Interatomic Interaction Models for Magnetic Materials:Recent Advances

Atomistic modeling is a widely employed theoretical method of computational materials science.It has found particular utility in the study of magnetic materials.Initially,magnetic empirical interatomic potentials or spinpolarized density functional theory(DFT)served as the primary models for describing interatomic interactions in atomistic simulations of magnetic systems.Furthermore,in recent years,a new class of interatomic potentials known as magnetic machine-learning interatomic potentials(magnetic MLIPs)has emerged.These MLIPs combine the computational efficiency,in terms of CPU time,of empirical potentials with the accuracy of DFT calculations.In this review,our focus lies on providing a comprehensive summary of the interatomic interaction models developed specifically for investigating magnetic materials.We also delve into the various problem classes to which these models can be applied.Finally,we offer insights into the future prospects of interatomic interaction model development for the exploration of magnetic materials.

Lipofuscins prepared by modification of photoreceptor cells via glycation or lipid peroxidation show the similar phototoxicity

AIM To investigate the effect of two ways of lipofuscin production(lipid peroxidation and glycation) on lipofuscin fluorescence characteristics and phototoxicity and to compare them with the properties of natural lipofuscin.METHODS Model lipofuscins were prepared on the basis of bovine photoreceptor outer segments(POS) with bisretinoid A2 E addition. One set of samples was prepared from POS modified by lipid peroxidation,while another set from POS modified by glycation with fructose. Fluorescent properties and kinetics of photoinduced superoxide generation of model lipofuscins and human retinal pigment epithelium(RPE) lipofuscin were compared. The fluorescence spectra of samples were measured at 365 nm excitation wavelength and 380-650 emission wavelength. RESULTS The fluorescence spectra of model lipofuscins are almost the same as the spectrum of natural lipofuscin. Visible light irradiation of both model lipofuscins and natural lipofuscin isolated from RPE cells leads to decrease of a fluorescence maximum at 550 nm and to appearance of a distinct,new maximum at 445-460 nm. The rate of photogeneration of reactive oxygen forms by both model lipofuscins was almost the same and approximately two times less than that of RPE lipofuscin granules.CONCLUSION These data suggest that fluorescent characteristics and phototoxicity of lipofuscin granules depend only to an insignificant degree on the oxidative modification of POS proteins and lipids,and generally are defined by the bisretinoid fluorophores contained in them.

Quantum dynamics of charge transfer on the one-dimensional lattice:Wave packet spreading and recurrence

The wave function temporal evolution on the one-dimensional （ID） lattice is considered in the tight-binding approxi- mation. The lattice consists of N equal sites and one impurity site （donor）. The donor differs from other lattice sites by the on-site electron energy E and the intersite coupling C. The moving wave packet is formed from the wave function initially localized on the donor. The exact solution for the wave packet velocity and the shape is derived at different values E and C. The velocity has the maximal possible group velocity v = 2. The wave packet width grows with time -t1/3 and its amplitude decreases ,- t-1/3. The wave packet reflects multiply from the lattice ends. Analytical expressions for the wave packet front propagation and recurrence are in good agreement with numeric simulations.

Experimental Study of the Antitumor Activity of Polymetalacrylates against Animal Transplantable Tumors

The antitumor activity of the fourteen polymetalacrylates against two models of murine solid tumors (Lewis lung carcinoma and Acatol adenocarcinoma) as well as the acute toxicity of these compounds has been studied. It was shown that polyacrylates of noble metals (argent, aurum, platinum), namely argacryl (М = Ag), auracryl (М = Au) and platacryl (М = Pt) were the most effective agents among tested compounds against studied tumors. Thus, the tumor growth inhibitory effect of argacryl against Lewis lung carcinoma was equal to 90%, the life-span of treated by this compound animals has increased on 50% in comparison with control. Auracryl induced the inhibition of the Lewis lung carcinoma and Acatol adenocarcinoma development on 60 and 65%, correspondingly and the increasing of the mean life-span of animals with Lewis lung carcinoma on 20% in comparison with control. Platacryl inhibited the growth of Lewis lung carcinoma on 40% increasing the mean life-span of animals on 25% in comparison with control. In this way it was established that argacryl is the agent with the strongest antitumor activity among studied polymetalacrylates. On the basis of obtained data it seems possible to consider polymetalacrylates as a group of agents with the potential antitumor activity suitable for the further deep experimental investigation.

