Physico-chemical characterization of protein-pigment interactions in tempera paint reconstructions: casein/cinnabar and albumin/cinnabar

In this work, we characterized paint reconstructions using ovalbumin and casein as binders, and cinnabar (HgS) as a pigment, before and after artificial ageing. Egg and casein are common paint binders that were used historically in the technique of tempera painting. Despite extensive research on the identification of proteinaceous binders in paintings, there is a substantial lack of knowledge regarding the ageing pathway of their protein content, and their chemical interaction with inorganic pigments. Thermogravimetric analysis, infrared spectroscopy and size-exclusion chromatography (SEC) were used to reveal the physico-chemical processes involved in the ageing of proteins in paintings. Taken together, the three techniques highlighted that proteins are subject to both cross-linking and hydrolysis upon ageing, and to a lesser extent, to oxidation of the side chains. Mercury–protein interactions were also revealed using a cold vapour generation atomic fluorescence spectrometer mercury-specific detector coupled to SEC. The study clearly showed that HgS forms stable complexes with proteins and acts as a sensitizer in cross-linking, hydrolysis and oxidation.     

1,6- and 1,7-naphthyridines. II. Synthesis from acyclic precursors

A number of 8-hydroxy-6-methyl-1,6-naphthyridin-5(6H)-one-7-carboxylic acid alkyl esters 3 and the isomeric 5-hydroxy-7-methyl-1,7-naphthyridin-8(7H)-one-6-carboxylic acid alkyl esters 4 were synthesized from acyclic precursors obtained starting from quinolinic anhydride 5. Thus, methanolysis of 5 afforded the hemiester 6 which treated with oxalyl chloride and sarcosine ethyl ester gave 3-(N-ethoxycarbonylmethyl-N-methylcarbamoyl)pyridine-2-carboxylic acid methyl ester 8. Compound 8 was cyclized to naphthyridines 3a-e with sodium alkoxides. The isomeric naphthyridines 4a-c were obtained by cyclization of the open intermediary 2-(N-ethoxycarbonylmethyl-N-methylcarbamoyl)pyridine-3-carboxylic acid methyl ester 9 obtained by a route that involves treatment of 5 with sarcosine ethyl ester and esterification with diazomethane. Spectroscopic properties (¹H nmr, uv, ir) of compounds 3 and 4 are discussed and confirmed the proposed structures.     

3-Oxo-1,2-benzoisothiazoline-2-acetic acid 1,1-dioxide derivatives. II. Reaction of amides with alkoxides

Reaction of some 3-oxo-1,2-benzoisothiazoline-2-acetamide 1,1-dioxides ( 1a-f ) with alkaline alkoxides was carried out under various conditions. Under mild conditions, 1a-f with sodium methoxide gave o-(N-carbox-amidomethylsulfamyl)benzoic acid methyl esters ( 2a-f, R = CH3 ). Compounds 1a or 2a reacted with sodium alkoxides under drastic conditions affording only ester 5 . Under the same conditions, 1b-d or 2b-d gave 4-hydroxy-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxides ( 3b-d ), while 1e-f or 2e-f afforded the acid 6 in variable amounts, together with the expected benzothiazines 3e-f . Isolation of ethyl ether as another product in the reaction of 1e-f with sodium ethoxide supports the suggestion that the formation of 6 involves the O-alkyl fission on the alkyl carbon of the esters 2e-f . An explanation of these results may be related to the acidic character of the amide hydrogen in compounds 2e-f .     

Morphology of poly(lactide)-block-poly(dimethylsiloxane)-block-polylactide high-χ triblock copolymer film studied by grazing incidence small-angle X-ray scattering

The morphologies of poly(lactide)-block-poly(dimethylsiloxane)-block-polylactide (PLA-b-PDMS-b-PLA) triblock copolymer films were studied using a combination of grazing-incidence small-angle X-ray scattering, X-ray reflectivity and scanning electron microscopy. This block copolymer is characterized by a high Flory–Huggins interaction parameter which leads to the self-assembly of periodic high-resolution nanodomains. In this article, we performed a detailed analysis of GISAXS patterns, in the frame of the Distorted Wave Born Approximation, in order to determine the morphology of blocks and their spatial arrangement. For a low volume fraction of PLA (17%), a three-dimensional hexagonal lattice of PLA spherical blocks is revealed, while, for a PLA fraction twice larger, in-plane (parallel) PLA lying cylinders adopt a two-dimensional centered rectangular lattice. Moreover, the in-depth electron density profile of the polymer film for the cylindrical morphology was extracted from the XRR data, revealing the presence of interfacial layers at the top surface and at the interface with the Si substrate.     

