Inside and outside of virus-like particles HBc and HBc/4M2e: A comprehensive study of the structure.

Hepatitis B virus core antigen (HBc) with the insertion of four external domains of the influenza A M2 protein (HBc/4M2e) form virus-like particles whose structure was studied using a combination of molecular modeling and cryo-electron microscopy (cryo-EM). It was also shown that self-assembling of the particles occurs inside bacterial cells, but despite the big inner volume of the core shell particle, purified HBc/4M2e contain an insignificant amount of bacterial proteins. It was shown that a fragment of the M2e corresponding to 4M2e insertion is prone to formation of amyloid-like fibrils. However, as the part of the immunodominant loop, M2e insertion does not show a tendency to intermolecular interaction. A full-atomic HBc-4M2e model with the resolution of about 3 Å (3.13 Å for particles of Т = 4 symmetry, 3.7 Å for particles of Т = 3 symmetry) was obtained by molecular modeling methods based on cryo-EM data.

Structural and functional state of various parts of skin microcirculation at an early stage of hypertension in working-age men.

STUDY PURPOSE: To conduct a cross-sectional study on the structural and functional characteristics of various parts of skin microcirculation in working-age men with newly diagnosed hypertension (HTN). MATERIALS AND METHODS: The study included 118 male participants (ages 30 to 60) who were not regularly taking any medicine, had no medical complaints, and subjectively considered themselves healthy at the time of study. All participants underwent a cross-sectional comprehensive medical examination. The following tests were performed: complete blood count, biochemical blood tests, video capillaroscopy (VCS), laser Doppler flowmetry (LDF) and photoplethysmography (PPG) on the left hand fingers, determination of flow-mediated vasodilation of the brachial artery, echocardiography, ultrasound of extracranial and femoral arteries, 24-h ambulatory blood pressure monitoring (ABPM). According to ABPM data, the participants were divided into two equal groups called a control group(CG) and a hypertension group(HG). There were 59 participants with normal BP in CG, and 59 participants with newly diagnosed HTN in HG. RESULTS: Nailfold VCS of the ring finger revealed no significant differences between the groups at the level of exchange microvessels. According to LDF data, there was no decrease in tissue perfusion and signs of an increase in the activity of endothelial, neurogenic, and myogenic regulation of the tone of precapillary arterioles in the HTN group. According to PPG of the index finger, in contrast to CG, HTN participants had significantly higher values of the following parameters: normalized augmentation index (Alp75) - 3.8 % and - 5.25 % (p < 0.005), stiffness index (SI) - 7.6 m/s and 7.35 m/s (p < 0.05), reflection index (RI) - 36.5 % and 28.4 % (p < 0.005), respectively. DISCUSSION: Working-age men in the early stage of HTN have neither capillary rarefaction nor an increase in the tone of skin precapillary arterioles. The largest contribution to peripheral vascular resistance in the onset of HTN is most likely made by large muscular arterioles, in which the neurogenic regulation of vascular tone predominates.

[Features of the course of non-ST elevation myocardial infarction in patients with a history of COVID-19].

