Atomic Force Microscopy Images Research Articles

Chaperone-Mediated Heterotypic Phase Separation Prevents the Amyloid Formation of the Pathological Y145Stop Prion Protein Variant.

Biomolecular condensates formed via phase separation of proteins and nucleic acids are crucial for the spatiotemporal regulation of a diverse array of essential cellular functions and the maintenance of cellular homeostasis. However, aberrant liquid-to-solid phase transitions of such condensates are associated with several fatal human diseases. Such dynamic membraneless compartments can contain a range of molecular chaperones that can regulate the phase behavior of proteins involved in the formation of these biological condensates. Here, we show that a heat shock protein 40 (Hsp40), Ydj1, exhibits a holdase activity by potentiating the phase separation of a disease-associated stop codon mutant of the prion protein (Y145Stop) either by recruitment into Y145Stop condensates or via Y145Stop-Ydj1 two-component heterotypic phase separation that arrests the conformational conversion of Y145Stop into amyloid fibrils. Utilizing site-directed mutagenesis, multicolor fluorescence imaging, single-droplet steady-state and picosecond time-resolved fluorescence anisotropy, fluorescence recovery after photobleaching, and fluorescence correlation spectroscopy, we delineate the complex network of interactions that govern the heterotypic phase separation of Y145Stop and Ydj1. We also show that the properties of such heterotypic condensates can further be tuned by RNA that promotes the formation of multicomponent multiphasic protein-RNA condensates. Our vibrational Raman spectroscopy results in conjunction with atomic force microscopy imaging reveal that Ydj1 effectively redirects the self-assembly of Y145Stop towards a dynamically-arrested non-amyloidogenic pathway, preventing the formation of typical amyloid fibrils. Our findings underscore the importance of chaperone-mediated heterotypic phase separation in regulating aberrant phase transitions and amyloid formation associated with a wide range of deadly neurodegenerative diseases.

Controlled ligation and elongation of uniformly truncated amyloid nanofibrils.

This study investigates the production and inter-fibril interactions of uniformly truncated amyloid nanofibrils. By varying extrusion cycles (0, 50, and 100) and using carbonate filters with 100 nm and 200 nm pore sizes, precise fibril length control was achieved. Atomic force microscopy (AFM) confirmed that the mean length of the truncated fibrils corresponded to the respective pore size as extrusion cycles increased. AFM imaging combined with bicinchoninic acid assay analysis elucidated the mechanism underlying fibril truncation during extrusion. Subsequent incubation at 60 °C revealed that 200 nm-long fibrils assembled into denser structures than 100 nm-long fibrils, likely due to strain energy introduced during truncation, which appears to facilitate twisting during ligation and elongation between truncated fibrils. These findings advance understanding of the end-to-end elongation mechanisms of amyloid nanofibrils, shedding light on their structural dynamics and polymorphic properties.

Impurity-induced step pinning and recovery in MOVPE-grown (100) β-Ga2O3 film

This study focuses on the impact of high-doping impurities (>1018 cm−3) on the morphology of homoepitaxially grown (100) 4° off β-Ga2O3 film, as well as incorporating insights from the Cabrera–Vermilyea model (C–V model). Using atomic force microscopy imaging, we reveal that under low-supersaturation conditions, dopant-induced impurities lead to irregular step formation and growth stalling, inducing the step-bunching formation consistent with C–V model predictions. Conversely, higher supersaturation conditions restore desired step-flow morphology, resembling low-impurity growth states. It is also shown that the step-bunching formed under lower supersaturation conditions and high-impurity concentration might induce unwanted structural defects and compensate the free carriers. These findings underscore the delicate interplay between dopant concentrations, growth morphology, and supersaturation in metalorganic vapor phase epitaxy-grown (100) β-Ga2O3 films, providing a comprehensive understanding of optimizing their electrical properties with respect to power electronics applications.

Nano-viscosimetry analysis of membrane disrupting peptide magainin2 interactions with model membranes.

