Proton Distribution Research Articles

Does Native Capillary Zone Electrophoresis-Mass Spectrometry Maintain the Structural Topology of Protein Complexes?

Native capillary zone electrophoresis-mass spectrometry (nCZE-MS) is a useful analytical tool for studying protein complexes. However, the extent to which the protein complexes maintain their native structural topology in nCZE-MS compared to traditional native MS (nMS) is still not fully characterized. In this technical note, we contribute to this topic by coupling nCZE-MS with surface-induced dissociation (SID) for two well-studied protein complexes (streptavidin and human recombinant C-reactive protein). SID cleaves the weakest interface of a given complex, making it a powerful diagnostic tool for identifying perturbations of protein complex structures based on fragmentation patterns. The SID fragmentation patterns of the two protein complexes from nCZE-MS under normal and charge-reducing conditions show a high similarity index compared to those from direct infusion. Additionally, nCZE-MS shows the potential to separate different conformations or different proton distributions that have subtle differences. Although only two cases are shown, the results suggest that nCZE-MS can maintain the native-like structural topology of protein complexes.

Proton Intensity Dropout in Isotropic Turbulence Regime during Gradual Solar Energetic Particle Events in Solar Cycle 23

Abstract When the Wind spacecraft started its only journey to Lagrange point L2 in 2003 October, it entered an isotropic turbulent environment with radially mean magnetic field ( B m) and slow solar wind speed (V SW). On October 26, it detected a particle intensity dropout interval following a gradual solar energetic particle event. In addition, it recorded three magnetic field rotations corresponding to one-sided increases in V SW, indicating the occurrence of magnetic switchback in the Alfvénic solar wind. Since the last switchback interval is just before the dropout interval, we studied the difference of the pitch angle distribution (PAD) of protons between them. In the switchback interval ( B m perpendicular to V sw), the PAD maximum is located at μ ∼ +1, where μ is the pitch angle cosine, while, in the dropout interval ( B m antiparallel to V sw), the maximum is at μ ∼ 0. The difference indicates that protons with greater gyroradii cannot be confined in the curved magnetic field lines and can be injected into the dropout region with μ ∼ 0. Therefore, the analysis of proton pitch angle scattering in the dropout interval can be greatly simplified due to the short duration of the interval and the sharp initial conditions. Compared with the analytical solution of the Fokker–Planck equation, we deduce that the parallel mean free path of 2.1 MeV protons is 3.7 ± 0.5 au, which means that the dropout of proton intensity in the isotropic turbulent regime is also caused by insufficient spatial diffusion of protons.

Mechanism of L-arginine improving the macroscopic and microscopic qualities of Acipenser schrenckii surimi gel under low-salt conditions and microwave irradiation: Significance of moisture migration and distribution.

Mechanism of L-arginine improving the macroscopic and microscopic qualities of Acipenser schrenckii surimi gel under low-salt conditions and microwave irradiation: Significance of moisture migration and distribution.

Generation and Distribution of Protons in the Nucleus According to New Axioms and Laws

Generation and Distribution of Protons in the Nucleus According to New Axioms and Laws

Kelvin Probe Force Microscopy Imaging of Plasticity in Hydrogenated Perovskite Nickelate Multilevel Neuromorphic Devices.

Ion drift in nanoscale electronically inhomogeneous semiconductors is among the most important mechanisms being studied for designing neuromorphic computing hardware. However, nondestructive imaging of the ion drift in operando devices directly responsible for multiresistance states and synaptic memory represents a formidable challenge. Here, we present Kelvin probe force microscopy imaging of hydrogen-doped perovskite nickelate device channels subject to high-speed electric field pulses to directly visualize proton distribution by monitoring surface potential changes spatially, which is also supported with finite element-based electric field distribution studies. First-principles calculations provide mechanistic insights into the origin of surface potential changes as a function of hydrogen donor doping that serves as the contrast mechanism. We demonstrate 128 (7-bit) nonvolatile conductance levels in such devices relevant to in-memory computing applications. The synaptic plasticity measurements are implemented in spiking neural networks and show promising results for classification (SciKit Learn's Iris and Wine data sets) and control (OpenAI's CartPole-v1 and BipedalWalker-v3) simulation tasks.

