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PubMed2025

Purification and Ultramicroscopic Observation of the Influenza A Virus Ribonucleoprotein Complex.

Influenza A virus (IAV) has an eight-segmented, single-stranded, negative-sense viral genomic RNA (vRNA). Each vRNA strand associates with nucleoproteins and an RNA-dependent RNA polymerase complex to form a viral ribonucleoprotein (vRNP) complex. IAV vRNPs adopt a flexible double-helical configuration that varies in length. Although the transcription and replication of vRNA take place in the context of vRNPs, the precise structural conformation of vRNPs during RNA synthesis remains partially elucidated. To unravel the intricate ultrastructure of the vRNP, it is necessary to purify it while preserving its native functionality. Herein, we introduce a comprehensive protocol for the purification of IAV vRNPs using glycerol gradient ultracentrifugation. Furthermore, we provide a method for the high-speed atomic force microscopy observation of vRNPs during viral RNA synthesis.

Ribonucleoproteins↗

PubMed2026

Identification and characterization of a wet adhesive protein extracted from Dreissena bugensis, the freshwater quagga mussel.

Mechanisms of wet adhesion have evolved in several aquatic organisms over millions of years. Yet, the repertoire of synthetic biocompatible wet adhesive materials is still limited. The byssus is a well-studied proteinaceous bioadhesive structure utilized by several bivalves to support sessile lifestyles in turbulent conditions. The quagga mussel (Dreissena bugensis) is a freshwater byssate and a notorious invasive species in the Great Lakes region. To identify adhesive proteins in the quagga mussel byssus, we utilized quantitative proteomics and found several proteins enriched at the byssus-substrate interface. Among the identified proteins was the Dbfp7 protein family. Dbfp7 is a small, polymorphic, and mostly disordered protein that lacks significant amounts of 3,4-dihydroxyphenylalanine (DOPA), a modified amino acid found in several marine mussel byssal proteins. Atomic force microscopy nanomechanical mapping of Dbfp7 films demonstrates that this protein exhibits adhesive ability in aqueous conditions. While DOPA is critical for marine mussel adhesion, interfacial electrochemistry of freshwater adhesive plaques suggests that freshwater byssates circumvent catechol-based adhesion. The functional characterization of Dbfp7 as a freshwater mussel adhesive protein advances the understanding of fundamental requirements for biocompatible wet adhesion, a crucial step for the development of bioinspired wet adhesive materials, such as improved medical adhesives.

Animals↗

PubMed2026

Blood Plasma Analysis in Ovarian Cancer Patients Using an AFM/MS Approach: Effect of Sample Dilution on Proteome Depth.

Early detection of ovarian cancer remains challenging because of the lack of sensitive and reproducible blood-based biomarkers. A major challenge in plasma proteomics is the extremely wide dynamic range of protein concentrations, which prevents simultaneous detection of both high- and low abundance proteins and limits the identification of disease-associated signals. In this study, we applied a combined atomic force microscopy and mass spectrometry (AFM/MS) approach to investigate how sample dilution affects plasma proteome coverage and the detection of differences between healthy donors and patients with stage I and stage III ovarian cancer. Plasma samples were analyzed at two dilution levels (1:100 and 1:10,000). At 1:100 dilution, a total of 235 proteins were identified across all samples, representing the union of all replicates and groups. The reproducible CORE proteome comprised 169 proteins in the Healthy group, 183 in the Stage I group, and 193 in the Stage III group. Differential analysis revealed distinct, non-overlapping protein sets at each dilution level. At 1:100 dilution, most altered proteins were decreased in patients and corresponded to major plasma components, including complement proteins and protease inhibitors. At 1:10,000 dilution, most altered proteins were increased and were predominantly immunoglobulin-related proteins, along with complement regulatory components. These findings show that sample dilution determines which fraction of the plasma proteome is observable. Here, proteome depth refers to the total number of non-redundant proteins accessible within the analytical workflow. When CORE sets from all groups were combined, 216 proteins were identified at 1:100 and 149 at 1:10,000, with 133 shared between the two dilution conditions. The higher dilution contributed 16 additional CORE proteins not detected in the 1:100 CORE union, increasing the combined CORE set to 232 proteins. Thus, higher dilution alone did not increase proteome depth, but provided complementary protein identifications that increased cumulative proteome depth when both dilution conditions were considered together. This effect reflects dilution-dependent selectivity in the composition of the detectable protein subset.