The rapid spread of antibiotic-resistant strains of bacteria has created an urgent need for new alternative antibiotic agents. Membrane disrupting antimicrobial peptides (AMPs): short amino acid sequences with bactericidal and fungicidal activity that kill pathogens by permeabilizing their plasma membrane may offer a solution for this global health crisis. Magainin 2 is an AMP secreted by the African clawed frog (Xenopus laevis) that is described as a toroidal pore former membrane disrupting AMP. Magainin 2 is one of the most thoroughly studied AMPs, yet its mechanism of action is still largely hypothetical: visual evidence of the pore formation is lacking, and the molecular mechanism leading to pore formation is still debated. In the present study, quartz crystal microbalance (QCM) based viscoelastic fingerprinting analysis supported by dye leakage experiments and atomic force microscopy (AFM) imaging was used to glean deeper insights into the mechanism of action. The effect of membrane charge, acyl chain unsaturation and cholesterol concentration were also investigated. The results show lipid specific disruptive mechanism of magainin 2. QCM nano-viscometry measurements revealed the presence of distinct stages in the mechanism of magainin 2 action that, with dye leakage data, confirm the existence of an initial transient pore stage that may result in peptide flip-flop between the outer and inner membrane leaflets. There is evidence of a further mechanistic stage at high peptide concentrations that is consistent with membrane collapse into a peptide-lipid mixed phase that is distinct from the transient pore formation. The results confirm some of the earliest hypotheses about magainin 2 action, while also highlighting the membrane modulating effect of this peptide.

A lifting-wavelet-based iterative thresholding correction for atomic force microscopy images with vertical distortion

A lifting-wavelet-based iterative thresholding correction for atomic force microscopy images with vertical distortion

Deep learning-based denoising for unbiased analysis of morphology and stiffness in amyloid fibrils.

Understanding the morphology of amyloid fibrils is crucial for comprehending the aggregation and degradation mechanisms of abnormal proteins implicated in various diseases, such as Alzheimer's disease, Parkinson's disease, type II diabetes, and various forms of amyloidosis. Atomic force microscopy (AFM) stands as the most representative method for studying amyloid fibril morphology. However, obstacles in AFM images, including noise, salt, and amorphous aggregates, often impede accurate sample quantification. In this study, we developed denoising software employing a U-Net deep learning architecture to address this issue. The software efficiently eliminated various impediments that interfere with fibril analysis in noisy AFM images, thereby facilitating precise quantification of amyloid fibrils. We also developed automated fibril analysis technologies using the denoised AFM images, leading to quicker, more precise, and more objective assessments of fibril morphology. Furthermore, we presented a method for fibril stiffness extraction from a modulus image through mask creation based on a denoised height image. Our approach secures time efficiency and precision in analyzing amyloid morphology, and we believe it will significantly advance the currently stagnant research on amyloid-related diseases.

Structural, Surface, and Optical Properties of Nitrogen-Doped Al:ZnO (NAZO) Thin Films Produced by a Thermionic Vacuum Arc Deposition Technology

Nitrogen (N)-doped Al:ZnO (NAZO) thin films were deposited on glass and indium tin oxide (ITO) coated glass by a thermionic vacuum arc (TVA) technique. The structural, surface morphology, and optical properties of the produced thin films were characterized by X-ray diffractometry (XRD), atomic force microscopy (AFM), and ultraviolet-visible spectroscopy. The microstructure properties of the produced thin films on two substrates were compared, and metal oxide phases were observed in the XRD patterns and photoluminescence spectra. 2.75, 3.10, and 3.30 eV band gaps were detected. The transmittance values were approximately 90% and 60% for the film deposited onto uncoated and ITO-coated glass, respectively. According to field-emission scanning electron microscopy and atomic force microscopy images, the crystallite size is nanoscale, and its dimensions are approximately 60 and 20 nm for the film deposited onto uncoated and ITO-coated glass substrates, respectively. Atomic ratios of zinc/aluminum were 9.25/0.56, and 5.42/0.22 for uncoated and ITO-coated glass substrate, respectively. All samples were coated with the same coating process, and no post-annealing process was applied to the sample.

Comprehensive characterization of tobacco-induced changes in enamel surface topography.

