Lateral Diffusion Research Articles

Deep inflow transport and dispersion in the Gulf of St. Lawrence revealed by a tracer release experiment

The Gulf of St. Lawrence is increasingly affected by bottom water hypoxia; however, the timescales and pathways of deep water transport remain unclear. Here, we present results from the Deep Tracer Release eXperiment (TReX Deep), during which an inert SF5CF3 tracer was released inshore of Cabot Strait at 279 m depth to investigate deep inflow transport and mixing rates. Dispersion was also assessed via neutrally-buoyant Swish floats. Our findings indicate that the tracer moves inland at 0.5 cm s−1, with an effective lateral diffusivity of 2 × 102 m2 s−1 over 1 year. Simplified 1D simulations suggest inflow water should reach the estuary head in 1.7 years, with the bulk arriving after 4.7 years. Basin-wide effective vertical diffusivity is around 10−5 m2 s−1 over 1 year; however, vertical diffusivity increases near the basin slopes, suggesting that turbulent boundary processes influence mixing. These results are compared to Lagrangian simulations in a regional 3D model to evaluate the capacity to model dispersion in the Gulf.

Film cooling performances of short fan-shaped-holes under oscillating freestream

Freestream oscillation presents a significant challenge in optimized design of short fan-shaped-hole, a good choice for more promising double-wall cooled blades. An experimental investigation was conducted to understand detailed effects of key geometrical parameters of the fan-shaped hole, freestream oscillating frequency and cooling air-to-mainstream blowing ratio on the unstable film cooling performances. The selected geometrical parameters included the length-to-diameter ratio, the lateral diffusion angle, and the length ratio of cylindrical section-to-diffusion section. Time-resolved planar quantitative light sheet technique was employed to visualize the temporal variations of jet trajectory and transported scalar concentrations. The experimental results indicated that freestream oscillation causes variations in jet mechanisms, changing the trend in film cooling with blowing ratio and reversing the universally-acknowledged harmful influence of non-fully development of cooling air in short tube. The optimized short-hole can achieve an increment up to 40% in film effectiveness under oscillating freestream, in comparison with the long-hole-jet. The primary principle of the optimized design of short shaped-hole is properly enlarging the lateral expansion angle, aiming at the higher steady film effectiveness while the lower unsteadiness due to the transient fluctuations. Further enlarging the length ratio can improve the stability of film cooling in an oscillating cycle.

Impact of Al Alloying/Doping on the Performance Optimization of HfO2-Based RRAM

Al alloying/doping in HfO2-based resistive random-access memory (RRAM) has been proven to be an effective method for improving the low-resistance state (LRS) retention. However, a detailed understanding of Al concentration on oxygen vacancy migration and resistive switching (RS) behaviors still needs to be included. Herein, the impact of Al concentration on the RS properties of the TiN/Ti/HfAlO/TiN RRAM devices is addressed. Firstly, it is found that the forming voltage, SET voltage, and RESET voltage can be regulated by varying the Al doping concentration. Moreover, we have demonstrated that the device with 15% Al shows the minimum cycle-to-cycle variability (CCV) and superior endurance (over 106). According to density-functional theory (DFT) calculations, it is found that the increased operation voltage, improved uniformity, and improved endurance are attributed to the elevated migration barrier of oxygen vacancy through Al doping. In addition, LRS retention characteristics of the TiN/Ti/HfAlO/TiN devices with different Al concentrations are compared. It is observed that the LRS retention is greatly enhanced due to the suppressed lateral diffusion process of oxygen vacancy through Al doping. This study demonstrates that Al alloying/doping greatly affects the RS behaviors of HfO2-based RRAM and provides a feasible way to improve the RS properties through changing the Al concentration.

Poly(Sitosterol)-Based Hydrophobic Blocks in Amphiphilic Block Copolymers for the Assembly of Hybrid Vesicles.

