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Steric control of copper nuclearity in sulfur ligated oxidase mimics alters catechol and phenoxazinone oxidation
Abstract Control over copper nuclearity is a key issue in bioinspired oxidation chemistry, yet its mechanistic consequences in sulfur-donor environments remain insufficiently understood. Here, remote tert-butyl substitution on a flexible dithioether-dithiolate ligand scaffold switches the preferred copper(II) assembly from binuclear [CuS 4 ] 2 to mononuclear [CutBuS 4 ], enabling a direct assessment of nuclearity effects within a common sulfur-ligated framework. Combined spectroscopic, electrochemical, stopped-flow kinetic, and DFT studies show that this steric perturbation modifies complex stability, productive substrate binding, and the extent to which catalytic turnover benefits from metal-metal cooperativity. In the aerobic oxidation of 3,5-di-tert-butylcatechol, both complexes follow a two-step sequence of rapid reversible substrate binding and slower oxidation, and both reach similar maximum turnover frequencies under saturating conditions, ca. 1700–1750 h − 1 . The binuclear [CuS 4 ] 2 nevertheless shows stronger productive substrate binding, with K M values of 3.4 vs. 5.0 mM for the mononuclear $$\:\left[CutBu{S}_{4}\right]$$ , respectively. In contrast, oxidation of o-aminophenol to aminophenoxazinone is strongly nuclearity-dependent, with [CuS 4 ] 2 displaying substantially higher activity than $$\:\left[CutBu{S}_{4}\right]$$ (2772 vs. 684 h − 1 ), consistent with a decisive role for dicopper cooperativity in oxidative coupling. Detection of H 2 O 2 and the lack of 4-nitrocatechol oxidation support an oxidase-type pathway in which catalytic competence depends on substrate reducing power and access to productive oxygen-dependent redox chemistry.
Tin perovskite transistors stabilized through volatile coordination
Engineered zwitterion-nanodelivery for precision targeting of brain metastases
Preparation and identification of chitosan and chitosan nanoparticles from crab byproducts
Abstract This study was designed to extract chitosan from blue crab shells and prepare chitosan nanoparicles via combination of chemical extraction process with mechanical ball-milling method. The size and surface charge of the NPs were evaluated in chitosan nanoparicles using dynamic light scattering (DLS). The prepared crab chitosan and chitosan nanoparicles were evaluated for their characteristics using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy coupled with Energy Dispersive X-ray analysis (SEM-EDX), Transmission Electron Microscopy (TEM) and viscosity measurements compared with commercial chitosan products. The DLS results of crab chitosan nanoparicles appeared to be the optimal chitosan nanoparicles with minimum particle size (192.74 ± 3.25 nm), zeta potential (25.15 ± 1.19 mV) smallest PDI (0.228 ± 0.011) in comparison with commercial nanoparicles had a particle size (245.47 ± 3.21 nm), zeta potential (32.24 ± 0.72 mV) smallest PDI (0.191 ± 0.055), respectively. The FTIR and XRD analyses indicated that α-chitosan mainly formed an amorphous structure along with a higher deacetylation degree. There are no diffraction peaks at 2θ ≈ 10°, showing that chitin was effectively deacetylated with a negligible content of residual chitin. Chitosan nanoparicles from crab had a particle size of about 84 nm based on Debye–Scherrer equation that is comparable to commercial nanoparticles. Crab chitosan nanoparicles has been shown to possess distinctly rough flake-like surfaces, while CS NP is compact spheres to cubes with reduced pore dimensions, as confirmed by SEM and TEM analyses. EDX with low residual mineral contents confirmed good purities of prepared materials. Rheological analysis indicated that chitosan extracted from crabs exhibited greater viscosity (31.707 to 42.849 mPa·s) than commercial chitosan (17.818 to 24.024 mPa·s), indicating a higher molecular weight and more significant intermolecular interactions. The overall chitosan yield was 11.02% of the crab shell dry weight. The findings suggest that blue crab shell waste is a value-added product. .
A unified vision-language model for precision oncology and biomarker prediction in neuroblastoma
Sexual selection and ecological-demographical context drive the evolution of same-sex sexual behaviour
Abstract The occurrence of same-sex sexual behaviours (SSB) has long attracted the attention of researchers in evolutionary biology since these interactions do not directly lead to reproduction. The frequency of SSB is expected to vary depending on sexual context, but whether it responds to populations’ ecological and demographical factors is unknown. Using experimental evolution in the seed beetle Callosobruchus maculatus , we explored the interactive effects of sexual selection intensity (polygamy vs. monogamy) and population spatial structure (undivided populations vs. divided metapopulations) in shaping the frequency of same-sex interactions. Males engaged more often in SSB than females. In undivided populations polygamy led to higher frequencies of male-male interactions, while SSB was more frequent in monogamous compared to polygamous lines when populations were divided. Our findings suggest that males are subject to stronger selection for higher frequency of SSB than females, and that the intensity of sexual selection is responsible for the frequency of SSB in large undivided populations. However, our results indicate that in divided populations softer selection operating in small subpopulations may lead to relaxed selection for mate discrimination, especially under monogamy. Our results point to a complex interaction between sexual selection evolutionary history and softness of selection shaping SSB.
Why paying peer reviewers works, according to a journal’s editor-in-chief
A statistical test for the benefits of personalizing interventions
From medicine to marketing to social sciences, the promise of tailoring interventions to individuals is undeniable. However, practical applications force weighing personalization’s potential benefits with its possible increased cost and fragility. We introduce a statistical hypothesis test that evaluates, given historical data, evidence that a personalized intervention policy’s performance will surpass deploying the best single intervention. The test maintains strict Type I error control while achieving asymptotic normality with the minimal possible variance under specified conditions. Results on diverse datasets from job training, depression treatment, education, and recommendation systems demonstrate the test’s versatility and its superior performance over alternatives. This test can support decision-makers throughout the intervention sciences by providing a simple and powerful quantification of the potential benefits of personalization.
Force-based reading and writing of individual single-atom magnets
Abstract The integration of single-atom bits enables the realization of the highest data-density memory. Reading and writing information to these bits through mechanical interactions opens the possibility of operating the magnetic devices with low heat generation and high density recording. To achieve this visionary goal, we demonstrate the use of magnetic exchange force microscopy to read and write the spin orientation of individual holmium adatoms on MgO thin films. The spin orientation of the holmium adatom is stabilized by the strong uniaxial anisotropy of the adsorption site and can be read out by measuring the exchange forces between the magnetic tip and the atom. The spin orientation can be written by approaching the tip closer to the holmium adatom. We explain this writing mechanism by the symmetry reduction of the adsorption site of the Ho adatom. These findings demonstrate the potential for information storage with minimal energy loss and pave the way for a new field of atomic-scale mechano-spintronics.
Ensartinib in Resected <i>ALK</i> -Positive Non–Small-Cell Lung Cancer
AlphaGo-driven generative machine learning framework for inverse topology synthesis and optimization of planar antennas
Backreaction of stimulated Hawking radiation in an optical analogue
Prison release is an opportunity for addiction research
The intersecting effects of race/ethnicity, wealth, education, and gender on AIDS among 28.3 million Brazilians
Immediate or Deferred Nonculprit-Lesion PCI
Effects of balance and strength training protocols to improve ankle joint stability in armed recruits
The hidden logic of emotion
Internal emotion models unify research across species and spark fresh ideas for treating anxiety and trauma