Investigation Of Structure Research Articles

Systematic revision of the genus Prionitis (Halymeniales, Rhodophyta) from Taiwan including P. foliagissima sp. nov. and P. imbricata comb. nov

ABSTRACT Grateloupia imbricata is widely distributed in the northwestern Pacific and northeastern Atlantic Oceans. Recent studies have revealed its close relationship to Prionitis, specifically P. taiwani-borealis from northern Taiwan. In this study, we identified a new species, P. foliagissima sp. nov. based on new G. imbricata-like collections from Taiwan. The female reproductive structures of both G. imbricata (= Prionitis imbricata comb. nov.) and P. foliagissima were examined. We demonstrated that the development of carpogonial branch and auxiliary cell ampullae before and after diploidization were similar to those of P. taiwani-borealis. Namely, in P. foliagissima and P. imbricata, the cells of ampullar filaments after diploidization branched a few times and elongated, together with secondarily produced medullary filaments, forming a cellular cluster surrounding the developing carposporophytes. Prionitis foliagissima can be distinguished from the other species of Prionitis found in Taiwan by its smaller thallus size, strongly twisted branches, as well as densely bullate surface. It was noted that the branched ampullar filaments of the two Prionitis species were weakly developed, which differed from those found in species of Phyllymenia (P. taiwanensis and P. huangiae) from Taiwan, where the cells of auxiliary cell ampullar filaments branched several times to form a dense cellular cluster, and in which most cells remained distinct through maturation of gonimoblasts. Further investigation of the female reproductive structures and postfertilization stages of other lesser-known species of Grateloupia, Prionitis, and Phyllymenia is necessary to understand the generic delineation in the Grateloupia/Prionitis/Phyllymenia complex.

Synthesis, spectroscopic, crystal structure and DFT investigation of the Cu(II) complex with mixed 2,2’-dimethylmalonate/2,2'-bipyridine ligands

In this study; a mixed ligand Cu(II) complex, [Cu(Me2mal)(bpy)(H2O)]∙H2O (Me2mal-2= Dimethylmalonate dianion, bpy=2,2'-bipyridine) was synthesized and characterized experimentally and theoretically by IR, UV and single crystal X-ray diffraction. The complex crystallizes in the orthorhombic system with space group Pnnm. In the complex, the Cu center is coordinated by a Me2mal-2 dianion and a bpy molecule, and the N2O2 exhibits square-planar geometry. The axial position was occupied by the water molecule. The crystal packing of the complex is stabilized by O-H…O hydrogen bonds and  interactions. The contribution of hydrogen bonding and  stacking interactions to crystal packing was also investigated. Theoretical calculations using the DFT method were also carried out in this study. DFT (B3LYP/6-31G) and TD-DFT (B3LYP/LanL2DZ) calculation methods were used to obtain the geometric, vibrational and electronic properties of the synthesized complex and the obtained theoretical calculation results and experimental results are presented comparatively in this study.

Molecular Structural Control of the Amorphous‐Crystalline Balance in Solids: Structure‐Phase Correlation in DADQs with Enhanced/Switchable Fluorescence

The amorphous/crystalline (A/C) assembly in molecular solids has a direct bearing on their attributes and applications, including mechanical, pharmaceutical, electronic and photophysical. A systematic analysis of the molecular features and interactions that determine the predilection towards the A, C or bi‐stable A‐C states is critical. This fundamental problem is addressed through an exhaustive investigation of a large family of alkoxyalkyl diaminodicyanoquinodimethanes (ROR′‐DADQs); enhancement of their fluorescence from the solution, to the A, to the C state serves as an excellent signature of the phase preference and temporal stability. Their thermal characteristics and single crystal structure investigations coupled with Hirshfeld surface analysis of the intermolecular interactions, not only confirm the spectroscopic observations, but also reveal the significant impact of the molecular structural features, key interactions like H‐bonds, and molecular orientations in the lattice, on the phase stability. These explorations lead to a basic structure‐phase correlation; its predictive power is demonstrated by identifying the borderline systems as functional phase change materials, and the subsequent verification through the reversible cycles of fluorescence switching between the A/C states. The factors promoting the A or C forms of molecular solids can guide the design of novel materials exploiting such supramolecular structures and their interconversions.

