Fibril Structure Research Articles

Water hyacinth biomass-based biochar: Preparation and characterizations for sustainable soil amendment

AbstractThis study investigates the utilization of biochar (WHBC) from water hyacinth biomass (WHBM) for sustainable soil amendment to improve soil quality. WHBM and WHBC are prepared and characterized with thermogravimetric analysis (TGA). For that, physiochemical, proximate, ultimate, and elemental analyses are done and characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDAX) to identify the suitability of soil amendment. WH biomass is carbonized with a limited air supply in a muffle furnace, and the study found that 300–664 °C temperature is the optimum condition for producing biochar from TGA. XRD of WHBC displayed more crystallinity than WHBM. FTIR of WHBC showed higher carbon stability increment than WHBM. The SEM micrograph of WHBM showed that compact, and fibril structures and WHBC revealed macroscopic changes that can significantly improve the soil properties. EDAX analysis of WHBM and WHBC proved that various soil nutrients can be helpful for plant growth. The study shows that WHBM can be utilized as a soil quality amendment material by converting it to biochar and an effective material for carbon storage in soils.

Elucidating the Unique J-Shaped Protomer Structure of Amyloid-β(1-40) Fibril with Cryo-Electron Microscopy

Although the structural diversity of amyloid-β (Aβ) fibrils plays a critical role in the pathology of Alzheimer’s disease (AD), the mechanisms underlying this diversity remain poorly understood. In this study, we report the discovery of a novel J-shaped protomer structure of Aβ40 fibrils, resolved at 3.3 Å resolution using cryo-electron microscopy. Under controlled conditions (20 mM sodium phosphate buffer, pH 8.0) designed to emphasize intra-protomer interactions and slow fibril elongation, the J-shaped structure revealed distinct salt bridges (e.g., D1-K28, R5-E22) that stabilize the fibril core. These findings expand our understanding of the free energy landscape of fibril formation, shedding light on how specific environmental factors, such as pH and ionic strength, may influence fibril polymorphism. Importantly, the unique features of the J-shaped protomer provide insights into the structural basis of amyloid plaque diversity in AD and suggest potential therapeutic strategies targeting intra-protomer interactions. This study underscores the importance of fibril polymorphism in AD pathology and offers a foundation for future research into fibril-targeted therapies.

The question of strains in AA amyloidosis

The existence of transmissible amyloid fibril strains has long intrigued the scientific community. The strain theory originates from prion disorders, but here, we provide evidence of strains in systemic amyloidosis. Human AA amyloidosis manifests as two distinct clinical phenotypes called common AA and vascular AA. Glomerular amyloid deposition of the kidney defines the common form, while in the vascular type amyloid deposits are massive in the renal medulla and in arteries throughout the body, while glomeruli are spared. By electron microscopy the two types appeared morphologically different. The common type was composed of dispersed fibrils which tended to be clustered whereas the vascular type was composed of longer and more distinct less clustered fibrils. Staining with fluorescent amyloid binding ligands analyzed by hyperspectral microscopy showed differential staining patterns between the two groups supporting the notion of human AA amyloid strains. AA amyloid staining was significantly different from systemic AL amyloid. Both types of AA (common and vascular) and AL amyloid fibrils were isolated and used to seed mouse AA amyloid in groups of inflamed NMRI mice (n = 9–10 per group). All but two mice showed amyloid deposits in the spleen induced by the human seeds. Amyloid binding ligand analysis was applied on the splenic amyloid deposits and revealed no clear significant difference between mice seeded with AA fibrils from different donors being vascular or common, but the AA deposits of mice given AL fibrils showed significantly different amyloid fluorescent signals compared to all groups of mice receiving AA fibrils. The combined results support the hypothesis that AA amyloid fibril structures can vary depending on the seed and may manifest as amyloid strains.

Investigation of All Disease-Relevant Lysine Acetylation Sites in α-Synuclein Enabled by Non-canonical Amino Acid Mutagenesis.