Enamel translucency, essential for the aesthetic appeal of teeth, is primarily determined by its thickness, quality, and refractive index. Several factors, including age, genetics, diet, oral hygiene practices, fluoride exposure, and acidic challenges, can influence enamel translucency. Tobacco use, in particular, leads to significant alterations in enamel appearance by penetrating its micropores, causing yellowing and browning. Prolonged exposure to tobacco results in demineralization, increasing enamel porosity and reducing its translucency. Over time, this exposure leads to permanent discoloration and structural degradation, rendering teeth dull and opaque. To assess these changes, various methods such as visual examinations, digital photography, spectrophotometry, stylus profilometry, and atomic force microscopy (AFM) are utilized. This study analyzed human enamel samples, including one unstained sample (Grade 0) and three tobacco-stained samples (Grades 1-3) according to Modified Lobene Stain Index (MLSI), to investigate the impact of tobacco exposure on enamel structure. The samples were thoroughly cleaned and dried to ensure accurate results. High-resolution AFM imaging was employed to assess surface roughness, porosity, and microstructural changes induced by tobacco staining. A stylus profilometer was used to trace the surface topography, providing detailed measurements of surface irregularities. Additionally, a spectrophotometer was utilized to evaluate the optical properties of the enamel, focusing on changes in translucency and light absorption due to tobacco exposure. AFM analysis revealed a clear progression of enamel surface roughness from Grade 0 to Grade 3. The Sa and Sq values increased significantly with the severity of tobacco staining, indicating greater surface degradation. The stylus profilometer data corroborated these findings, with rising Ra values as the degree of staining intensified, highlighting the topographical alterations caused by tobacco exposure. Spectrophotometric analysis further demonstrated a decrease in enamel reflectance and an increase in light absorption from mild to severe staining, underscoring the detrimental optical effects of tobacco on enamel. The combined use of AFM, stylus profilometry, and spectrophotometry provided a comprehensive assessment of the impact of tobacco staining on enamel translucency and surface roughness. The findings show that as staining severity increases, enamel translucency diminishes, and surface roughness worsens. These alterations not only affect the aesthetic appearance of teeth but also have potential implications for enamel functionality and long-term oral health.

Synergistic effect and mechanism of ferric ion modified citric acid depressant in the flotation separation of scheelite from cassiterite

Scheelite and cassiterite often coexist in skarn deposits, which are prone to excessive crushing during dissociation, and gravity separation faces a challenge. However, research on flotation separation is limited. This study aimed to investigate the selective depression behavior and depression mechanism of a combined depressant containing ferric chloride and citric acid on cassiterite to successfully achieve the flotation separation of scheelite and cassiterite. Experimental studies on single minerals and artificially mixed minerals indicated that the individual ferric chloride or citric acid exhibited weak depressive abilities and poor selectivity toward cassiterite. However, a combination of ferric chloride and citric acid in a mass ratio of 3:7 achieved better separation results. At a pH of 8, with a concentration of 1 × 10–3 mol/L mixed depressant, and a sodium oleate concentration of 5 × 10–5 mol/L, scheelite and cassiterite exhibited recovery of 73.35 % and 19.98 %, with grades of 61.76 % and 16.18 %, respectively. Fourier–transform infrared spectroscopy and X–ray photoelectron spectroscopy analyses revealed that the mixed depressant strongly chemically adsorbed on the cassiterite surface, forming FeOOH at ferric species sites. Contact angle measurements indicated a significant reduction in surface hydrophobicity of the cassiterite surface due to mixed depressant components. Atomic force microscopy imaging analysis elucidated the adsorption morphology of the mixed depressant depressive component FeOOH on the cassiterite surface in both 2D and 3D imaging, indicating abundant high–intensity reagent peak adsorption. Therefore, the mixed depressant enhanced the selectivity of the depressant, facilitating the effective separation of scheelite and cassiterite.

P-type doping in edge-enriched MoS2-x nanostructures via RF-generated nitrogen plasma.