Paraplaconeis dorofeyukae sp. nov. (Cymbellales, Bacillariophyceae)—a new species from Mongolia, described based on molecular and morphological investigations

An unknown species of the diatom genus Paraplaconeis was discovered during a field study of freshwater environments in Central Mongolia. In the course of further study, two monoclonal strains were acquired for the unknown species. The strains were utilized for molecular-genetic analysis on SSU rRNA and rbcL genes. As a result of the molecular investigation and careful morphological examination of valve structure with light and scanning electron microscopy, we propose the description of a new species—Paraplaconeis dorofeyukae sp. nov.—in this article. The new species is morphologically compared to similar taxa from the Paraplaconeis placentula group. Paraplaconeis dorofeyukae sp. nov. can be distinguished from related species by a combination of valve dimensions, morphology of apices and central area, and external valve ultrastructure.

Numerical investigation of an anti-symmetric nanophotonic structure for accelerating sub-relativistic electron beams

This study investigates an anti-symmetrically positioned nanophotonic dual-pillar structure, in which the dielectric and vacuum components are evenly distributed along the direction of electron propagation, with each dielectric pillar facing a vacuum region. Our numerical simulation results show that the previously proposed symmetric dielectric grating structure, where dielectric pillars facing each other are alternated with vacuum gaps, is accompanied by a deceleration region, preventing the achievement of high gradients during the acceleration process. By contrast, the anti-symmetric grating structure eliminates the deceleration field and generates a uniformly distributed acceleration field. This requires that the two oppositely directed laser beams crossing the structure in the transverse region must have a phase shift of π in the anti-symmetric case. This structure has significant potential for accelerating sub-relativistic electron beams. In this numerical simulation, the initial energy of the sub-relativistic electron beams is selected as 79 keV. The acceleration gradient provided by the symmetric design for sub-relativistic electrons is approximately 70 MeV/m; however, the anti-symmetric structure can provide a maximum acceleration gradient of up to ∼430 MeV/m.

Investigation of Defect Structure and Optical Properties of Sc(0,1,2,3 mol%): Ce: Fe: LiNbO3 Crystals

Investigation of Defect Structure and Optical Properties of Sc(0,1,2,3 mol%): Ce: Fe: LiNbO3 Crystals

Exploring the pharmacological potential of Macrobrachium acanthurus hemocyanin: preliminary biological activity studies

Hemocyanin (Hc) is a copper-containing hemoprotein found in the hemolymph of invertebrates such as mollusks and arthropods. It plays essential roles in oxygen transport, immune defense, and molting processes. Due to their antiviral, antimicrobial, and phenoloxidase (PO) activities, Hcs hold significant potential in biotechnology. This study aims to obtain the Hc from the shrimp Macrobrachium acanthurus and perform preliminary biological activity tests (PO and antimicrobial activity) of this Hc. The results will serve as a basis for future structural and biological investigations of this unique protein. HcMac was purified using ultracentrifugation and size exclusion liquid chromatography (SEC). PO activity was induced by the surfactant SDS in the presence of dopamine hydrochloride, monitored by optical absorption at 475 nm using a spectrophotometer. Tests were performed to evaluate the inhibitory activity against Candida neoformans, Candida albicans and some fish pathogens. The results demonstrated that the surfactant SDS induced PO activity, with optimal formation observed at an SDS concentration of 1.0 mmol L-1. However, HcMac did not exhibit antimicrobial activity in the tests performed. Despite this, we cannot rule out the hypothesis that this Hc has biological activity and an immunological role, since it showed PO activity.

Synthesis, investigation of the crystal structure, DFT and in silico medicinal potential of nicotinonitrile substituted quinazolindione as potential anticancer scaffold

Cancer is now regarded as one of the leading causes of death for people worldwide. Here, we have reported the synthesis of a new dihydroquinazoline derivative namely, 5-acetyl-4-(4-methoxyphenyl)-6-methyl-2-(((4-oxo-3,4-dihydro-quinazolin-2-yl)methyl)thio)nicotinonitrile (4). Its structure was characterised by IR and NMR and confirmed by XRD analysis. In the molecule (4), the dihydroquinazoline moiety is planar. The acetyl and phenyl substituents on the pyridine ring are rotated out of its plane to minimise steric interactions. In the crystal, a layered structure is formed by N—H···O, C—H···O, and C—H···N hydrogen bonds and π-stacking interactions. The large gap between the highest and lowest molecular orbitals indicates high stability. Moreover, the synthesised nicotinonitrile-substituted quinazolinone was screened for medicinal characteristics and drug-likeness estimates. The synthetic ligand was docked with three enzymes, including HER2 (PDB ID: 3WSQ), EGFR (PDB ID: 5WB7), and the extracellular domain of Tdp enzyme (PDB ID: 6N0D), where binding affinities of −8.02, −6.88, and −6.67 Kcal/mol, binding efficiencies of −0.24, −0.21, and −0.20 Kcal/mol and the inhibition constants 1.31, 9.07, and 12.84 µM against the target substrates Tdp1, EGFR, and HER2 protein were found, respectively. Molecular dynamics simulations validated the stability of the docked complexes.