Aim      To study the clinical course of non-ST segment elevation myocardial infarction (NSTEMI) in hospitalized patients after COVID-19 and to evaluate the effect of baseline characteristics of patients on the risk of complications.Material and methods  The study included 209 patients with NSTEMI; 104 of them had had COVID-19. The course of myocardial infarction (MI) was analyzed at the hospital stage, including evaluation of the incidence rate of complications (fatal outcome, recurrent MI, life-threatening arrhythmias and conduction disorders, pulmonary edema, cardiogenic shock, ischemic stroke, gastrointestinal bleeding).Results Mean age of patients after COVID-19 was 61.8±12.2 years vs. 69.0±13.0 in the comparison group (p<0.0001). The groups were comparable by risk factors, clinical data, and severity of coronary damage. Among those who have had СOVID-19, there were fewer patients of the GRACE high risk group (55.8 % vs. 74.3 %; p<0.05). Convalescent COVID-19 patients had higher levels of C-reactive protein and troponin I (p<0.05). The groups did not significantly differ in the incidence of unfavorable NSTEMI course (p>0.05). However, effects of individual factors (postinfarction cardiosclerosis, atrial fibrillation, decreased SpO2, red blood cell concentration, increased plasma glucose) on the risk of complications were significantly greater for patients after COVID-19 than for the control group (p<0.05).Conclusion      Patients with NSTEMI, despite differences in clinical history and laboratory data, are characterized by a similar risk of death at the hospital stage, regardless of the past COVID-19. Despite the absence of statistically significant differences in the incidence of in-hospital complications, in general, post-COVID-19 patients showed a higher risk of complicated course of NSTEMI compared to patients who had not have COVID-19. In addition, for this category of patients, new factors were identified that previously did not exert a clinically significant effect on the incidence of complications: female gender, concentration of IgG to SARS-CoV-2 ≥200.0 U/l, concentration of С-reactive protein ≥40.0 mg/l, total protein <65 g/l. These results can be used for additional stratification of risk for cardiovascular complications in patients with MI and also for development of individual protocols for evaluation and management of NSTEMI patients with a history of COVID-19.

Parameters of cutaneous microvasculature in men of working age with newly diagnosed arterial hypertension.

OBJECTIVE: To investigate structural and functional features of cutaneous microvasculature in men of working age with newly diagnosed arterial hypertension (AH). MATERIALS AND METHODS: The study included 161 apparently healthy men from 30 to 60 years, who underwent a comprehensive examination of cardiovascular system "from the heart to the capillaries". Control group (CG) included 60 normotensive men. AH group included 101 men with elevated BP. RESULTS: There is no rarefaction of the capillary bed and latent fluid retention in the interstitial space in the skin in men with AH. No data were obtained for increased endothelial, neurogenic and myogenic tone of resistive cutaneous precapillary arterioles in AH group, but a decrease in the perfusion efficiency of the endothelial and myogenic mechanisms of tissue perfusion modulation was noted. CONCLUSION: Obtained results allow making the assumption that metabolic disorders at the level of capillaries that are of a systemic nature prevail in men with the onset of AH.

Anaerobic oxidation of petroleum hydrocarbons in enrichment cultures from sediments of the Gorevoy Utes natural oil seep under methanogenic and sulfate-reducing conditions.

This article presents the first experimental data on the ability of microbial communities from sediments of the Gorevoy Utes natural oil seep to degrade petroleum hydrocarbons under anaerobic conditions. Like in marine ecosystems associated with oil discharge, available electron acceptors, in particular sulfate ions, affect the composition of the microbial community and the degree of hydrocarbon conversion. The cultivation of the surface sediments under sulfate-reducing conditions led to the formation of a more diverse bacterial community and greater loss of n-alkanes (28%) in comparison to methanogenic conditions (6%). Microbial communities of both surface and deep sediments are more oriented to degrade polycyclic aromatic hydrocarbons (PAHs), to which the degree of the PAH conversion testifies (up to 46%) irrespective of the present electron acceptors. Microorganisms with the uncultured closest homologues from thermal habitats, sediments of mud volcanoes, and environments contaminated with hydrocarbons mainly represented microbial communities of enrichment cultures. The members of the phyla Firmicutes, Chloroflexi, and Caldiserica (OP5), as well as the class Deltaproteobacteria and Methanomicrobia, were mostly found in enrichment cultures. The influence of gas-saturated fluids may be responsible for the presence in the bacterial 16S rRNA gene libraries of the sequences of "rare taxa": Planctomycetes, Ca. Atribacteria (OP9), Ca. Armatimonadetes (OP10), Ca. Latescibacteria (WS3), Ca. division (AC1), Ca. division (OP11), and Ca. Parcubacteria (OD1), which can be involved in hydrocarbon oxidation.

Observation of Stark many-body localization without disorder.