Humans↗

PubMed2026

CONCR lncRNA organizes a 3'-end structural domain that engages DDX11 for DNA replication and sister chromatid cohesion.

CONCR (DDX11-AS1) is a long noncoding RNA (lncRNA) necessary for the establishment of sister chromatid cohesion. Despite its activity, whether it contains structural elements essential for its function remains unknown. We determined CONCR structural organization and its functional relevance by integrating selective 2'-hydroxyl acylation analyzed by primer extension and mutational profiling (SHAPE-MaP), atomic force microscopy (AFM), evolutionary analyses, cryo-electron microscopy (cryo-EM), and cellular genetic studies. We found that CONCR molecular topology is modular, with highly structured domains connected by flexible linkers. A large 3'-end domain is responsible for binding to DDX11 helicase, can trigger DDX11 ATPase activity, and is essential for proper DNA replication and sister chromatid cohesion. This 3' end comprises two helical arms connecting two multiway junctions with structural motifs conserved among all primate groups and required for DDX11 binding and sister chromatid cohesion. Our results highlight the critical role of RNA structure in CONCR function, with a highly structured 3'-end domain acting as a loading and activation platform for DDX11 helicase.

DEAD-box RNA Helicases↗

PubMed2026

Bridging-driven condensation by eukaryotic SMC complexes is a conserved feature of genome organization.

The Structural Maintenance of Chromosome (SMC) protein family plays a central role in higher-order genome organization through ATP-dependent DNA loop extrusion by cohesin and condensin and other processes. Whether these activities fully account for the complexity of chromosome architecture remains unknown. Here, we uncover a conserved ATP-independent mechanism of chromatin condensation by SMC complexes, occurring via biomolecular condensation. Using single-molecule fluorescence imaging, we show that a variety of SMCs form dynamic DNA-bound condensates that exhibit key features of biomolecular condensates, including droplet coalescence, fluorescence recovery after photobleaching, and rapid exchange with free SMC complexes. Atomic force microscopy analysis of human cohesin-DNA assemblies reveals DNA-length-dependent clustering, providing evidence for bridging-driven condensation. Analyses of in vivo super-resolution imaging and high-throughput chromosome conformation capture (Hi-C) data indicate that these condensates form chromatin-associated clusters with multi-loop structures. Together, our results establish that SMC complexes employ ATP-independent phase condensation as well as ATP-dependent activities to shape genome architecture. This work reveals a broadly conserved principle of chromosomal organization across eukaryotes.

Chromosomal Proteins, Non-Histone↗

PubMed2025

Reverse transcription progression and genome length regulate HIV-1 core elasticity and disassembly.

The structural and mechanical properties of the HIV-1 core are critical for successful infection, balancing stability for early replication and controlled disassembly for genome release. Recent studies have highlighted the role of core elasticity in nuclear entry, yet the molecular determinants regulating this property remain poorly understood. Here, atomic force microscopy (AFM) was used to investigate the relationship between reverse transcription progression, genome length, core elasticity, and disassembly. The results demonstrate that reverse transcription induces a gradual loss of elasticity, rendering the core increasingly brittle as DNA synthesis progresses. Cores containing shorter genomes remained highly elastic, whereas those with longer genomes exhibited increased brittleness, structural damage, and a higher degree of disassembly, after 4 hours of reverse transcription. Additionally, cores from an RNase H-deficient HIV-1 mutant retained high elasticity. These findings provide insight into the interplay between genome synthesis, core integrity, and nuclear entry, supporting a model in which reverse transcription-generated mechanical stress facilitates uncoating. Furthermore, early-stage reverse transcription preserved core elasticity, suggesting a temporal window for successful nuclear import before structural destabilization compromises infectivity.

HIV-1↗

PubMed2026

Physicochemical characterization of nanoparticles in highly diluted preparations and exploratory plasma proteomic correlates in an N-of-1 study.