Structural and property investigation of ceramic composite coating fabricated on titanium alloys by high power diode laser alloying

The laser alloying technique is proposed and demonstrated to synthesize titanium silver nitride-based (Ti-Ag-N, TiN/TiAg) composite coating on Ag electroplated Cp-Ti and Ti6Al4V substrates under nitrogen shielding. The laser alloying was carried out using a continuous wave mode fiber coupled diode laser at 980 nm laser wavelength. Nitrogen shielding was useful to avoid interference from atmospheric oxygen and induce the formation of titanium nitride (TiN) phases. The formation of the TiN/TiAg composite was confirmed through surface morphology studies. The microstructural features and microhardness values (around 1000 HV0.2) confirmed the formation of composite Ti-Ag-N phases in the titanium alloy surface. In Ti6Al4V substrate laser alloyed with Ag and N, the formation of dendrites and columnar growth of the composite phases were observed. Ag was homogeneously distributed in the Ti/Ni matrix, and as the Ag coating thickness increased, the average microhardness of the laser alloyed coating decreased slightly.

Chronic RNA G-quadruplex Accumulation in Aging and Alzheimer's Disease.

As the world population ages, new molecular targets in aging and Alzheimer's Disease (AD) are needed to combat the expected influx of new AD cases. Until now, the role of RNA structure in aging and neurodegeneration has largely remained unexplored. In this study, we examined human hippocampal postmortem tissue for the formation of RNA G-quadruplexes (rG4s) in aging and AD. We found that rG4 immunostaining strongly increased in the hippocampus with both age and with AD severity. We further found that neurons with accumulation of phospho-tau immunostaining contained rG4s, that rG4 structure can drive tau aggregation, and that rG4 staining density depended on APOE genotype in the human tissue examined. Combined with previous studies showing the dependence of rG4 structure on stress and the extreme power of rG4s at oligomerizing proteins, we propose a model of neurodegeneration in which chronic rG4 formation is linked to proteostasis collapse. These morphological findings suggest that further investigation of RNA structure in neurodegeneration is a critical avenue for future treatments and diagnoses.

Investigation of the microbial community structures and function in subsurface sediments

In this study, microbial community structures were analyzed in a 5-meter-long sediment core collected from Tennessee, USA, to reveal the diversity and ecological roles of underground microorganisms. Using advanced molecular biology techniques, we classified the microorganisms in the samples and analyzed their distribution in different sedimentary layers. The results show that the microbial communities have obvious stratified distribution characteristics and are closely related to the physical and chemical properties of the sediments. This study improves our understanding of subsurface microbial ecology.

Material selection and performance analysis of RF-MEMS switch for MM-WAVE applications

This paper presents the design, simulation, and investigation of a fundamental structure for capacitive MEMS switches in a shunt configuration. The main objective is to select materials that achieve low actuation voltage while maintaining RF and dynamic performance, especially for mm-wave applications. The proposed design consists of a Fixed-Fixed flexure beam with dimensions of 260 μm in length, 100 μm in width, and 0.5 μm in thickness. Considering the impact of squeeze film, 60 holes are integrated into the beam membrane, each measuring 64 μm² (8µm x 8µm), and a final gap of 1.9 μm is implemented. The suitability of materials for the beam membrane and dielectric layer in capacitive MEMS switches has been thoroughly examined through a combination of theoretical analysis and software simulations. Aluminum (Al) has emerged as the ideal choice for the beam membrane in mm-wave applications. This preference is defensible by its simulated results to offer a low pull-in voltage of 4V, a quality factor of 1.18, and a switching time of 67 microseconds. Similarly, Si3N4 has been identified as appropriate material, offering a upstate capacitance of 91fF and a downstate capacitance of 7.1pF.

