On the role of electron impact in an atmospheric-pressure microwave discharge in liquid <Emphasis Type="Italic">n</Emphasis>-heptane

The role of electron impact in the dissociation of n-heptane in an atmospheric-pressure microwave discharge in liquid n-heptane was investigated using a self-consistent two-dimensional model. The model includes the Navier–Stokes equations for a two-phase subsonic flow of incompressible liquid and compressible gas, the heat conduction equation, Maxwell’s equations for the microwave field, the Boltzmann equation for plasma electrons, and the balance equations for the electron density and weight fraction of n-heptane in the gaseous and liquid phases. It is shown that the effect of electron impact is negligible at times longer than 10^–3 s.     

Transport Effects on Multiple-Component Reactions in Optical Biosensors

Optical biosensors are often used to measure kinetic rate constants associated with chemical reactions. Such instruments operate in the surface–volume configuration, in which ligand molecules are convected through a fluid-filled volume over a surface to which receptors are confined. Currently, scientists are using optical biosensors to measure the kinetic rate constants associated with DNA translesion synthesis—a process critical to DNA damage repair. Biosensor experiments to study this process involve multiple interacting components on the sensor surface. This multiple-component biosensor experiment is modeled with a set of nonlinear integrodifferential equations (IDEs). It is shown that in physically relevant asymptotic limits these equations reduce to a much simpler set of ordinary differential equations (ODEs). To verify the validity of our ODE approximation, a numerical method for the IDE system is developed and studied. Results from the ODE model agree with simulations of the IDE model, rendering our ODE model useful for parameter estimation.     

Antarctic red macroalgae: a source of polyunsaturated fatty acids

The n-3 and n-6 series of polyunsaturated fatty acids (PUFAs) are important for numerous metabolic functions that reduce the risk of inflammation, cancer, and heart diseases. These fatty acids (FAs) have been detected in high concentrations in some species of algae. The amount of the n-3 and n-6 PUFAs is closely associated with abiotic factors, such as solar radiation intensity, salinity, and temperature variation. However, abiotic influence on PUFA levels, along with the physiological function of these molecules in algae, remains inconclusive. In the present study, the quantities of the n-3 and n-6 in Antarctic red algae species Iridaea cordata, Palmaria decipiens, Plocamium cartilagineum, and Pyropia endiviifolia were determined. The lipids were extracted from the macroalgae according to the method followed by Bligh and Dyer (1959) and converted to methyl esters for further analysis using gas chromatography. The main n-6 PUFA identified and quantified in this study of Antarctic red algae were linoleic acid (18:2n-6), dihomo-γ-linolenic acid (20:3n-6), and arachidonic acid (20:4n-6). The eicosapentaenoic acid was detected at high concentrations in all species, with approximately 62.8% of total FA in P. endiviifolia, 75.4% in P. decipiens, 50.4% in I. cordata, and 20.1% in P. cartilagineum. The results corroborate those of the literature and show that PUFAs increased in red algae environments, with increased production of n-3 and n-6 PUFAs.     

Probing structure,thermochemistry, electron affinity,and magnetic moment of thulium-doped silicon clusters TmSi<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 3–10) and their anions with density functional theory

The most stable structures and electronic properties of TmSi _n (n?=?3–10) clusters and their anions have been probed by using the ABCluster global search technique combined with the PBE, TPSSh, and B3LYP density functional methods. The results revealed that the most stable structures of neutral TmSi _n and their anions can be regarded as substituting a Si atom of the ground state structure of Si _n?+?1 with a Tm atom. The reliable AEAs, VDEs and simulated PES of TmSi _n (n?=?3–10) are presented. Calculations of HOMO-LUMO gap revealed that introducing Tm atom to Si cluster can improve photochemical reactivity of the cluster. The NPA analyses indicated that the 4f electron of Tm atom in TmSi _n (n?=?3–10) and their anions do not participate in bonding. The total magnetic moments of TmSi _n are mainly provided by the 4f electrons of Tm atom. The dissociation energy of Tm atom from the most stable structure of TmSi _n and their anions has been calculated to examine relative stability.     

