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Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 511
Author(s):  
Yu Suzuki ◽  
Takanori Higashi ◽  
Takahiro Yamamoto ◽  
Hideyasu Okamura ◽  
Takehiro K. Sato ◽  
...  

Spider dragline silk is a biopolymer with excellent mechanical properties. The development of recombinant spider silk protein (RSP)-based materials with these properties is desirable. Formic acid (FA) is a spinning solvent for regenerated Bombyx mori silk fiber with excellent mechanical properties. To use FA as a spinning solvent for RSP with the sequence of major ampullate spider silk protein from Araneus diadematus, we determined the conformation of RSP in FA using solution NMR to determine the role of FA as a spinning solvent. We assigned 1H, 13C, and 15N chemical shifts to 32-residue repetitive sequences, including polyAla and Gly-rich regions of RSP. Chemical shift evaluation revealed that RSP is in mainly random coil conformation with partially type II β-turn structure in the Gly-Pro-Gly-X motifs of the Gly-rich region in FA, which was confirmed by the 15N NOE data. In addition, formylation at the Ser OH groups occurred in FA. Furthermore, we evaluated the conformation of the as-cast film of RSP dissolved in FA using solid-state NMR and found that β-sheet structure was predominantly formed.


Molbank ◽  
10.3390/m1318 ◽  
2022 ◽  
Vol 2022 (1) ◽  
pp. M1318
Author(s):  
R. Alan Aitken ◽  
Anna L. G. Gidlow ◽  
Russel S. Ramsewak ◽  
Alexandra M. Z. Slawin

The X-ray structure of the title compound, obtained as a byproduct in a natural product synthesis, has been determined and shows an unusual pattern featuring chains of molecules with both intra- and intermolecular hydrogen bonding of the OH groups.


Biomolecules ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 90
Author(s):  
Maria Laura Alfieri ◽  
Lucia Panzella ◽  
Riccardo Amorati ◽  
Alice Cariola ◽  
Luca Valgimigli ◽  
...  

The activity of natural phenols is primarily associated to their antioxidant potential, but is ultimately expressed in a variety of biological effects. Molecular scaffold manipulation of this large variety of compounds is a currently pursued approach to boost or modulate their properties. Insertion of S/Se/Te containing substituents on phenols may increase/decrease their H-donor/acceptor ability by electronic and stereo-electronic effects related to the site of substitution and geometrical constrains. Oxygen to sulphur/selenium isosteric replacement in resveratrol or ferulic acid leads to an increase in the radical scavenging activity with respect to the parent phenol. Several chalcogen-substituted phenols inspired by Vitamin E and flavonoids have been prepared, which in some cases prove to be chain-breaking antioxidants, far better than the natural counterparts. Conjugation of catechols with biological thiols (cysteine, glutathione, dihydrolipoic acid) is easily achieved by addition to the corresponding ortho-quinones. Noticeable examples of compounds with potentiated antioxidant activities are the human metabolite 5-S-cysteinyldopa, with high iron-induced lipid peroxidation inhibitory activity, due to strong iron (III) binding, 5-S-glutathionylpiceatannol a most effective inhibitor of nitrosation processes, and 5-S-lipoylhydroxytyrosol, and its polysulfides that proved valuable oxidative-stress protective agents in various cellular models. Different methodologies have been used for evaluation of the antioxidant power of these compounds against the parent compounds. These include kinetics of inhibition of lipid peroxidation alkylperoxyl radicals, common chemical assays of radical scavenging, inhibition of the OH• mediated hydroxylation/oxidation of model systems, ferric- or copper-reducing power, scavenging of nitrosating species. In addition, computational methods allowed researchers to determine the Bond Dissociation Enthalpy values of the OH groups of chalcogen modified phenolics and predict the best performing derivative. Finally, the activity of Se and Te containing compounds as mimic of glutathione peroxidase has been evaluated, together with other biological activities including anticancer action and (neuro)protective effects in various cellular models. These and other achievements are discussed and rationalized to guide future development in the field.


Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 337
Author(s):  
Adam Chyzy ◽  
Damian Pawelski ◽  
Vladyslav Vivcharenko ◽  
Agata Przekora ◽  
Michael Bratychak ◽  
...  