Exploring the Potential of Gold Nanoparticles in Proton Therapy: Mechanisms, Advances, and Clinical Horizons.

Proton therapy represents a groundbreaking advancement in cancer radiotherapy, leveraging the unique spatial energy distribution of protons to deliver precise, high-dose radiation to tumors while sparing surrounding healthy tissues. Despite its clinical success, proton therapy faces challenges in optimizing its therapeutic precision and efficacy. Recent research has highlighted the potential of gold nanoparticles to enhance proton therapy outcomes. Due to their high atomic number and favorable biological properties, gold nanoparticles act as radiosensitizers by amplifying the generation of secondary electrons and reactive oxygen species upon proton irradiation. This enhances DNA damage in tumor cells while preserving healthy tissues. Additionally, functionalization of gold nanoparticles with tumor-targeting ligands offers improved precision, making proton therapy more effective against a broader range of cancers. This review synthesizes current knowledge on the mechanisms of gold nanoparticle radiosensitization, preclinical evidence, and the technological hurdles that must be addressed to integrate this promising approach into clinical practice, aiming to advance the efficacy and accessibility of proton therapy in cancer therapy.

Bayesian Approach to Equipartition Estimation of Magnetic Field Strength

Abstract Magnetic fields, together with cosmic rays (CRs), play an important role in the dynamics and evolution of galaxies, but are difficult to estimate. Energy equipartition between magnetic fields and CRs provides a convenient way to approximate magnetic field strength from radio observations. We present a new approach for calculating the equipartition magnetic field strength based on Bayesian methods. In this approach, the magnetic field is a random variable that is distributed according to a posterior distribution conditional on synchrotron emission and the size of the emitting region. It allows for the direct application of the general formulas for total and polarized synchrotron radiation without the need to invert these formulas, which has limited the equipartition method to highly simplified cases. We have derived the equipartition condition for the case of different low-energy breaks, slopes, and high-energy cutoffs of power-law spectra of the CR proton and electron distributions. The derived formalism was applied in the general case of a magnetic field consisting of both uniform and randomly oriented field components. The applied Bayesian approach naturally provides the uncertainties in the estimated magnetic field strengths resulting from the uncertainties in the observables and the assumed values of the unknown physical parameters. In the examples presented, we used two different Markov Chain Monte Carlo methods to generate the posterior distribution of the magnetic field. We have also developed a web application called BMAG that implements the described approach for different models and observational parameters of real sources.

Preliminary results on the transverse flow of charged K mesons emitted from Ag+Ag collisions at beam energy of 1.58 GeV/nucleon measured with HADES

In this contribution, preliminary results on the flow of charged K mesons emitted from semicentral Ag+Ag collisions at a beam kinetic energy of 1.58 GeV/nucleon measured with HADES are presented as v1,2 coefficients mapped in the scaled rapidity – transverse momentum phase space. The coefficients, extracted by fitting a Fourier series to the azimuthal angle distributions, are corrected for the finite resolution of the event plane reconstruction, but not yet for inefficiencies related to the local track density in the detector. The K± flow is compared to the corresponding distributions for protons emitted from the same system. These comparisons suggest a repulsive potential between the K+ and nuclear matter, while conclusions for the K− are not possible to be drawn at this point, due to high statistical uncertainties.

Proton diffusion and hydrogen/deuterium exchange in amorphous solid water at temperatures from 114 to 134 K.

