Su una formula diK. Petr per il calcolo numerico degl' integrali definiti

Sunto Si danno le condizioni necessarie e sufficienti per la validità di una formula diK. Petr, la quale fornisce uno sviluppo adatto per il calcolo numerico degl'integrali definiti.     

Als Reagens auf Kaliumverbindungen

Ohne Zusammenfassung     

Méthodes de calcul différentiel absolu et leurs applications

Sans résumé     

First Evidence of Anti-Steatotic Action of Macrotympanain A1, an Amphibian Skin Peptide from Odorrana macrotympana

Many different amphibian skin peptides have been characterized and proven to exert various biological actions, such as wound-healing, immunomodulatory, anti-oxidant, anti-inflammatory and anti-diabetic effects. In this work, the possible anti-steatotic effect of macrotympanain A1 (MA1) (FLPGLECVW), a skin peptide isolated from the Chinese odorous frog Odorrana macrotympana, was investigated. We used a well-established in vitro model of hepatic steatosis, consisting of lipid-loaded rat hepatoma FaO cells. In this model, a 24 h treatment with 10 µg/mL MA1 exerted a significant anti-steatotic action, being able to reduce intracellular triglyceride content. Accordingly, the number and diameter of cytosolic lipid droplets (LDs) were reduced by peptide treatment. The expression of key genes of hepatic lipid metabolism, such as PPARs and PLINs, was measured by real-time qPCR. MA1 counteracted the fatty acid-induced upregulation of PPARγ expression and increased PLIN3 expression, suggesting a role in promoting lipophagy. The present data demonstrate for the first time a direct anti-steatotic effect of a peptide from amphibian skin secretion and pave the way to further studies on the use of amphibian peptides for beneficial actions against metabolic diseases.     

Bounds on the crossing resolution of complete geometric graphs

The crossing resolution of a geometric graph is the minimum crossing angle at which any two edges cross each other. In this paper, we present upper and lower bounds to the crossing resolution of the complete geometric graphs.     

Helmholtz conditions,covariance, and invariance identities

This paper is concerned with the problem of finding a multiplier matrixg which converts a prescribed system of second-order ordinary differential equations to the Euler-Lagrange form. Sufficient conditions for the existence of a multiplier matrix are given in the form of an infinite system of linear algebraic equations, provided the entries ofg may be regarded as components of a (0, 2) symmetric tensor field. As an application, conditions for the local existence of a metric tensor compatible with a given torsion-free connection are deduced.     

Multiple Proton Confinement in the M2 Channel from the Influenza A Virus

The tetrameric M2 protein bundle of the influenza A virus is the proton channel responsible for the acidification of the viral interior, a key step in the infection cycle. Selective proton transport is achieved by successive protonation of the conserved histidine amino acids at position 37. A recent X-ray structure of the tetrameric transmembrane (TM) domain of the protein (residues 22-46) resolved several water clusters in the channel lumen, which suggest possible proton pathways to the His37 residues. To explore this hypothesis, we have carried out molecular dynamics (MD) simulations of a proton traveling towards the His37 side chains using MD with classical and quantum force fields. Diffusion through the first half of the channel to the "entry" water cluster near His37 may be hampered by significant kinetic barriers due to electrostatic repulsion. However, once in the entry cluster, a proton can move to one of the acceptor His37 in a nearly barrierless fashion, as evidenced both by MD simulations and a scan of the potential energy surface (PES). Water molecules of the entry cluster, although confined in the M2 pore and restricted in their motions, can conduct protons with a rate very similar to that of bulk water.     

Efficient and Modular Synthesis of New Structurally Diverse Functionalized [n]Paracyclophanes by a Ring‐Distortion Strategy

With the goal of synthesizing new [n]paracyclophanes, the expansion of the scope of a strategy originally disclosed by Winterfeldt et al., was investigated. This approach involves sequential Diels–Alder/retro‐Diels–Alder reactions, the applications of which have been constrained so far to steroid derivatives. An efficient access to new functionalized [9]‐, [10]‐, and [16]paracyclophanes, including original cage architectures, was developed from readily available building blocks using thermal electrocyclization and a cycloaddition/cycloreversion sequence as the key steps.     

Chemo-enzymatic Synthesis of 6″-O-(3-Arylprop-2-enoyl) Derivatives of the Flavonol Glucoside Isoquercitrin

A chemo-enzymatic approach to some 6″-O-(3-arylprop-2-enoyl) derivatives of the flavonol glucoside isoquercitrin ( 2a ) was explored to overcome the inability to directly introduce these acyl moieties by an enzyme-catalyzed reaction of 2a with the corresponding activated esters. This new approach was based on the regioselective introduction of a methyl malonate residue at the CH₂OH of the sugar moiety by catalysis with the protease subtilisin (→ 22a ). The mixed diester 22a was then subjected to chemoselective hydrolysis of the methoxycarbonyl function by another enzyme, biophine esterase (→ 23 ). Finally, the malonic monoester 23 was reacted in a Knoevenagel-type condensation with benzaldehyde, 4-hydroxybenzaldehyde, or 4-hydroxy-3-methoxybenzaldehyde to afford the target 6″-O-(3-arylprop-2-enoyl) isoquercitrins 2b–d .     

Monte Carlo simulation of liquid Br2: Test of an effective hamiltoniain

Monte Carlo simulations for the structure of a fluid of molecules interacting with a pair potential having one Lennard- Jones center plus a quadrupole interaction is reported. The numerical experiments are compared with an approximation method previously suggested and with experimental results for the liquid Br₂ structure. This effective pair potential turns out to be unable to reproduce the Br₂ structure while the approximation method is only useful for quadrupole moments less than 1.2 × 10^?40 C m².