The physicochemical properties of highly diluted homeopathic preparations remain insufficiently characterized. This study investigated particulate features of Kali carbonicum (K2CO3) at 50-millesimal potencies (LM4-LM7, ∼1:50,000 dilutions per step) and explored plasma proteomic changes in a placebo-controlled N-of-1 trial. Scanning electron microscopy showed larger particle size in Kali carbonicum (67.3 nm) than in the lactose control (47.5 nm) at LM4 in a descriptive comparison. Dynamic light scattering showed no significant differences in size, polydispersity, or zeta potential among Kali carbonicum, lactose control, and solvent blank, accounting for vial-level clustering. Atomic force microscopy showed more compact dendritic assemblies in Kali than in lactose controls, suggesting trituration influences self-organization. Raman spectroscopy of LM7 detected carbonate-associated bands absent in controls. Plasma proteomics identified six FDR-significant proteins during Kali exposure, including increased S100A9, with exploratory enrichment for inflammation, cytoskeletal, and motility terms. These findings are exploratory and do not imply causality.

Proteomics↗

PubMed2025

Nitrate modulates pectin metabolism and cell wall mechanics during cell expansion in Arabidopsis.

Nitrate is a key nutrient and one of the most important nitrogen sources for land plants. Besides its nutritional role, nitrate is a signal molecule that regulates plant gene expression, metabolism, physiology, growth, and development. In cotyledons and true leaves, nitrate promotes growth by inducing cell expansion. Plant cell expansion requires changes in the cell wall. However, there is scant information on the influence of nitrate on cell wall metabolism and properties during cell expansion and growth. Here, we demonstrate that nitrate availability modulates pectin metabolism, a major polysaccharide of the primary cell wall. Using colorimetric assays, immunohistochemistry, and confocal microscopy, we show that nitrate enhances methylesterified pectin during cotyledon cell expansion. This is achieved by increasing galacturonic acid (GalA) deposition as homogalacturonan (HG) and by decreasing global PME activity. We further show that this regulation is dependent on nitrate signaling pathway components, including NRT1.1 and NLP7. Pectin methylesterification state impacts the mechanical properties of the cell wall. We characterized cell wall elasticity changes during nitrate-induced expansion using atomic force microscopy (AFM) and automatic confocal microextensometry (ACME). We found that nitrate induces cell wall softening at both cellular and whole-tissue levels during this expansion process. Our results indicate pectin metabolism plays an important role in nitrate-induced cell expansion and cotyledon growth in Arabidopsis. We provide insights into the interplay between nitrate signaling, cell wall metabolism, and biomechanical properties for cell expansion. Our results contribute to our understanding of how plants sense and respond to environmental cues for growth.

Pectins↗

PubMed2025

Single-Cell Force Spectroscopy Uncovers Root Zone- and Bacteria-Specific Interactions.

Understanding root-bacteria interactions with plant growth-promoting rhizobacteria (PGPR) is key to developing effective biofertilizers for sustainable agriculture. We performed single-cell force spectroscopy using the atomic force microscope (AFM) to study the primary attachment of two PGPR, Bacillus velezensis and Pseudomonas defensor, to different regions of Arabidopsis thaliana roots. Force measurements with individual cells uncovered distinct attachment strategies by each strain, involving binding via micrometer-long polymers from both bacteria and root surfaces. Flagella differentially affected the binding interactions of each PGPR; their removal altered binding characteristics differently for each strain, highlighting the importance of flagella in early root colonization. Using silica beads to mimic the negatively charged bacteria, we demonstrated the influence of electrostatic forces on root-bacteria interactions. We also examined interactions with abiotic surfaces of varying surface energies, revealing the roles of hydrophilic and hydrophobic forces in initial binding. Our measurements show that differences in the physicochemical properties of bacteria and roots are responsible for variations in primary attachment strategies between PGPR strains and root regions. Parallel fluorescence measurements corroborated our AFM single-cell analysis. Overall, our results provide a nanoscale view of bacterial attachment to roots, offering key insights into how beneficial bacteria colonize roots, crucial for enhancing biofertilizer effectiveness.

Plant Roots↗

PubMed2025

DNA Nanostructure Self-Assembly in an Aqueous Ionic Liquid Solution with Enhanced Stability and Target Binding Affinity.