Alkylation of 3,5-Dimethylisothiazole. A Regioselective Synthesis of S-Alkyl-3-methylisothiazoles

3,5-Dimethylisothiazole reacts sequentially with lithiumdiisopropylamide (molar ratio 1:1) and alkyl halides (in excess) affording 5-alkyl-3-methylisothiazoles in excellent yields. When a two-fold excess of base is used, a mixture of 5-monoalkylated and 3,5-dialkylated products is obtained. Sodium amide was also tried as deprotonating agent, but the yield in final products was lower.     

Combined Heterogeneous Metal/Chiral Amine: Multiple Relay Catalysis for Versatile Eco‐Friendly Synthesis

Herein is described a versatile and broad synergistic strategy for expansion of chemical space and the synthesis of valuable molecules (e.g. carbocycles and heterocycles), with up to three quaternary stereocenters, in a highly enantioselective fashion from simple alcohols (31 examples, 95:5 to >99.5:0.5 e.r.) using integrated heterogeneous metal/chiral amine multiple relay catalysis and air/O₂ as the terminal oxidant. A novel highly 1,4‐selective heterogeneous metal/amine co‐catalyzed hydrogenation of enals was also added to the relay catalysis sequences.     

Improved Stability and Tunable Functionalization of Parallel β-Sheets via Multicomponent N-Alkylation of the Turn Moiety

In contrast to the myriad of methods available to produce α-helices and antiparallel β-sheets in synthetic peptides, just a few are known for the construction of stable, non-cyclic parallel β-sheets. Herein, we report an efficient on-resin approach for the assembly of parallel β-sheet peptides in which the N-alkylated turn moiety enhances the stability and gives access to a variety of functionalizations without modifying the parallel strands. The key synthetic step of this strategy is the multicomponent construction of an N-alkylated turn using the Ugi reaction on varied isocyano-resins. This four-component process assembles the orthogonally protected turn fragment and incorporates handles serving for labeling/conjugation purposes or for reducing peptide aggregation. NMR and circular dichroism analyses confirm the better-structured and more stable parallel β-sheets in the N-alkylated peptides compared to the non-functionalized variants.     

GABA<Subscript>A</Subscript>receptor γ2 subunit knockdown mice have enhanced anxiety-like behavior but unaltered hypnotic response to benzodiazepines

Background  

Gamma-aminobutyric acid type A receptors (GABA_A-Rs) are the major inhibitory receptors in the mammalian brain and are modulated by a number of sedative/hypnotic drugs including benzodiazepines and anesthetics. The significance of specific GABA_A-Rs subunits with respect to behavior and in vivo drug responses is incompletely understood. The γ2 subunit is highly expressed throughout the brain. Global γ2 knockout mice are insensitive to the hypnotic effects of diazepam and die perinatally. Heterozygous γ2 global knockout mice are viable and have increased anxiety-like behaviors. To further investigate the role of the γ2 subunit in behavior and whole animal drug action, we used gene targeting to create a novel mouse line with attenuated γ2 expression, i.e., γ2 knockdown mice.     

Implications of rainfall temporal resolution for soil-moisture and transpiration modeling

Dimensionless groups of parameters characterizing an ecosystem are valuable indicators for the a priori assessment of the effect of rainfall data resolution on predictions of soil moisture and transpiration. Knowledge of these dimensionless groups enables identification of appropriate levels of rainfall data resolution, when using historical rainfall directly or when using it to derive rainfall model parameters for use in models of soil–plant–climate systems. Detailed simulation studies of the soil, plant, and climate systems in Colorado and Texas, highly resolved in time and vertical space, show that historical rainfall data resolved at the daily level allow accurate prediction of soil-moisture and transpiration dynamics for smaller time resolutions. These results support inferences based on the dimensionless groups. Furthermore, no significant improvement in the prediction of soil-moisture and transpiration dynamics is attained, when representing rainfall through a more complex Neyman–Scott model rather than the simple rectangular pulses Poisson model.