Amphiphilic block copolymer and lipids can be assembled into hybrid vesicles (HVs), which are an alternative to liposomes and polymersomes. Block copolymers that have either poly(sitostryl methacrylate) or statistical copolymers of sitosteryl methacrylate and butyl methacrylate as the hydrophobic part and a poly(carboxyethyl acrylate) hydrophilic segment are synthesized and characterized. These block copolymers assemble into small HVs with soybean L-α-phosphatidylcholine (soyPC), confirmed by electron microscopy and small-angle X-ray scattering. The membrane's hybrid nature is illustrated by fluorescence resonance energy transfer between labeled building blocks. The membrane packing, derived from spectra when using Laurdan as an environmentally sensitive fluorescent probe, is comparable between small HVs and the corresponding liposomes with molecular sitosterol, although the former show indications of transmembrane asymmetry. Giant HVs with homogenous distribution of the block copolymers and soyPC in their membranes are assembled using the electroformation method. The lateral diffusion of both building blocks is slowed down in giant HVs with higher block copolymer content, but their permeability toward (6)-carboxy-X-rhodamine is higher compared to giant vesicles made of soyPC and molecular sitosterol. This fundamental effort contributes to the rapidly expanding understanding of the integration of natural membrane constituents with designed synthetic compounds to form hybrid membranes.

Numerical investigation of mesoscale multiphase mass transport mechanism in fibrous porous media

At present, the proton exchange membrane fuel cell (PEMFC) is one of the most promising new energy solutions. The structure and material properties of the gas diffusion layer (GDL) are important factors that restrict the efficient water management and structural stability of PEMFCs. The complex mesoscopic fibrous porous structure of the GDL results in complex multiphase flow dynamics problems that have highly nonlinear characteristics. It is difficult to describe the details of mesoscopic multiphase coupled transport dynamics and numerically solve problems in which there is a two-phase flow with a high-density ratio. To solve these problems, a mesoscopic multiphase coupled transport model based on a lattice Boltzmann method and volume-of-fluid (LBM-VOF) model is proposed. Moreover, we also discuss the mechanism of the interaction between the fibrous porous structure and internal multiphase flow. The results obtained illustrate that the proposed method can obtain dynamic details of the flow field for fibrous porous media. The surface wettability of fibres strongly influences both the distribution and stability of liquid water clusters within porous materials. Concurrently, the fibre diameter assumes a pivotal role in governing lateral water diffusion and exclusion efficiency. This work lays a foundation for efficient water and thermal management of PEMFCs.

The effect of skin diffusion kinetics of isopropyl ester permeation enhancers on drug permeation: Role of lateral spread and penetration characteristics

The purpose of present work was to study the effects of permeation enhancers’ two kinetic behaviors of simultaneous lateral diffusion and vertical penetration in the skin on its enhancing effect. The skin diffusion kinetics of isopropyl ester permeation enhancers were characterized by the innovative concentric tape peeling study and Raman imaging, which were quantitatively assessed through innovative parameters, namely, lateral-to-vertical penetration amount (CL-V) and lateral-to-vertical penetration distance (DL-V). The enhancement effect of permeation enhancers on drug flurbiprofen (FLU) was assessed by in vitro skin permeation tests, which were confirmed by transdermal water loss and skin resistance study. The relationship between kinetic parameters of permeation enhancers and permeation parameters of FLU was carried out by correlation analysis. The molecular mechanisms of effect of skin diffusion kinetics of permeation enhancers on drug permeation were characterized by molecular docking, modulated-temperature differential scanning calorimetry (MTDSC), Raman spectra, solid-state NMR and molecular dynamic simulation. The results indicated skin diffusion kinetics of short-chain (C8–C12) isopropyl ester permeation enhancers were governed by vertical penetration, while long-chain (C14–C18) ones were characterized by lateral spread. Quadratic correlation between CL-V and enhancement ratio of permeation-retention ratio of FLU (ERQ/R) (R2 = 0.95), DL-V and enhancement ratio of permeation area (ERA) of FLU (R2 = 0.98) indicating that varied skin diffusion kinetics of permeation enhancers directly influenced the barrier function of stratum corneum (SC) and further enhancing drug permeation. In terms of molecular mechanism, long-chain isopropyl ester enhancers had good miscibility with SC, leading to their high CL-V and DL-V, and causing strong interaction strength with SC and resulting in weaker skin barrier function for drug permeation. In summary, in comparison to short-chain isopropyl ester enhancers that relied on penetration, long-chain ones that depended on lateral spread exhibited greater enhancement efficacy, which guided the application of enhancers in transdermal formulations.