In this study, well-known oligomers containing ethyl methacrylate (EMA) and glycidyl methacrylate (GMA) components for the synthesis of the oligomeric network [P(EMA)-co-(GMA)] were used. In order to change the hydrophobic character of the [P(EMA)-co-(GMA)] to a more hydrophilic one, the oligomeric chain was functionalized with ethanolamine, xylitol (Xyl), and L-ornithine. The oligomeric materials were characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy, scanning electron microscopy, and differential thermogravimetric analysis. In the final stage, thanks to the large amount of -OH groups, it was possible to obtain a three-dimensional hydrogel (HG) network. The HGs were used as a matrix for the immobilization of methylene blue, which was chosen as a model compound of active substances, the release of which from the matrix was examined using spectrophotometric detection. The cytotoxic test was performed using fluid extracts of the HGs and human skin fibroblasts. The cell culture experiment showed that only [P(EMA)-co-(GMA)] and [P(EMA)-co-(GMA)]-Xyl have the potential to be used in biomedical applications. The studies revealed that the obtained HGs were porous and non-cytotoxic, which gives them the opportunity to possess great potential for use as an oligomeric network for drug reservoirs in in vitro application.


2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Savita A. Kundaikar ◽  
Sudesh M. Morajkar ◽  
Wolfgang Bensch ◽  
Bikshandarkoil R. Srinivasan

Abstract The reaction of Na2MoO4·2H2O with 2-amino-2-(hydroxymethyl)propane-1,3-diol (LH) in water at room temperature results in the formation of the heterometallic coordination polymer [Mo2O6L2(Na2(H2O)4)]·2H2O 1 (L = 2-amino-3-hydroxy-2-(hydroxymethyl)propan-1-olato). The structure of 1 consists of a neutral (Mo2O6) unit located on an inversion center. The Mo atoms exhibit hexa-coordination and are bonded to two terminal and two bridging oxido ligands, an alkoxide oxygen and the amine N atoms of an anionic ligand L– resulting in the formation of an edge-sharing {Mo2O8N2} bioctahedron. The Na+ cations of a centrosymmetric bis(μ2-aqua)-bridged (Na2(H2O)4)2+ unit are penta-coordinated and bonded to two symmetry related L– ligands via the oxygen atoms of their OH groups. The µ3-bridging tetradentate binding mode of L– results in the formation of a two-dimensional heterometallic coordination polymer. The constituents of 1 viz. (Mo2O6), (L)–, (Na2(H2O)4)2+ and lattice water molecules are interlinked with the aid of three varieties of hydrogen bonding interactions. The corresponding tungstate reported recently has been obtained through a similar synthetic protocol and is isostructural.


SPE Journal ◽  
2022 ◽  
pp. 1-17
Author(s):  
Emanuel Ricky ◽  
Musa Mpelwa ◽  
Chao Wang ◽  
Bahati Hamad ◽  
Xingguang Xu

Summary Drilling fluid rheology and fluid loss property are fundamental parameters that dictate the effectiveness and easiness of a drilling operation. Maintaining these parameters under high temperatures is technically challenging and has been an exciting research area for the drilling industry. Nonetheless, the use of drilling mud additives, particularly synthetic polymers, threaten ecological environments. Herein, modified corn starch (MCS) was synthesized, characterized, and investigated as an environmentally friendly rheology enhancer and filtration loss controlling agent for water-based mud (WBM) at high temperatures. The experimental results indicated that MCS exhibits better performance in improving rheological properties and fluid loss controlling ability for WBM than the commonly used mud additives. With the addition of an optimal concentration (0.3 wt%), MCS improved the rheology and fluid loss behavior of WBM formulation at harsh aging temperature (220°C) by practically 4 times and 1.7 times, respectively. The MCS was revealed to perform superbly over polyanionic cellulose (PAC) addition at all investigated temperatures. The better performance of the MCS was ascribed to the improved entanglements in the mud system owing to the additional hydroxyl (OH) groups. Besides, the Herschel-Bulkley model was found to be a constitutive model that described the rheological properties of the investigated muds satisfactorily. Moreover, the MCS was found to exhibit acceptable biodegradability properties.


2022 ◽  
Vol 130 (1) ◽  
pp. 160
Author(s):  
Л.А. Бобрева ◽  
Н.В. Сидоров ◽  
Н.А. Теплякова ◽  
М.Н. Палатников ◽  
С.А. Климин ◽  
...  