Thermalization is a ubiquitous process of statistical physics, in which a physical system reaches an equilibrium state that is defined by a few global properties such as temperature. Even in isolated quantum many-body systems, limited to reversible dynamics, thermalization typically prevails1. However, in these systems, there is another possibility: many-body localization (MBL) can result in preservation of a non-thermal state2,3. While disorder has long been considered an essential ingredient for this phenomenon, recent theoretical work has suggested that a quantum many-body system with a spatially increasing field-but no disorder-can also exhibit MBL4, resulting in 'Stark MBL'5. Here we realize Stark MBL in a trapped-ion quantum simulator and demonstrate its key properties: halting of thermalization and slow propagation of correlations. Tailoring the interactions between ionic spins in an effective field gradient, we directly observe their microscopic equilibration for a variety of initial states, and we apply single-site control to measure correlations between separate regions of the spin chain. Furthermore, by engineering a varying gradient, we create a disorder-free system with coexisting long-lived thermalized and non-thermal regions. The results demonstrate the unexpected generality of MBL, with implications about the fundamental requirements for thermalization and with potential uses in engineering long-lived non-equilibrium quantum matter.

Old dog, new tricks: Influenza A virus NS1 and in vitro fibrillogenesis.

The influenza NS1 protein is involved in suppression of the host immune response. Recently, there is growing evidence that prion-like protein aggregation plays an important role in cellular signaling and immune responses. In this work, we obtained a recombinant, influenza A NS1 protein and showed that it is able to form amyloid-like fibrils in vitro. Using proteolysis and subsequent mass spectrometry, we showed that regions resistant to protease hydrolysis highly differ between the native NS1 form (NS1-N) and fibrillar form (NS1-F); this indicates that significant structural changes occur during fibril formation. We also found a protein fragment that is capable of inducing the process of fibrillogenesis at 37 °C. The discovery of the ability of NS1 to form amyloid-like fibrils may be relevant to uncovering relationships between influenza A infection and modulation of the immune response.

Cold and distant: structural features of the nucleoprotein complex of a cold-adapted influenza A virus strain.

Two influenza A nucleoprotein variants (wild-type: G102R; and mutant: G102R and E292G) were studied with regard to macro-molecular interactions in oligomeric form (24-mers). The E292G mutation has been previously shown to provide cold adaptation. Molecular dynamics simulations of these complexes and trajectory analysis showed that the most significant difference between the obtained models was distance between nucleoprotein complex strands. The isolated complexes of two ribonucleoprotein variants were characterized by transmission electron microscopy and differential scanning fluorimetry (DSF). Presence of the E292G substitution was shown by DSF to affect nucleoprotein complex melting temperature. In the filament interface peptide model, it was shown that the peptide corresponding in primary structure to the wild-type NP (SGYDFEREGYS) is prone to temperature-dependent self-association, unlike the peptide corresponding to E292G substitution (SGYDFGREGYS). It was also shown that the SGYDFEREGYS peptide is capable of interacting with a monomeric nucleoprotein (wild type); this interaction's equilibrium dissociation constant is five orders of magnitude lower than for the SGYDFGREGYS peptide. Using small-angle neutron scattering (SANS), the supramolecular structures of isolated complexes of these proteins were studied at temperatures of 15, 32, and 37 °C. SANS data show that the structures of the studied complexes at elevated temperature differ from the rod-like particle model and react differently to temperature changes. The data suggest that the mechanism behind cold adaptation with E292G is associated with a weakening of the interaction between strands of the ribonucleoprotein complex and, as a result, the appearance of inter-chain interface flexibility necessary for complex function at low temperature.Communicated by Ramaswamy H. Sarma.

Coherent optical nanotweezers for ultracold atoms.

There has been a recent surge of interest and progress in creating subwavelength free-space optical potentials for ultracold atoms. A key open question is whether geometric potentials, which are repulsive and ubiquitous in the creation of subwavelength free-space potentials, forbid the creation of narrow traps with long lifetimes. Here, we show that it is possible to create such traps. We propose two schemes for realizing subwavelength traps and demonstrate their superiority over existing proposals. We analyze the lifetime of atoms in such traps and show that long-lived bound states are possible. This work allows for subwavelength control and manipulation of ultracold matter, with applications in quantum chemistry and quantum simulation.