UV-B Radiation Disrupts Membrane Lipid Organization and Suppresses Protein Mobility of GmNARK in Arabidopsis.

While it is well known that plants interpret UV-B as an environmental cue and a potential stressor influencing their growth and development, the specific effects of UV-B-induced oxidative stress on the dynamics of membrane lipids and proteins remain underexplored. Here, we demonstrate that UV-B exposure notably increases the formation of ordered lipid domains on the plasma membrane (PM) and significantly alters the behavior of the Glycine max nodule autoregulation receptor kinase (GmNARK) protein in Arabidopsis leaves. The GmNARK protein was located on the PM and accumulated as small particles in the cytoplasm. We found that UV-B irradiation interrupted the lateral diffusion of GmNARK proteins on the PM. Furthermore, UV-B light decreases the efficiency of surface molecule internalization by clathrin-mediated endocytosis (CME). In brief, UV-B irradiation increased the proportion of the ordered lipid phase and disrupted clathrin-dependent endocytosis; thus, the endocytic trafficking and lateral mobility of GmNARK protein on the plasma membrane are crucial for nodule formation tuning. Our results revealed a novel role of low-intensity UV-B stress in altering the organization of the plasma membrane and the dynamics of membrane-associated proteins.

P‐22: Fabrication of Ultra Short Channel Oxide Thin Film Transistors

By utilizing flat display panel manufacturing equipment and innovative techniques, we have successfully developed short channel Top‐gate amorphous InGaZnO4 thin‐film transistors (TG a‐IGZO TFTs) at Gen4.5. Despite the challenge of facing issues with the lateral diffusion of hydrogen during process and short channel effects, we managed to optimize the uniformity and drain‐induced barrier lowering with the novel structure of TFTs. After optimizing the device structure, we have achieved short channel TFTs with channel length of 1.3um, Vth of ‐ 0.03V, mobility of 9.77 cm2 /Vs, and DIBL of 29mV/V, and successfully make a demo of 7.1inch miniLED with the ultra short channel TFTs.

Exploring the Fundamental Spatial Limits of Magnetic All-Optical Switching.

All-optical switching (AOS) results in ultrafast and deterministic magnetization reversal upon single laser pulse excitation, potentially supporting faster and more energy-efficient data storage. To explore the fundamental limits of achievable bit densities in AOS, we have used soft X-ray transient grating spectroscopy to study the ultrafast magnetic response of a GdFe alloy after a spatially structured excitation with a periodicity of 17 nm. The ultrafast spatial evolution of the magnetization in combination with atomistic spin dynamics and microscopic temperature model calculations allows us to derive a detailed phase diagram of AOS as a function of both the absorbed energy density and the nanoscale excitation period. Our results suggest that the minimum size for AOS in GdFe alloys, induced by a nanoscale periodic excitation, is around 25 nm and that this limit is governed by ultrafast lateral electron diffusion and by the threshold for optical damage.

Hairpin protein partitioning from the ER to lipid droplets involves major structural rearrangements.

Lipid droplet (LD) function relies on proteins partitioning between the endoplasmic reticulum (ER) phospholipid bilayer and the LD monolayer membrane to control cellular adaptation to metabolic changes. It has been proposed that these hairpin proteins integrate into both membranes in a similar monotopic topology, enabling their passive lateral diffusion during LD emergence at the ER. Here, we combine biochemical solvent-accessibility assays, electron paramagnetic resonance spectroscopy and intra-molecular crosslinking experiments with molecular dynamics simulations, and determine distinct intramembrane positionings of the ER/LD protein UBXD8 in ER bilayer and LD monolayer membranes. UBXD8 is deeply inserted into the ER bilayer with a V-shaped topology and adopts an open-shallow conformation in the LD monolayer. Major structural rearrangements are required to enable ER-to-LD partitioning. Free energy calculations suggest that such structural transition is unlikely spontaneous, indicating that ER-to-LD protein partitioning relies on more complex mechanisms than anticipated and providing regulatory means for this trans-organelle protein trafficking.