Aggregates of α-synuclein (αS) are hallmarks of synucleinopathies, including Parkinson's Disease (PD) and Multiple System Atrophy (MSA). We have recently shown that αS lysine acetylation in the soluble monomer pool varies between healthy controls, PD, and MSA patients. To study the effects of lysine acetylation at all disease-relevant sites of αS, we first compared production of acetylated αS through either native chemical ligation or non-canonical amino acid (ncAA) mutagenesis. Since yields were comparable, ncAA mutagenesis was deemed superior for scanning many acetylation sites. We expressed and purified 12 disease-relevant variants and studied their binding to membranes as well as their aggregation propensities, and found that acetylation of lysine 12, 43, and 80 had particularly strong effects. To understand the implications for acetylation of monomeric αS found in healthy cells, we performed NMR experiments to study protein conformation and fluorescence correlation spectroscopy experiments to quantify lipid binding. We also investigated the effects of acetylation at lysine 12, 43, and 80 on fibril seeding in neurons. Collectively, our biochemical and cell biological investigations indicated that acetylation of K 80 could inhibit aggregation without conferring negative effects on monomer function in healthy cells. Therefore, we studied the structures of fibrils with K 80 acetylation through cryo-electron microscopy to uncover the structural basis for these effects. Finally, we identified inhibition of HDAC8 as a way of potentially increasing acetylation at K 80 and other inhibitory sites for therapeutic benefit.

Polyhydroxybutyrate as a Novel Biopolymer for Dental Restorative Materials: Biological and Morphological Analysis

Polyhydroxybutyrate (PHB) is a biopolymer produced by bacteria. This study aimed to implement the production process of experimental medical-grade PHB and to evaluate its morphology and biocompatibility compared to conventional resin-based composites (RBCs). PHB raw material was produced via biological process and then the membrane was generated via electrospinning specifically for this study and imaged with Micro-Computed Tomography (Micro-CT) and scanning electron microscopy (SEM). MTS assay was used to assess the cytotoxicity of PHB compared to other materials. Test groups included two packable resin composites (Point 4-Kerr, G-aenial anterior-GC), two flowable resin composites (Filtek Ultimate Flowable-3M ESPE, Nova Compo HF-Imicryl), a compomer (Nova Compomer-Imicryl), a fissure-sealant (Fissured Nova Plus-Imicryl), and the PHB membrane (Innovaplast Biotechnology Inc., Eskisehir, Turkey). A control group consisting of cells without any test material was also produced. To perform the MTS assay, disc-shaped specimens of the aforementioned materials were prepared and then incubated with mouse fibroblast cells (L929) for 24 and 48 h. Micro-CT and SEM images revealed a homogeneous and fibrillary structure of the PHB. MTS assay revealed the highest cell viability in the PHB, Nova Compomer, and Fissured Nova Plus groups after 24 h. PHB and Nova Compomer showed the highest viability rates at 48 h while other RBCs had rates below 25% (p < 0.05). Considering the cell viability data and its fibrillary structure, from a biological point of view, PHB seems a promising biopolymer that might have applications in the field of dental restorative materials.

Antarctic Krill Protein Amyloid Fibrils as a Novel Iron Carrier for the Improvement of Iron Deficiency.

Iron fortification with food supplements remains the primary dietary strategy for improving iron deficiency anemia (IDA). This study used Antarctic krill protein for fibrillar design to form an Antarctic krill protein amyloid fibril (AKAF). The results indicated that peptides generated by proteolysis were a prerequisite for fibril assembly, forming elongated fibril structures and cross-linking upon heating. During this process, hydrogen bonds were rearranged, forming ordered β-sheet conformations (49.36 ± 0.21%); π-π stacking interactions among aromatic residues contributed to fibril formation. Further studies showed that AKAF effectively maintained iron in a bioavailable state and exhibited a high binding capacity (60.67 ± 0.69%). Moreover, the AKAF-iron complex markedly ameliorated hematological abnormalities in IDA mice, enhanced iron storage in the liver and spleen, and positively influenced the expression of iron homeostasis genes. This complex was also effective in alleviating gastric inflammatory responses induced by IDA. Overall, AKAF holds promise as an efficient iron delivery carrier.

