Browse Articles

Size-dependent phase change in energy storage materials: Comparing the impact of solid-state wetting and of coherency stress

Coherent phase transformations in interstitial solid solutions or intercalation compounds with a miscibility gap are of practical relevance for energy storage materials and specifically for metal hydride or lithium-ion compound nanoparticles. Different conclusions on the size-dependence of the transformation conditions are reached by modeling or theory focusing on the impact of either one (internal, solid-state-) critical-point wetting of the nanoparticle surface or coherency constraints from solute-saturated surface layers. We report a hybrid numerical approach, combining atomistic grand canonical Monte Carlo simulation with a continuum mechanics analysis of coherency stress and modeling simultaneously wetting and mechanical constraints. When the ratio between chemical and misfit-strain-related contributions to the solute-solute interaction energy takes values realistic for interstitial solutions—which are typical for energy storage materials—we find that the impact of solid-state wetting is weak and that of coherency stress is dominant. Specifically, mechanical interaction can act to reduce the phase transformation hysteresis at small system size, and it can make the solid more binding for solute, thereby reducing the “plateau” chemical potential at phase coexistence. We present equations for the impact of coherency stress on the size-dependence of upper consolute temperature, plateau chemical potential, and charging/discharging hysteresis.

Recognized Outstanding Reviewers for <i>Circulation</i> in 2024

Phase transitions in chromatin: Mesoscopic and mean-field approaches

By means of a minimal physical model, we investigate the interplay of two phase transitions at play in chromatin organization: (1) liquid–liquid phase separation within the fluid solvating chromatin, resulting in the formation of biocondensates; and (2) the coil–globule crossover of the chromatin fiber, which drives the condensation or extension of the chain. In our model, a species representing a domain of chromatin is embedded in a binary fluid. This fluid phase separates to form a droplet rich in a macromolecule (B). Chromatin particles are trapped in a harmonic potential to reproduce the coil and globular phases of an isolated polymer chain. We investigate the role of the droplet material B on the radius of gyration of this polymer and find that this radius varies nonmonotonically with respect to the volume fraction of B. This behavior is reminiscent of a phenomenon known as co-non-solvency: a polymer chain in a good solvent (S) may collapse when a second good solvent (here B) is added in low quantity and expands at higher B concentration. In addition, the presence of finite-size effects on the coil–globule transition results in a qualitatively different impact of the droplet material on polymers of various sizes. In the context of genetic regulation, our results suggest that the size of chromatin domains and the quantity of condensate proteins are key parameters to control whether chromatin may respond to an increase in the quantity of chromatin-binding proteins by condensing or expanding.

A signaling molecule from intratumor bacteria promotes trastuzumab resistance in breast cancer cells

Emerging evidence indicates that intratumor bacteria exist as an active and specific tumor component in many tumor types beyond digestive and respiratory tumors. However, the biological impact and responsible molecules of such local bacteria–tumor direct interaction on cancer therapeutic response remain poorly understood. Trastuzumab is among the most commonly used drugs targeting the receptor tyrosine-protein kinase erbB-2 (ErbB2) in breast cancer, but its resistance is inevitable, severely limiting its clinical effectiveness. Here, we demonstrate that the quorum-sensing signaling molecule N-(3-oxo-dodecanoyl) homoserine lactone (3oc), a chemical compound released by Pseudomonas aeruginosa ( P. aeruginosa ), one tumor-resident bacteria with a relative high abundance in breast cancer, promotes breast cancer cell resistance to trastuzumab. Mechanically, 3oc directly leads to spontaneous dimerization of the transforming growth factor β (TGF-β) type II serine/threonine kinase receptor on the cell membrane in a ligand-independent manner. The 3oc-induced TGF-β signaling subsequently triggers ErbB2 phosphorylation and its downstream target activation, overcoming the inhibition effect of trastuzumab on ErbB2. With specific real-time qPCR, fluorescence in situ hybridization imaging, and liquid chromatography ionization tandem mass spectrometry analyses of clinical samples, we confirmed that P. aeruginosa and its signaling molecule 3oc exist in breast cancer tissues and there is a clinical correlation between P. aeruginosa colonization and trastuzumab resistance. This work expands the biological functions of intratumor bacteria in cancer treatment responsiveness and provides a unique perspective for overcoming trastuzumab resistance.