Consequences of ligand bivalency in interactions involving particulate receptors: equilibrium and kinetic studies with Sephadex-concanavalin A, butylagarose-phosphorylase b, and Fc receptor-IgG dimer interactions as model systems

Theoretical consideration is given to the interaction of a bivalent ligand with particulate receptor sites, not only from the viewpoint of quantitatively describing the binding behavior but also from that of the kinetics of ligand release upon infinite dilution of a receptor-ligand mixture. In the latter regard, a general expression is derived that describes the time dependence of the amount of ligand bound as a function of two rate constants for the stepwise dissociation of cross-linked ligand-receptor complex and a thermodynamic parameter expressing the initial ratio of singly linked to doubly linked ligand-receptor complexes. An experimental study of the interaction between Sephadex and concanavalin A is then used to illustrate application of this recommended theoretical approach for characterizing the binding behavior and dissociation kinetics of a bivalent ligand for a system in which all ligand-receptor interactions may be described by a single intrinsic association constant. Published results on the interaction of phosphorylase b with butylagarose are also shown to comply with this simplest model of the bivalent ligand hypothesis; but those for the interaction between immunoglobulin G (IgG) dimers and Fc receptors require modification of the model by incorporation of different intrinsic association constants for the successive binding of receptor sites to the bivalent ligand. These results emphasize the need to consider ligand bivalency as a potential phenomenon in studies of interactions between protein ligands and particulate receptors and illustrate procedures by which the effects of ligand bivalency may be identified and characterized.     

Mathematical modeling and computer simulation of isoelectric focusing with electrochemically defined ampholytes

A mathematical model of isoelectric focusing at the steady state has been developed for an M-component system of electrochemically defined ampholytes. The model is formulated from fundamental principles describing the components' chemical equilibria, mass transfer resulting from diffusion and electromigration, and electroneutrality. The model consists of ordinary differential equations coupled with a system of algebraic equations. The model is implemented on a digital computer using FORTRAN-based simulation software. Computer simulation data are presented for several two-component systems showing the effects of varying the isoelectric points and dissociation constants of the constituents.     

Reexamination of structures,stabilities, and electronic properties of holmium-doped silicon clusters HoSi<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 12–20)

The total energies, growth patterns, equilibrium geometries, relative stabilities, hardnesses, intramolecular charge transfer, and magnetic moments of HoSi _n (n?=?12–20) clusters have been reexamined theoretically using two different density functional schemes in combination with relativistic small-core Stuttgart effective core potentials (ECP28MWB) for the Ho atoms. The results show that when n?=?12–15, the most stable structures are predicted to be exohedral frameworks with a quartet ground state, but when n?=?16–20, they are predicted to be endohedral frameworks with a sextuplet ground state. These trend in stability across the clusters (gauged from their dissociation energies) was found to be approximately the same regardless of the DFT scheme used in the calculations, with HoSi₁₃, HoSi₁₆, HoSi₁₈, and HoSi₂₀ calculated to be more stable than the other clusters. The results obtained for cluster hardness indicated that doping the Ho atom into Si₁₃ and Si₁₆ leads to the most stable HoSi _n clusters, while doping Ho into the other Si _n clusters increases the photochemical sensitivity of the cluster. Analyses of intracluster charge transfer and magnetic moments revealed that charge always shifts from the Ho atom to the Si _n cluster during the creation of exohedral HoSi _n (n?=?12–15) structures. However, the direction of charge transfer is reversed during the creation of endohedral HoSi _n (n?=?16–20) structures, which implies that Ho acts as an electron acceptor when it is encapsulated in the Si _n cage. Furthermore, when the most stable exohedral HoSi _n (n?=?12–15) structures are generated, the 4f electrons of Ho are virtually unchanged and barely participate in intracluster bonding. However, in the most stable endohedral HoSi _n (n?=?16–20) frameworks, a 4f electron does participate in bonding. It does this by transferring to the 5d orbital, which hybridizes with the 6s and 6p orbitals and then interacts with Si valence sp orbitals. Meanwhile, the total magnetic moments of the HoSi _n (n?=?16–20) clusters are considerably higher than those of HoSi _n (n?=?12–15). Interestingly, the endohedral HoSi₁₆ and HoSi₂₀ clusters can be viewed as the most suitable building blocks for novel high-density magnetic storage nanomaterials and for novel optical and optoelectronic photosensitive nanomaterials, respectively.     

Induced Bivalent Interlocking and the Course of Meiotic Chromosome Synapsis

WHEN chromosomes pair at meiosis the bivalents so formed do not normally interlock. Heat-treatments can, however, induce bivalent interlocking in the locust Locusta migratoria. Only the longest bivalents interlock and usually only two are found per cell; two “rod” bivalents, with single chiasmata, two “ring” bivalents, each with two or three chiasmata, or one “rod” and one “ring” bivalent (Fig. 1a, b and c). The nature of this interlocking and the metaphase orientational and congressional properties of interlocked bivalents are analysed in detail elsewhere¹.     