Preparation of Hydroxyapatite-Aligned Collagen Sheets and Their Evaluation for Fibroblast Adhesion and Collagen Secretion.

The structure of many native tissues consists of aligned collagen (Col) fibrils, some of which are further composited with dispersed hydroxyapatite (HAp) nanocrystals. Accurately mimicking this inherent structure is a promising approach to enhance scaffold biocompatibility in tissue engineering. In this study, biomimetic sheets composed of highly aligned Col fibrils were fabricated using a plastic compression and tension method, followed by the deposition of HAp nanocrystals on the surface via an alternate soaking method. The fabricated Col sheets exhibited high solid density, retained the native periodicity (D-band) of Col fibrils, and displayed plate-like HAp nanocrystals dispersed on their surface. In vitro experiments demonstrated that these sheets could regulate fibroblasts adhesion, inducing more elongated nuclei and oriented actin bundles on the aligned Col sheets. Analysis of focal adhesion assembly revealed greater cell focal adhesions on the aligned composite sheets compared to those with random Col fibril structures. Fibroblasts cultured on aligned Col with partly HAp-mineralized sheets exhibited the highest cell-extracellular matrix (ECM) protein secretion, highlighting that HAp incorporation and fibroblast alignment synergistically promote early ECM formation and wound healing. These results suggest that highly aligned Col fibrils with dispersed HAp nanocrystals, closely mimicking the microarchitecture of natural tissues, have significant potential to control cell adhesion and protein secretion for tissue engineering applications.

Lipidic folding pathway of α-Synuclein via a toxic oligomer

Aggregation intermediates play a pivotal role in the assembly of amyloid fibrils, which are central to the pathogenesis of neurodegenerative diseases. The structures of filamentous intermediates and mature fibrils are now efficiently determined by single-particle cryo-electron microscopy. By contrast, smaller pre-fibrillar α-Synuclein (αS) oligomers, crucial for initiating amyloidogenesis, remain largely uncharacterized. We report an atomic-resolution structural characterization of a toxic pre-fibrillar aggregation intermediate (I1) on pathway to the formation of lipidic fibrils, which incorporate lipid molecules on protofilament surfaces during fibril growth on membranes. Super-resolution microscopy reveals a tetrameric state, providing insights into the early oligomeric assembly. Time resolved nuclear magnetic resonance (NMR) measurements uncover a structural reorganization essential for the transition of I1 to mature lipidic L2 fibrils. The reorganization involves the transformation of anti-parallel β-strands during the pre-fibrillar I1 state into a β-arc characteristic of amyloid fibrils. This structural reconfiguration occurs in a conserved structural kernel shared by a vast number of αS-fibril polymorphs including extracted fibrils from Parkinson’s and Lewy Body Dementia patients. Consistent with reports of anti-parallel β-strands being a defining feature of toxic αS pre-fibrillar intermediates, I1 impacts viability of neuroblasts and disrupts cell membranes, resulting in an increased calcium influx. Our results integrate the occurrence of anti-parallel β-strands as salient features of toxic oligomers with their significant role in the amyloid fibril assembly pathway. These structural insights have implications for the development of therapies and biomarkers.

Pseudo-Phosphorylated Tau Forms Paired Helical Filaments in the Presence of High-Curvature Cholesterol-Containing Lipid Membranes.

The tau protein misfolds in neurodegenerative diseases such as Alzheimer's disease (AD). These pathological tau aggregates are associated with neuronal membranes, but molecular structural information about how disease-like tau fibrils interact with the lipid membrane is scarce. Here, we use solid-state NMR to investigate the structure of a tau construct bearing four AD-relevant phospho-mimetic mutations (4E tau) with cholesterol-containing high-curvature lipid membranes, which mimic the membrane of synaptic vesicles in neurons. We show that 4E tau adopts the AD paired helical filament (PHF) fold in the presence of the membrane at high protein concentrations. Moreover, it inserts into the membrane-water interface with an orientation that suggests possible bridging of multiple lipid vesicles. At lower protein concentrations, moderate chemical shift changes are observed, indicating a perturbation of the PHF structure by the lipids. Removal of the phospho-mimetic mutations led to a qualitatively different β-sheet conformation. These results indicate that posttranslational modifications impact the tau fibril structure more strongly than lipid membranes, but the membrane modulates the conformational equilibria of the aggregates.