In this work, we report an intuitive magnetron sputtering technique for the synthesis of vertically aligned MoS2 (v-MS) nanostructures. The morphology and orientation of the as-synthesized nanostructures can be modified by altering the parameters of the sputtering process. This work emphasizes the versatility of magnetron sputtering to synthesize edge-enriched vertically aligned 2D nanostructures. These structures have diverse applications, such as those in optoelectronics, hydrogen evolution, sensing, energy storage and catalysis. The vertically aligned nanostructure of MoS2 was confirmed using the field emission scanning electron microscopy and Raman spectroscopy techniques. Furthermore, we studied the plasma-based nitrogen doping process with minimal damage for introducing nitrogen atoms into 2D nanomaterials. A plasma discharged into a nitrogen environment, assisted by a simple radio frequency (RF) power supply, was employed for p-type doping in v-MS. The successful doping of nitrogen was investigated by Raman spectroscopy and X-ray photoelectron spectroscopy. Atomic force microscopy images confirmed the little surface damage resulting from the nitrogen doping technique. The change in work function resulting from doping was examined by Kelvin probe force microscopy and ultraviolet photoelectron spectroscopy. Optical emission spectroscopy (OES) study revealed the role of nitrogen plasma ions in doping with minimal surface damaging. This work demonstrates the effective alteration of the work function of the MoS2 nanomaterial via plasma treatment.

Morphological approach to understanding mineral alteration and nanoparticle formation under alkaline conditions using granitic rock thin sections

The cement components in deep geological disposal facilities (DGFs) for spent nuclear fuel can increase groundwater pH, potentially altering minerals within natural barriers. Mineral (biotite, quartz, plagioclase, chlorite, and K-feldspar) dissolution and secondary-phase precipitation were investigated to provide visually integrated understanding of multifaceted processes. This study was based on the morphological features of granitic rock thin sections exposed to alkaline aqueous solutions (initial pH: pHo 9 and 13) using atomic force microscopy (AFM), micro-X-ray fluorescence, and scanning electron microscopy/energy-dispersive X-ray spectroscopy. Batch kinetic-alteration tests were conducted from 4 h to 20 d. The minerals exhibited more pronounced changes in surface roughness and Si release at pHo 13 than at pHo 9. Furthermore, precipitates were more abundant on the mineral surfaces at pHo 9 than at pHo 13. Fe (oxy)hydroxides and Al (oxy)hydroxides prevailed as precipitates at pHo 9, whereas Ca (oxy)hydroxides dominated at pHo 13 (pH ≥ 12.8). These findings indicate that the aqueous solutions were significantly involved in the formation of the secondary-phase precipitates. Interestingly, secondary-phase precipitates formed not only on the surface of mineral (i.e., biotite) providing constituent ions but also on the surfaces of adjacent minerals (i.e., quartz and plagioclase). Moreover, the possibility of a multistep process involving Al precursors for nucleation of gibbsite precipitates on the surface of K-feldspar at pHo 9 and colloidal particle formation through surface modification, often overlooked in mineral research, were identified via AFM image analysis. This methodological approach using rock thin sections can provide new visual insights regarding the dissolution–precipitation processes, including nucleation reactions, under conditions closely resembling the expected environmental settings within DGFs.

In Vitro Investigation of Novel Peptide Hydrogels for Enamel Remineralization.

This study investigates the microstructure of dental enamel following demineralization and re-mineralization processes, using DIAGNOdent scores and images obtained via scanning electron microscopy (SEM), atomic force microscopy (AFM), and microhardness (Vickers). The research evaluates the effects of two experimental hydrogels, Anti-Amelogenin isoform X (ABT260, S1) and Anti-Kallikrein L1 (K3014, S2), applied to demineralized enamel surfaces over periods of 14 and 21 days. The study involved 60 extracted teeth, free from cavities or other lesions, divided into four groups: a positive group (+), a negative group (-) and groups S1 and S2. The last three groups underwent demineralization with 37% phosphoric acid for 20 min. The negative group (-) was without remineralization treatment. The DIAGNOdent scores indicate that the S1 group treated with Anti-Amelogenin is more effective in remineralizing the enamel surface compared to the S2 group treated with Anti-Kallikrein. These findings were corroborated by SEM and AFM images, which revealed elongated hydroxyapatite (HAP) nanoparticles integrated into the demineralized structures. Demineralization reduced enamel microhardness to about 1/3 of a healthy one. Both tested hydrogels restored enamel hardness, with S1 being more effective than S2. Both peptides facilitated the interaction between the newly added minerals and residual protein binders on the enamel surface, thereby contributing to effective enamel restoration.