Global Rounds Afghanistan: A Critical Overview of Cardiovascular Medicine

Analytical derivative approaches for vibro-polaritonic structures and properties. I. Formalism and implementation

Vibro-polaritons are hybrid light–matter states that arise from the strong coupling between the molecular vibrational transitions and the photons in an optical cavity. Developing theoretical and computational methods to describe and predict the unique properties of vibro-polaritons is of great significance for guiding the design of new materials and experiments. Here, we present the ab initio cavity Born–Oppenheimer density functional theory (CBO-DFT) and formulate the analytic energy gradient and Hessian as well as the nuclear and photonic derivatives of dipole and polarizability within the framework of CBO-DFT to efficiently calculate the harmonic vibrational frequencies, infrared absorption, and Raman scattering spectra of vibro-polaritons as well as to explore the critical points on the cavity potential energy surface. The implementation of analytic derivatives into the electronic structure package is validated by a comparison with the finite-difference method and with other reported computational results. By adopting appropriate exchange–correlation functionals, CBO-DFT can better describe the structure and properties of molecules in the cavity than CBO-Hartree–Fock method. It is expected that CBO-DFT is a useful tool for studying the polaritonic structures and properties.

Partial PdAu nanoparticle embedding into TiO ₂ support accentuates catalytic contributions from the Au/TiO ₂ interface

Despite the broad catalytic relevance of metal–support interfaces, controlling their chemical nature, the interfacial contact perimeter (exposed to reactants), and consequently, their contributions to overall catalytic reactivity, remains challenging, as the nanoparticle and support characteristics are interdependent when catalysts are prepared by impregnation. Here, we decoupled both characteristics by using a raspberry-colloid-templating strategy that yields partially embedded PdAu nanoparticles within well-defined SiO 2 or TiO 2 supports, thereby increasing the metal–support interfacial contact compared to nonembedded catalysts that we prepared by attaching the same nanoparticles onto support surfaces. Between nonembedded PdAu/SiO 2 and PdAu/TiO 2 , we identified a support effect resulting in a 1.4-fold higher activity of PdAu/TiO 2 than PdAu/SiO 2 for benzaldehyde hydrogenation. Notably, partial nanoparticle embedding in the TiO 2 raspberry-colloid-templated support increased the metal–support interfacial perimeter and consequently, the number of Au/TiO 2 interfacial sites by 5.4-fold, which further enhanced the activity of PdAu/TiO 2 by an additional 4.1-fold. Theoretical calculations and in situ surface-sensitive desorption analyses reveal facile benzaldehyde binding at the Au/TiO 2 interface and at Pd ensembles on the nanoparticle surface, explaining the connection between the number of Au/TiO 2 interfacial sites (via the metal–support interfacial perimeter) and catalytic activity. Our results demonstrate partial nanoparticle embedding as a synthetic strategy to produce thermocatalytically stable catalysts and increase the number of catalytically active Au/TiO 2 interfacial sites to augment catalytic contributions arising from metal–support interfaces.

Response by Sun et al to Letter Regarding Article, “Piezo1-Mediated Neurogenic Inflammatory Cascade Exacerbates Ventricular Remodeling After Myocardial Infarction”

The bcc coating of Lennard-Jones crystal nuclei vanishes with a change of local structure detection algorithm

Since the influential work of ten Wolde, Ruiz-Montero, and Frenkel [Phys. Rev. Lett. 75, 2714 (1995)], crystal nucleation from a Lennard-Jones fluid has been regarded as a paradigmatic example of metastable crystal ordering at the surface of a critical nucleus. We apply seven commonly used local structure detection algorithms to characterize crystal nuclei obtained from transition path sampling simulations. The polymorph composition of these nuclei varies significantly depending on the algorithm used. Our results indicate that one should be very careful when characterizing the local structure near solid–solid and solid–fluid interfaces. Particles near such interfaces exhibit a local structure distinct from that of bulk fluid or bulk crystal phases. We argue that incorporating outlier detection into the local structure detection method is beneficial, leading to greater confidence in the classification results. Interestingly, the bcc coating nearly disappears when adopting a machine learning method with outlier detection.

