The $$L^p$$ L p -Calderón–Zygmund inequality on non-compact manifolds of positive curvature

Annals of Global Analysis and Geometry - We construct, for $$p>n$$ , a concrete example of a complete non-compact n-dimensional Riemannian manifold of positive sectional curvature which does...     

Circular dichroism and theoretical studies on the inclusion of the antimalarian drug Licochalcone-A in β-cyclodextrin

The Induced Circular Dichroism of the complex formed by inclusion of Licochalcone-A (a powerful antimalarian of natural origin) and β-cyclodextrin was measured and calculated. The association constant was determined by titration experiments of ICD and fluorescence. The lowest energy conformations of the complex were obtained through docking procedures and their Circular Dichroism was evaluated within the Tinoco framework. The geometry of the complex was found to be consistent with the main experimental features.     

Novel scaling behavior of directed polymers: Disorder distribution with long tails

We study the problem of directed polymers (DP) on a square lattice. The distribution of disorder is assumed to be independent but non-Gaussian. We show that for distributions with a power-law tailP() 1/||¹⁺ , where>2, so that the mean and variance are well defined, the scaling exponentv of the DP model depends on in a continuous fashion.     

On the dehydration enthalpies of some beta-aluminas

The energetics of the dehydration reaction of single crystal (Na, Na 50%-Li, Li) and ceramic Na beta-aluminas have been studied.From the dependence of the dehydration enthalpy values on the water content it has been deduced that lattice water can be bound in two different ways i.e. by ion-dipole interactions with conducting cations and by hydrogen bonds with spinel block oxygens. As expected, the first one gives binding energies depending on the nature of the monovalent cation (H=84.5 and 59.4 kJ/mol H₂O for Li and Na beta-alumina respectively). In contrast, the enthalpy change associated with the second one is identical for the three beta-aluminas (H=15.1 kJ/mol H₂O). The ceramic Na beta-alumina undergoes a surface reaction too (with CO₂) leading to the formation of carbonates and bicarbonates.

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Zusammenfassung Die Energetik der Dehydratisierungsreaktion von Einkristallen von Na-, Na (50%)/Li- und Li- sowie von Na--Aluminiumoxid wurde untersucht. Aus der Abhängigkeit der Dehydratisierungsenthalpie vom Wassergehalt ergibt sich, daß Wasser auf zwei verschiedene Weisen gebunden ist, nämlich durch Ion-Dipol-Wechselwirkung mit leitenden Kationen und durch Wasserstoffbrückenbindungen mit Sauerstoffatomen. Wie zu erwarten war werden für die ersteren von der Natur der einwertigen Kationen abhängige Bindungsenergien (H=84.1 kJ/Mol H₂O bzw. 59.4 kJ/Mol H₂O für Li- bzw. Na--Alumina) erhalten. Die auf die zweite Wechselwirkung zurückzuführenden Enthalpieänderung ist dagegen für die drei-Aluminiumoxide identisch (H=15.1 kJ/Mol H₂O). Das keramische Na--Aluminiumoxid zeigt auch eine Oberflächenreaktion mit CO₂, die zur Bildung von Carbonaten und Bicarbonaten führt.

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(Na, Na 50%-Li, Li)- -- . , - . , Li — Na-- , , 84.5 59.4 / ₂. , - 15.1 / ₂. Na- , .

     

The inelastic hard dimer gas: a nonspherical model for granular matter

We study a two-dimensional gas of inelastic smooth hard dimers. Since the collisions between dimers are dissipative, being characterized by a coefficient of restitution alpha<1, and no external driving force is present, the energy of the system decreases in time and no stationary state is achieved. However, the resulting nonequilibrium state of the system displays several interesting properties in close analogy with systems of inelastic hard spheres, whose relaxational dynamics has been thoroughly explored. We generalize to inelastic systems a recently method introduced [G. Ciccotti and G. Kalibaeva, J. Stat. Phys. 115, 701 (2004)] to study the dynamics of rigid elastic bodies made up of different spheres held together by rigid bonds. Each dimer consists of two hard disks of diameter d, whose centers are separated by a fixed distance a. By describing the rigid bonds by means of holonomic constraints and deriving the appropriate collision rules between dimers, we reduce the dynamics to a set of equations which can be solved by means of event-driven simulation. After deriving the algorithm we study the decay of the total kinetic energy, and of the ratio between the rotational and the translational kinetic energy of inelastic dimers. We show numerically that the celebrated Haff's homogeneous cooling law t(-2), describing how the kinetic energy of an inelastic hard-sphere system with a constant coefficient of restitution decreases in time, holds even in the case of these nonspherical particles. We fully characterize this homogeneous decay process in terms of appropriate decay constants and confirm numerically the scaling behavior of the velocity distributions.     