Bio-Orchestration of Cellular Organization and Human-Preferred Sensory Texture in Cultured Meat.

For cultured meat to effectively replace traditional meat, it is essential to develop scaffolds that replicate key attributes of real meat, such as taste, nutrition, flavor, and texture. However, one of the significant challenges in replicating meat characteristics with scaffolds lies in the considerable gap between the stiffness preferred by cells and the textural properties desired by humans. To address this issue, we focused on the microscale environment conducive to cell growth and the macro-scale properties favored by humans. This led to the development of the adaptive bio-orchestrating anisotropic scaffold (ABS), which satisfies both cellular and human requirements. The ABS is produced using the anisotropic freeze-initiated ion coordination method, which sequentially aligns and enhances the fibril structure of food-derived proteins, effectively bridging the gap between cellular and culinary perspectives. Notably, the microenvironments of the ABS exhibited exceptional myoblast cell differentiation, with macro-scale 3D mechanical textures that are consistent regardless of the chewing direction, due to the aligned fibril and cell structure. The ABS containing bovine myotubes demonstrated a mechanical texture nearly identical to that of beef sirloins.

Passaging Human Tauopathy Patient Samples in Cells Generates Heterogeneous Fibrils with a Subpopulation Adopting Disease Folds.

The discovery by cryo-electron microscopy (cryo-EM) that the neu-ropathological hallmarks of different tauopathies, including Alzheimer's disease, corticobasal degeneration (CBD), and progressive supranuclear palsy (PSP), are caused by unique misfolded conformations of the protein tau is among the most profound developments in neurodegenerative disease research. To capitalize on these discoveries for therapeutic development, one must achieve in vitro replication of tau fibrils that adopt the representative tauopathy disease folds, which represents a grand challenge for the field. A widely used approach has been seeded propagation using pathological tau fibrils derived from post-mortem patient samples in biosensor cells that expresses a fragment of the tau protein known as K18, or Tau4RD, containing the microtubule-binding repeat domain of tau as the substrate. The new insights from cryo-EM raised the question of whether the Tau4RD fragment is capable of adopting characteristic tau folds found in CBD and PSP patient fibrils, and whether cell-passaged and amplified tau fibrils can be used as seeds to achieve cell-free assembly of recombinant 4R tau into fibrils without the addition of cofactors. Using Double Electron Electron Resonance (DEER) spectroscopy, we discovered that cell-passaged pathological seeds generate heterogeneous fibrils that are, however, distinct between the CBD and PSP lysate-seeded fibrils, and vastly different from heparin-induced tau fibril structures. Moreover, the lysate-seeded fibrils contain a characteristic sub-population that resembles the disease fold corresponding to the respective starting patient sample. These findings indicate that templated propagation using CBD and PSP patient-derived fibrils is possible with a tau fragment that does not contain the entire pathological fibril core, but also that additional mechanisms must be tuned to converge on a homogeneous fibril population.

Different types of anions mediated the formation of rice glutelin fibrils: Aggregation behaviors and structural characteristics.

Anions have more pronounced effect on the aggregation power of proteins than cations. Herein, the effect of different types of anions on rice glutelin (RG) based fibrils formation was investigated. The fibrils yield and growth rate of RG were enhanced with various anions, due to the specific ions effect and intermolecular interaction. It was observed that the fibrillization rate of RG followed the specific order: Br->I->F->NO3->Cl->CH3COO->ClO-. In addition, the chaotropes (e.g., I-) interacted more favorably with hydrophobic residues to form needle-like periodic structure, whereas the kosmotropes (e.g., CH3COO-) preferred to form larger fibrils clusters due to the stronger shielding effect. Consequently, various anions profoundly influenced the unfolding, dimerization, reorganization of protein, as well as the formation of crucial β-sheet structure. This study helps to understand how the structure of fibrils can be tuned through different anions.