Characteristic of Polysaccharide Complexes from <Emphasis Type="Italic">Centaurea scabiosa</Emphasis> L. and <Emphasis Type="Italic">Centaurea pseudomaculosa</Emphasis> Dobrocz.

We characterized polysaccharide complexes from Centaurea scabiosa L. and Centaurea pseudomaculosа Dobrocz. We proposed the technique of sequential selection of water-soluble polysaccharides and pectin substances from the aerial parts of studied objects. We have discovered that the content of water-soluble polysaccharides in the aerial parts of C. scabiosa was 2.8 times higher (2.7 ± 0.3%, n = 3) than in C. pseudomaculosа (0.97 ± 0.50%, n = 3). The content of pectin substances in the aerial parts of C. scabiosa was 2 times higher (7.6 ± 0.4%, n = 3) than in C. pseudomaculosа (3.9 ± 0.3%, n = 3). The residues of D-galacturonic acid, L-rhamnose, D-xylose, D-mannose, D-glucose, and D-galactose are the monomeric units of polysaccharide complexes from C. scabiosa and C. pseudomaculosa. Using ion-exchange chromatography, three polysaccharide fractions (molecular weights 667, 722, and 1027 kDa), whose monomer units are D-galacturonic acid, L-rhamnose, D-galactose, D-xylose, and D-glucose were isolated from the water-soluble polysaccharides of C. scabiosa.     

Properties of the sugar carrier in baker's yeast

A kinetic test evolved for distinguishing between mobile carrier transport in which one or two substrate molecules are transported at a time was applied to sugar transport inSaccharomyces cerevisiae and it was found that the mechanism here involves attachment of one sugar molecule to one molecule of carrier. Incidental to the test, the dissociation constants of some sugar-carrier complexes were determined. The diversity of sugar transport mechanisms in different cells is discussed.     

Cerebrospinal fluid Presenilin-1 increases at asymptomatic stage in genetically determined Alzheimer’s disease

Background

Presenilin-1 (PS1), the active component of the intramembrane γ-secretase complex, can be detected as soluble heteromeric aggregates in cerebrospinal fluid (CSF). The aim of this study was to examine the different soluble PS1 complexes in the lumbar CSF (CSF-PS1) of individuals with Alzheimer’s disease (AD), particularly in both symptomatic and asymptomatic genetically determined AD, in order to evaluate their potential as early biomarkers.

Methods

Western blotting, differential centrifugation and co-immunoprecipitation served to determine and characterize CSF-PS1 complexes. We also monitored the assembly of soluble PS1 into complexes in a cell model, and the participation of Aβ in the dynamics and robustness of the stable PS1 complexes.

Results

There was an age-dependent increase in CSF-PS1 levels in cognitively normal controls, the different complexes represented in similar proportions. The total levels of CSF-PS1, and in particular the proportion of the stable 100–150 kDa complexes, increased in subjects with autosomal dominant AD that carried PSEN1 mutations (eight symptomatic and six asymptomatic ADAD) and in Down syndrome individuals (ten demented and ten non-demented DS), compared with age-matched controls (n?=?23), even prior to the appearance of symptoms of dementia. The proportion of stable CSF-PS1 complexes also increased in sporadic AD (n?=?13) and mild-cognitive impaired subjects (n?=?12), relative to age-matched controls (n?=?17). Co-immunoprecipitation demonstrated the association of Aβ oligomers with soluble PS1 complexes, particularly the stable complexes.

Conclusions

Our data suggest that CSF-PS1 complexes may be useful as an early biomarker for AD, reflecting the pathology at asymptomatic state.

     

New fluorescent macrolide derivatives for studying interactions of antibiotics and their analogs with the ribosomal exit tunnel

Novel fluorescent derivatives of macrolide antibiotics related to tylosin bearing rhodamine, fluorescein, Alexa Fluor 488, BODIPY FL, and nitrobenzoxadiazole (NBD) residues were synthesized. The formation of complexes of these compounds with 70S E. coli ribosomes was studied by measuring the fluorescence polarization depending on the ribosome amount at constant concentration of the fluorescent substance. With the synthesized fluorescent tylosin derivatives, the dissociation constants for ribosome complexes with several known antibiotics and macrolide analogs previously obtained were determined. It was found that the fluorescent tylosin derivatives containing BODIPY FL and NBD groups could be used to screen the binding of novel antibiotics to bacterial ribosomes in the macrolide-binding site.     