NdFeO3 as a new electrocatalytic material for the electrochemical monitoring of dopamine

A new electrochemical sensor, based on NdFeO₃ nanoparticles as electrocatalytic material, was proposed here for the detection of dopamine (DA). NdFeO₃ nanoparticles were first synthesized by a simple thermal treatment method and subsequent annealing at high temperature (700 °C). The prepared electrocatalytic material has been characterized in detail by SEM-EDX, XRD, and Raman techniques. Characterization results display its sheet-like morphology, constituted by a porous network of very small orthorhombic NdFeO₃ nanoparticles. NdFeO₃ electrocatalytic material was then used to modify the working electrode of screen-printed carbon electrodes (SPCEs). Electrochemical tests demonstrated that NdFeO₃– modified screen-printed carbon electrode (NdFeO₃/SPCE) exhibited a remarkable enhancement of the dopamine electrooxidation, compared to the bare SPCE one. The analytical performance of the developed sensor has been evaluated for the detection of this analyte by means of the square-wave voltammetry (SWV) technique. The modified electrode showed two linear concentration ranges, from 0.5 to 100 μM and 150 to 400 μM, respectively, a limit of detection (LOD) of 0.27 μM (at S/N = 3), and good reproducibility, stability, and selectivity. Additionally, we also report an attempt made to propose the modified sensor for the simultaneous detection of dopamine and uric acid (UA). The procedure was also applied for the determination of dopamine in spiked real samples. So, this paper reports for the first time the use of a modified NdFeO₃ screen-printed electrode for developing an electrochemical sensor for the quantification of important biomolecules.

Graphical abstract

     

Sequestration within biomolecular condensates inhibits Aβ-42 amyloid formation

Biomolecular condensates are emerging as an efficient strategy developed by cells to control biochemical reactions in space and time by locally modifying composition and environment. Yet, local increase in protein concentration within these compartments could promote aberrant aggregation events, including the nucleation and growth of amyloid fibrils. Understanding protein stability within the crowded and heterogeneous environment of biological condensates is therefore crucial, not only when the aggregation-prone protein is the scaffold element of the condensates but also when proteins are recruited as client molecules within the compartments. Here, we investigate the partitioning and aggregation kinetics of the amyloidogenic peptide Abeta42 (Aβ-42), the peptide strongly associated with Alzheimer''s disease, recruited into condensates based on low complexity domains (LCDs) derived from the DEAD-box proteins Laf1, Dbp1 and Ddx4, which are associated with biological membraneless organelles. We show that interactions between Aβ-42 and the scaffold proteins promote sequestration and local increase of the peptide concentration within the condensates. Yet, heterotypic interactions within the condensates inhibit the formation of amyloid fibrils. These results demonstrate that biomolecular condensates could sequester aggregation-prone proteins and prevent aberrant aggregation events, despite the local increase in their concentration. Biomolecular condensates could therefore work not only as hot-spots of protein aggregation but also as protective reservoirs, since the heterogenous composition of the condensates could prevent the formation of ordered fibrillar aggregates.

Biomolecular condensates sequester an aggregation-prone peptide and prevent its aggregation, showing that heterotypic interactions within the condensates can prevent the formation of amyloid fibrils, despite the local increase in concentration.     

A Formal Total Synthesis of (+)-Methyl Trachyloban-18-oate and (+)-Methyl 16-Oxo-17-norkauran-18-oate: Regio- and Diastereoselective Preparation of Methyl (13S)-13-Hydroxyisoatisiren-18-oate from (−)-Abietic Acid

A novel preparation of methyl (13S)-13-hydroxyisoatisiren-18-oate ( 4 ), a key-intermediate in a synthesis of (+)-methyl trachyloban-18-oate ((+)- 1 ), from (?)-abietic acid, is described. Since (?)- 1 has been previously converted into (?)-methyl 16-oxo-17-norkauran-18-oate ((?)- 16 ), our preparation of 4 constitutes also a formal total synthesis, from (?)-abietic acid, of (+)- 16 . Key steps in this approach were the allene photoaddition to podocarp-8(14)-en-13-one ( 5 ) and the conversion of the endo-toluene-4-sulfonate 11 into the exo-benzoate 12b .