Enhancement of physicochemical and techno-functional properties of soy protein isolate amyloid fibrils by moderate ultrasonic pretreatment

Plant protein can be functionally strengthened by its modification into amyloid fibrils, which has drawn growing interest. In this study, we investigated the effects of ultrasonic pretreatment on the fibrillation kinetics, physicochemical properties, and functional aspects of soy protein isolate amyloid fibrils (SPF). Firstly, soy protein isolates (SPI) were subjected to ultrasonic pretreatment by regulating time and power under neutral conditions. Subsequently, the pretreated SPI was converted into SPF through acidic heating. The results indicated that ultrasonic pretreatment significantly improved surface hydrophobicity and solubility of SPI through ultrasound’s cavitation and thermal effects. Thioflavin T fluorescence assay revealed SPF40 (450 W, 40 min) had the fastest growth rate, 104.23 % higher than SPF0 (without ultrasonic pretreatment), while SPF10 (450 W, 10 min) had the highest fibril yield, 20.97 % higher than SPF0. Physicochemical analysis showed that ultrasonic pretreatment accelerated the formation of SPF from SPI by exposing the surface hydrophobic groups, lowering the zeta potential, breaking down original fibrils into shorter fibrils, and altering the secondary structure from α-helices into β-sheets. Morphological examination by transmission electron microscopy exhibited a higher maturation state, showing more rigid and straight fibrils structure in SPF10 compared to SPF0. Functionally, SPF with ultrasonic pretreatment had higher emulsifying activity than SPI and SPF0. Rheological analysis further confirmed SPF emulsions’ better mechanical strength over SPI emulsions. Overall, this study demonstrates that ultrasonic pretreatment is an effective way to enhance the formation and properties of SPF, which can be further applied to developing advanced protein products and novel functional food systems.

Exploring Acoustic Detection of α-Synuclein Fibrils.

Over the past decades, the incidence of Parkinson's disease (PD) cases has doubled in industrialized countries. While patients over 70years old still represent more than half of the cases, the disease is increasingly affecting younger individuals. Environmental factors have been implicated, such as the effects of certain pesticides or chemicals on neurons, such as rotenone or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Researchers have also demonstrated the influence of genetic mutations in younger patients. A-synuclein is a protein encoded by the SNCA gene, known to undergo various mutations in hereditary cases of PD. These mutations alter the composition and spatial arrangements of α-synuclein. The proteins, originally of linear shape, aggregate during the progression of PD, forming fibrillary structures that propagate through brain tissues. Among the physical therapies investigated for treating α-synuclein aggregation, ultrasonic waves, capable of altering protein and cell behaviors, have recently been used to disrupt α-synuclein fibrils within tissues in cellular and animal models, with the hope of developing treatments based on ultrasound properties. However, detecting fibrils typically requires invasive and non-biocompatible chemical compounds or cumbersome machinery. In this study, our acoustic experimental setup allowed us to investigate the response of α-synuclein to ultrasound perturbations. By capturing the transmitted wave across proteins over a frequency range 10kHz to 10MHz, no ultrasound signature indicating the presence of proteins was observed.Significance Statement: The results report there is no ultrasound signature of the presence of α-synuclein fibrils, from 10kHz to 10MHz.

Heterotypic Interactions of Amyloid β and the Islet Amyloid Polypeptide Produce Mixed Aggregates with Non-Native Fibril Structure.

Amyloid aggregates are hallmarks of the pathology of a wide range of diseases, including type 2 diabetes (T2D) and Alzheimer's disease (AD). Much epidemiological and pathological evidence points to significant overlap between AD and T2D. Individuals with T2D have a higher likelihood of developing AD; moreover, colocalized aggregates of amyloid β (Aβ) and the islet amyloid polypeptide (IAPP), the two main peptides implicated in the formation of toxic amyloid aggregates in AD and T2D, have also been identified in the brain. However, how these peptides interact with each other is not well understood, and the structural facets of heterotypic mixed fibrils formed via such interactions remain elusive. Here we use atomic force microscopy augmented with infrared spectroscopy to probe the secondary structure of individual aggregates formed via heterotypic interactions of Aβ and IAPP and provide unequivocal direct evidence of mixed aggregates. Furthermore, we show that co-aggregation of the peptides from the monomeric stage leads to the formation of unique polymorphs, in which both peptides undergo structural deviation from their native states, whereas seeding with preformed IAPP fibrils leads to aggregates similar to native Aβ. These findings highlight how heterotypic interactions between amyloidogenic peptides can lead to polymorphic diversity proteinopathies.