Effects of the Nonsteroidal MRA Finerenone With and Without Concomitant SGLT2 Inhibitor Use in Heart Failure

BACKGROUND: Patients with heart failure (HF) with mildly reduced or preserved ejection fraction face heightened long-term risks of morbidity and mortality. Sodium-glucose cotransporter-2 inhibitors (SGLT2i) and the nonsteroidal mineralocorticoid receptor antagonist finerenone have both been shown to reduce the risk of cardiovascular events in this population, but the effects of their combined use are not known. METHODS: FINEARTS-HF (Finerenone Trial to Investigate Efficacy and Safety Superior to Placebo in Patients With Heart Failure) was a randomized, double-blind, placebo-controlled trial of finerenone in patients with HF and left ventricular ejection fraction ≥40%. Baseline SGLT2i use was a prespecified subgroup. The primary outcome was a composite of total (first and recurrent) worsening HF events and cardiovascular death. We first assessed for evidence of treatment heterogeneity on the basis of baseline SGLT2i use. We further examined SGLT2i uptake during the trial and evaluated the treatment effects of finerenone accounting for baseline and during-trial use of SGLT2i in time-varying analyses. RESULTS: Among 6001 participants, 817 (13.6%) were treated with an SGLT2i at baseline. During 2.6 years median follow-up, treatment with finerenone similarly reduced the risk of the primary outcome in participants treated with an SGLT2i (rate ratio, 0.83 [95% CI, 0.60–1.16]) and without an SGLT2i at baseline (rate ratio, 0.85 [95% CI, 0.74–0.98]; P interaction =0.76). In follow-up, 980 participants initiated SGLT2i, which was less frequent in the finerenone arm compared with placebo (17.7% versus 20.1%; hazard ratio, 0.86 [95% CI, 0.76–0.97]). Time-updated analyses accounting for baseline and subsequent use of SGLT2i did not meaningfully alter the treatment effects of finerenone on the primary end point. CONCLUSIONS: The treatment benefits of the nonsteroidal mineralocorticoid receptor antagonist finerenone were observed irrespective of concomitant use of an SGLT2i. These data suggest that the combined use of SGLT2i and a nonsteroidal mineralocorticoid receptor antagonist may provide additive protection against cardiovascular events in patients with HF with mildly reduced or preserved ejection fraction. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT04435626.

The scientific reason to cook with simmering rather than vigorously boiling water

Nanoscale self-assembly and water retention properties of silk fibroin–riboflavin hydrogel

Silk-fibroin hydrogels have gained considerable attention in recent years for their versatile biomedical applications. The physical properties of a complex hydrogel, comprising silk fibroin and riboflavin, surpass those of the silk fibroin-hydrogel without additives. This study investigates silk fibroin–riboflavin (silk–RIB) hydrogel at the atomistic level to uncover molecular structures and chemical characteristics specific to silk fibroin and riboflavin molecules in an aqueous medium. The interplay between hydrophilic riboflavin and hydrophobic silk fibroin polymers facilitates the formation of solubilized silk fiber, which subsequently evolves into a nano-scale hydrogel over time. Eventually, the interlinked RIB stacks form a scaffold that not only accommodates silk fibroin aggregates but also encloses water pockets, preserving the moisture level and enhancing the thermal conductivity of the hydrogel. To explore water retention properties and the role of ions, two sets of simulations of semi-hydrated hydrogel in the presence and absence of ions are conducted. The presence of ions significantly influences the dynamics of RIB and silk fibroin. Favorable interactions with the ions impede the unrestricted diffusion of these larger molecules, potentially leading to a stable structure capable of retaining water for a prolonged duration. The complete removal of water results in further shrinkage of the anhydrous silk–RIB hydrogel or xerogel (XG), yet its porosity and structural integrity remain intact. These findings offer valuable insights into the behavior of silk fibroin hydrogel and XG, paving the way for materials engineering in aqueous environments to develop biomedical devices with customized functional properties.

CryoEM structure of an MHC-I/TAPBPR peptide-bound intermediate reveals the mechanism of antigen proofreading

Class I major histocompatibility complex (MHC-I) proteins play a pivotal role in adaptive immunity by displaying epitopic peptides to CD8+ T cells. The chaperones tapasin and TAPBPR promote the selection of immunogenic antigens from a large pool of intracellular peptides. Interactions of chaperoned MHC-I molecules with incoming peptides are transient in nature, and as a result, the precise antigen proofreading mechanism remains elusive. Here, we leverage a high-fidelity TAPBPR variant and conformationally stabilized MHC-I, to determine the solution structure of the human antigen editing complex bound to a peptide decoy by cryogenic electron microscopy (cryo-EM) at an average resolution of 3.0 Å. Antigen proofreading is mediated by transient interactions formed between the nascent peptide binding groove with the P2/P3 peptide anchors, where conserved MHC-I residues stabilize incoming peptides through backbone-focused contacts. Finally, using our high-fidelity chaperone, we demonstrate robust peptide exchange on the cell surface across multiple clinically relevant human MHC-I allomorphs. Our work has important ramifications for understanding the selection of immunogenic epitopes for T cell screening and vaccine design applications.

