal critical insights into the origins of monotreme lifestyles

Reply to Apanovich and Weeks: Exceptions exist, as recognized in the paper, but are too rare to challenge the original findings

Reply to Ogutu et al.: Cattle–wild herbivore interaction studies warrant new lenses from community ecology and environmental justice

Correction for Yin et al., Tau accumulation induces synaptic impairment and memory deficit by calcineurin-mediated inactivation of nuclear CaMKIV/CREB signaling

Correction for Guo et al., Targeting amyloid-β in glaucoma treatment

Short-term study fails to capture negative impacts of livestock intensification on wildlife

Why excluding regenerative grazing skews beef’s carbon profile

Bleating, growling, barking, and spitting: Metaphorical extensions and valency patterns of verbs of speaking

This corpus-based and qualitative study examines the valency patterns of Croatian verbs that encode verbal activity and belong to the semantic field of verbs of speaking through metaphorical and metonymic extensions, using a cognitive linguistics framework, specifically the usage-based model. The analysis focuses on examples such as the metaphoric use of animal sounds (e.g., blejati ‘to bleat’) and verbs associated with bodily processes (e.g., srati ‘to shit’), which often convey negative or stereotypical attitudes towards speakers or messages, or even extreme disdain. This paper contributes to the understanding of cross-domain figurative extensions of verb meanings and their valency adaptations. A dataset of 438 example sentences containing 152 verbs with figurative extensions targeting the domain of speaking was meticulously compiled from Croatian corpora. This dataset enabled a manual annotation and analysis of the transfer and adaptation of valency patterns across domains. The study addresses the following key questions: 1. What source domains are used for verbs of speaking as targets? 2. Do verbs retain the valency patterns of the source domain or adopt those of the target domain? 3. Is the passivization of transitive verbs possible in metaphorical contexts? The findings indicate that with a metaphorical shift in meaning, verbs often adopt new valency patterns from the target domain. Our examples of valency pattern change as a result of a metaphorical meaning shift demonstrate that verbs can appear with arguments not explicitly subcategorized by the verb itself.

Nurses’ perspectives and experience in caring for patients undergoing hemodialysis at Benjamin Mkapa hospital in Dodoma, Tanzania: A qualitative study

Background Caring for patients undergoing hemodialysis is a challenge for nurses. Poor quality of care in hemodialysis is reported to have a significant contribution to the high mortality rate among patients. Improving the health outcomes of the patient requires an in-depth exploration of the perspectives and views of nurses working in the hemodialysis unit. However, there is a paucity of information regarding the perspectives and experiences of nurses working in Hemodialysis units, particularly in resource-constrained countries like Tanzania. This study aimed to explore the perspectives and experiences of nurses caring for patients undergoing hemodialysis. Materials and Methods An explorative qualitative study was conducted among nurses working in Hemodialysis units at Benjamin Mkapa Hospital in Dodoma, Tanzania. A purposive sampling method was used to select the participants. Ten in-depth interviews were conducted using a semi-structured interview guide and an audio recorder as the main data collection tools. A thematic analysis approach was used to analyze the data. Findings Three themes and the associated subthemes emerged from this study. 1) Conducive environments for the provision of nursing care 2) Challenges affecting hemodialysis care, and 3) Strategies for improving hemodialysis care. A good nurse-patient relationship, financial incentives, and availability of equipment facilitate the provision of care among patients. Treatment costs, problems in adhering to dialysis prescriptions, and staff shortages were the challenges affecting hemodialysis care. On the other hand, increasing dialysis centres, training nurses, and free health insurance coverage were strategies for improving hemodialysis care. Conclusion The findings highlighted several key aspects related to the perspectives and experiences of providing nursing care for patients undergoing hemodialysis. The conducive working environment, coupled with financial incentives, is an important factor in improving nurses’ care for patients undergoing hemodialysis. However, the high costs related to the utilization of hemodialysis services are the challenge to achieving better outcomes.

Clinical study outcomes in IgA nephropathy: A systematic literature review and narrative synthesis

Introduction IgA nephropathy (IgAN) is an inflammatory kidney disease which, if left untreated, often progresses to kidney failure (KF). This systematic literature review identifies, collates, summarizes, and assesses the quality of clinical trial data describing the efficacy of therapies used for IgAN. Methods Ovid Embase, PubMed, CENTRAL, and the Cochrane database of systematic reviews were searched on October 18th, 2021, and updated on December 12th, 2023. Electronic searches were supplemented with manual searches of key conferences, clinical trial registries, and bibliography screening. PRISMA and Cochrane guidelines were followed. Results A total of 6710 references were identified (electronic and manual searches), of which 6483 were excluded. This resulted in 254 references reporting 183 studies which met our inclusion criteria. The majority of these IgAN studies (98/183 studies [60%]) had a non-randomized or single-arm design and/or a small population size or focused on dietary and traditional medicine, resulting in a high risk of bias and necessitated additional filtering to prioritize larger (n>30) randomized assessment of pharmacological interventions reporting key clinical outcomes. This additional filtering resulted in 76 randomized controlled trials (100 references) selected for narrative synthesis; 60 reported proteinuria outcomes and 18 reported estimated glomerular filtration rate (eGFR) outcomes. Conclusions Until recently, the evidence has been mixed or inconsistent across studies for the efficacy of IgAN treatments in reducing proteinuria or slowing eGFR decline due to a high risk of bias in many included studies. The latest large, phase 3 NefIgArd (NCT03643965) and PROTECT (NCT03762850) clinical trials have demonstrated a meaningful reduction in proteinuria and eGFR decline for patients with IgAN receiving targeted-release formulation budesonide (TRF-B) or sparsentan. Results from other high-quality randomized controlled trials with a follow-up period of at least 2 years are still required to better support advancements in the management of IgAN.