Tendon-targeted knockout of collagen XI disrupts patellar and Achilles tendon structure and mechanical properties during murine postnatal development

ABSTRACT Background Collagen XI is a fibril-forming collagen typically associated with type II collagen tissues but is also expressed in type I collagen-rich tendons, especially during development. We previously showed that tendon-targeted (Scx-Cre) Col11a1 knockout mice have smaller tendons in adulthood with aberrant fibril structure and impaired mechanical properties. However, the manifestation of this phenotype is not clearly understood. Therefore, our objective is to define the spatiotemporal roles of collagen XI in tendon structure-function during postnatal development. Given the high expression of collagen XI during embryonic development, we hypothesized that collagen XI knockout leads to the deposition of weakened extracellular matrix during early postnatal timepoints, disrupting the establishment of tendon structure and function. Methods Patellar and Achilles tendons from postnatal (P) days 0, 10, 20, and 30 tendon-targeted scleraxis-Cre heterozygous and homozygous Col11a1 knockout mice were evaluated for morphology, nuclear organization, fibril morphology, mechanical properties, and gene expression. Results At P0, there were no differences in tendon length or fibril diameter of either tendon. By P10, striking structural and functional differences emerged, with collagen XI deficiency resulting in increased tendon length, a heterogeneous and larger diameter population of fibrils, and inferior mechanical properties in both patellar and Achilles tendons. Differences increased in magnitude through P30, supporting our hypothesis that impaired structure-function during postnatal development may drive tendon lengthening and reduced mechanical properties. Conclusions Though collagen XI is a quantitatively minor component of the tendon extracellular matrix, these results highlight the critical role of collagen XI in the acquisition of tendon structure-function.

Automated fibril structure calculations in Xplor-NIH.

Amyloid fibrils are protein assemblies that are pathologically linked to neurodegenerative diseases. Fibril structures can aid development of highly specific ligands for diagnostic imaging and therapeutics. Solid-state NMR (SSNMR) is a viable approach to solving fibril structures; however, most SSNMR protocols require manual analysis of extensive spectral data, presenting a major bottleneck to determining structures. Standard automation; routines fall short for symmetric multimeric assemblies like amyloids due to high cross peak degeneracy and the need to account for multiple protein subunits. Here, we employ the probabilistic assignment for structure determination protocol in conjunction with strict; symmetry in Xplor-NIH structure determination software, demonstrating the methodology using data from a previous structure of an α-synuclein (Asyn) fibril implicated in Parkinson disease. The automated protocol generated a structure of comparable, if not superior, quality in a few days of computational time, reducing the manual effort required; to solve amyloid structures by SSNMR.