Cryptotanshinone-Induced Permeabilization of Model Phospholipid Membranes: A Biophysical Study.

The Danshen terpenoid cryptotanshinone (CPT) is gaining enormous interest in light of its various outstanding biological activities. Among those, CPT has been shown to interact with cell membranes and, for instance, to have antibacterial activity. Several works have shown that CPT alone, or in combination with other drugs, can effectively act as an antibiotic against various infectious bacteria. Some authors have related the mechanism underlying this action to CPT-membrane interaction. This work shows that CPT readily partitions into phosphatidylcholine membranes, but there is a limiting capacity of accommodation of ca. 1 mol CPT to 3 mol phospholipid. The addition of CPT to unilamellar liposomes composed of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) causes membrane permeabilization, as shown by fluorescent probe leakage. This process has been kinetically studied, as well as its modulation by incorporation of phosphatidylethanolamine or phosphatidylglycerol, as a model for pathogenic cell membranes. The thermotropic behavior of 1,2-dimyristoylphosphatidylcholine (DMPC) model membranes is weakly affected by CPT, but the terpenoid causes significant dehydration of the polar region of the bilayer and weak disordering of the acyl chain palisade, as observed in Fourier-transform infrared spectroscopy (FTIR) results. Small-angle X-ray scattering (SAXS) shows that CPT increases DMPC bilayer thickness, which could be due to localization near the phospholipid/water interface. Molecular dynamics (MD) simulations show that the lateral diffusion coefficient of the phospholipid increases with the presence of CPT. CPT extends from the polar head region to the center of the bilayer, being centered between the carbonyl groups and the unsaturated region of the POPC, where there is greater overlap. Interestingly, the free energy profiles of a water molecule crossing the lipid membrane show that the POPC membrane becomes more permeable in the presence of CPT. In summary, our results show that CPT perturbs the physicochemical properties of the phospholipid membrane and compromises its barrier function, which could be of relevance to explain part of its antimicrobial or anticancer activities.

Supported Biomembrane Systems Incorporating Multiarm Polymers and Bioorthogonal Tethering.

To functionalize interfaces with supported biomembranes and membrane proteins, the challenge is to build stabilized and supported systems that mimic the native lipid microenvironment. Our objective is to control substrate-to-biomembrane spacing and the tethering chemistry so proteoliposomes can be fused and conjugated without perturbation of membrane protein function. Furthermore, the substrates need to exhibit low protein and antibody nonspecific binding to use these systems in assays. We have employed protein orthogonal coupling schemes in concert with multiarm poly(ethylene glycol) (PEG) technology to build supported biomembranes on microspheres. The lipid bilayer structures and tailored substrates of the microsphere-supported biomembranes were analyzed via flow cytometry, confocal fluorescence, and super-resolution imaging microscopy, and the lateral fluidity was quantified using fluorescence recovery after photobleaching (FRAP) techniques. Under these conditions, the 4-arm-PEG20,000-NH2 based configuration gave the most desirable tethering system based on lateral diffusivity and coverage.

A numerical investigation on the influence of trench holes upon the film cooling effectiveness of hydrogen- and ammonia-enriched gas turbine vanes

Hydrogen- or ammonia-enriched gas turbines are gaining increased attention for their environmentally friendly operation. To comprehend the effect of low-carbon fuels on vane cooling, this study employs numerical simulations to investigate for the first time the film cooling performance of a C3X turbine vane under hydrogen or ammonia combustion, with the mainstream water vapor content (MWVC) ranging from 0% to 100%. The simulations are conducted with the SST γ-θ transition model in the commercial software Ansys CFX. The results reveal a tendency of decreasing cooling effectiveness with increasing MWVC. However, serrated trench exhibits an effective guiding effect, thus enhancing the coolant lateral diffusion. Additionally, the serrated trench design minimizes the risk of coolant separation from the wall. The simulations indicate that the serrated trench significantly mitigates the decline in film cooling effectiveness caused by the MWVC increment, resulting in a noteworthy enhancement of cooling effectiveness by 122.49% to 193.54% over conventional cylindrical film holes. This study represents a preliminary exploration of turbine vane cooling for hydrogen- or ammonia- enriched gas turbines, establishing a foundation for subsequent turbine vane film cooling structure design. Its significance lies in facilitating the efficient operation of these turbines towards achieving zero-carbon emission targets and advancing innovative green technologies.