Preventing Site-Specific Calpain Proteolysis of Junctophilin-2 Protects Against Stress-Induced Excitation-Contraction Uncoupling and Heart Failure Development

BACKGROUND: Excitation-contraction (E-C) coupling processes become disrupted in heart failure (HF), resulting in abnormal Ca 2+ homeostasis, maladaptive structural and transcriptional remodeling, and cardiac dysfunction. Junctophilin-2 (JP2) is an essential component of the E-C coupling apparatus but becomes site-specifically cleaved by calpain, leading to disruption of E-C coupling, plasmalemmal transverse tubule degeneration, abnormal Ca 2+ homeostasis, and HF. However, it is not clear whether preventing site-specific calpain cleavage of JP2 is sufficient to protect the heart against stress-induced pathological cardiac remodeling in vivo. METHODS: Calpain-resistant JP2 knock-in mice (JP2 CR ) were generated by deleting the primary JP2 calpain cleavage site. Stress-dependent JP2 cleavage was assessed through in vitro cleavage assays and in isolated cardiomyocytes treated with 1 μmol/L isoproterenol by immunofluorescence. Cardiac outcomes were assessed in wild-type and JP2 CR mice 5 weeks after transverse aortic constriction compared with sham surgery using echocardiography, histology, and RNA-sequencing methods. E-C coupling efficiency was measured by in situ confocal microscopy. E-C coupling proteins were evaluated by calpain assays and Western blotting. The effectiveness of adeno-associated virus gene therapy with JP2 CR , JP2, or green fluorescent protein to slow HF progression was evaluated in mice with established cardiac dysfunction. RESULTS: JP2 proteolysis by calpain and in response to transverse aortic constriction and isoproterenol was blocked in JP2 CR cardiomyocytes. JP2 CR hearts are more resistant to pressure-overload stress, having significantly improved Ca 2+ homeostasis and transverse tubule organization with significantly attenuated cardiac dysfunction, hypertrophy, lung edema, fibrosis, and gene expression changes relative to wild-type mice. JP2 CR preserves the integrity of calpain-sensitive E-C coupling–related proteins, including ryanodine receptor 2, Ca V 1.2, and sarcoplasmic reticulum calcium ATPase 2a, by attenuating transverse aortic constriction–induced increases in calpain activity. Furthermore, JP2 CR gene therapy after the onset of cardiac dysfunction was found to be effective at slowing the progression of HF and superior to wild-type JP2. CONCLUSIONS: The data presented here demonstrate that preserving JP2-dependent E-C coupling by prohibiting the site-specific calpain cleavage of JP2 offers multifaceted beneficial effects, conferring cardiac protection against stress-induced proteolysis, hypertrophy, and HF. Our data also indicate that specifically targeting the primary calpain cleavage site of JP2 by gene therapy approaches holds great therapeutic potential as a novel precision medicine for treating HF.

Open-boundary molecular dynamics of ultrasound using supramolecular water models

Ultrasound can be used to manipulate protein function and activity, as well as for targeted drug delivery, making it a powerful diagnostic and therapeutic modality with wide applications in sonochemistry, nanotechnology, and engineering. However, a general particle-based approach to ultrasound modeling remains challenging due to the significant disparity between characteristic time scales governing ultrasound propagation. In this study, we use open-boundary molecular dynamics to simulate ultrasound waves in liquid water under ambient conditions by employing supramolecular water models, i.e., the Martini 3, dissipative particle dynamics, and many-body dissipative particle dynamics models. We demonstrate that our approach successfully reproduces the solution of the traveling wave equation and captures the velocity dispersion characteristic of high-frequency ultrasound waves.