Modeling Structures and Spectra of Fluorescent Proteins in the Coordinate-Locking Cluster Approach: Application to the Photoswitchable Protein AsFP595

An interest in the fluorescent protein asFP595 is due to unexplained puzzles in its photophysical behavior. We report the results of calculations of structures, absorption, and emission bands in asFP595 by considering model molecular clusters in the coordinate-locking scheme. Both trans and cis conformations of the anionic chromophore are considered. Equilibrium geometry coordinates on the ground potential energy surface were optimized in the density functional theory approaches by considering both large- and reduced-size clusters. The cluster size was reduced to locate positions of the minimum energy points on the excited-state potential surface by using the configuration interaction singles approach. Vertical excitation energies and oscillator strengths were computed by using the ZINDO method. We show that consideration of large clusters mimicking the protein-containing pocket is an essential issue to calculate positions of absorption and emission bands with the accuracy compatible to experiments.

Metal and Ligand Control on Structure and Functions of Ni(Fe)ARD:Role of Supramolecular Structures

Role of Ni(Fe)-macrostructures due to H-bonds in mechanisms of Ni(Fe)ARD action in methionine salvage pathway is discussed.The AFM method was used to research the possibility of the formation of stable supramolecular nanostructures based on Ni(Fe)ARD model systems{Ni(acac)_(2)+L^(2)+Tyr}(L^(2)=NMP(NMP=N-Methyl-2-pirrolidone)),His(His=L-Histidine),Tyr(Tyr=L-Tyrosine)---with the assistance of intermolecular H-bonds.In the course of scanning of investigated samples,it has been found that the structures based on model systems are fixed on a surface strongly enough due to H-bonding.The self-assembly-driven growth of the supramolecular structures on modified Silicone surface based on researched complexes,due to H-bonds and perhaps the other non-covalent interactions was observed.

Relationships between a Thiol-Disulfide System and Liposoluble Antioxidants with Cytogenetic Indices in Humans Exposed to Low Doses Radiation

This work presents the results of biochemical examination of people exposed to irradiation as a result of the Chernobyl catastrophe. In remote period ( in 4, 5, 6 and 7 years) after Chernobyl accident we studied the state of the redox system of glutathione(GSH, GSSG) and the response of the system of essential lipid antioxidants (vitamin E, A) in blood plasma of people of various ages. An analysis of correlations between cytogenetic indices in lymphocytes and levels of reduced glutathione and liposoluble antioxidants in the plasma of peripheral blood in children born after the Chernobyl accident and liquidators is presented. The cumulative doses for the examined group of children received by their mothers from 0.8 to 70 cSv and liquidators received, on average, the highest irradiation doses from 0.1 to 150 cSv. A complex relationship between lipo-and water-soluble antioxidants level in plasma in human population (children living in radionuclide-contaminated regions and the Chernobyl liquidators) exposed to chronic low-level radiation after the Chernobyl accident was demonstrated. The obtained experimental data indicate different responses of the human population water-and fat-soluble antioxidants system to low (from 0.1 to 20 cSv) and high (from 20 to 150 cSv) doses of ionizing radiation.

Structure,magnetic and adsorption properties of novel FePt/h-BN heteromaterials

Nanomaterials with high specific surface area and high absorption capacity are attracting increased interest aimed at imparting the desired magnetic properties.This work is devoted to the study of the effect of heat treatment in a hydrogen atmosphere on the microstructure,adsorption and magnetic properties of heterogeneous FePt/h-BN nanomaterials.Obtained via the polyol process,FePt nanoparticles(NPs)had a size<2 nm and were uniformly distributed over the surface of hexagonal boron nitride(h-BN)nanosheets.The temperature-activated fcc→fct phase transformation in ultrafine FePt NPs has been well documented.FePt NPs act as active centers dissociating H2 molecules and transfer adsorbed hydrogen atoms to the h-BN.Density functional theory(DFT)calculations also indicate that the h-BN substrate can absorb hydrogen adsorbed on the FePt NPs.This hydrogen circulation in the FePt/h-BN system promoted the fcc→fct phase transformation and allowed to control the magnetic properties.FePt/h-BN nanomaterials also exhibited a high adsorption capacity with respect to various organic dyes.