Multifaceted Activity of Fabimycin: Insights from Molecular Dynamics Studies on Bacterial Membrane Models.

Membranes─cells' essential scaffolds─are valid molecular targets for substances with an antimicrobial effect. While certain substances, such as octenidine, have been developed to target membranes for antimicrobial purposes, the recently reported molecule, fabimycin (F2B)─a novel agent targeting drug-resistant Gram-negative bacteria─has not received adequate attention regarding its activity on membranes in the literature. The following study aims to investigate the effects of F2B on different bacterial membrane models, including simple planar bilayers and more complex bilayer systems that mimic the Escherichia coli shell equipped with double inner and outer bilayers. Our results show that F2B exhibited more pronounced interactions with bacterial membrane systems compared to the control PC system. Furthermore, we observed significant changes in local membrane property homeostasis in both the inner and outer membrane models, specifically in the case of lateral diffusion, membrane thickness, and membrane resilience (compressibility, tilt). Finally, our results showed that the effect of F2B differed in a complex system and a single membrane system. Our study provides new insights into the multifaceted activity of F2B, demonstrating its potential to disrupt bacterial membrane homeostasis, indicating that its activity extends the currently known mechanism of FabI enzyme inhibition. This disruption, coupled with the ability of F2B to penetrate the outer membrane layers, sheds new light on the behavior of this antimicrobial molecule. This highlights the importance of the interaction with the membrane, crucial in combating bacterial infections, particularly those caused by drug-resistant strains.

Assessing Modeled Mesoscale Stirring Using Microscale Observations

Abstract We assess the representation of mesoscale stirring in a suite of models against an estimate derived from microstructure data collected during the North Atlantic Tracer Release Experiment (NATRE). We draw heavily from the approximate temperature variance budget framework of Ferrari and Polzin. This framework assumes two sources of temperature variance away from boundaries: first, the vertical stirring of the large-scale mean vertical gradient by small-scale turbulence; and second, the lateral stirring of large-scale mean along-isopycnal gradients by mesoscale eddies. Temperature variance so produced is transformed and on average transferred down scales for ultimate dissipation at the microscale at a rate χ estimated using microstructure observations. Ocean models represent these pathways by a vertical mixing parameterization, and an along-isopycnal lateral mixing parameterization (if needed). We assess the rate of variance production by the latter as a residual from the NATRE dataset and compare against the parameterized representations in a suite of model simulations. We find that variance production due to lateral stirring in a Parallel Ocean Program version 2 (POP2) 1/10° simulation agrees well, to within the estimated error bars, with that inferred from the NATRE estimate. A POP2 1° simulation and the Estimating the Circulation and Climate of the Ocean Version 4 release 4 (ECCOV4r4) simulation appear to dissipate an order of magnitude too much variance by applying a lateral diffusivity, when compared to the NATRE estimate, particularly below 1250 m. The ECCOV4r4-adjusted lateral diffusivities are elevated where the microstructure suggests elevated χ sourced from mesoscale stirring. Such elevated values are absent in other diffusivity estimates suggesting the possibility of compensating errors and caution in interpreting ECCOV4r4’s adjusted lateral diffusivities. Significance Statement We look at whether microstructure turbulence observations can provide a useful metric for judging the fidelity of representation of mesoscale stirring in a suite of models. We focus on the region of the North Atlantic Tracer Release Experiment (NATRE), the site of a major ocean turbulence observation campaign, and use an approximate variance budget framework for the region with observational estimates from Ferrari and Polzin (2005). The approach provides a novel framework to evaluate the approximate representation of mesoscale stirring in a variety of models.

