Electronic Resonance Research Articles

Passaging Human Tauopathy Patient Samples in Cells Generates Heterogeneous Fibrils with a Subpopulation Adopting Disease Folds.

The discovery by cryo-electron microscopy (cryo-EM) that the neu-ropathological hallmarks of different tauopathies, including Alzheimer's disease, corticobasal degeneration (CBD), and progressive supranuclear palsy (PSP), are caused by unique misfolded conformations of the protein tau is among the most profound developments in neurodegenerative disease research. To capitalize on these discoveries for therapeutic development, one must achieve in vitro replication of tau fibrils that adopt the representative tauopathy disease folds, which represents a grand challenge for the field. A widely used approach has been seeded propagation using pathological tau fibrils derived from post-mortem patient samples in biosensor cells that expresses a fragment of the tau protein known as K18, or Tau4RD, containing the microtubule-binding repeat domain of tau as the substrate. The new insights from cryo-EM raised the question of whether the Tau4RD fragment is capable of adopting characteristic tau folds found in CBD and PSP patient fibrils, and whether cell-passaged and amplified tau fibrils can be used as seeds to achieve cell-free assembly of recombinant 4R tau into fibrils without the addition of cofactors. Using Double Electron Electron Resonance (DEER) spectroscopy, we discovered that cell-passaged pathological seeds generate heterogeneous fibrils that are, however, distinct between the CBD and PSP lysate-seeded fibrils, and vastly different from heparin-induced tau fibril structures. Moreover, the lysate-seeded fibrils contain a characteristic sub-population that resembles the disease fold corresponding to the respective starting patient sample. These findings indicate that templated propagation using CBD and PSP patient-derived fibrils is possible with a tau fragment that does not contain the entire pathological fibril core, but also that additional mechanisms must be tuned to converge on a homogeneous fibril population.

Comparison of Microwave-assisted Synthesis and Steglich Thioesterification for the Modification of Nanotubes

: Organo-modified carbon nanotubes have recently gained the interest of many research groups. The potential for applying a new generation of organo-modified carbon nanotubes in many technological fields reveals the importance of covalent modifications on nanotubes. In this study, using the microwave synthesis method, multi-walled carbon nanotube (MWCNT) thiophenol derivatives were obtained with a thioesterification reaction. For this purpose, MWCNT-COOH was obtained from MWCNT by oxidation, and MWCNT-COCl was synthesized from MWCNT-COOH. The MWCNT-CO-S- (ortho/meta/para-methyl/methoxy-phenyl) (MA1-MA6) compounds were synthesized through both microwave synthesis methods starting with MWCNT-COCl and Steglich ester reaction of MWCNT-COOH. Products were characterized using Fourier Transform- Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR), Thermogravimetric Analysis (TGA), and Transmission Electron Spectroscopy (TEM) methods. Furthermore, step numbers, reaction times, and temperatures of obtained molecules, MA1-MA6, were compared. Steglich esterification was found to be the most effective technique for creating these compounds. The photoluminescent characteristics of MWCNT, MWCNT-COOH, and MA1-MA6 compounds were examined. The intensity of the photoluminescence (PL) was found to vary with the location of the functional group. It was detected that the MA2 compound had the highest photoluminescence intensity (6.9x102 a.u.), while the MA1 compound had the secondhighest photoluminescence intensity (6.9x102 a.u.). MA1 and MA2 were radiated at low wavelengths of 475- 490 nm with high PL values. Possible transitions were n→π* transitions, with high PL values obtained because of the oxygen atom in the methoxy group. It is expected that these materials will find use in imaging devices operating at high temperatures, particularly because structures containing methoxy groups exhibit favourable photoluminescence properties.

Comparative study of electron transport through aromatic molecules on gold nanoparticles: insights from soft X-ray spectroscopy of condensed nanoparticle films versus flat monolayer films.