Four-Dimensional Printing of β-Tricalcium Phosphate-Modified Shape Memory Polymers for Bone Scaffolds in Osteochondral Regeneration

The use of scaffolds for osteochondral tissue regeneration requires an appropriate selection of materials and manufacturing techniques that provide the basis for supporting both cartilage and bone tissue formation. As scaffolds are designed to replicate a part of the replaced tissue and ensure cell growth and differentiation, implantable materials have to meet various biological requirements, e.g., biocompatibility, biodegradability, and mechanical properties. Osteoconductive materials such as tricalcium phosphate ceramics and some biodegradable polymers appear to be a perfect choice. The present work evaluates the structural, mechanical, thermal, and functional properties of a shape memory terpolymer modified with β-tricalcium phosphate (β-TCP). A new approach is using the developed materials for 4D printing, with a particular focus on its applicability in manufacturing medical implants. In this study, the manufacturing parameters of the scaffold components were developed. The scaffolds were examined via scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and mechanical testing. The cytotoxicity result was obtained with an MTT assay, and the alkaline phosphatase (ALP) activity was measured. The structural and microstructural investigations confirmed the integration of β-TCP into the filament matrix and scaffolds. Thermal stability was enhanced as β-TCP delayed depolymerization of the polymer matrix. The shape memory studies demonstrated effective recovery. The in vitro cell culture studies revealed the significantly increased cell viability and alkaline phosphatase (ALP) activity of the β-TCP-modified terpolymer after 3 weeks. The developed terpolymer can be tailored for applications in which partial shape recovery is acceptable, such as bone scaffolds.

Rational Modification of a Cross-Linker for Improved Flexible Protein Structure Modeling.

Chemical cross-linking/mass spectrometry (XL-MS) has emerged as a complementary tool for mapping interaction sites within protein networks as well as gaining moderate-resolution native structural insight with minimal interference. XL-MS technology mostly relies on chemoselective reactions (cross-linking) between protein residues and a linker. DSSO represents a versatile cross-linker for protein structure investigation and in-cell XL-MS. However, our assessment of its shelf life and batch purity revealed decomposition of DSSO in anhydrous solution via a retro-Michael reaction, which may reduce the active ingredient down to below 90%. To mitigate the occurrence of this degradative mechanism, we report the rational design and synthesis of DSSO-carbamate, which contains an inserted nitrogen atom in the DSSO backbone structure. This modification to DSSO yielded remarkably favorable stability against such decomposition, which translated to higher cross-link and monolink recovery when performing XL-MS on monomeric flexible proteins. Recently, XL-MS has been leveraged against AlphaFold2 and other protein structure prediction algorithms for improved prediction of flexible monomeric multiconformational proteins. To this end, we demonstrate that our novel cross-linker, termed DSSO-carbamate, generated more accurate protein structure predictions when combined with AlphaFold2, on account of its increased recovery of cross-links and monolinks, compared to DSSO. As such, DSSO-carbamate represents a useful addition to the XL-MS community, particularly for protein structure prediction.

Women in Boardrooms and Firm Performance: A Review of the Recent Trends, Global Scenario, and Way Forward

The aim of this review paper is to explore the literature on board gender diversity (BGD) as a corporate governance strategy and whether it brings a favourable impact on firm’s performance. While referring to previous empirical studies, we found a mixed view of the impact of women on boards (WOB) on firm’s performance (FP), but the majority of literature does present a business case for having women directors. To establish the quality and objectivity of this review paper, articles from several high-ranked journals which were published between 2001 and 2023 were selected, and a structured investigation was carried out to prepare a clear meta-analytic presentation of the theme. The findings from chosen research have been categorised, synthesised, and summarised to touch upon the role of gender in corporate boardrooms across four major continents and put forward its implications. Through our cross-continent analysis, we discover stronger positive WOB-FP relationships in developed nations (with higher gender parity scores) than in emerging economies. Our research underpinnings suggest scanty research in the African Subcontinent emanating from inadequacies of a conducive and progressive business environment, while still asserting a positive WOB-FP link. Critical mass and resource dependency theories have also influenced a large section of the literature. This study pulls out many important themes from empirical research on board gender diversity that has been undertaken for over two decades now which aids in identifying pitfalls in the global context and establishing a research agenda for the future.

Identification and analysis of the genetic diversity of Dermacentor everestianus using mitochondrial 16S rRNA and COI sequences in the Xizang Autonomous Region of China