The reaction coefficient for hydrogen/deuterium (H/D) exchange and the diffusion of hydrated excess protons within amorphous solid water (ASW) are characterized as a function of temperature. For these experiments, water films are deposited on a Pt(111) substrate at 108K, and reactions with pre-adsorbed hydrogen atoms produce hydrated protons. Upon heating, protons diffuse within the water, and H/D exchange occurs when they encounter D2O probe molecules deposited in the films. The time-dependent concentration of D2O is monitored with infrared spectroscopy, and it indicates the protons diffusion from the substrate and establish an equilibrium distribution prior to significant H/D exchange for temperatures 114K ≤T≤ 134K. By controlling the distance between the D2O molecules and the substrate, we probe the distribution of protons within the film. It decays as x-2 for the examined range of x (12-52nm) due to the electric field that develops between the diffusing protons and their image charges in the metal substrate. This agrees with the theoretical distance scaling for the equilibrated proton concentration in a dielectric near a metal boundary. From the proton concentration and the measured D2O decay rate, a lower bound for the proton diffusion coefficient ranging from 10-20m2/s at 114K to 10-18m2/s at 134K is estimated. The diffusion coefficient has an activation energy of 0.40eV, which is comparable to energies reported for molecular translations and rotations of H2O, suggesting they may play a critical role in the proton diffusion mechanism within ASW.

Effect of Relaxation Times on Magnetization of Blood Proton Spins at Steady State using Improved Bloch NMR Fluid Flow Equation

Nuclear magnetic resonance (NMR) is a phenomenon that involves the absorption and re-emission of electromagnetic radiation by blood proton spins flowing through human vessels. NMR is governed by Bloch NMR fluid flow equation, which can be used to define the magnetization of blood proton spins. In the existing literature, the Bloch NMR fluid flow equation has been derived, and it has been observed that the equation does not incorporate certain NMR and blood flow parameters. In this paper, we derived a novel Bloch NMR magnetization flow equation that encompasses NMR parameters such as Larmor frequency of spinning protons and static magnetic field. We utilized the principle of dimensional homogeneity to check the validity of our newly derived NMR flow equation. Furthermore, we investigated the effect of transverse relaxation times of arterial, venous and capillary blood on magnetization of blood spinning protons. We employed Laplace transform method to obtain the steady state solution of the improved Bloch NMR fluid flow equation. MATLAB and Origin software tools were used for data analysis and simulations. Results showed that for varied transverse relaxation times of arterial, venous and capillary blood, respectively, the magnetization distribution of blood spinning protons consists of two components: the linear and the non-linear components. The findings of the study also indicated that capillary blood proton spins exhibit phase coherence. The simulated results may be used by spectroscopists to improve the accuracy of NMR/magnetic resonance imaging (MRI) experiments.

Minimum (Dip) And Maximum (Bump) in Proton’s Single Diffractive Dissociation at the LHC

A dip-bump structure in the squared four-momentum transfer (t) distribution of proton’s single and double diffractive distributions is predicted around t ≈ −4 GeV2 for single diffractive distribution at LHC energies.

Ionization loss spectra of high-energy protons in an oriented crystal at various incidence angles with respect to a crystalline plane

The ionization energy loss distributions (spectra) of high-energy protons in oriented silicon crystals are considered on the basis of computer simulation. Evolution of the spectra with the change of the angle θ between the particle momentum and the crystal (110) plane is investigated. It is shown that both the most probable and the average energy loss change non-monotonically with the increase of θ. While at small θ these losses are lower than their values in a disoriented crystal, at larger θ they can be higher than these values. The dependence of the most probable energy loss on θ contains a discontinuity, which however might be challenging to register experimentally. Additionally, the influence of dechanneling and the incident beam divergence on the spectra of planar channeled protons is demonstrated.

Contribution of Protonation to the Dielectric Relaxation Arising from Bacteriopheophytin Reductions in the Photosynthetic Reaction Centers of Rhodobacter sphaeroides.