Understanding electron transport in self-assembled monolayers on metal nanoparticles (NPs) is crucial for developing NP-based nanodevices. This study investigates ultrafast electron transport through aromatic molecules on NP surfaces via resonant Auger electron spectroscopy (RAES) with a core-hole-clock (CHC) approach. Aromatic molecule-coated Au NPs are deposited to form condensed NP films, and flat monolayers are prepared for comparison. Soft X-ray techniques, including X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy, confirm oriented monolayers in both NP and flat films. The nuclear dynamics is studied via ion yield measurements. After subtracting secondary processes, the ion yield spectra of the condensed NP films reveal site-selective desorption of the methyl ester group by resonant core excitation. The ultrafast electron transport time from the carbonyl group through the phenyl rings to the metal surfaces in the condensed NP films is successfully determined via the RAES-CHC approach by subtracting inelastic scattering components. The chain length of the aromatic molecules influence the electron transport time in the NP films, reflecting the trends observed in the flat films. This evidence supports ultrafast electron transport via the through-bond model, independent of interactions between the molecules adsorbed on an NP itself or adjacent NPs. Identifying and subtracting background spectral components of the condensed NP films allows accurate analysis of the ultrafast dynamics. This study suggests that insights gained from electron transport processes in the flat monolayer films can be extrapolated to practical NP-molecule interfaces, providing valuable insights for the molecular design of NP-based devices.

Indole-containing inhibitors with improved efficacy targeting the gyrase of Mycobacterium tuberculosis

Abstract Tuberculosis is a major cause of mortality worldwide, with drug-resistant strains complicating its treatment. We report the discovery of small-molecule inhibitors targeting the gyrase of Mycobacterium tuberculosis, the bacterium responsible for tuberculosis. Gyrase, a type II topoisomerase, consists of two subunits: GyrA, which breaks and rejoins DNA, and GyrB, which contains the ATPase domain responsible for ATP binding and hydrolysis. An indole scaffold identified by nuclear magnetic resonance fragment screening was grown into drug-sized candidates through computational optimization, chemical synthesis and functional selection. Several indole-containing gyrase inhibitors were found to be specific for the GyrB subunit of M. tuberculosis. Structural studies using double electron–electron resonance spectroscopy between the Mn(II) ion in the catalytic site of GyrB and a nitroxide-labeled inhibitor provided insights into the potential docking sites of the protein target. Key chemical descriptors essential for gyrase binding were identified for the small-molecule inhibitors using data-driven algorithms. Our results demonstrate the effectiveness of fragment screening and computational optimization in drug discovery. The inhibitors presented in this study are promising candidates for further pharmacological studies in vivo.

Super-Resolved Fluorescence Lifetime Imaging of Single Cy3 Molecules and Quantum Dots Using Time-Correlated Single Photon Counting with a Four-Pixel Fiber Optic Array Camera.

Time-resolved single molecule localization microscopy (TR-SMLM) with a 2 × 2 pixel fiber optic array camera was combined with time-correlated single photon counting (TCSPC) to obtain super-resolved fluorescence lifetime images of individual Cy3 dye molecules and individual colloidal CdSe/CdS/ZnS core/shell/shell semiconductor quantum dots (QDs). The characteristic blinking and bleaching behavior of the Cy3 and the blinking behavior of the QD emitters were used as distinguishing optical characteristics to isolate them and determine their centroid locations with spatial resolution below the optical diffraction limit. TCSPC was used to characterize the fluorescence lifetime and intensity corresponding to each emitter location. The mean centroid locations of the QDs could be determined with a precision of ∼1-4 nm, and the mean centroid locations of the Cy3 molecules could be determined with a precision of ∼2-9 nm, depending on the number of photons collected during the observation time. In a super-resolved fluorescence lifetime image with a single Cy3 dye molecule and a single QD separated by ∼34 nm, the two emitters were distinguished based on the average photon arrival times with respect to the excitation laser pulse observed during time intervals when only one emitter was in the on state, ∼6 ns for Cy3 and ∼17 ns for the QD. The mean distance between the two emitters was determined with a precision of ∼8 nm. The feasibility of using this super-resolved fluorescence lifetime imaging technique to investigate QD-dye complexes that use Förster resonance energy transfer (FRET) and/or electron transfer to form optical biosensors is discussed.