Nonapoptotic role of EGL-1 in exopher production and neuronal health in <i>Caenorhabditis elegans</i>

While traditionally studied for their proapoptotic functions in activating the caspase, research suggests BH3-only proteins also have other roles such as mitochondrial dynamics regulation. Here, we find that EGL-1, the BH3-only protein in Caenorhabditis elegans , promotes the cell-autonomous production of exophers in adult neurons. Exophers are large, micron-scale vesicles that are ejected from the cell and contain cellular components such as mitochondria. EGL-1 facilitates exopher production potentially through regulation of mitochondrial dynamics. Moreover, an endogenous, low level of EGL-1 expression appears to benefit dendritic health. Our findings provide insights into the role of neuronal BH3-only protein in mitochondrial dynamics, downstream exopher production, and ultimately neuronal health.

Efficacy and Safety of Finerenone in Patients With Primary Aldosteronism: A Pilot Randomized Controlled Trial

Retractions caused by honest mistakes are extremely stressful, say researchers

Multidimensional quantum dynamics with explicitly correlated Gaussian wave packets using Rothe’s method

In a previous publication [S. E. Schrader et al., J. Chem. Phys. 161, 044105 (2024)], it has been shown that Rothe’s method can be used to solve the time-dependent Schrödinger equation for the hydrogen atom in a strong laser field using time-dependent Gaussian wave packets. Here, we generalize these results, showing that Rothe’s method can propagate arbitrary numbers of thawed, complex-valued, Explicitly Correlated Gaussian (ECGs) functions with dense correlation matrices for systems with varying dimensionality. We consider the multidimensional Hénon–Heiles potential and show that the dynamics can be quantitatively reproduced using only 30 Gaussians in 2D and that accurate spectra can be obtained using 20 Gaussians in 2D and 30–40 Gaussians in 3D and 4D. Therefore, the relevant multidimensional dynamics can be described at high quality using only a small number of ECGs that give a very compact representation of the wave function. This efficient representation, along with the demonstrated ability of Rothe’s method to propagate Gaussian wave packets in strong fields and ECGs in complex potentials, paves the way for accurate molecular dynamics calculations beyond the Born–Oppenheimer approximation in strong fields.

Device-Measured 24-Hour Movement Behaviors and Blood Pressure: A 6-Part Compositional Individual Participant Data Analysis in the ProPASS Consortium

BACKGROUND: Blood pressure (BP)–lowering effects of structured exercise are well-established. Effects of 24-hour movement behaviors captured in free-living settings have received less attention. This cross-sectional study investigated associations between a 24-hour behavior composition comprising 6 parts (sleeping, sedentary behavior, standing, slow walking, fast walking, and combined exercise-like activity [eg, running and cycling]) and systolic BP (SBP) and diastolic BP (DBP). METHODS: Data from thigh-worn accelerometers and BP measurements were collected from 6 cohorts in the Prospective Physical Activity, Sitting and Sleep consortium (ProPASS) (n=14 761; mean±SD, 54.2±9.6 years). Individual participant analysis using compositional data analysis was conducted with adjustments for relevant harmonized covariates. Based on the average sample composition, reallocation plots examined estimated BP reductions through behavioral replacement; the theoretical benefits of optimal (ie, clinically meaningful improvement in SBP [2 mm Hg] or DBP [1 mm Hg]) and minimal (ie, 5-minute reallocation) behavioral replacements were identified. RESULTS: The average 24-hour composition consisted of sleeping (7.13±1.19 hours), sedentary behavior (10.7±1.9 hours), standing (3.2±1.1 hours), slow walking (1.6±0.6 hours), fast walking (1.1±0.5 hours), and exercise-like activity (16.0±16.3 minutes). More time spent exercising or sleeping, relative to other behaviors, was associated with lower BP. An additional 5 minutes of exercise-like activity was associated with estimated reductions of –0.68 mm Hg (95% CI, –0.15, –1.21) SBP and –0.54 mm Hg (95% CI, –0.19, 0.89) DBP. Clinically meaningful improvements in SBP and DBP were estimated after 20 to 27 minutes and 10 to 15 minutes of reallocation of time in other behaviors into additional exercise. Although more time spent being sedentary was adversely associated with SBP and DBP, there was minimal impact of standing or walking. CONCLUSIONS: Study findings reiterate the importance of exercise for BP control, suggesting that small additional amounts of exercise are associated with lower BP in a free-living setting.