The pH dependence of the free energy level of the flash-induced primary charge pair P+IA- was determined by a combination of the results from the indirect charge recombination of P+QA- and from the delayed fluorescence of the excited dimer (P*) in the reaction center of the photosynthetic bacterium Rhodobacter sphaeroides, where the native ubiquinone at the primary quinone binding site QA was replaced by low-potential anthraquinone (AQ) derivatives. The following observations were made: (1) The free energy state of P+IA- was pH independent below pH 10 (-370 ± 10 meV relative to that of the excited dimer P*) and showed a remarkable decrease (about 20 meV/pH unit) above pH 10. A part of the dielectric relaxation of the P+IA- charge pair that is not insignificant (about 120 meV) should come from protonation-related changes. (2) The single exponential decay character of the kinetics proves that the protonated/unprotonated P+IA- and P+QA- states are in equilibria and the rate constants of protonation konH +koffH are much larger than those of the charge back reaction kback ~103 s-1. (3) Highly similar pH profiles were measured to determine the free energy states of P+QA- and P+IA-, indicating that the same acidic cluster at around QB should respond to both anionic species. This was supported by model calculations based on anticooperative proton distribution in the cluster with key residues of GluL212, AspL213, AspM17, and GluH173, and the effect of the polarization of the aqueous phase on electrostatic interactions. The larger distance of IA- from the cluster (25.2 Å) compared to that of QA- (14.5 Å) is compensated by a smaller effective dielectric constant (6.5 ± 0.5 and 10.0 ± 0.5, respectively). (4) The P* → P+QA- and IA-QA → IAQA- electron transfers are enthalpy-driven reactions with the exemption of very large (>60%) or negligible entropic contributions in cases of substitution by 2,3-dimethyl-AQ or 1-chloro-AQ, respectively. The possible structural consequences are discussed.

Depth profiling of implanted D in silicates: Contribution of solar wind protons to water in the Moon and terrestrial planets

The solar wind protons implanted in silicate material and combined with oxygen are considered crucial for forming OH/H O on the Moon and other airless bodies. This process may also have contributed to hydrogen delivery to planetary interiors through the accretion of micrometre-sized dust and planetesimals during early stages of the Solar System. This paper experimentally investigates the depth distribution of solar wind protons in silicate materials and explores the mechanisms that influence this profile. We simulated solar wind irradiation by implanting 3 keV D ions in three typical silicates (olivine, pyroxene, and plagioclase) at a fluence of sim 1.4 × 10 ions/cm . Fourier transform infrared spectroscopy was used to analyse chemical bond changes, while transmission electron microscopy (TEM) characterised microstructural modifications. Nanoscale secondary ion mass spectrometry (NanoSIMS) was employed to measure the D/ O ratio and determine the depth distribution of implanted deuterium. The newly produced OD band (at 2400–2800 cm –1 ) in the infrared spectrum reveals the formation of O–D bonds in the irradiated silicates. The TEM and NanoSIMS results suggest that over 73<!PCT!> of the implanted D accumulated in fully amorphous rims with a depth of 70 nm, while 25<!PCT!> extended inwards to sim 190 nanometres, resulting in partial amorphisation. The distribution of these deuterium particles is governed by the collision processes of the implanted particles, which involve factors such as initial energy loss, cascade collisions, and channelling effects. Furthermore, up to 2<!PCT!> of the total implanted D penetrated the intact lattice via diffusion, reaching depths ranging from hundreds of nanometres to several micrometres. Our results suggest that implanted solar wind protons can be retained in silicate interiors, which may significantly affect the hydrogen isotopic composition in extraterrestrial samples and imply an important source of hydrogen during the formation of terrestrial planets.