Rapid Analysis of DEER Signals Including Short Distances.

Double electron electron resonance (DEER) spectroscopy is an important technique to measure distance distributions P(r) for studying protein structures and protein-protein interactions. DEER data analysis can at times become challenging due to the lack of a detailed analytical signal expression or numerical methods with rapid computation time. We have derived an analytical expression κFULL, which includes both the pseudo-secular dipolar coupling (PSDC) and the finite pulse effects, especially important for shorter distances. Analyses of experiments by κFULL yield accurate and consistent P(r) values for three DEER nitroxide-rulers with distances (rAVG) in the range of 15 to 32 Å, while the current standard analysis produces erroneous results for rAVG < 20 Å. Computation times for deriving P(r) vary between 1 min and 4 min, which is usually much shorter than previous methods that include pseudo-secular and other effects. The expression can be applied to all types of DEER spin probes with little or no modifications.

New Arylalkenyl α-Pyrones from Cryptocarya densiflora.

Four previously undescribed arylalkenyl α-pyrones, designated as crydensiones A‒D (1‒4), were isolated from the twigs and leaves of Cryptocarya densiflora. Their structures were determined through comprehensive spectroscopic analyses together with quantum chemical calculations of electronic circular dichroism (ECD) and nuclear magnetic resonance (NMR)data. All isolates were assessed for cytotoxicity against HCT-116 (colon), A549 (lung), and MDA-MB-231 (breast) cancer cell lines; however, none demonstrated significant activity.

Hyper-Raman spectroscopy of non-proteinogenic amino acids.

We report 532-nm and 1064-nm excited hyper-Raman (HR) spectra of representative non-proteinogenic amino acids, including α-, β-, and γ-amino acids. Different from the common 20 proteinogenic amino acids, natural non-proteinogenic amino acids cannot be incorporated into proteins during translation, while they are indispensable as intermediates in many processes like biosynthesis and neurotransmitters. In 532-nm excited HR spectra, the COO─ symmetric stretching bands are commonly intense, and the NH3+ bands are clearly observable. In addition, based on the reported IR and Raman study, we found that some HR bands are IR-active but Raman-inactive. In contrast, HR signals with the 1064-nm excitation are much weaker than the 532-nm excitation. Nevertheless, we observed the COO─ scissoring band unexpectedly, much stronger than other bands with the 1064-nm excitation. Our results suggest that the electronic resonance effect plays a role in enabling us to detect HR signals in the UV region readily. We expect that this study provides a supplementary reference for HR spectroscopy of natural amino acids.

Quantification of Rapid Cooling of Glycerol/Water Solutions Based on Photoluminescence from Thioflavin T.

Rapid cooling to a solid state allows intermediates in chemical and biomolecular processes that occur in solution near room temperature to be trapped for subsequent measurements by magnetic resonance spectroscopies, electron microscopy, or other techniques. In time-resolved solid state nuclear magnetic resonance and rapid freeze-quench electron paramagnetic resonance studies, solutions are typically frozen by spraying into a cold bath or onto a cold metal surface. Although simulations suggest freezing on millisecond or submillisecond time scales, direct experimental measurements of cooling rates have been elusive. Here, we describe a method for quantification of rapid cooling rates based on measurements of temperature-dependent photoluminescence from thioflavin T (ThT). In our experiments, a jet of ThT solution in glycerol/water, with 10.8 m/s jet velocity and 30 μm diameter, freezes on a cold, rotating copper surface. Images of ThT photoluminescence on the copper surface indicate that the cooling rate of the solution increases linearly with the surface velocity over the 0.45-6.2 m/s range. At surface velocities greater than 3.8 m/s, the time to cool from 300 to 260 K or from 300 to 230 K is less than 100 μs or less than 700 μs. The experimental results do not agree quantitatively with calculations in which a layer of glycerol/water cools by thermal conduction when suddenly brought in contact with a cold copper surface. Discrepancies between experimental results and simplistic calculations illustrate the importance of direct measurements of cooling rates.