[Pneumocephaly: an expert assessment in determining the severity of harm to health]. / Pnevmotsefaliya: ekspertnaya otsenka opredeleniya tyazhesti vreda zdorov'yu.

The purpose of the work is the analysis of etiology and pathogenesis of pneumocephaly in various injuries, diseases and pathological conditions for the reasonable determination of the severity of health damage during forensic medical examinations. The analysis of literature data on the causes and mechanisms of pneumocephaly is given. Attention is paid to the assessment of pneumocephaly in determining the health damage in patients with traumatic brain injury or if it is suspected. It is proposed to consider pneumocephaly as an indirect sign of a skull fracture. In case of pneumocephaly, a radiologically confirmed fracture is necessary to justify serious health damage. The medical documents of the victim should be examined to exclude concomitant diseases and pathological conditions that can lead to pneumocephaly.

Ultrastructural Changes in the Air-Blood Barrier of Rats in Acute Intoxication with Furoplast Pyrolysis Products.

Rats were exposed to fluoroplast-4 pyrolysis products (sample weight 2.6 g, pyrolysis temperature 440-750°C, pyrolysis duration 4 min) containing perfluoroisobutylene over 15 min. Lung tissue samples for histological and electron microscopic examination were isolated in 3 and 30 min after intoxication and processed routinely. Histological examination revealed no structural changes in the lungs. In ultrathin sections of rat lungs, some changes in the structure of type I pneumocytes were detected in 3 min after the exposure: detachment of cytoplasmic processes and the appearance of transcytosis pores. These changes attested to impaired cell-cell interactions and their adhesion to the basement membrane, where structural disorganization and edema of the collagen matrix were observed. In 30 min following exposure, the signs of damage to type I pneumocytes became more pronounced. The increase in the equivalents of transcellular and paracellular permeability in the alveolar lining profile was observed. No changes in the pulmonary capillary endotheliocytes were detected, which suggest that type I pneumocytes are the primary target of the toxic effect of perfluoroisobutylene. The vulnerability of a particular cell population, in view of specific metabolism of these cells, can be the key to deciphering of the mechanisms of the toxic effect of pyrolysis products of fluorinated polymer materials.

Evidence for the First Excited State of

The ^{7}H system was populated in the ^{2}H(^{8}He,^{3}He)^{7}H reaction with a 26 AMeV ^{8}He beam. The ^{7}H missing mass energy spectrum, the ^{3}H energy and angular distributions in the ^{7}H decay frame were reconstructed. The ^{7}H missing mass spectrum shows a peak, which can be interpreted either as unresolved 5/2^{+} and 3/2^{+} doublet or one of these states at 6.5(5) MeV. The data also provide indications of the 1/2^{+} ground state of ^{7}H located at 1.8(5) MeV with quite a low population cross section of ∼25 µb/sr within angular range θ_{c.m.}≃(17°-27°).

Towards the Limits of Existence of Nuclear Structure: Observation and First Spectroscopy of the Isotope

The most remote isotope from the proton dripline (by 4 atomic mass units) has been observed: ^{31}K. It is unbound with respect to three-proton (3p) emission, and its decays have been detected in flight by measuring the trajectories of all decay products using microstrip detectors. The 3p emission processes have been studied by the means of angular correlations of ^{28}S+3p and the respective decay vertices. The energies of the previously unknown ground and excited states of ^{31}K have been determined. This provides its 3p separation energy value S_{3p} of -4.6(2) MeV. Upper half-life limits of 10 ps of the observed ^{31}K states have been derived from distributions of the measured decay vertices.

Fluctuation-Induced Torque on a Topological Insulator out of Thermal Equilibrium.

