Explore the vast range of titles available.

Magnetite (Fe₃O₄) and hematite (Fe₂O₃) nanoparticles hold significant potential for catalysis, environmental remediation, biomedicine, and energy generation. However, conventional synthesis methods for iron-oxide nanoparticles (IONPs) are often complicated or involve hazardous reagents, limiting scalability. Although plant extract-mediated green synthesis offers better alternatives, many rely on rare or expensive biomaterials and hazardous precursors or pH-adjusting chemicals, compromising eco-friendliness and cost-effectiveness. To address these challenges, we developed a truly green, efficient, and economical protocol for synthesizing the nanoparticles smaller than 50 nm. Widely available Moringa oleifera (Moringa) and Psidium guajava (Guava) leaf extracts, along with a relatively low-cost, non-toxic FeSO₄·7 H₂O precursor at an optimized concentration, were employed without any harmful chemicals for pH adjustment. Additionally, a unique calcination strategy was applied. This method produced nanoparticles with an average size of 20–30 nm, confirmed by Field Emission Scanning Electron Microscopy (FESEM). Crystalline structures of the magnetite and hematite nanoparticles were validated by X-Ray Diffraction (XRD), and Fe–O bonding with organic capping was identified by Fourier Transform Infrared Spectroscopy (FTIR). These nanoparticles exhibited superparamagnetic behavior with saturation magnetization of 6–13 emu/g, measured by Vibrating Sample Magnetometry (VSM), and strong optical absorption with band gaps from 1.52 to 4.78 eV, determined by UV-Vis spectroscopy and Tauc’s plots. Preliminary antibacterial and photocatalytic tests showed moderate bioactivity, highlighting potential environmental and biomedical uses. This eco-friendly, scalable approach combines abundant natural extracts and avoids the use of harmful chemicals, advancing sustainable production of magnetite and hematite nanoparticles and addressing a critical gap in green nanotechnology.

The aim of this work was the synthesis of hybrid materials of iron (II)-based therapeutic systems via the sol-gel method. Increasing amounts of polyethylene glycol (PEG 6, 12, 24, 50 wt%) were added to SiO2/Fe20 wt% to modulate the release kinetics of the drug from the systems. Fourier-transform infrared (FTIR) spectroscopy was used to study the interactions between different components in the hybrid materials. The release kinetics in a simulated body fluid (SBF) were investigated, and the amount of Fe2+ released was detected via ultraviolet-visible spectroscopy (UV-Vis) after reaction with ortho-phenanthroline. Furthermore, biological characterization was carried out. The bioactivity of the synthesized hybrid materials was evaluated via the formation of a layer of hydroxyapatite on the surface of samples soaked in SBF using spectroscopy. Finally, the potential antibacterial properties of seven different materials against two different bacteria—E. coli and S. aureus—were investigated.

The fossiliferous deposits within the lower-lying Jacovec Cavern in the locality of Sterkfontein yielded valuable hominin remains, including the StW 578 specimen. Because StW 578 mainly preserves the calotte, the taxonomic status of this specimen has been a matter of discussion. Within this context, here we employed high-resolution microtomography and a landmark-free registration method to explore taxonomically diagnostic features in the external surface of the StW 578 calotte. Our comparative sample included adult humans and common chimpanzees as well as one Australopithecus africanus specimen (Sts 5). We partially restored the StW 578 calotte digitally and compared it to extant specimens and Sts 5 using a landmark-free registration based on smooth and invertible surface deformation. Our comparative shape analysis reveals morphological differences with extant humans, especially in the frontal bones, and with extant chimpanzees, as well as intriguing specificities in the morphology of the StW 578 parietal bones. Lastly, our study suggests morphological proximity between StW 578 and Sts 5. Given the intimate relationship between the brain and the braincase, as well as the integration of the hominin face and neurocranium, we suggest that cranial vault shape differences between StW 578 and extant humans, if confirmed by further analyses, could be either explained by differences in brain surface morphology or in the face. Besides providing additional information about the morphology of the Jacovec calotte that will be useful in future taxonomic discussion, this study introduces a new protocol for the landmark-free analysis of fossil hominin cranial shape.