Electroless Synthesis of Cobalt Nanowires in Magnetic Field and their Characterization by Resonant Magnetometry Methods

In this paper, a simple and effective low-temperature electroless chemical method that provides the synthesis of cobalt micro- and nanowires due to the processes of self-organization of magnetic cobalt nanoparticles under the influence of a magnetic field, using the technology of chemical synthesis of magnetic nanoparticles and nanowires is proposed. Cobalt nanoparticles have magnetic dipole moments. An external magnetic field forces them to be oriented parallel to it. Dipole-dipole interactions between magnetic nanoparticles lead to attraction between cobalt nanoparticles leading to their self-organization into nanowires, reducing their total energy. The resulting smaller nanoparticles fill the gaps between the ordered nanoparticles, leading to the formation of smooth cobalt nanowires. The magnetic and structural properties of the synthesized and commercial nanowires polarized by a magnetic field in the epoxy matrix were studied using the resonant radio-frequency magnetometry and electron microscopy methods. These methods are of interest for optimizing the coercive force of cobalt nanowires with a view to their possible use in creating permanent magnets that do not use rare earth elements, as well as in information processing devices and sensors.

Double Plasma Resonance in Electron–Positron Plasma at the Pulsar Magnetosphere

Double Plasma Resonance in Electron–Positron Plasma at the Pulsar Magnetosphere

Probing coherence properties of shallow implanted NV ensembles under different oxygen terminations

Abstract Nitrogen vacancy (NV) color centers in diamond have shown great potential for various applications in quantum technology due to their long coherence times, high sensitivity to magnetic fields and atomic scale resolution. However, one major challenge in utilizing near surface NV centers is the decoherence caused by spins and charges fluctuating on the surface, which affects the spin properties of the sensors. To reduce the induced noise, various oxygen surface treatments such as low power oxygen plasma treatment and annealing under oxygen atmosphere have been explored to terminate the diamond surface and reduce its impact on NV coherence. We showed that the NV center’s coherence time can be enhanced up to a factor of 3 over a large spectral range of noise. Double electron–electron resonance measurements revealed an extra source of decoherence, scaling similarly as the P1 spin bath. The improvement in coherence times is accompanied with an increase in measured ketone/ether content and reduction of sp2 signal in x-ray photoelectron spectroscopy measurements. Finally we compared the performance of different NV ensembles and surface treatments for sensing external proton spins. The oxygen annealing is an effective procedure of enhancing the spin coherence times and reducing broad band spin noise experienced by shallow implanted ensemble NV centers in diamond.

The kinetic analog of the pressure–strain interaction

Energy transport in weakly collisional plasma systems is often studied with fluid models and diagnostics. However, the applicability of fluid models is limited when collisions are weak or absent, and using a fluid approach can obscure kinetic processes that provide key insights into the physics of energy transport. Kinetic diagnostics retain all of the information in 3D-3V phase space and thereby reach beyond the insights of fluid models to elucidate the mechanisms responsible for collisionless energy transport. In this work, we derive the Kinetic Pressure–Strain (KPS): a kinetic analog of the pressure–strain interaction, which is the channel between flow energy density and internal energy density in fluid models. Through two case studies of electron Landau damping, we demonstrate that the KPS diagnostic can elucidate kinetic mechanisms that are responsible for energy transport in this channel, just as the related field–particle correlation is known to identify kinetic mechanisms of transport between electromagnetic field energy density and kinetic energy density in particle flows. In addition, we show that resonant electrons play a major role in transferring energy between fluid flows and internal energy during the process of Landau damping.