Manufacturing process of liposomal Formation: A coarse-grained molecular dynamics simulation

A method of producing liposomes has been previously developed using a continuous manufacturing technology that involves a co-axial turbulent jet in co-flow. In this study, coarse-grained molecular dynamics (CG-MD) simulations were used to gain a deeper understanding of how the self-assembly process of liposomes is affected by the material attributes (such as the concentration of ethanol) and the process parameters (such as temperature), while also providing detailed information on a nano-scale molecular level. Specifically, the CG-MD simulations yield a comprehensive internal view of the structure and formation mechanisms of liposomes containing DPPC, DPPG, and cholesterol molecules. The importance of this work is that structural details on the molecular level are proposed, and such detail is not possible to obtain through experimental studies alone. The assessment of structural properties, including the area per lipid, diffusion coefficient, and order parameters, indicated that a thicker bilayer was observed at higher ethanol concentrations, while a thinner bilayer was present at higher temperatures. These conditions led to more water penetrating the interior of the bilayer and an unstable structure, as indicated by a larger contact area between lipids and water, and a higher coefficient of lipid lateral diffusion. However, stable liposomes were found through these evaluations at lower ethanol concentrations and/or lower process temperatures. Furthermore, the CG-MD model was further compared and validated with experimental and computational data including liposomal bilayer thickness and area per lipid measurements.

Asymptotic analysis of particle cluster formation in the presence of anchoring sites

The aggregation or clustering of proteins and other macromolecules plays an important role in the formation of large-scale molecular assemblies within cell membranes. Examples of such assemblies include lipid rafts, and postsynaptic domains (PSDs) at excitatory and inhibitory synapses in neurons. PSDs are rich in scaffolding proteins that can transiently trap transmembrane neurotransmitter receptors, thus localizing them at specific spatial positions. Hence, PSDs play a key role in determining the strength of synaptic connections and their regulation during learning and memory. Recently, a two-dimensional (2D) diffusion-mediated aggregation model of PSD formation has been developed in which the spatial locations of the clusters are determined by a set of fixed anchoring sites. The system is kept out of equilibrium by the recycling of particles between the cell membrane and interior. This results in a stationary distribution consisting of multiple clusters, whose average size can be determined using an effective mean-field description of the particle concentration around each anchored cluster. In this paper, we derive corrections to the mean-field approximation by applying the theory of diffusion in singularly perturbed domains. The latter is a powerful analytical method for solving two-dimensional (2D) and three-dimensional (3D) diffusion problems in domains where small holes or perforations have been removed from the interior. Applications range from modeling intracellular diffusion, where interior holes could represent subcellular structures such as organelles or biological condensates, to tracking the spread of chemical pollutants or heat from localized sources. In this paper, we take the bounded domain to be the cell membrane and the holes to represent anchored clusters. The analysis proceeds by partitioning the membrane into a set of inner regions around each cluster, and an outer region where mean-field interactions occur. Asymptotically matching the inner and outer stationary solutions generates an asymptotic expansion of the particle concentration, which includes higher-order corrections to mean-field theory that depend on the positions of the clusters and the boundary of the domain. Motivated by a recent study of light-activated protein oligomerization in cells, we also develop the analogous theory for cluster formation in a three-dimensional (3D) domain. The details of the asymptotic analysis differ from the 2D case due to the contrasting singularity structure of 2D and 3D Green’s functions.Graphical abstract2D model of diffusion-based protein cluster formation in the presence of anchoring cites and particle recycling. a A set of N anchoring sites at positions xj\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ extbf{x}}_j$$\\end{document}, j=1,…,N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$j=1,\\ldots ,N$$\\end{document}, in a bounded domain Ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega $$\\end{document}. b Diffusing particles accumulate at the anchoring sites resulting in the formation of particle aggregates or clusters Uj\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\mathcal {U}}}_j$$\\end{document}. c The clusters are dynamically maintained by a combination of lateral diffusion outside the clusters and particle recycling

Dynamic structure of E. coli cytoplasm: supramolecular complexes and cell aging impact spatial distribution and mobility of proteins