Sub-ablation-threshold light-induced modification of thin ruthenium layers detected using optical reflectance

In semiconductor device manufacturing, wafer materials may be exposed to intense light sources by optical metrology tools. The desired light fluence often needs to be maximized to levels just below the optical damage threshold of materials deposited on the wafer, such as ruthenium. We, therefore, investigate light-induced permanent structural changes to thin Ru films after exposure to single 400nm wavelength femtosecond pulses in the fluence regime before catastrophic damage. For fluences below that where full-ablation occurs, small optical increases in the reflectivity of up to 4% are observed in the aftermath with a weak probe beam. In this fluence regime, dark-field, scanning electron, and atomic force microscopy images reveal morphological changes such as top-level ablation, where only the top part of the ruthenium layer is ablated whereas the lower part still remains on the substrate, and nanovolcano formation. However, neither top-level ablation nor nanovolcano formation is responsible for the reflection increase. Instead, Electron Backscatter Diffraction reveals that in this low fluence regime where reflectivity increases, Ru grains melt and resolidify into larger grains, which is likely responsible for the observed reflectivity increases. This result is reminiscent of our earlier work on aluminum layers and it suggests that there may be more metals that display this behavior.

Quantitative Measurement of Interfacial Adhesion of CVD Grown Bilayer WS2 on Various Substrates.

The interfacial adhesion between transition metal dichalcogenides (TMDs) and the growth substrate significantly influences the employment of flakes in various applications. Most previous studies have focused on MoS2 and graphene, particularly their interaction with SiO2/Si substrates. In this work, the adhesion strength of CVD-grown bilayer WS2 is directly measured using the nano scratch technique on three different substrates-Sapphire, SiO2/Si, and fused quartz. The scratch test is performed using a Berkovich tip of ≈100nm radius, mounted to a 2D transducer, capable of measuring normal and lateral forces simultaneously. The critical load is calculated from the Atomic Force Microscopy (AFM) images. The critical load for delamination is lowest for the Sapphire substrate (10 µN) and highest for the SiO2/Si substrate (29 µN). MD simulation has also been performed, and the results agree with experimental observations. The pull-off force, an essential indicator for the easy removal and transfer of 2D materials, shows the least pull-off force of 2.56 nN for WS2 on sapphire and the highest, 2.83 nN, for WS2 on SiO2/Si.

Chitosan/TiO2/Rosmarinic Acid Bio-Nanocomposite Coatings: Characterization and Preparation

This study aimed to develop and characterize bio-nanocomposite coatings by incorporating titanium nanoparticles (TiO2 NPs) (30–50 nm) (10 mg/L), which have antimicrobial effects, and rosmarinic acid (RA) (0.005 mg/mL), which has strong antioxidant and antimicrobial activities, into the chitosan matrix using the solvent casting method. The prepared bio-nanocomposite coatings were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM-EDX), and atomic force microscopy (AFM). In the XRD analysis, the crystal structure of the bio-nanocomposite coating material was evaluated, but the absence of the expected TiO2 NPs diffraction peak in the coating containing TiO2 NPs was discussed in detail. The TiO2 NPs decreased the crystallinity, compared to the control film, while rosmarinic acid increased the order of the molecular matrix. FT-IR analysis showed the presences of O–H, C=O, and C–O bonds in the coating materials, and the changes in the positions and intensities of the bands observed in the FTIR spectra of the bio-nanocomposite coatings (CHT and CHTRA) proved that TiO2 NPs and RA were successfully integrated into the chitosan matrix. The broadening and flattening of the bands belonging to OH groups (3288–3356 cm−1) indicated that the hydrogen bonds in the chitosan matrix were strengthened during the formation of the bio-nanocomposite structure. The bands representing the C=O stretching vibrations at 1659 cm−1 (amide I) and the N–H bending vibrations at 1558 cm−1 (amide II) indicated protein-based features in the structure of chitosan and confirmed the existence of the bio-nanocomposite structure. The SEM-EDX analysis showed that TiO2 NPs were distributed homogeneously on the chitosan surface, but there was aggregation in places. The AFM images revealed that when TiO2 NPs and RA were added to the chitosan matrix, the surface topography became more homogeneous, and a topographic pattern was formed in the range of 0–20.4 nm. Therefore, it is concluded that these bio-nanocomposite coatings can be used in antimicrobial surfaces and food packaging areas and should be optimized with different antioxidant and nanoparticle combinations in the future.