Sterkfontein is the most prolific single source of Australopithecus fossils, the vast majority of which were recovered from Member 4, a cave breccia now exposed by erosion and weathering at the landscape surface. A few other Australopithecus fossils, including the StW 573 skeleton, come from subterranean deposits [T. C. Partridge et al., Science 300, 607–612 (2003); R. J. Clarke, K. Kuman, J. Hum. Evol. 134, 102634 (2019)]. Here, we report a cosmogenic nuclide isochron burial date of 3.41 ± 0.11 million years (My) within the lower middle part of Member 4, and simple burial dates of 3.49 ± 0.19 My in the upper middle part of Member 4 and 3.61 ± 0.09 My in Jacovec Cavern. Together with a previously published isochron burial date of 3.67 ± 0.16 My for StW 573 [D. E. Granger et al., Nature 522, 85–88 (2015)], these results place nearly the entire Australopithecus assemblage at Sterkfontein in the mid-Pliocene, contemporaneous with Australopithecus afarensis in East Africa. Our ages for the fossil-bearing breccia in Member 4 are considerably older than the previous ages of ca. 2.1 to 2.6 My interpreted from flowstones associated with the same deposit. We show that these previously dated flowstones are stratigraphically intrusive within Member 4 and that they therefore underestimate the true age of the fossils.

The sodium potassium pump (Na+,K+‐ATPase) shows a high selectivity for K+ over Na+ binding from the extracellular medium. To understand the K+ selectivity in the presence of a high concentration of competing Na+ ions requires consideration of more than just ion binding affinities. Here, equilibrium‐based calculations of the extracellular occupation of the Na+,K+‐ATPase transport sites by Na+ and K+ are compared to fluxes through Na+ and K+ transport pathways. The results show that, under physiological conditions, there is a 332‐fold selectivity for pumping of K+ from the extracellular medium into the cytoplasm relative to Na+, whereas equilibrium calculations alone predict only a 7.5‐fold selectivity for K+. Thus, kinetic effects make a major contribution to the determination of extracellular K+ selectivity. Selective pumping by the Na+,K+‐ATPase of K+ ions across cell plasma membranes is not due to differences in Na+ and K+ equilibrium ion binding affinities alone. Much faster kinetics of occlusion of K+ over Na+ on the protein's extracellular face perturbs the ion binding equilibria and explains the virtual exclusive inward pumping of K+ under physiological conditions.

The effect of cholesterol removal by methyl- β-cyclodextrin on the dipole potential, ψ d, of membrane vesicles composed of natural membrane lipids extracted from the kidney and brain of eight vertebrate species was investigated using the voltage-sensitive fluorescent probe di-8-ANEPPS. Cyclodextrin treatment reduced cholesterol levels by on average 80% and this was associated with an average reduction in ψ d of 50 mV. Measurements of the effect of a range of cholesterol derivatives on the ψ d of DMPC lipid vesicles showed that the magnitude of the effect correlated with the component of the sterol’s dipole moment perpendicular to the membrane surface. The changes in ψ d observed could not be accounted for solely by the electric field originating from the sterols’ dipole moments. Additional factors must arise from sterol-induced changes in lipid packing, which changes the density of dipoles in the membrane, and changes in water penetration into the membrane, which changes the effective dielectric constant of the interfacial region. In DMPC membranes, the cholesterol-induced change in ψ d was biphasic, i.e., a maximum in ψ d was observed at ∼35–45 mol %, after which ψ d started to decrease. We suggest that this could be associated with a maximum in the strength of DMPC-cholesterol intermolecular forces at this composition.

Isochron burial dating with cosmogenic nuclides 26 Al and 10 Be shows that the skeleton of the australopithecine individual known as ‘Little Foot’ is around 3.67 million years old, coeval with early Australopithecus from East Africa; a manuport dated to 2.18 million years ago from the Oldowan tool assemblage conforms with the oldest age previously suggested by fauna. An early date for 'Little Foot' australopithecine The cave infillings at Sterkfontein in South Africa contain some of the richest assemblages of fossil hominins in the world. The problem with Sterkfontein and many caves like it is that it is notoriously difficult to date such sediments : they accumulate in a haphazard way with many episodes of deposition, erosion and reworking. Darryl Granger et al . use isochron burial dating with cosmogenic nuclides 26 Al and 10 Be to show that the breccia containing the substantially complete skeleton of the australopithecine individual known as 'Little Foot' is around 3.67 million years old, coeval with Australopithecus afarensis ('Lucy') from East Africa. The earliest stone tools from Sterkfontein are dated to around 2.18 million years ago, a similar age to tools from nearby sites such as Swartkrans. The cave infills at Sterkfontein contain one of the richest assemblages of Australopithecus fossils in the world, including the nearly complete skeleton StW 573 (‘Little Foot’) 1 , 2 , 3 , 4 in its lower section, as well as early stone tools 5 , 6 , 7 in higher sections. However, the chronology of the site remains controversial 8 , 9 , 10 , 11 , 12 , 13 , 14 owing to the complex history of cave infilling. Much of the existing chronology based on uranium–lead dating 10 , 11 and palaeomagnetic stratigraphy 8 , 12 has recently been called into question by the recognition that dated flowstones fill cavities formed within previously cemented breccias and therefore do not form a stratigraphic sequence 4 , 14 . Earlier dating with cosmogenic nuclides 9 suffered a high degree of uncertainty and has been questioned on grounds of sediment reworking 10 , 11 , 13 . Here we use isochron burial dating with cosmogenic aluminium-26 and beryllium-10 to show that the breccia containing StW 573 did not undergo significant reworking, and that it was deposited 3.67 ± 0.16 million years ago, far earlier than the 2.2 million year flowstones found within it 10 , 11 . The skeleton is thus coeval with early Australopithecus afarensis in eastern Africa 15 , 16 . We also date the earliest stone tools at Sterkfontein to 2.18 ± 0.21 million years ago, placing them in the Oldowan at a time similar to that found elsewhere in South Africa at Swartkans 17 and Wonderwerk 18 .