Low‐Frequency Whistler Waves Excited by Electron Butterfly Distributions in Turbulent Reconnection Outflow

AbstractWhistler waves, leading to electron scattering and energy transport, are frequently observed in magnetic reconnection. High‐energy electrons produced by magnetic reconnection are expected to excite low‐frequency whistler waves. However, the study on low‐frequency whistler waves in magnetic reconnection is still quite scarce. Utilizing high‐resolution data from the Magnetospheric Multiscale (MMS) mission, we provide observations of low‐frequency whistler waves in a turbulent reconnection outflow. The quasi‐antiparallel propagating whistler waves have power peaked at ∼0.1 and wave number of ∼0.43 in the plasma rest frame. It can be excited through the cyclotron resonance by the electron butterfly distributions, which can be interpreted by a model comprising the addition of electron beams hosting perpendicular anisotropy to electron isotropy distributions. The energy of resonant electrons is calculated as 1.06∼4.16 keV, the parts corresponding to lower frequency (&lt;∼0.1) falling into suprathermal energy range. Our study can promote the understanding of generation of whistler waves in magnetic reconnection.

Real-Time TDDFT Using Noncollinear Functionals.

Recently, we proposed a method to generalize collinear functionals to noncollinear functionals, called multicollinear approach, which has been applied in density functional theory (DFT) and linear-response time-dependent DFT (TDDFT) for the ground state and excited states calculations, respectively. In this work, we demonstrate the application of this method in real-time TDDFT by simulating electronic absorption spectra, Rabi resonance, and precession of a two-magnetic center system. Thanks to the nonvanishing local exchange-correlation torque provided by multicollinear functionals, research into the torques in the evolution of magnetization vector is carried out, which is useful for the exploration on spin dynamics.

New eco-friendly succinimide linseed oil resin: synthesis, characterization, DFT and docking studies for surface coating

Purpose The purpose of this study is to develop a new protective coating formulation for industrial use, using new eco-friendly succinimide linseed oil resin. Design/methodology/approach Epoxidized linseed oil and N-(4-hydroxy phenyl) succinimide are reacted to create succinimide-modified epoxy (SIE) compounds. The synthesized compound was confirmed by different analyses, gas chromatography, Fourier transform infrared, proton nuclear magnetic resonance and scanning electron microscopy. The prepared compound has been blended with a primer paint formulation, then their physical and mechanical properties have been studied. Density function theory is used to calculate Frontier molecular orbital including highest occupied molecular orbital and least unoccupied molecular orbital to indicate the charge transfer from molecule to biological media and molecular electrostatic potential map was used to indicate the chemically reactive zone suitable for drug action. Findings The results of the paint formulation confirmed their best performance and provided good mechanical properties and high chemical and corrosion resistance. Research limitations/implications Resin compounds are the most used antimicrobial additives. Other functionalities of these compounds, such as corrosion inhibitors, might be studied to see if they are suited for these applications. Practical implications Because of the efficiency of the SIE when incorporated with primer, paint against microbial has also been examined in silico using the docking study which contributed to the analysis of their protein binding. This type of epoxy compound is environmentally friendly and can be used as a biocide with different paint formulations. As a result, paint compositions including this compound as additives can be used as dual-purpose paint and for a variety of industrial applications. Originality/value This research demonstrates how a low-cost paint composition based on synthesized SIE compounds may be used as a dual-function paint for industrial use.

Model-predictive kinetic control with data-driven models on EAST

Abstract In this work, model-predictive control (MPC) was combined for the first time with singular perturbation theory, and an original plasma kinetic control method based on extremely simple data-driven models and a two-time-scale MPC algorithm has been developed. A comprehensive review is presented in this paper. Slow and fast semi-empirical models are identified from data, by considering the fast kinetic plasma dynamics as a singular perturbation of a quasi-static equilibrium, which itself is governed, on the slow time scale, by the flux diffusion equation. This control technique takes advantage of the large ratio between the time scales involved in magnetic and kinetic plasma transport. It is applied here to the simultaneous control of the safety factor profile, q(x), and of several kinetic variables, such as the poloidal beta parameter, βp, and the internal inductance parameter, li, on the EAST tokamak. In the experiments, the available control actuators were lower hybrid current drive (LHCD) and co-current neutral beam injection (NBI) from different sources. Ion cyclotron resonant heating (ICRH) and electron cyclotron resonant heating (ECRH) are used as additional actuators in control simulations. In the controller design, an observer provides, in real time, an estimate of the system states and of the mismatch between measured and predicted outputs, which ensures robustness to model errors and offset-free control. A number of control applications are described in the paper, either in nonlinear simulations with EAST-like parameters or in real experiments on EAST. Various controller configurations were tested, with up to three controlled variables chosen among q0 = q(x=0), q1 = q(x=0.5), βp and li. Both the extensive nonlinear simulations and the experiments described in this paper have demonstrated the relevance of combining model-predictive control, data-driven models and singular perturbation methods for plasma kinetic control.