Topological insulators with the time reversal symmetry broken exhibit strong magnetoelectric and magneto-optic effects. While these effects are well understood in or near equilibrium, nonequilibrium physics is richer yet less explored. We consider a topological insulator thin film, weakly coupled to a ferromagnet, out of thermal equilibrium with a cold environment (quantum electrodynamics vacuum). We show that the heat flow to the environment is strongly circularly polarized, thus carrying away angular momentum and exerting a purely fluctuation-driven torque on the topological insulator film. Utilizing the Keldysh framework, we investigate the universal nonequilibrium response of the TI to the temperature difference with the environment. Finally, we argue that experimental observation of this effect is within reach.

Interaction-induced transition in the quantum chaotic dynamics of a disordered metal.

We demonstrate that a weakly disordered metal with short-range interactions exhibits a transition in the quantum chaotic dynamics when changing the temperature or the interaction strength. For weak interactions, the system displays exponential growth of the out-of-time-ordered correlator (OTOC) of the current operator. The Lyapunov exponent of this growth is temperature-independent in the limit of vanishing interaction. With increasing the temperature or the interaction strength, the system undergoes a transition to a non-chaotic behaviour, for which the exponential growth of the OTOC is absent. We conjecture that the transition manifests itself in the quasiparticle energy-level statistics and also discuss ways of its explicit observation in cold-atom setups.

Floquet engineering of optical lattices with spatial features and periodicity below the diffraction limit.

Floquet engineering or coherent time periodic driving of quantum systems has been successfully used to synthesize Hamiltonians with novel properties. In ultracold atomic systems, this has led to experimental realizations of artificial gauge fields, topological band structures, and observation of dynamical localization, to name just a few. Here we present a Floquet-based framework to stroboscopically engineer Hamiltonians with spatial features and periodicity below the diffraction limit of light used to create them, by time-averaging over various configurations of a 1D optical Kronig-Penney (KP) lattice. The KP potential is a lattice of narrow subwavelength barriers spaced by half the optical wavelength ( λ / 2 ) and arises from the nonlinear optical response of the atomic dark state. Stroboscopic control over the strength and position of this lattice requires time-dependent adiabatic manipulation of the dark-state spin composition. We investigate adiabaticity requirements, and shape our time-dependent light fields to respect these requirements. We apply this framework to show that a λ / 4 -spaced lattice can be synthesized using realistic experimental parameters. As an example, we discuss mechanisms that limit lifetimes in these lattices, explore candidate systems with their limitations, and study adiabatic loading into the ground band of these lattices.

Dark State Optical Lattice with a Subwavelength Spatial Structure.

We report on the experimental realization of a conservative optical lattice for cold atoms with a subwavelength spatial structure. The potential is based on the nonlinear optical response of three-level atoms in laser-dressed dark states, which is not constrained by the diffraction limit of the light generating the potential. The lattice consists of a one-dimensional array of ultranarrow barriers with widths less than 10 nm, well below the wavelength of the lattice light, physically realizing a Kronig-Penney potential. We study the band structure and dissipation of this lattice and find good agreement with theoretical predictions. Even on resonance, the observed lifetimes of atoms trapped in the lattice are as long as 44 ms, nearly 10^{5} times the excited state lifetime, and could be further improved with more laser intensity. The potential is readily generalizable to higher dimensions and different geometries, allowing, for example, nearly perfect box traps, narrow tunnel junctions for atomtronics applications, and dynamically generated lattices with subwavelength spacings.

Photon Subtraction by Many-Body Decoherence.

We experimentally and theoretically investigate the scattering of a photonic quantum field from another stored in a strongly interacting atomic Rydberg ensemble. Considering the many-body limit of this problem, we derive an exact solution to the scattering-induced spatial decoherence of multiple stored photons, allowing for a rigorous understanding of the underlying dissipative quantum dynamics. Combined with our experiments, this analysis reveals a correlated coherence-protection process in which the scattering from one excitation can shield all others from spatial decoherence. We discuss how this effect can be used to manipulate light at the quantum level, providing a robust mechanism for single-photon subtraction, and experimentally demonstrate this capability.