Modified double-averaged Hamiltonian in hierarchical triple systems

In this work, we introduce a modified double-averaging approach by considering the shortterm effects and formulate a more accurate double-averaged Hamiltonian (in comparison to the classical octupole-level Hamiltonian) for hierarchial triple systems. The Hamiltonian is expressed as a power series in the ratio of the semi-major axes of the inner and outer binaries. Both the Delaunay's elements and the classical orbit elements are adopted to describe the motion. To derive the secular Hamiltonian, the short-term oscillations in the Hamiltonian are averaged out by means of a double-averaging approach. In particular, during the average over the orbital period of the outer binary, the periodic corrections to the secular motion are taken into account. Based on the double-averaged Hamiltonian, we provide two versions of equations of secular motion, given in the form of canonic relations and Lagrange planetary equations. The resulting secular evolution equations can be utilized to reproduce the long-term behaviours for those physical systems where the perturbations coming from the disturbing bodies are relatively strong. To test the approach, we use the averaged Hamiltonian to predict the longterm motions of a planet in a stellar binary system and natural satellites in Sun-planet systems. Simulation results show that the modified Hamiltonian can reproduce secular behaviours with high accuracy. Additionally, the comparison of dynamical models truncated at different orders indicates that the secular Hamiltonian with inclusion of higher order terms has better accuracy in predicting long-term evolution

Probe lifetime around natural satellites with obliquity

The dynamics of a probe orbiting a moon can be significantly influenced by the noncoincidence between the moon’s equatorial and orbital planes. Thus, we performed a general analysis about the effects of the angle (obliquity) between the above-mentioned planes and of the angle (nodal phasing) between the nodal lines of the mother planet’s apparent orbit and the probe orbit on the lifetime of the probe. The lifetime, strictly correlated to the variations in eccentricity of the probe orbit, was evaluated starting from low values of the semi-major axis, moderate eccentricity, and high inclination to offer high ground spatial resolution and extend latitudinal coverage of the natural satellite. This investigation, carried out through numerical simulations, may be useful for identifying the optimal initial conditions of the probe’s orbit elements, leading to an important increase in the probe lifetime in missions devoted to the exploration of natural satellite

Effects of model membranes on lysozyme amyloid aggregation

Abstract The study of the interaction between lipid membranes and amyloidogenic peptides is a turning point for understanding the processes involving the cytotoxicity of peptides involved in neurodegenerative diseases. In this work, we perform an experimental study of model membrane–lysozyme interaction to understand how the formation of amyloid fibrils can be affected by the presence of polar and zwitterionic phospholipid molecules (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine [POPC] and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol [POPG]). The study was conducted above and below the critical micellar concentration (CMC) using dynamic light scattering (DLS), atomic force microscopy (AFM), UV–Vis spectrophotometry, and the quartz crystal microbalance (QCM). Our results show that the presence of phospholipids appears to be a factor favoring the formation of amyloid aggregates. Spectrophotometric and DLS data revealed that the quantity of β {\rm{\beta }} -structure increases in the presence of POPG and POPC at different concentrations. The presence of POPG and POPC increases the speed of the nucleation process, without altering the overall structures of the fibrillar final products

The histidine phosphocarrier kinase/phosphorylase from bacillus subtilis is an oligomer in solution with a high thermal stability

The histidine phosphocarrier protein (HPr) kinase/phosphorylase (HPrK/P) modulates the phosphorylation state of the HPr protein, and it is involved in the use of carbon sources by Gram-positive bacteria. Its X-ray structure, as concluded from crystals of proteins from several species, is a hexamer; however, there are no studies about its conformational stability, and how its structure is modified by the pH. We have embarked on the conformational characterization of HPrK/P of Bacillus subtilis (bsHPrK/P) in solution by using several spectroscopic (namely, fluorescence and circular dichroism (CD)) and biophysical techniques (namely, small-angle X-ray-scattering (SAXS) and dynamic light-scattering (DLS)). bsHPrK/P was mainly a hexamer in solution at pH 7.0, in the presence of phosphate. The protein had a high conformational stability, with an apparent thermal denaturation midpoint of ~70¿ C, at pH 7.0, as monitored by fluorescence and CD. The protein was very pH-sensitive, precipitated between pH 3.5 and 6.5; below pH 3.5, it had a molten-globule-like conformation; and it acquired a native-like structure in a narrow pH range (between pH 7.0 and 8.0). Guanidinium hydrochloride (GdmCl) denaturation occurred through an oligomeric intermediate. On the other hand, urea denaturation occurred as a single transition, in the range of concentrations between 1.8 and 18 µM, as detected by far-UV CD and fluorescence

LA PUNTEGGIATURA NEI SOTTOTITOLI INTERLINGUISTICI DI SERIE TELEVISIVE ANGLOSASSONI

Il contributo affronta il tema della punteggiatura nel sottotitolaggio interlinguistico di serie tv. Tra i motivi di interesse di questo genere testuale, oltre ad alcune caratteristiche peculiari (compresenza di più codici comunicativi, rapporto col parlato filmico ecc.), c’è anche la grande diffusione di questi prodotti audiovisivi presso le giovani generazioni, dunque il suo potenziale impatto modellizzante rispetto alle nuove forme di scrittura. A un inquadramento generale sui caratteri del sottotitolaggio, segue l’analisi di tre segni interpuntivi (virgola, due punti, puntini di sospensione) in un corpus di 12 episodi presi da 10 serie tv in lingua inglese. Punctuation in interlingual subtitles of Anglo-Saxon television series This paper deals with Italian punctuation marks in TV show subtitles. What makes this type of text interesting, apart from some very specific features (coexistence of different communication codes, connection between punctuation marks and spoken language etc.), is the widespread use of audiovisual products, especially among young audiences, hence the possible influence on new forms of writing. We first describe the main features of subtitling; then we analyze three punctuation marks (comma, colon, ellipsis) in a corpus of 12 episodes taken from 10 TV shows in English

