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Abstract: A lipopeptide is designed that contains an epitope from simian virus T-antigen (SV40T, PKKKRKV) conjugated to an N-terminal palmitoyl (C16-) moiety, with the aim to act as an effective cell-penetrating lipopeptide, with additional aggregation propensity conferred by the lipid chain. A combination of cryo-TEM and small-angle X-ray scattering (SAXS) is used to show that the lipopeptide forms micelles, but mixtures with DNA lead to formation of fractal cluster-like co-assemblies due to intercalation of the DNA and peptide. Spectroscopic studies using fluorescence and circular dichroism (along with fiber X-ray diffraction) show that the peptide interacts with DNA and inserts into the groove. Confocal microscopy along with flow cytometry confirms delivery of DNA into both HeLa and mouse embryonic stem cells (mESCs) in pluripotent state, and the system shows excellent cytocompatibility as confirmed by MTT assays. Our data indicate that the lipopeptide may outperform the DNA transfection agent lipofectamine in DNA delivery into these stem cells and it enables DNA delivery into the cytoplasm and nucleus.

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Abstract: A hydrogel formed by a short peptide is presented that exhibits remarkable stimuli-responsiveness and plasticity, undergoing a morphological transformation from nanofibers to nanospheres in the presence of monovalent (Li+, Na+, K+) or trivalent (Al3+, Fe3+) metal ions under physiological conditions. The nanofibrillar structure of the hydrogel was examined using transmission electron microscopy (TEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and X-ray diffraction (XRD) studies and atomistic molecular dynamics simulations, in complement, to explain the nanostructural transitions at the microscopic level. Interestingly, exposure to divalent metal ions (Mg2+, Ca2+, Co2+, Ni2+) induces a unique shrinking (syneresis) behavior, accompanied by a morphological shift to nanoribbons. Both simulations and SAXS analysis confirm that these ions cause a contraction in the packing of gelator peptides, significantly reducing the interpeptide distance. This ion-specific adaptability confers tunable physicochemical properties and morphological plasticity. Hydrogels incorporating mono- or trivalent ions exhibit enhanced thermal stability and mechanical strength relative to ion-free counterparts, underscoring the reinforcing role of metal coordination. Strikingly, shrunken gels formed in the presence of divalent ions display even greater stiffness than freshly prepared gels in the absence of any metal ions, suggesting that syneresis acts as a postassembly strengthening mechanism. These findings highlight a versatile, stimuli-responsive soft material in which ion-peptide interactions orchestrate nanoscale morphology, mesoscale network architecture, and macroscopic mechanical performance-opening avenues for adaptive hydrogel systems in targeted biomedical, sensing, and controlled-release applications.

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Abstract: A variable temperature X-ray total-scattering study of K2IrCl6 reveals compelling evidence for local symmetry breaking in this material. While the average crystal structure remains cubic down to 11 K, consistent with earlier reports, large anisotropic chloride displacements suggest short-range distortions of the IrCl6 octahedra. Pair distribution function analysis confirms that the local structure is better described by a monoclinic P21/n model featuring a mix of in-phase and out-of-phase octahedral tilts. This behavior mirrors observations in related K2MX6 halides, where thermally driven cubic-to-monoclinic transitions occur. High-pressure synchrotron measurements further reveal two structural transitions: cubic Fm3̅m to tetragonal P4/mnc at 12.0 GPa, and tetragonal to monoclinic P21/n at 15.1 GPa. Both transitions are reversible on decompression. Lattice parameter refinements indicate anisotropic compression with the bulk modulus increasing dramatically from 23 GPa in the cubic phase to 121 GPa in the monoclinic structure. These results demonstrate that both temperature reduction and applied pressure drive K2IrCl6 toward lower-symmetry phases. Overall, this study provides the first direct local-structure evidence of symmetry breaking in K2IrCl6 and highlights the complex interplay among pressure, temperature, and local structure in vacancy-ordered double perovskites.

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Abstract: Candida glabrata is the second leading cause of mortality in immunocompromised patients hospitalized for invasive candidiasis (IC). Several drugs have been available to treat this disease for decades, such as polyenes, azoles, echinocandins, flucytosine, and, in critical cases, amphotericin B. However, these antifungals’ constant and routine use have led to the development of resistance mechanisms, making the design and development of new drugs indispensable. The first step for the design and subsequent synthesis of a new chemical molecule as a potential antifungal is the identification of new therapeutic targets. In that pathway, our working group has identified moonlight-like cell wall proteins (CWPs) in different Candida species that can act as potential antifungal targets. One of these moonlight-like CWPs is phosphoglycerate kinase (Pgk) from C. glabrata. Once Pgk was identified as a potential therapeutic target in different human pathogens, the first step to perform drug design against this moonlight-like CWP was the elucidation of the three-dimensional (3D) structure since the 3D structure is key to understanding the interactions between a drug candidate and its target at the molecular level. In the present work, we aimed to elucidate the 3D structure of C. glabrata Pgk. To elucidate the 3D structure of this protein, the recombinant protein was expressed, purified, and structurally resolved by means of a structural analysis by small-angle X-ray scattering (SAXS). Additionally, in order to evaluate its potential as a therapeutic target, we have performed molecular docking studies and enzymatic activity assays with pure Pgk using known antifungals amphotericin B, nystatin, and fluconazole and with the new plausible drugs, such as nilotinib and netupitant. Our results showed some similarities and differences with orthologous Pgk proteins from other organisms, which was expected since Pgk has been observed to have evolved in the kingdoms of life. Molecular docking studies showed that Pgk interacts with all of the compounds tested. In enzyme activity assays, a change in the kinetic parameter Km on the enzyme Pgk was observed in response to its interaction with nilotinib, netupitant, and amphotericin B. Thus, our results allow us to propose Pgk from C. glabrata as a possible therapeutic target against candidiasis. We consider it essential to design and develop new molecules specifically targeting this enzyme, which will contribute to a decrease in mortality associated with IC and improve the patient’s quality of life.

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Abstract: Purpose: To study the structural arrangement of crystallin proteins in the human lens during development. Methods: Fetal human lenses were acquired from the UK Human Developmental Biology Resource and examined at four developmental stages; postconception weeks (pcw) 8 to 9 (n = 5), 12 to 13 (n = 3), 16 to 17 (n = 6), and 20 to 21 (n = 3). Small-angle X-ray scattering patterns were obtained as raster scans across the entirety of each lens using a 0.1 nm-wavelength, synchrotron X-ray beam measuring 200 × 150 µm at the specimen. Analysis of each small-angle X-ray scattering pattern provided a measure of the average nearest neighbor spacing and the extent of spatial order in the crystallin protein array. Results: Crystallins in the lens center became compacted as development progressed, with the average spacing measuring 19.9 nm at 8 to 9 pcw, 19.6 nm at 12 to 13 pcw, 18.7 nm at 16 to 17 pcw, and 17.7 nm at 20 to 21 pcw. The spatial order of the crystallin proteins in the lens center also decreased with time as indicated by a parameter called the coherence distance, which measured 26.9 nm at 8 to 9 pcw, 24.7 nm at 12 to 13 pcw, 24.6 nm at 16 to 17 pcw, and 24.9 nm at 20 to 21 pcw. Spacing and spatial order were consistently higher at the lens periphery, compared with the center, at all developmental stages studied. Conclusions: Spatiotemporal modifications in the array of crystallin proteins occur as the human lens develops. These are perhaps reflective of a shift in the relative proportions of crystallin subtypes present and have potential implications for the lens's developing refractive index.