Using disease‐selective cell lines to investigate tau strain biology

AbstractBackgroundIn tauopathies, the protein tau misfolds into a b‐sheet conformation that self‐templates and spreads throughout the brain causing progressive degeneration. Biological and structural data have shown that the shape, or strain, that tau adopts when it misfolds determines which disease a patient will develop. We previously used HEK293T cells expressing TauRD‐YFP to show that tau strain formation is isoform‐specific. However, the field remains unable to differentiate between strains using the same isoforms, which is a critical requirement for the successful development of strain‐specific diagnostics. In this work, we hypothesize that single point mutations can be used to disrupt the misfolded tau conformations in a disease‐specific manner, enabling differentiation between tauopathies.MethodWe built a panel of HEK293T cells expressing several disease‐linked and novel mutations in 4R tau, which we selected based on mutagenesis modeling aimed at selectively inhibiting replication of tau prions isolated from either corticobasal degeneration (CBD) or progressive supranuclear palsy (PSP) patient samples. Infection conditions in the cell lines were optimized for a 384‐well plate using tau prions isolated from Tg(MAPT*P301S+/+) and non‐transgenic B6/J mice before testing human patient samples. Cells were imaged using the LionheartFX and infection was determined using custom algorithms developed in Gen5 software.ResultSamples isolated from control mice do not cause aggregation in the cell lines tested. By comparison, tau prions isolated from Tg(MAPT*P301S+/+) mice cause aggregation in some cells, but other point mutations inhibited tau prion replication. Intriguingly, the same mutations inhibited replication of tau prions isolated from PSP patient samples, but not CBD samples. Notably, within this targeted region of the protein, the cryo‐EM structures of tau fibrils in PSP patients and Tg(MAPT*P301S+/+) mice show some homology.ConclusionWe have developed two cell lines that selectively replicate tau prions isolated from CBD patient samples. To our knowledge, this is the first assay capable of differentiating between two different 4R tau prion strains, representing a significant advancement towards the development of disease‐specific diagnostic tools.

A closer look at pathogenic amyloid-β in Alzheimer’s disease using cryo-electron microscopy: a narrative review

Alzheimer’s disease is a progressive neurodegenerative disorder that affects millions of people worldwide. The identification of amyloid-β in Alzheimer’s disease brains, together with the association of mutations in the amyloid-β precursor protein with Alzheimer’s disease pathology, is the basis of the amyloid cascade hypothesis, which suggests that amyloid-β plays a central role in Alzheimer’s disease pathogenesis. Recent studies have further highlighted the role of intraneuronal amyloid-β in Alzheimer’s disease development. Moreover, the success of anti-amyloid-β immunotherapies supports the amyloid cascade hypothesis, emphasizing the importance of targeting specific amyloid-β conformations to achieve better therapeutic outcomes. In recent years, cryo-electron microscopy has become an invaluable tool for obtaining near-atomic resolution images of protein assemblies, and multiple structures of brain-derived amyloid fibrils have been elucidated. In this article, we review the role of pathogenic amyloid-β according to the amyloid cascade hypothesis and explore the relationship between intraneuronal amyloid-β accumulation and the development of key pathological features of Alzheimer’s disease—amyloid plaques and neurofibrillary tangles. We also connect cryo-electron microscopy structures of amyloid-β aggregates with amyloid-β-targeting treatment and highlight recent advances and future research directions. The application of cryo-electron microscopy can provide molecular insights into amyloid-β structure, which is expected to help uncover the underlying mechanisms of Alzheimer’s disease and provide new therapeutic strategies for the clearance of amyloid-β aggregates.

Multifunctional Nitrogen-Doped Carbon Dots to Inhibit the Aggregation of Aβ Peptide and Depolymerize the Aβ Fibrils by Modulating Reactive Oxygen Species.

Multifunctional nitrogen-doped carbon dots (N-CDs) were synthesized, and the morphology, composition, and spectral properties of N-CDs were characterized by multiple characterization techniques. The inhibition of β-amyloid (Aβ) peptide aggregation and the destruction of the Aβ fibril structure by N-CDs were also studied. The conformational transition and morphology of Aβ42 in the presence of N-CDs were monitored by far-UV circular dichroism (CD) spectroscopy and transmission electron microscopy (TEM). The results demonstrated that the prepared N-CDs could effectively inhibit Aβ42 peptide aggregation and depolymerize Aβ fibrils. Furthermore, the inhibition and disaggregation mechanism of existing Aβ42 fibrils by N-CDs was studied by electron paramagnetic resonance spectroscopy (EPR). The results showed that the modulation of reactive oxygen species (ROS) by N-CDs and multiple interactions between N-CDs and Aβ42 fibrils played a crucial part in restraining and reducing the aggregation of Aβ42. Our work demonstrates the therapeutic potential of N-CDs in suppressing Aβ42 peptide aggregation and destroying existing Aβ42 fibrils, which provides a new perspective strategy in the treatment of Alzheimer's disease (AD).