Taurine Stabilizing Effect on Lysozyme

none6Taurine is an important organic osmolyte in mammalian cells, and it weakens inflammation and oxidative stress mediated injuries in some diseases. Recently, taurine has been demonstrated to play a therapeutic role against neurodegenerative disorders, although its parallel involvement in several biochemical mechanisms makes not clear taurine specific role in these diseases. Furthermore, the stabilizing effect of this molecule in terms of protein stability is known, but not deeply investigated. In this work we explore by Circular Dichroism the stabilizing impact of taurine in lysozyme thermal denaturation and its influence in lysozyme aggregation into amyloid fibrils. Taurine even at low concentration modifies protein-protein interactions in lysozyme native state, as revealed by Small Angle X-ray Scattering experiments, and alters the amyloid aggregation pattern without completely inhibiting it, as confirmed by UV/Vis spectroscopy with Congo Red and by Atomic Force Microscopy. Evaluation of the cytotoxicities of the amyloid fibrils grown in presence or in absence of taurine is investigated on SH-SY5Y neuroblastoma cells.openMastrella, Leonardo; Moretti, Paolo; Pieraccini, Silvia; Magi, Simona; Piccirillo, Silvia; Ortore, Maria GraziaMastrella, Leonardo; Moretti, Paolo; Pieraccini, Silvia; Magi, Simona; Piccirillo, Silvia; Ortore, Maria Grazi

Synthesis and Evaluation of Monoaryl Derivatives as Transthyretin Fibril Formation Inhibitors

Transthyretin (TTR) is a homo-tetrameric protein characterized by four identical β-sheet rich monomers assembled together to form a tetramer that is crossed, along the 2-fold symmetry axis, by two similar binding pockets named thyroxin binding sites. Under unknown conditions, TTR can misfold and aggregate triggering the amyloidosis onset. One therapeutic approach consists to stabilize the tetramer with synthetic small molecules that bind TTR binding site hindering the first step of fibril formation. Here, we report the synthesis of new 2-((benzyloxy)imino)acetic, -propanoic and -butanoic acid derivatives, results of their turbidimetric UV assay and the docking study of new monoaryl compounds. The obtained results suggest that, for this class of compounds, (i) the chlorine atom in ortho position on the aromatic ring is the best substituent; (ii) the linker inversion still allows the interaction with thyroxine binding sites; and (iii) the steric hindrance in R1 position is detrimental for the activity

Dynamics of the Intrinsically Disordered Inhibitor IF7 of Glutamine Synthetase in Isolation and in Complex with its Partner

Glutamine synthetase (GS) catalyzes the ATP-dependent formation of glutamine from glutamate and ammonia. The activity of Synechocystis sp. PCC 6803 GS is regulated, among other mechanisms, by protein-protein interactions with a 65-residue-long, intrinsically disordered protein (IDP), named IF7. IDPs explore diverse conformations in their free states and, in some cases, in their molecular complexes. We used both nuclear magnetic resonance (NMR) at 11.7 T and small angle X-ray scattering (SAXS) to study the size and the dynamics in the picoseconds-to-nanosecond (ps-ns) timescale of: (i) isolated IF7; and (ii) the IF7/GS complex. Our SAXS findings, together with MD results, show: (i) some of the possible IF7 structures in solution; and, (ii) that the presence of IF7 affected the structure of GS in solution. The joint use of SAXS and NMR shows that movements of each amino acid of IF7 were uncorrelated with those of its neighbors. Residues of IF7 with the largest values of the relaxation rates (R1, R2 and ηxy), in the free and bound species, were mainly clustered around: (i) the C terminus of the protein; and (ii) Ala30. These residues, together with Arg8 (which is a hot-spot residue in the interaction with GS), had a restricted mobility in the presence of GS. The C-terminal region, which appeared more compact in our MD simulations of isolated IF7, seemed to be involved in non-native contacts with GS that help in the binding between the two macromolecules.Ministerio de Economía y Competitividad RTI 2018-097991- BI0

Focus on Human Monoamine Transporter Selectivity. New Human DAT and NET Models, Experimental Validation, and SERT Affinity Exploration

The most commonly used antidepressant drugs are the serotonin transporter inhibitors. Their effects depend strongly on the selectivity for a single monoamine transporter compared to other amine transporters or receptors, and the selectivity is roughly influenced by the spatial protein structure. Here, we provide a computational study on three human monoamine transporters, i.e., DAT, NET, and SERT. Starting from the construction of hDAT and hNET models, whose three-dimensional structure is unknown, and the prediction of the binding pose for 19 known inhibitors, 3D-QSAR models of three human transporters were built. The training set variability, which was high in structure and activity profile, was validated using a set of in-house compounds. Results concern more than one aspect. First of all, hDAT and hNET three-dimensional structures were built, validated, and compared to the hSERT one; second, the computational study highlighted the differences in binding site arrangement statistically correlated to inhibitor selectivity; third, the profiling of new inhibitors pointed out a conservation of the inhibitory activity trend between rabbit and human SERT with a difference of about 1 order of magnitude; fourth, binding and functional studies confirmed 4-(benzyloxy)-4-phenylpiperidine 20a-d and 21a-d as potent SERT inhibitors. In particular, one of the compounds (compound 20b) revealed a higher affinity for SERT than paroxetine in human platelets