Non-Covalent Interactions of Lotus Root Polysaccharides and Polyphenols and their Regulatory Mechanism on Macrophage Functions.

Despite the interaction between polyphenols and polysaccharides in food products, their specific non-covalent interactions and effects on macrophage functions are not well understood. Therefore, the interaction and mechanism of purified lotus root polysaccharide (PLRP) with polyphenols, and the regulatory mechanisms of the PLRP-polyphenol complex on the macrophage functionals were studied. By combining ferulic acid (FA) and chlorogenic acid (CHA) with PLRP, the complexes PLRP-FA, PLRP-CHA and the physical mixtures PLRP&FA and PLRP&CHA were prepared, where their mass ratios of polyphenols to PLRP were 143.97 and 601.67 mg g-1. Nuclear magnetic resonance (NMR), Fourier-transform infrared (FTIR), Ultraviolet (UV), and Transmission electron microscopy (TEM) analyses confirmed that PLRP and polyphenols may engage in non-covalent interactions via hydrogen bonds and hydrophobic interactions. We confirmed that non-covalent interactions led to high molecular weight, dense complexes. Both PLRP and its polyphenol complexes stimulated NO production by macrophages to varying degrees without exacerbating lipopolysaccharide-induced inflammatory responses. PLRP and PLRP-polyphenol complexes repaired cells with impaired antioxidant capacity, depending on doses. Those results indicated that after the combination of lotus root polysaccharide and polyphenol, the molecular weight and conformation changed significantly, which influenced the biological activity. RNA-seq analysis suggested that the regulatory mechanism of PLRP-polyphenol complex in macrophages may mainly involve oxidative phosphorylation, FoxO, TNF, IL-17, MAPK, NF-kappa B, and other signaling pathways. This study investigated the effects of polyphenol binding on the physicochemical characteristics and functional activities of polysaccharides, which provided references for the development of polysaccharide functional products and the control of nutritional quality.

Spin polarization effect on linear polarization of photon emission following resonant electron capture of lithiumlike ions

Spin polarization effect on linear polarization of photon emission following resonant electron capture of lithiumlike ions

Crop resilience enhancement through chitosan-based hydrogels as a sustainable solution for water-limited environments

Frequent droughts significantly affect agricultural productivity and highlight the need for effective solutions to improve water availability for crops. This study investigates the potential of chitosan-based hydrogels, biodegradable biopolymers known for their water-retaining properties, to improve soil moisture and promote plant growth during drought periods. Chitosan hydrogels were synthesized using Pluronic F127 and compared with chitosan and chitosan in combination with sodium alginate (CS/Alg-Na). Comprehensive chemical characterizations were performed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and field emission scanning electron microscopy (FESEM). The CS/Pl-F127 hydrogels showed high porosity and a water absorption capacity of 81.5 %, while the CS/Alg-Na exhibited a denser network with a capacity of 93.35 % and improved mechanical strength. Plants in the CS/Pl-F127 hydrogel had a shoot elongation rate of 5.9 mm/day on Day 9, which continued until Day 40. In contrast, shoot elongation in the CS/Alg-Na hydrogel peaked at 7.1 mm/day on Day 20 and maintained growth under drought conditions until Day 33. These results show that all chitosan-based hydrogels improve water use efficiency. CS/Alg-Na provides the best support for plant growth under drought conditions, followed by CS/Pl-F127 and pure chitosan.