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Abstract: Introduction: Z-disk proteins play an essential role in stabilizing the contractile muscle apparatus. Genetic variants in these proteins are associated with cardiomyopathies, a group of genetic cardiac diseases linked to sudden cardiac death. Several studies have identified pathogenic variants in two prominent Z-disk proteins, alpha-actinin (ACTN2) and filamin C (FLNC). Notably, a 2014 study identified the ACTN2 variant M228T in a family of 11 patients with cardiomyopathy. Similarly, a recent investigation uncovered the FLNC variant M82K in two cardiomyopathy families. Both variants reside within the actin-binding domain of their respective Z-disk proteins, which is crucial for organizing and binding actin-thin filaments. However, the mechanisms by which these variants alter protein structure and function remain undefined. This study investigated the structural alterations and functional consequences associated with the ACTN2-M228T and FLNC-M82K variants. Methods: To explore the structural modifications in the ACTN2-M228T and FLNC-M82K mutant proteins, structural modelling approaches were employed. Additionally, recombinant proteins were expressed in a bacterial system and subsequently purified. A comprehensive array of biophysical techniques was utilized to detect alterations in protein structure. Functional assessments were performed using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) that incorporated the ACTN2-M228T variant. Results: Structural modeling predictions revealed that both ACTN2-M228T and FLNC-M82K variants share a common mechanism that adversely impact the regulatory function of the actin-binding domain. This hypothesis was further evaluated using actin-binding assays. The mutant proteins exhibited increased aggregation identified through mass photometry and size exclusion chromatography coupled with either multi-angle light scattering or small-angle X-ray scattering (SAXS). Moreover, both variants demonstrated reduced solubility and structural stability based on solubility and enzymatic digestion assays. The thermal stability of mutant proteins was also compromised, as assessed through SAXS and differential scanning fluorimetry. To correlate the identified structural alterations with disease mechanisms, the functional implications of ACTN2-M228T variant were assessed using an iPSC-CM model. Mutant cardiomyocytes showed increased ACTN2 aggregate formation and upregulation of hypertrophy, fibrosis, and autophagy markers. Furthermore, significant degradation of ACTN2 was observed through biochemical fractionation assays. ACTN2 destabilization was further evaluated using proteasome and protease inhibitors targeting the ubiquitin-proteosome system and the autophagy-lysosomal pathway, to elucidate their potential roles in the protein degradation process. Conclusion: Collectively, this study provides valuable insights into the effects of Z-disk variants on protein structure and function. The integration of structural and functional approaches represents a crucial step towards understanding disease pathways for cardiomyopathy-linked Z-disk variants.

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Abstract: The fabrication of superlattices is nontrivial because nanoparticles are notoriously difficult to employ due to the complex nanoscale forces among them. An effective way to manipulate these nanoscale forces is to use a soft corona around the solid core. The soft corona can be engineered to alter the forces between nanoparticles—either attracting or repelling them, and thereby influence their self-assembly process. Here, a deep analysis is proposed on how amines of different lengths (C8 to C18) can influence the hierarchical superlattice organization of cerium oxide nanoparticles, from both structural and energetic perspectives, and the consequent optical properties. The aim is to demonstrate how it is possible to shift from disordered to ordered aggregates and how to obtain one structure instead of another by modulating the geometrical and energetic parameters of soft corona/solid core nanoparticles. The results show that organic coating plays a key role in the self-aggregation process of superlattices with advanced optical properties, thereby broadening the range of potential applications for nanoparticles.

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Abstract: Structural characterization of commercially available gluten-free pasta is achieved here by combining small-angle x-ray and neutron scattering with contrast variation, and compared to the analogous regular gluten-containing pasta variety. In particular, the use of neutron and contrast variation allowed us to isolate the information about the gluten matrix and the starch granules. The broad peak that reflects the structure of the starches is lost as a function of cooking. This effect is more dramatic for the gluten-free pasta, indicating that the absence of gluten strongly promotes the gelation of the starches. Furthermore, the presence of salt in the cooking water is found to preserve the structural properties of the pasta, while at the same time it promotes the degradation of the starch granules. This study is the first step for a structural characterization of commercially-available pasta, moving forward the classic model system used so far to achieve information on the relation between pasta microstructure and its digestibility.

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Abstract: Factor XIIa (FXIIa) is generated from its zymogen factor XII (FXII) by contact with polyanions such as inorganic polyphosphates. FXIIa cleaves the substrates prekallikrein and factor XI, triggering inflammatory cascades and plasma coagulation. From the N-terminus, FXII has fibronectin type II (FnII), epidermal growth factor-1 (EGF1), fibronectin type I (FnI), EGF2 and kringle domains. The N-terminal domains of FXII mediate polyanion and Zn2+ binding. To understand how ligand binding to polyanions and Zn2+ is coordinated across multiple domains, we determined the crystal structure of recombinant FXII domains 1–5 (FXIIHC5) to 3.4 Å resolution. A separate crystal structure of the isolated FXII FnII domain at 1.2 Å resolution revealed two bound Zn2+ ions. In FXIIHC5 a head-to-tail interaction is formed between the FnII and kringle domains, co-localizing the lysine-binding sites of the kringle domain and the cation-binding site of the FnII domain. Two FXIIHC5 monomers interlock, burying a large surface area of 2067 Å2, such that two kringle domains point outwards separated by a distance of 20 Å. The polyanion-binding site in the EGF1 domain is localized onto a plane together with the FnII and FnI domains. Using native mass spectrometry, we detected a major FXIIHC5 monomer peak and a minor dimer peak. Small-angle X-ray scattering and gel-filtration chromatography revealed the presence of monomers and dimers in solution. These FXII N-terminal domain structures provide a holistic framework to understand how the mosaic domain structure of FXII assembles diverse ligand-binding sites in three dimensions.

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Abstract: Metal nanocrystals (M-NCs) and their supramolecular assemblies have attracted significant interest from the scientific community due to their wide range of applications arising from the possibility of accurately tuning the M-NCs properties through self-assembly into supramolecular aggregates. In this study, we investigate the complex interplay between capping agent surface coverage and solvent-capping agent interactions in the self-assembly process of M-NCs into supramolecular structures. Specifically, we explore the self-assembly behavior of gold (Au-NCs), silver (Ag-NCs), and platinum (Pt-NCs) nanocrystals upon functionalization with oleic acid (OA) in water using a microemulsion approach. Through a multi-technique analysis, we demonstrate the critical role of ligand density and solvent choice in driving the formation of highly ordered supramolecular structures. By increasing the surface coverage of the M-NC ligands, we observed a transition to more organised assemblies, with the interaction between the oleylamine alkyl chain and the functionalization medium further modulating the type of supramolecular arrangement. Moreover, we highlight the profound influence of both the external environment and supramolecular aggregation on the optical properties of the M-NCs. This work provides crucial insights into the factors that govern nanocrystals’ self-assembly and optical behavior, with broad implications for the design and application of nanomaterials in nanotechnology and materials science.