Ticks serve as vectors and reservoirs for a variety of pathogens, including protozoa, bacteria, and viruses, that cause tick-borne diseases in both humans and livestock. Despite their widespread distribution, their genetic diversity and population structure in Xizang have not been thoroughly investigated. In this study, sheep ticks were identified from four counties by microscopy, followed by genetic analysis of Dermacentor everestianus populations in Xizang based on mitochondrial 16S rRNA and cytochrome oxidase subunit 1 (COI) gene sequences. D. everestianus was the predominant species and 16S rRNA gene sequence analysis revealed nine haplotypes with seven nucleotide variations, showing a mean haplotype diversity (Hd) of 0.505 and mean nucleotide diversity (Pi) of 0.00129. Similarly, the COI sequences revealed 28 haplotypes with 26 nucleotide variations, yielding a mean Hd of 0.828 and a mean Pi of 0.00279. Molecular variance analysis (AMOVA) indicated that most genetic variation occurs within populations. In addition, neutral test analyses suggested potential bottleneck events in the D. everestianus populations. The haplotype network had a star-like distribution with the common haplotypes A1, A2, B1, and B5. The phylogenetic tree separated haplotypes of both genes into two branches on the haplotype network indicating no distinct geographical clustering. This study is the first to highlight the prevalence of D. everestianus in Xizang, revealing moderate genetic differentiation among the four populations, possibly due to host mobility. This intensive investigation of genetic variation and population structure contributes valuable insights into the current population genetics of D. everestianus in Xizang, China.

The Future of Structural Geology in the 21st Century – Moving from Mesoscale to Nanoscale Observations in Tectonically Deformed Rocks

ABSTRACT The importance of integrating field studies with various micro-and nano-scale structural geological investigations using petrographic microscope, scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) is highlighted in this paper. The author’s past studies dealing with SEM-EBSD and TEM investigations to decipher deformation mechanism of magnetite are taken as examples to support the robustness of investigating nanostructures in thin films excavated parallel to the kinematic reference frame. In addition, the author also shares a work flow involving collection of oriented field samples, followed by petrophysical investigations (e.g., porosity, permeability, P-wave velocity of oriented samples, etc.), 3D fabric analysis (e.g., AMS, X-ray micro-CT of oriented samples), 2D-microstructural analysis in oriented thin sections (petrography, SEM imaging including in-lens, EBSD, etc.) and finally nanostructural studies in oriented thin films using TEM (in that order). The importance of this integrated approach to evaluate structures at different scales and utilize the results for fundamental research as well as applications such as in the field of understanding fluid flow, mineralization, geothermal systems and radioactive waste management is discussed. Hence the paper provides an overview to the reader about some of the possibilities that exist today (21st century) in the field of structural geology.

The Evolving T Cell Receptor Recognition Code: The Rules Are More Like Guidelines.

αβ T cell receptor (TCR) recognition of peptide-MHC complexes lies at the core of adaptive immunity, balancing specificity and cross-reactivity to facilitate effective antigen discrimination. Early structural studies established basic frameworks helpful for understanding and contextualizing TCR recognition and features such as peptide specificity and MHC restriction. However, the growing TCR structural database and studies launched from structural work continue to reveal exceptions to common assumptions and simplifications derived from earlier work. Here we explore our evolving understanding of TCR recognition, illustrating how structural and biophysical investigations regularly uncover complex phenomena that push against paradigms and expand our understanding of how TCRs bind to and discriminate between peptide/MHC complexes. We discuss the implications of these findings for basic, translational, and predictive immunology, including the challenges in accounting for the inherent adaptability, flexibility, and occasional biophysical sloppiness that characterize TCR recognition.

Structural and electrochemical investigation of P2-Na0.67Fe0.5Mn0.5O2 high-performance sodium ion cathode materials

Structural and electrochemical investigation of P2-Na0.67Fe0.5Mn0.5O2 high-performance sodium ion cathode materials

A novel bis-phosphonyl C-glycoside: the first synthesis of C-(1,6-deoxy-β-D-glucopyranosyl)dimethylphosphonate, a stable bisphosphonate to probe the mechanism of β-phosphoglucomutase.

β-Phosphoglucomutase (β-PGM) catalyzes the interconversion of β-D-glucose-1-phosphate and β-D-glucose-6-phosphate sequentially utilizing a transient aspartyl-phospho enzyme and a β-D-glucose-1,6-bisphosphate intermediate. Herein, we report the first synthesis of the isosteric, cleavage resistant, phosphonate analogue C-(1,6-deoxy-β-D-glucopyranosyl)dimethylphosphonate, to aid in mechanistic and structural investigations of β-PGM and its phosphate transfer process. The introduction of the 'pseudo anomeric' phosphonate was accomplished through methylenephosphonate anion addition to gluconolactone, whilst the second phosphonate was installed at C-6 of the β-D-glucopyranosyl moiety using a Horner-Wadsworth-Emmons (HWE) reaction on the C-6 aldehyde. The synthesis was completed in 10 steps with 8% overall yield.