The reactions of phenolic reagents with α-bromo Michael acceptors in the K2CO3-acetone system. A stereospecific AdSNE process.

α-bromo Michael acceptors undergo ipso-substitution by phenol or benzenethiol in the K₂CO₃-acetone system, the reaction originating the (Z) isomers, via a stereospecific Ad_SNE process.     

Interconversion of the thiazine and thiazolidine system of β-lactam antibiotics,electrochemical cleavage of kamiya's disulphide promoted by bromide ion

A new transformation of Kamiya's disulphide ($\text{1}$) into the bromopenam derivative ($\text{4}$) has been carried out by electrolyzing the disulphide ($\text{1}$) in protic solvents in the presence of Me₄NBr. The transformation occurs through an intermediate episulphonium-bromide ion pair in which the bromide appears to tightly linked to the sulphur.     

5‐(5‐Nitropyridin‐2‐yldithio)‐1‐phenyl‐1H‐tetrazole

In the title disulfide, C₁₂H₈N₆O₂S₂, all bond lengths and angles are within normal ranges, and the molecules are linked into centrosymmetric R₂²(20) dimers by simple C—H...N interactions. Weak intermolecular C—H...π(arene) and π–π interactions, involving the benzene CH groups and the benzene rings, and the pyridine rings, respectively, further stabilize and reinforce the crystal structure.     

Synthesis and characterization of a bunchy oligonucleotide forming a monomolecular parallel quadruplex structure in solution

A cluster of four d(TG₄T) hexanucleotides with the 3′-ends linked together by a bunchy spacer has been synthesized and shown to form a monomolecular parallel quadruplex 5 in solution characterized by four G-quartets. ¹H NMR spectroscopy and CD thermal denaturation experiments indicate the monomolecular quadruplex (5) to be more stable than the tetramolecular counterpart [d(TG₄T)]₄.     

On the iteration of the adjunction process for surfaces of negative Kodaira dimension

Let (X,L) be a pair consisting of a smooth, complex, projective surface X and L a very ample line bundle on it. Suppose that the Kodaira dimension K(X) of X is negative. Then using the results obtained by A.J.Sommese and A.Van de Ven in [11], we find that the sectional genus, g_k=g(L_k), of the successive iterated minimal reductions (X_k,L_k), see 1. for the definition, reach a maximum value and then monotonically decrease to a final value g_n=g(L_n)g=g(L). This result gives a concrete way to express any pair (X,L), with K(X)=–, in terms of a minimal model.     

A sensitive continuous-flow bioluminescent system for determining ethanol in serum and saliva

A continuous-flow system, based on NAD(P)H:FMN oxidoreductase and bacterial luciferase co-immobilized on a nylon coil placed in front of a photomultiplier, and alcohol dehydrogenase separately immobilized on a second nylon coil, is described for the assay of ethanol in serum and saliva. The flow is air-segmented and 5–50-μl samples are required. The sample throughput is 25–30 h^?1 with no carryover. The detection limit is 1 μmol l^?1 ethanol (50 pmol injected) and the response is linear between 50 and 2500 pmol of ethanol. The relative standard deviation is 3–10% for both within-day and between-day assays, and serum and saliva can be analyzed directly. The immobilized enzymes are satisfactorily stable and up to 900 samples can be analyzed with one enzyme reactor.     

Bioluminescence flow system for determination of branched-chain l-amino acids in serum and urine

A continuous-flow bioluminescence method for determinations of branched-chain l-amino acids in serum and urine is described. Serum can be analyzed directly after simple filtration. Response is linear for 20-2000 pmol in the biological matrix. Leucine dehydrogenase is immobilized onto a nylon coil separated from the reactor coil containing bacterial bioluminescence enzymes. The stability of the immobilized is high (lifetime > two months) and more than 900 samples can be analyzed with the use of a few mg of enzymes. The results obtained agree well with those obtained by ion-exchange chromatography (amino acid analyzer).     

Interpretation of electronic spectra of aromatic hydrocarbons by the “molecules in molecules” method

The molecules in molecules method has been applied to five groups of hydrocarbon molecules or ions. Energy, polarisation and intensity of electronic transitions have been compared with experimental data and previous theoretical results. The results show that the method is applicable even when there is relevant conjugation between the fragments.

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Zusammenfassung Die molecules in molecules-Methode wurde auf fünf Gruppen von Kohlenwasserstoff-Molekülen angewandt. Energie, Polarisation und Intensität von elektronischen Übergängen wurden mit experimentellen und theoretischen Resultaten verglichen. Die Resultate beweisen, daß die Methode anwendbar ist, auch wenn eine wesentliche Konjugation zwischen den Fragmenten besteht.

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Resumé La méthode molecules in molecules a té appliquée à cinq groupes de molécules ou ions d'hydrocarbures. On a comparé les energies, la polarisation et l'intensité des transitions électroniques avec les données experimentales et les données théoriques qu'on avait précedemment calculées. Les résultats indiquent que la méthode est appliquable, même lorsqu'on a une conjugation assez importante entre les fragments.

     

Characterization of the Trans-Epithelial Transport of Green Tea (C. sinensis) Catechin Extracts with In Vitro Inhibitory Effect against the SARS-CoV-2 Papain-like Protease Activity

This work describes an untargeted analytical approach for the screening, identification, and characterization of the trans-epithelial transport of green tea (Camellia sinensis) catechin extracts with in vitro inhibitory effect against the SARS-CoV-2 papain-like protease (PLpro) activity. After specific catechin extraction, a chromatographic separation obtained six fractions were carried out. The fractions were assessed in vitro against the PLpro target. Fraction 5 showed the highest inhibitory activity against the SARS-CoV-2 PLpro (IC₅₀ of 0.125 μg mL⁻¹). The untargeted characterization revealed that (−)-epicatechin-3-gallate (ECG) was the most abundant compound in the fraction and the primary molecule absorbed by differentiated Caco-2 cells. Results indicated that fraction 5 was approximately 10 times more active than ECG (IC₅₀ value equal to 11.62 ± 0.47 μg mL⁻¹) to inhibit the PLpro target. Overall, our findings highlight the synergistic effects of the various components of the crude extract compared to isolated ECG.     

New Coumarin Dipicolinate Europium Complexes with a Rich Chemical Speciation and Tunable Luminescence

Europium (III) luminescent chelates possess intrinsic photophysical properties that are extremely useful in a wide range of applications. The lack of examples of coumarin-based lanthanide complexes is mainly due to poor photo-sensitization attempts. However, with the appeal of using such a versatile scaffold as antenna, especially in the development of responsive molecular probes, it is worth the effort to research new structural motifs. In this work, we present a series of two new tris coumarin-dipicolinate europium (III) complexes, specifically tailored to be either a mono or a dual emitter, tuning their properties with a simple chemical modification. We also encountered a rich chemical speciation in solution, studied in detail by means of paramagnetic NMR and emission spectroscopy.