INFLUENCE OF SPIRO-OMETAD FILM THICKNESS ON THE STRUCTURAL AND ELECTRICAL PROPERTIES OF PEROVSKITE SOLAR CELLS

This work investigates the effect of the hole transport layer (HTL) thickness of Spiro-OMeTAD on the electrical transport properties in perovskite solar cells (PSCs).Spiro-OMeTAD films were obtained by the spin-coating method at centrifuge rotation speedsfrom 2000 to 7000 rpm. The thickness and morphology of the Spiro-OMeTAD films were studied by atomic force microscopy (AFM). From the obtained AFM image data, an increase in the surface root mean square (rms) value is observed with decreasing film thickness. A decrease in film thickness leads to an increase in Energy gap (Eg)from 2.97 eV to 3.01 eV. We observe that at a layer thickness of 260 nm, the efficiency of the cells reaches its maximum value; further increasing the layer thickness reduces the efficiency. Analysis of the impedance spectra of PSCs showed that the optimal layer thickness reduces the HTL resistance and increases the recombination resistance at the perovskite/HTL interface, which increases the effective lifetime of charge carriers. Images of the surface and current distribution of Spiro-OMeTAD on the surface of the perovskite layer were studied.A non-uniform current distribution on the surface of the samples was revealed, the observed spots with high conductivity are interpreted as perovskite quantum dots, which have better photovoltaic characteristics.Keywords: Perovskite solar cells, hole transport layer,Spiro-OMeTAD, conductive-AFM, current-voltage characteristics, impedance measurements.1. Introduction In recent years, organic-inorganic perovskite solar cells have attracted much attention from the global scientific community. The unprecedented development of PSCs is driven by their high optical absorption coefficient, tunable bandgap, low cost, ease of fabrication, and great potential to achieve higher efficiency compared to c-Si solar cells [1–3].To increase the efficiency and stability of PSCs, work is being done to search and optimize the composition of all parts of the solar cell, not only the perovskite itself, but also theso-called transport layers. The hole-conducting transport layer plays an important role in the efficiency of charge transfer and extraction of photoexcited perovskite, HTL is important for power conversion efficiency (PCE) and stability in PSCs. Transportlayers typically consist of small organic molecules, polymers, or inorganic materials such as oxides. The energy level of the HTL material must coincide with the maximum

Melittin-Induced Structural Transformations in DMPG and DMPS Lipid Membranes: A Langmuir Monolayer and AFM Study.

In this study, we explore the interactions between melittin, a cationic antimicrobial peptide, and model lipid membranes composed of the negatively charged phospholipids 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) and 1,2-dimyristoyl-sn-glycero-3-phosphoserine (DMPS). Using the Langmuir monolayer technique and atomic force microscopy (AFM), we reveal novel insights into these interactions. Our key finding is the observation of the ripple phase in the DMPS bilayer on mica, a phenomenon not previously reported for negatively charged single bilayers. This discovery is significant given the critical role of phosphatidylserine (PS) in cancer biology and the potential of melittin as an anticancer agent. We also highlight the importance of subphase composition, as melittin interacts preferentially with lipids in the liquid-condensed phase; thus, selecting the appropriate subphase composition is crucial because it affects lipid behavior and consequently melittin interactions. Our results show that melittin incorporates into lipid monolayers in both liquid-expanded and liquid-condensed phases, enhancing membrane fluidity and disorder, but is expelled from DMPS in the solid phase. AFM imaging further reveals that melittin induces substantial structural changes in the DMPG membrane and forms the ripple phase in the DMPS bilayers. Despite these alterations, melittin does not cause pore formation or membrane rupture, suggesting strong electrostatic adsorption on the membrane surface that prevents penetration. These findings highlight the differential impacts of melittin on lipid monolayers and bilayers and underscore its potential for interacting with membranes without causing disruption.