Protein diffusion is a critical factor governing the functioning and organization of a cell’s cytoplasm. In this study, we investigate the influence of (poly)ribosome distribution, cell aging, protein aggregation, and biomolecular condensate formation on protein mobility within the E. coli cytoplasm. We employ nanoscale single-molecule displacement mapping (SMdM) to determine the spatial distribution of the proteins and to meticulously track their diffusion. We show that the distribution of polysomes does not impact the lateral diffusion coefficients of proteins. However, the degradation of mRNA induced by rifampicin treatment leads to an increase in protein mobility within the cytoplasm. Additionally, we establish a significant correlation between cell aging, the asymmetric localization of protein aggregates and reduced diffusion coefficients at the cell poles. Notably, we observe variations in the hindrance of diffusion at the poles and the central nucleoid region for small and large proteins, and we reveal differences between the old and new pole of the cell. Collectively, our research highlights cellular processes and mechanisms responsible for spatially organizing the bacterial cytoplasm into domains with different structural features and apparent viscosity.

Nonstereotypical Distribution and Effect of Ergosterol in Lipid Membranes.

Ergosterol, found in fungi and some protist membranes, is understudied compared with cholesterol from animal membranes. Generally, ergosterol is assumed to modulate membranes in the same manner as cholesterol, based on their similar chemical structures. Here we reveal some fundamental structural and dynamical differences between them. Neutron diffraction shows that ergosterol is embedded in the lipid bilayer much shallower than cholesterol. Ergosterol does not change the membrane thickness as much as cholesterol does, indicating little condensation effect. Neutron spin echo shows that ergosterol can rigidify and soften membranes at different concentrations. The lateral lipid diffusion measured by quasielastic neutron scattering indicates that ergosterol promotes a jump diffusion of the lipid, whereas cholesterol keeps the same continuous lateral diffusion as the pure lipid membrane. Our results point to quite distinct interactions of ergosterol with membranes compared with cholesterol. These insights provide a basic understanding of membranes containing ergosterol with implications for phenomena such as lipid rafts and drug interactions.

Strong Immunity to Drain-Induced Barrier Lowering in ALD-Grown Preferentially Oriented Indium Gallium Oxide Transistors.

Drain-induced barrier lowering (DIBL) is one of the most critical obstacles degrading the reliability of integrated circuits based on miniaturized transistors. Here, the effect of a crystallographic structure change in InGaO [indium gallium oxide (IGO)] thin-films on the DIBL was investigated. Preferentially oriented IGO (po-IGO) thin-film transistors (TFTs) have outstanding device performances with a field-effect mobility of 81.9 ± 1.3 cm2/(V s), a threshold voltage (VTH) of 0.07 ± 0.03 V, a subthreshold swing of 127 ± 2.0 mV/dec, and a current modulation ratio of (2.9 ± 0.2) × 1011. They also exhibit highly reliable electrical characteristics with a negligible VTH shift of +0.09 (-0.14) V under +2 (-2) MV/cm and 60 °C for 3600 s. More importantly, they reveal strong immunity to the DIBL of 17.5 ± 1.2 mV/V, while random polycrystalline In2O3 (rp-In2O3) and IGO (rp-IGO) TFTs show DIBL values of 197 ± 5.3 and 46.4 ± 1.2 mV/V, respectively. This is quite interesting because the rp- and po-IGO thin-films have the same cation composition ratio (In/Ga = 8:2). Given that the lateral diffusion of oxygen vacancies from the source/drain junction to the channel region via grain boundaries can reduce the effective length (Leff) of the oxide channel, this improved immunity could be attributed to suppressed lateral diffusion by preferential growth. In practice, the po-IGO TFTs have a longer Leff than the rp-In2O3 and -IGO TFTs even with the same patterned length. The effect of the crystallographic-structure-dependent Leff variation on the DIBL was corroborated by technological computer-aided design simulation. This work suggests that the atomic-layer-deposited po-IGO thin-film can be a promising candidate for next-generation electronic devices composed of the miniaturized oxide transistors.