Effect of 3D printing accuracy by wheat starch gel combined with canola oil

Effect of 3D printing accuracy by wheat starch gel combined with canola oil

Production and measurement of a stellar neutron spectrum at 30 keV

A few years ago, we theoretically studied the production of a stellar neutron spectrum at kT = 30 keV using a shaped proton beam impinging on a thick lithium target. Here, we first measure the proton distribution to better control the produced neutron spectrum. Then, we measure the forward-emitted angle-integrated neutron spectrum of the 7Li(p,n)7Be reaction via time-of-flight neutron spectrometry with such proton distribution. The result resembles a stellar neutron spectrum at kT = 30 keV. This method avoids in activation experiments the need for spectrum correction. In the case of spherical samples, no knowledge of the cross-section of the isotope being measured by activation would be necessary. Therefore, the present method is of interest for isotopes with unknown or poorly known cross-sections, such as branching points in astrophysics. The key point of our method is the experimental control of the proton distribution that impinges on the lithium target.

Simultaneous Occurrence of Electromagnetic and Quasi‐Electrostatic Magnetosonic Waves

AbstractMagnetosonic (MS) waves usually manifest as electromagnetic fluctuations, while quasi‐electrostatic magnetosonic (QEMS) waves have been recently reported. Here we present an intriguing coexistence of low harmonic electromagnetic magnetosonic (EMMS) waves and QEMS waves within the same band. Ion Bernstein instabilities are calculated based on the observed proton distribution. Effective growth rates can occur in the first‐fourth harmonic bands with a broad wave number range when the wave normal angle is sufficiently large. In each harmonic band, the MS waves would transform from electromagnetic to electrostatic as the wave number increases. This study reveals that the simultaneous occurrence of EMMS and QEMS arises from the expansive excitation range of MS waves in ‐space, thereby implying the potential resonant interactions between MS and particles in a broad energy spectrum.

High-Temperature Mechanical–Conductive Behaviors of Proton-Conducting Ceramic Electrolytes in Solid Oxide Fuel Cells

Proton-conducting solid oxide fuel cells (P-SOFCs) are widely studied for their lower working temperatures than oxygen-ion-conducting SOFCs (O-SOFCs). Due to the elevated preparation and operation temperatures varying from 500 °C to 1500 °C, high mechanical stresses can be developed in the electrolytes of SOFCs. The stresses will in turn impact the electrical conductivities, which is often omitted in current studies. In this work, the mechanical–conductive behaviors of Y-doped BaZrO3 (BZY) electrolytes for P-SOFCs under high temperatures are studied through molecular dynamics modeling. The Young’s moduli of BZY in fully hydrated and non-hydrated states are calculated with different Y-doping concentrations and at different temperatures. It is shown that Y doping, oxygen vacancies, and protonic point defects all lead to a decrease in the Young’s moduli of BZY at 773 K. The variations in the conductivities of BZY are then investigated by calculating the diffusion rates of protons in BZY at different triaxial, biaxial, and uniaxial strains from 673 K to 873 K. In all cases, the diffusion rate present a trend of first increasing and then decreasing from compression state to tension state. The variations in elementary affecting factors of proton diffusion, including hydroxide rotation, proton transfer, proton trapping, and proton distribution, are then analyzed in detail under different strains. It is concluded that the influences of strains on these factors collectively determine the changes in proton conductivity.

Linear polarization of the helium D<sub>3</sub> line by accelerated protons in the solar chromosphere

In the article, we have studied the impact linear polarization of the helium D3line that takes place in the solar chromosphere under the action of protons accelerated in solar flares. The dependence of the energy distribution of protons on the distance traveled inside the chromosphere is calculated. The ratio of the concentrations of nonthermal protons and thermal electrons at different depths is theoretically determined. From the calculation of the degree of linear polarization of the helium line D3for different layers of the chromosphere, the region of probable formation of the line is determined.

Preparation and characterization of lactoferrin-polyphenol conjugate with stabilizing effects on fish oil high internal phase Pickering emulsions

Preparation and characterization of lactoferrin-polyphenol conjugate with stabilizing effects on fish oil high internal phase Pickering emulsions