Nuclear sphingomyelin in neurodegenerative diseases

Introduction:Recently,sphingolipids(SphLs)have become increasingly appreciated as a family of molecules involved in the growth,differentiation,and death of the central nervous system cells.The disequilibrium among the different SphLs leads to changes in the neuronal cell physiology and induces the development of neurodegenerative diseases(Alessenko and Albi,2020).Sphingomyelin(SM),sphinganin(Sphn),sphingosine(Sph),sphingosine-1-phosphate(S1P)and ceramide(Cer)are the most well-studied group of SphLs responsible for neurodegeneration,as well as derived molecules such as glucosylceramide or cerebroside(GCer)and galactosylceramide(GalCer)and finally more complex molecules such as as gangliosides.

Molecular docking of cyanine and squarylium dyes with SARS-CoV-2 proteases NSP3, NSP5 and NSP12

Background:The outbreak and continued spread of coronavirus infection(COVID-19)sets the goal of finding new tools and methods to develop analytical procedures and tests to detect,study infection and prevent morbidity.Methods:The noncovalent binding of cyanine and squarylium dyes of different classes(60 compounds in total)with the proteases NSP3,NSP5,and NSP12 of SARS-CoV-2 was studied by the method of molecular docking.Results:The interaction energies and spatial configurations of dye molecules in complexes with NSP3,NSP5,and NSP12 have been determined.Conclusion:A number of anionic dyes showing lower values of the total energy Etot could be recommended for practical research in the development of agents for the detection and inactivation of the coronavirus.

The unfinished Nobel race of Eugene Zavoisky: to the 75th anniversary of EPR discovery

On 21, January 2019 there will be 75 years when electron paramagnetic resonance (EPR) was discovered by Eugene (Yevgeny)Konstantinovich Zavoisky (Fig. 1) in 1944 in the USSR. This method has revolutionized the study of various physical, chemical and biological systems, and the importance of Zavoisky’s discovery is acknowledged by the EPR scientific community all over the world.

磷掺杂剂和石墨烯包覆层对NiCo_(2)S_(4)电催化剂析氢活性和耐久性的协同影响

探索具有优异导电性和稳定性的非贵金属电催化剂对氢经济至关重要.本研究将杂原子掺杂和石墨烯包覆相结合,以控制NiCo_(2)S_(4)(NCS)蛋黄壳微球的电子性能,并抵抗酸性介质中H_(2)O和O_(2)的腐蚀.密度泛函理论(DFT)模拟结合综合表征和实验首次揭示了在NCS中引入P杂原子不仅加速了电子从体相向表面的转移动力学,而且降低了掺杂P原子附近活性S位上的析氢反应势垒.利用DFT计算的穿透能垒预测了rGO覆盖层在P掺杂NCS(P-NCS)表面对质子的渗透性和对H_(2)O和O_(2)分子的抵抗性等重要功能,并用X射线光电子能谱对新催化剂和回收催化剂进行了验证.利用P掺杂剂和rGO覆盖层分别辅助电荷传递和质子传递,通过二者的协同作用获得了催化活性和耐久性之间的平衡.因此,优化后的P-NCS/rGO在70 mV的低过电位下实现了10 mA cm^(-2)的电流密度,并具有令人满意的80小时耐用性.本工作阐明了石墨烯覆盖硫化物催化剂可通过调控电子结构和质子/分子穿透提高电催化性能.

Bilayered semiconductor graphene nanostructures with periodically arranged hexagonal holes

We present a theoretical study of new nanostructures based on bilayered graphene with periodically arranged hexagonal holes （bilayered graphene antidots）. Our ab initio calculations show that fabrication of hexagonal holes in bigraphene leads to connection of the neighboring edges of the two graphene layers with formation of a hollow carbon nanostructure sheet which displays a wide range of electronic properties （from semiconductor to metallic）, depending on the size of the holes and the distance between them. The results were additionally supported by wave packet dynamical transport calculations based on the numerical solution of the time-dependent Schr/Sdinger equation.