DNA nanostructure-enabled functional constructs have shown potential to improve healthcare outcomes by offering advanced disease diagnostic and therapeutic strategies. Translating this potential of DNA nanostructure-based constructs to real life applications relies on maintaining and enhancing the structural integrity and functions of the surface-anchored moieties. In this study, we explored the possibility of utilizing choline dihydrogen phosphate (CDHP) solution, an aqueous solution of ionic liquid, to assemble DNA nanostructures of different sizes and complexities with enhanced biostability and ligand binding affinity. We show successful formation of the DNA nanostructures in aqueous CDHP solution using gel electrophoresis, atomic force microscopy (AFM), and circular dichroism (CD). Biostability assays reveal that the aqueous CDHP solution may provide passive protection to DNA nanostructures against DNase I and human serum for up to 48 h. We also demonstrate that this enhanced biostability arises both from the structural conformation imparted during CDHP-mediated folding and from the presence of free CDHP ions in the solution. Notably, removal of free ions reduced the passive protection effect, but did not eliminate it, indicating the contribution of both folding and surrounding free ions. Using flow cytometry and surface plasmon resonance assays, we show that the presence of aqueous CDHP solution can enhance the binding of aptamer-functionalized DNA nanostructures to specific receptors on acute myeloid leukemia (AML) cells. Our strategy of using ionic liquid solution for one-pot preparation with enhanced stability and functionality offers a robust, simpler and faster alternative for DNA nanostructure-based constructs.

Ionic Liquids↗

PubMed2025

Nuclear rupture in confined cell migration triggers nuclear actin polymerization to limit chromatin leakage.

Upon cell migration in confined space, such as during cancer metastasis, mechanical forces from the extracellular matrix act onto the nucleus leading to nuclear envelope (NE) rupture, chromatin leakage and genomic instability. Here we found that during confined migration, NE rupture triggers dynamic nuclear F-actin formation dependent on the formins DIAPH1 and DIAPH3. We show that DIAPH3 dynamically and transiently relocates to the nucleus upon NE rupture. Interfering with DIAPH1/3 or with nuclear actin polymerization resulted in nuclear instability during confined migration. Notably, nuclear formin activity or actin assembly limit NE rupture-induced chromatin leakage. Similarly, silencing of Ataxia Telangiectasia and Rad3-related protein (ATR) reduced NE rupture-triggered nuclear F-actin assembly and increased chromatin leakage. Consistent with this, ATR promotes the phosphorylation of DIAPH3 at S1072 adjacent to its autoregulatory domain to promote nuclear actin polymerization. Using atomic force microscopy, we found that nuclear actin assembly or nuclear DIAPH3 activity promotes nuclear stiffness in an ATR-dependent manner. Thus, our study identifies an ATR-formin module that regulates nuclear mechanical properties through induction of intranuclear actin scaffolding.

Formins↗

PubMed2025

FACS-Proteomics strategy toward extracellular vesicles single-phenotype characterization in biological fluids: exploring the role of leukocyte-derived EVs in multiple sclerosis.

BACKGROUND: The isolation and proteomics characterization of extracellular vesicles (EVs) from body fluids is challenging due to their vast heterogeneity. We have recently demonstrated that Fluorescence-activated Cell Sorting (FACS) efficiently isolates the whole EV circulating compartment directly from untouched body fluids enabling a comprehensive EV proteomics analysis. RESULTS: Here, we characterized, for the first time, a single-phenotype EV subset by sorting leukocyte-derived EVs (Leuko EVs) from peripheral blood and tears of healthy volunteers. Using an optimized and patented staining protocol of the whole EV compartment we identified and excluded non-EV particles, debris and damaged EVs. We further isolated, using an anti-CD45 antibody, Leuko EVs (CD45+ EVs), reaching a high level of purity (> 90%). Purified Leuko EVs were characterized using atomic force microscopy, nanoparticle tracking, and shotgun proteomics analysis revealing a similar coded protein cargo in both biological fluids. Subsequently, the same workflow was applied to tears from Relapsing-Remitting Multiple Sclerosis (RRMS) patients, revealing a Leuko EVs protein cargo enrichment that reflects the neuroinflammatory condition characteristics of RRMS. This enrichment was evidenced by the activation of upstream regulators TGFB1 and NFE2L2, which are associated with inflammatory responses. Additionally, the analysis identified markers indicative of endothelial cell proliferation and the development of enhanced vascular networks, with AGNPT2 and VEGF emerging as activated upstream regulators. These findings indicate the complex interplay between inflammation and angiogenesis in RRMS. CONCLUSIONS: In conclusion, our combined FACS-Proteomics strategy offers a promising approach for biomarker discovery, analysing cell-specific EV phenotypes directly from untouched body fluids, advancing the clinical value of tears EVs and improving the understanding of EV-mediated processes in vivo. Data are available via ProteomeXchange with the identifier PXD049036 and in EV-TRACK knowledgebase with ID: EV240150.