Highly Air-Stable N-Doped Two-Dimensional Violet Phosphorus with Atomically Flat Surfaces.

Few-layer violet phosphorus (VP) shows excellent potential in optoelectronic applications due to its unique in-plane anisotropy and high mobility. However, the poor air stability of VP severely limits its practical applications. This article reports highly air-stable VP obtained by a two-step nitrogen plasma treatment where the nitrogen volume flow rate is controlled to coordinate physical etching and chemical doping. Specially, this plasma process can remove partial oxidations formed on the VP surface with barely etching to the intrinsic VP surface but efficiently incorporates nitrogen into VP, resulting in surface nitrogen-doped VP (N-VP) nanosheets with atomically smooth surfaces that exhibit excellent air stability. Atomic force microscopy images show that the N-VP nanosheet, nearing a monolayer thickness, maintained its surface morphology and flatness unchanged in ambient air for over 60 days. The improved stability of N-VP can be partly due to its atomically smooth surface, which reduces the number of active or oxidation sites. Further elucidation was made by density functional theory calculations, showing that this ultrastability may intrinsically be attributed to repairing P vacancies by N dopants. This research provides a feasible strategy for significantly enhancing the durability of VP.

Determining structures of RNA conformers using AFM and deep neural networks.

Much of the human genome is transcribed into RNAs1, many of which contain structural elements that are important for their function. Such RNA molecules-including those that are structured and well-folded2-are conformationally heterogeneous and flexible, which is a prerequisite for function3,4, but this limits the applicability of methods such as NMR, crystallography and cryo-electron microscopy for structure elucidation. Moreover, owing to the lack of a large RNA structure database, and no clear correlation between sequence and structure, approaches such as AlphaFold5 for protein structure prediction do not apply to RNA. Therefore, determining the structures of heterogeneous RNAs remains an unmet challenge. Here we report holistic RNA structure determination method using atomic force microscopy, unsupervised machine learning and deep neural networks (HORNET), a novel method for determining three-dimensional topological structures of RNA using atomic force microscopy images of individual molecules in solution. Owing to the high signal-to-noise ratio of atomic force microscopy, this method is ideal for capturing structures of large RNA molecules in distinct conformations. In addition to six benchmark cases, we demonstrate the utility of HORNET by determining multiple heterogeneous structures of RNase P RNA and the HIV-1 Rev response element (RRE) RNA. Thus, our method addresses one of the major challenges in determining heterogeneous structures of large and flexible RNA molecules, and contributes to the fundamental understanding of RNA structural biology.

Study on desorption mechanism and thermal stability of OTS coating as an anti‐relaxation material

AbstractThis research explores the desorption mechanism and thermal stability of octadecyltrichlorosilane (OTS, CH3(CH2)17SiCl3) coating on quartz slides and in alkali‐metal vapour cells. The morphological thermal‐changes, energy dissipation diversity, and anti‐relaxation characteristic of OTS coatings before and after exposure to Cs atoms by Fourier transform infrared spectroscopy, water contact angle measurement, atomic force microscopy imaging, collision energy dissipation analysis, and free induction decay of Cs atoms are measured systematically. The results show that the OTS coatings exhibit the best thermal stability under the specific process conditions, and the homogeneous and dense structure makes the adsorption of alkali‐metal atoms more stable, which effectively reduces surface energy dissipation and prolongs the relaxation time of Cs atoms. The study provides certain reference for efficient anti‐relaxation coating fabrication and coated cell application.