We have analyzed complex defects due to the presence of hydrogen bonds in the crystal structure in nominally pure lithium niobate crystals with different Li/Nb ratio, in crystals alloyed with magnesium and zinc in a wide concentration range (LiNbO3 : Mg (0.19-5.91 mol.% MgO) and LiNbO3 : Zn (0.04-6.5 mol. % ZnO)) and in the double-alloyed crystals (LiNbO3 : Y(0.24) : Mg(0.63 wt. %) and LiNbO3 : Gd (0.25) : Mg(0.75 wt. %)), obtained by technology of direct melt alloying, and also in the double-alloyed crystal (LiNbO3 : Mg(5. 05 mol.% MgO) : Fe(0.009 mol.% Fe2O3)) grown from a charge synthesized using the technology of homogeneous alloying with magnesium and iron Nb2O5. We revealed the influence of doping impurities on the concentration of OH-groups, the type and localization of complex defects in the crystal structure. The change in the number of hydrogen atom positions in the structure of the LiNbO3 crystal allow us to judge with sufficient accuracy whether the crystal composition is stoichiometric or congruent. For doped crystals of different compositions data were obtained testifying to changes in the character of complexation of OH-groups with point defects of the cationic sublattice with formation of defects: MеLi-OH-, MеLi-MеNb-OН. A change in the mechanism of entry of the dopant cation into the structure dramatically affects the change in the properties of the crystal.The difference in the frequencies (and, correspondingly, in the values of the quasi-elastic constants of the O-H bonds) in the spectrum of a congruent crystal and doped crystals can also be contributed by differences in the electronegativity and ionic radii of the principal and doping cations.


2022 ◽  
Author(s):  
Carina Proença ◽  
Ana T. Rufino ◽  
José Miguel P. Ferreira de Oliveira ◽  
Marisa Freitas ◽  
Pedro A. Fernandes ◽  
...  

Flavonoids may be effective inhibitors of SI in Caco-2/TC7 cells when using natural substrates maltose and sucrose. The chemical features that favor the SI inhibition by flavonoids are the presence of –OH groups at C-3, C-3′, C-4′, C-7 and C-8.


Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 102
Author(s):  
Imane Aadnan ◽  
Omar Zegaoui ◽  
Abderrahim El Mragui ◽  
Joaquim Carlos Gomes Esteves da Silva

In this investigation, a hybrid-biocomposite “ZnO-Bentonite/Chitosan” was synthesized using inexpensive and environmentally friendly materials (Bentonitechitosan) and (ZnO). It was used as a photocatalyst for water remediation. The structural, optical, thermal, and morphological properties of the synthesized hybrid-biocomposite were investigated using XRD, FTIR spectroscopy, UV-vis diffuse reflectance spectroscopy, TGA, XPS, and SEM-EDS. The thermal measurements showed that the decomposition of CS was postponed progressively by adding PB and ZnO, and the thermal stability of the synthesized hybrid-biocomposite was improved. The characterization results highlighted strong interactions between the C–O, C=O, -NH2, and OH groups of chitosan and the alumina-silica sheets of bentonite on the one side, and between the functional groups of chitosan (-NH2, OH) and ZnO on the other side. The photocatalytic efficiency of the prepared hybrid-biocomposite was assessed in the presence of Methyl Orange (MO). The experiments carried out in the dark showed that the MO removal increased in the presence of Zn-PB/CS hybrid-biocomposite (86.1%) by comparison with PB (75.8%) and CS (65.4%) materials. The photocatalytic experiments carried out under visible light showed that the MO removal increased 268 times in the presence of Zn-PB/CS by comparison withZnO.The holes trapping experiments indicated that they are the main oxidative active species involved in the MO degradation under both UV-A and visible light irradiations.


2021 ◽  
Vol 25 (9) ◽  
pp. 1707-1713
Author(s):  
O.O.E. Onawumi ◽  
A.A. Sangoremi ◽  
O.S. Bello

This study was carried out to prepare groundnut shell (GS) and eggshell (ES) into activated carbon (AC) and characterize the AC using Association of Official Analytical Chemists (AOAC) and American Standard for Testing and Materials (ASTM) methods. The AC produced was characterized for: pH, moisture content, volatile matter, ash content, fixed carbon, bulk density and surface area. Surface functional groups and surface morphology were also determined using Fourier Transformed Infrared (FT-IR) and Scanning Electron Microscope (SEM) respectively. The ranges of the following results were achieved for the biomasses: Groundnut shell Activated Carbon (GSAC) and Eggshell Activated Carbon (ESAC) respectively: pH (6.80±0.101−7.80±0.011); moisture content (14.10±0.101−12.90±.110%); volatile matter (9.20±0.112−9.90±0.012%); ash content (8.98±0.111−5.80±0.111%); fixed carbon (67.70±0.010−71.40±110%); bulk density (370.00±0.000−380.00−0.000 g/L); surface area (880.00±0.100−800.00±0.000 m2/g). The agro-wastes have high carbon contents and low inorganic which make them viable adsorbents. FT-IR analysis revealed the presence of oxygen surface complexes such as carbonyls and OH groups on the surface of the ACs in addition to good pore structures from SEM studies revealed that the agro-wastes could be good precursors for ACs production. The overall results showed that the AC produced from the agro-wastes can be optimally used as good and effective adsorbents, thereby ensuring cheaper, readily available and affordable ACs for the treatment of effluent, waste water and used oils.


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