Local surface equilibrium equations for currentless magnetic configurations

Invariant local surface equilibrium equations are derived that interrelate the absolute value of the magnetic field B, the absolute value of the gradient of the magnetic flux |?Φ|, the local shear s, and the plasma pressure on nested equilibrium magnetic surfaces in currentless configurations. Examples of applying these equations to analysis of symmetric and isodynamic equilibria are considered.     

DNA sequence-specific ligands: XV. Synthesis and spectral characteristics of a new series of dimeric bisbenzimidazoles DB(1, 2, 6, 8, 9, 10, 12)

Seven fluorescent symmetric dimeric bisbenzimidazoles DB(n) capable of occupying up to one turn of the double-stranded B-form DNA have been designed and synthesized with the aim to develop DNAdependent enzyme inhibitors. The DB(n) compounds contain four 2,6-substituted benzimidazole fragments and differ by the length of the oligomethylene linker (n = 1, 2, 6, 8, 9, 10, 12) between the bisbenzimidazole blocks. The formation of DB(n)–double-stranded DNA complexes and the localization of the ligands in the DNA minor groove have been confirmed by a number of physicochemical methods.     

Evaluation of the new TNM-staging system for thymic malignancies: impact on indication and survival

Background

The objective of this study is the evaluation of the Masaoka-Koga and the International Association for the Study of Lung Cancer (IASLC)/International Thymic Malignancy Interest Group (ITMIG) proposal for the new TNM-staging system on clinical implementation and prognosis of thymic malignancies.

Methods

A retrospective study of 76 patients who underwent surgery between January 2005 and December 2015 for thymoma. Kaplan–Meier survival analysis was used to determine overall and recurrence-free survival rates.

Results

Indication for surgery was primary mediastinal tumor (n =?55), pleural manifestation (n =?17), or mediastinal recurrence (n =?4) after surgery for thymoma. Early Masaoka-Koga stages I (n =?9) and II (n =?14) shifted to the new stage I (n =?23). Advanced stages III (Masaoka-Koga: n =?20; ITMIG/IASLC: n =?17) and IV (Masaoka-Koga: n =?33; ITMIG/IASLC: n =?35) remained nearly similar and were associated with higher levels of WHO stages. Within each staging system, the survival curves differed significantly with the best 5-year survival in early stages I and II (91%). Survival for stage IV (70 to 77%) was significantly better compared to stage III (49 to 54%). Early stages had a significant longer recurrence-free survival (86 to 90%) than advanced stages III and IV (55 to 56%).

Conclusions

The proportion of patients with IASLC/ITMIG stage I increased remarkably, whereas the distribution in advanced stages III and IV was nearly similar. The new TNM-staging system presents a clinically useful and applicable system, which can be used for indication, stage-adapted therapy, and prediction of prognosis for overall and recurrence-free survival.

     

<Emphasis Type="Italic">l</Emphasis>=1 diocotron instability of single charged plasmas

The linear stability analysis of the l=1 diocotron perturbations in a low density single charged plasma confined in a cylindrical Penning trap is critically revisited. Particular attention is devoted to the instability due to the presence of one or more stationary points in the radial profile of the azimuthal rotation frequency. The asymptotic analysis of Smith and Rosenbluth for the case of a single-bounded plasma column (algebraic instability proportional to t^1/2) is generalized in a few respects. In particular, the existence of unperturbed density profiles that give rise to l=1 algebraic instabilities growing with time proportionally to t^1?1/m, m≥ 3 being the order of a stationary point in the rotation frequency profile, and even proportionally to t, is pointed out. It is also shown that smoothing the density jumps of a multistep density profile can convert algebraically growing perturbations into exponentially decaying modes. The relevant damping rates are computed. The asymptotic analysis (t → ∞) of the fundamental diocotron perturbations is then generalized to the case of a cylindrical Penning trap with an additional coaxial inner conductor. It is shown that the algebraic instability found in the case of a single-bounded plasma column becomes exponential at longer times. The relevant linear growth rate is computed by a suitable inverse Laplace transform (contour integral in the complex plane). In the particular case of an uncharged inner conductor of radius a, the growth rate is shown to scale as a^4/3 for a → 0. The theoretical results are compared with the numerical solution of the linearized two-dimensional drift Poisson equations.     