The catalytic α-subunits of both the Na + ,K + -ATPase and the gastric H + ,K + -ATPase possess lysine-rich N-termini which project into the cytoplasm. Due to conflicting experimental results, it is currently unclear whether the N-termini play a role in ion pump function or regulation, and, if they do, by what mechanism. Comparison of the lysine frequencies of the N-termini of both proteins with those of all of their extramembrane domains showed that the N-terminal lysine frequencies are far higher than one would expect simply from exposure to the aqueous solvent. The lysine frequency was found to vary significantly between different vertebrate classes, but this is due predominantly to a change in N-terminal length. As evidenced by a comparison between fish and mammals, an evolutionary trend towards an increase of the length of the N-terminus of the H + ,K + -ATPase on going from an ancestral fish to mammals could be identified. This evolutionary trend supports the hypothesis that the N-terminus is important in ion pump function or regulation. In placental mammals, one of the lysines is replaced by serine (Ser-27), which is a target for protein kinase C. In most other animal species, a lysine occupies this position and hence no protein kinase C target is present. Interaction with protein kinase C is thus not the primary role of the lysine-rich N-terminus. The disordered structure of the N-terminus may, via increased flexibility, facilitate interaction with another binding partner, e.g. the surrounding membrane, or help to stabilise particular enzyme conformations via the increased entropy it produces. Graphical Abstract

Lysosomes have crucial roles in regulating eukaryotic metabolism and cell growth by acting as signalling platforms to sense and respond to changes in nutrient and energy availability 1 . LYCHOS (GPR155) is a lysosomal transmembrane protein that functions as a cholesterol sensor, facilitating the cholesterol-dependent activation of the master protein kinase mechanistic target of rapamycin complex 1 (mTORC1) 2 . However, the structural basis of LYCHOS assembly and activity remains unclear. Here we determine several high-resolution cryo-electron microscopy structures of human LYCHOS, revealing a homodimeric transmembrane assembly of a transporter-like domain fused to a G-protein-coupled receptor (GPCR) domain. The class B2-like GPCR domain is captured in the apo state and packs against the surface of the transporter-like domain, providing an unusual example of a GPCR as a domain in a larger transmembrane assembly. Cholesterol sensing is mediated by a conserved cholesterol-binding motif, positioned between the GPCR and transporter domains. We reveal that the LYCHOS transporter-like domain is an orthologue of the plant PIN-FORMED (PIN) auxin transporter family, and has greater structural similarity to plant auxin transporters than to known human transporters. Activity assays support a model in which the LYCHOS transporter and GPCR domains coordinate to sense cholesterol and regulate mTORC1 activation. Cryo-electron microscopy structures of the human lysosomal transmembrane protein LYCHOS show that it comprises a transporter-like domain fused to a G-protein-coupled receptor, and that the transporter domain is similar to the plant PIN family.

Anions and cations have long been recognized to be capable of modifying the functioning of various membrane-related physiological processes. Here, a fluorescent ratio method using the styrylpyridinium dyes, RH421 and di-8-ANEPPS, was applied to determine the effect of a range of anions and cations on the intramembrane dipole potential of dimyristoylphosphatidylcholine vesicles. It was found that certain anions cause a decrease in the dipole potential. This could be explained by binding within the membrane, in support of a hypothesis originally put forward by A. L. Hodgkin and P. Horowicz [1960, J. Physiol. (Lond.) 153:404–412.] The effectiveness of the anions in reducing the dipole potential was found to be ClO 4 − > SCN − > I − > NO 3 − > Br − > Cl − > F − > SO 4 2−. This order could be modeled by a partitioning of ions between the membrane and the aqueous phase, which is controlled predominantly by the Gibbs free energy of hydration. Cations were also found to be capable of reducing the dipole potential, although much less efficiently than can anions. The effects of the cations was found to be trivalent > divalent > monovalent. The cation effects were attributed to binding to a specific polar site on the surface of the membrane. The results presented provide a molecular basis for the interpretation of the Hofmeister effect of lyotropic anions on ion transport proteins.