Humans↗

PubMed2025

Nanoscale Epigenetic Profiling of Colorectal Cancer Cell-Derived Exosomes via Single-Vesicle Nanoscopy.

Exosomes play critical roles in cancer diagnosis and treatment as they carry molecular information that reflects the epigenetic state of their parent cells. For the first time, nanoscale epigenetic profiling of individual exosomes derived from colorectal cancer cell lines is demonstrated via photo-induced force microscopy (PiFM). Exosomes from three cell lines with distinct CpG island methylator phenotype (CIMP) status are analyzed at the single-vesicle level. The nano-IR method provides simultaneous high-resolution topographical and spectroscopic data, revealing detailed vibrational signatures that distinguish CIMP-high (HCT116 and HT29) exosomes from CIMP-negative (SW480) ones. Notably, exosomes from CIMP-high cells exhibit red-shifted amide I and nucleic acid region compared to those from CIMP-negative cells, a shift attributed to increased 5-methylcytosine (5mC) modifications, as verified by quantum chemical calculations. Furthermore, these measurements reveal heterogeneity among individual exosomes, suggesting the presence of distinct subpopulations with unique epigenetic profiles, demonstrating the importance of single-vesicle resolution to detect molecular variations that remain obscured in ensemble studies. These findings present the potential of PiFM-based single-vesicle analysis to identify epigenetic markers in exosomes, laying the groundwork for its application in refined cancer diagnostics and targeted therapeutic strategies.

Humans↗

PubMed2026

Transforming Curcuma longa leaf waste into cellulose scaffolds.

The constant dearth of transplantable tissues and organs in India required the development of substitute biomaterials for tissue engineering. Plant-based decellularized scaffolds have become attractive options because of their abundance, ethical acceptability, architectural diversity, and lower risks of zoonotic transmission. Curcuma longa leaves were investigated in this study as a possible source of cellulose-based scaffolding for use in biomedical applications. After cuticle removal, an immersion decellularization technique utilizing sodium dodecyl sulphate (SDS) and triton-X-100 was developed to successfully remove cellular and nuclear material while maintaining leaf parenchyma architecture. Histology, DAPI staining, scanning electron microscopy, and a notable decrease in leftover DNA content all demonstrated efficient decellularization. When contrasted with native leaves, the resultant decellularized C. longa leaf scaffolds showed significant increase in porosity, water vapor transmission rate and swelling percent, and significantly lower contact angle with an optimum surface roughness promoting cell adhesion. Mechanical test manifest higher tensile strength with decreased stiffness. Fourier transform infrared spectra of leaf scaffold reveals persistence of different components except cuticle but the intensity of different peaks was decreased. The leaf scaffolds showed superior hemocompatibility and excellent compatibility with Madin-Darby canine kidney cells (MDCK) which is demonstrated by cell attachment and proliferation. MTT assay of seeded scaffold showed significantly higher metabolically active cell. In vivo subcutaneous implantation of decellularized scaffolds showed host tissue incorporation, accumulation of collagen, and neovascularization. C. longa leaf scaffolds can be utilized as cost effective and sustainable biomaterials for soft tissue engineering and regenerative medicine.

Curcuma↗

PubMed2026

Seeing and Feeling DNA Methylation: Single-Molecule Biophysics Meets Machine Learning.

DNA methylation at 5-methylcytosine (5mC) is crucial for embryonic development and cellular function, while aberrant patterns strongly drive disease onset and progression. Its reversible nature offers substantial therapeutic potential, emphasizing the need for precise, context-specific genome wide 5mC mapping. Conventional techniques such as bisulfite sequencing and ensemble biosensor assays are hindered by DNA degradation, amplification bias, high cost, and inability to resolve single-molecule structural and mechanical effects of methylation. This review examines advances in single-molecule biophysical methods (nanopore sensing, smFRET, optical/magnetic tweezers, and AFM) that provide direct, label-free/minimally invasive 5mC detection, along with quantitative insights into DNA conformation, mechanics, and protein-DNA interactions. These techniques complement traditional methylome mapping by linking genomic localization to molecular mechanisms. Emerging machine-learning approaches are revolutionizing analysis, particularly in nanopore sensing, while promising applications in smFRET, tweezers, and AFM address throughput and reproducibility challenges. Their convergence promises scalable, high-resolution epigenetic profiling, advancing precision epigenomics toward clinical application.

DNA Methylation↗