Change in linker DNA conformation upon histone H1.5 binding to nucleosome: Fluorescent microscopy of single complexes

A method for fluorescently labeled DNA synthesis, which makes it possible to assemble mononucleosomes with 40 bp linkers, was developed. Cy3 and Cy5 labels were introduced into the linkers at distances of 10 bp before the first nucleotide and 15 bp after the last nucleotide of the nucleosome positioning DNA sequence, respectively. Without histone H1.5, f luorescence microscopy of single complexes revealed two equally probable states of nucleosomes. The states were different in the linker conformation: the open one with the energy transfer efficiency (E) between the labels of 0.06 and the closed one with E = 0.37, when the linkers are brought together. Binding of histone H1.5 with nucleosomes occurs in a range of nanomolar concentrations, and the complex formation rate is significantly higher as compared with its dissociation rate. The significant convergence of the DNA linkers (E = 0.73) is observed in these complexes together with the higher conformation uniformity in the region where the labels are localized. The developed nucleosomal constructs represent highly sensitive f luorescent sensors that can be used for the analysis of structural linker rearrangements. Also, in combination with microscopy of single complexes, they are suitable for studying the structure of complexes of nucleosomes with different chromatin architectural proteins.     

Determination of mosquito Larvicidal potential of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> Cry11Ba fusion protein through molecular docking

Mosquitoes spread deadly infections around the world. Since decades Bacillus thuringiensis (Bt) δ-endotoxins have been used successfully as a biopesticide for controlling mosquito larvae. However, over a few years, mosquito larvae have evolved tolerance against Bt δ-endotoxins, rendering them ineffective for mosquito control. Such a problem entails the development of improved toxins with enhanced toxicity, affinity towards a wide range of mosquito receptors and ability to overcome or delay the resistance buildup. In this study, using in silico tools, we aimed to design a fusion protein by fusing active region of Bt subsp. jegathesan Cry11Ba protein with Aedes aegypti TMOF (trypsin modulating oostatic factor). Using computational study, the fusion protein was validated and its mosquitocidal potential was determined through molecular docking against cadherin and aminopeptidase N midgut receptors of Aedes aegypti, Anopheles gambiae and Culex quinquefasciatus. Molecular docking revealed that from Cry11Ba-TMOF fusion protein, domain II amino acids of Cry11Ba protein showed hydrogen bond interactions with cadherin and aminopeptidase N receptors of the targeted mosquitoes. These results conclude that Cry11Ba-TMOF fusion protein has a strong affinity for the receptors of Ae.aegypti, An.gambiae and Cx.quinquefasciatus. Thus the designed fusion protein can be used as a potent mosquitocidal agent for the control of targeted mosquitoes.     

Anomalous pinch in the T-11M tokamak in an enhanced-collisionality regime

The formation of a peaked bell-shaped profile of the electron density n _e (r) in the T-11M tokamak (B _t=1 T, R/a = 0.7/0.2 m, I _p = 100 kA, t _shot ≤ 300 ms, Li and C limiters) was observed in Li experiments carried out in the near-plateau collisionality regime (the collisionality parameter at one-half of the minor radius was v* ≥ 0.5) under the conditions of low hydrogen recycling and intense hydrogen influx from the plasma edge. It is well known that peaked n _e (r) profiles are observed in collisionless regimes at v* values as low as 10^?1–10^?2 or in impurity-contaminated discharges, in which this effect can be attributed to the impurity accumulation on the plasma column axis. Moreover, a bell-shaped n _e (r) profile in discharges with low n _e can result from the ionization of hydrogen atoms at the column axis, where they arrive from the plasma edge due to cascade charge-exchange. In quasi-steady lithium discharges in T-11M, however, peaked n _e (r) profiles were observed at a relatively high central electron density n _e (0) and relatively high collision frequency, such that the influence of impurities on the n _e (r) profile could be ignored (Z _eff = 1.1±0.1). To explain this effect, one has to assume that the pinching of hydrogen ions in T-11M is anomalous. The lower estimate of the observed pinch velocity is 4 ± 1 m/s, which is three to five times higher than the velocity of the neoclassical (Ware) pinch, characteristic of these conditions. The work is devoted to the experimental study of this effect.