Collection of Finite Lattices Generated by a Poset

It is proved that the collection of all finite lattices with the same partially ordered set of meet-irreducible elements can be ordered in a natural way so that the obtained poset is a lattice. Necessary and sufficient conditions under which this lattice is Boolean, distributive and modular are given.     

Binding behavior of amino acid conjugates of indole-3-acetic acid to immobilized human serum albumin

The affinity of indole-3-acetic acid (IAA), indole-3-propionic acid, indole-3-butyric acid and 24 of their amino acid conjugates to immobilized human serum albumin, as expressed by the retention factor k (determined by HPLC), was dependent on (1) lipophilicity, (2) chirality and (3) functional groups in the amino acid moiety; in some cases conformation plays an additional role. Two lipophilicity-related parameters afforded quantitative correlations with k: retention on a C18 reversed-phase column (experimental approach) and the distance between the hydrophilic and hydrophobic poles of the molecules (in silico approach). Most compounds examined are possible metabolic precursors of IAA, an experimental tumor therapeutic.     

Natural Deep Eutectic Solvent (NADES) Extraction Improves Polyphenol Yield and Antioxidant Activity of Wild Thyme (Thymus serpyllum L.) Extracts

Wild thyme (Thymus serpyllum L.) herbal dust has been recognized as a potential underutilized resource for the recovery of antioxidants. The aim of this paper was to optimize natural deep eutectic solvent (NADES) extraction of polyphenols to obtain improved antioxidant activity of extracts determined by selected in vitro assays (DPPH, FRAP, and ABTS). Twenty different NADES systems were investigated in the first step of the screening of the extraction solvent and l-proline (Pro)–glycerine (Gly) based solvents provided the best results. Preliminary experiments organized by 2⁵⁻¹ fractional factorial design narrowed down the number of extraction factors from five (temperature, extraction time, NADES type, water content and L/S ratio) to three and determined their experimental domain for the final step. A face-centered central composite design with temperature (40–55–70 °C), extraction time (60–120–180 min) and L/S ratio (10–20–30 g NADES/g sample) was applied for influence analysis and process optimization. Multi-response optimization suggested a temperature of 65 °C, time of extraction of 180 min and L/S ratio of 28 g NADES/g DW as optimal extraction parameters. Experimental validation confirmed good agreement between experimental and predicted results in the extract obtained at optimal conditions and the interactions in the most suitable NADES (N16; Pro–Gly–H₂O; 1:2:1) were confirmed by the ¹H-NMR.     

Gas Phase H/D Exchange of Sodiated Amino Acids: Why Do We See Zwitterions?

The gas-phase interaction of sodiated amino acids and sodiated amino acid methyl esters with various deuterium donors is investigated by combining results of H/D exchange reactions with those from density functional theory and molecular dynamics calculations. Discrepancy between experimentally and theoretically obtained structures for sodium cationized amino acids is explained by deuterium donor caused perturbation of the most stable amino acid conformation. Detailed study of H/D exchange mechanism on sodiated amino acids shows that the H/D exchange reaction is preceded by a multistep quasi-isoenergetic transition (perturbation) from a charge solvated to zwitterionic structure in the amino acid. Although the computation refers to the system AlaNa(+) and D(2)O, these mechanisms apply to all amino acids, except those where a functional side-chain group takes part in the perturbation process. The suggested perturbation mechanism applies also for other deuterium donors such as CD(3)OD or even ND(3) and indicates that a single water molecule suffices to convert the sodiated amino acid from charge solvated to zwitterionic form.     

Electrochemical decolorization of C.I. Acid Orange 3 in the presence of sodium chloride at iridium oxide electrode

The electrocatalytic degradation of C.I. Acid Orange 3 from simulated wastewater by indirect electrochemical oxidation using an IrO_x electrode was investigated. The effects of different operating parameters on the rate of dye decolorization were studied. The influences of mixing, electrolyte concentration, applied current, and initial dye concentration were examined. The change in dye concentration was followed by ultraviolet–visible spectroscopy, while the formation of reaction intermediates was established using high-performance liquid chromatography–mass spectrometry analysis. Ultraviolet–visible spectroscopy showed a decrease of the absorption peak at 374 nm during the electrolysis and the appearance of a new absorption maximum at 460 nm. The decolorization reaction can be followed only at 460 nm. Four intermediate products (two mono- and two dichlorinated) were detected. At the end of the study, a phytotoxicity assay was performed to determine the effectiveness of the applied method. The results showed that the applied electrochemical treatment of C.I. Acid Orange 3 leads to a decrease in phytotoxicity from 53 to 28%.     

Synthesis and alkali metal complexation studies of novel cage-functionalized cryptands

The synthesis of novel cage-functionalized cryptands 1–5 containing adamantane-, 2-oxaadamantane- or noradamantane-moiety [i.e., 1,3-diethyladamantano[2.2.0]cryptand (1), 1,3-diethoxyadamantano[2.2.2]cryptand (2), 1,3-di[(ethyloxy)methyl]adamantano[2.2.2]-cryptand (3), 1,3-di[(ethyloxy)methyl]-2-oxaadamantano[2.2.3]cryptand (4), and 1,2-diethyloxynoradamantano[2.2.2]cryptand (5)] and their alkali metal binding properties are reported. The results obtained by extraction experiments showed that all the cryptands displayed lower extraction capabilities than the parent [2.2.2]cryptand. However, cryptands 1 and 2 showed much higher selectivity toward K⁺ than the reference [2.2.2]cryptand. When the third bridge is enlarged by two additional CH₂-groups as well as by two oxygen atoms, as in cryptands 3 and 4, the complexational abilities for bigger cations (K⁺, Rb⁺ and Cs⁺) are enhanced. Cryptand 5 displayed very good extraction capabilities of all cations, but showed practically no selectivity towards any of the alkali metal cation. The experimental findings are corroborated by calculation studies consisting of force field based conformational search using Monte Carlo method followed by investigation of the stabilities of the complexes of cryptands with Na⁺ and K⁺ metal ions in chloroform by means of quantum chemical calculations at the density functional theory level.     

New Mechanistic Proposal for Some Heptamolybdate-Ion-Catalyzed Isomerizations

Heptamolybdate-ion(HM)-catalyzed C(2) epimerization of D-glucose and racemization of D-glyceraldehyde proceed with comparable rates and activation parameters; HM catalyzes the isomerization of glucal and galactal triacetates as well. For all of the above transformations, a common, new mechanism is proposed that invokes stabilization of 3-oxa-allylic cation species by the central Mo(VI) atom.     

NMR Spectroscopic Study of Camphanic Acid,Rh2[Camphanate]4, and its Adducts with 1,4-Benzodiazepines

The H and ¹³C NMR spectra of chiral camphanic acid, lactonc of (1S,3R)-1-hydroxy-2,2,3-trimethyl-cyclopentan-1,3-dicarboxylic acid (1), and dirhodium tetracamphanate complex (2) were completely assigned on the basis of one- and two-dimensional NMR experiments. The NMR spectra of the adducts of dirhodium tetracamphanate 2 with 5-pyrido-1, 4-benzodiazepin-2-ones 3 and 4, complexes with catalytic activity, support the assignation and also revealed two different types of axial complexation of these nitrogen ligands.     

Posets Generated by Irreducible Elements

Let J be a fixed partially ordered set (poset). Among all posets in which J is join-dense and consists of all completely join-irreducible elements, there is an up to isomorphism unique greatest one, the Alexandroff completion L. Moreover, the class of all such posets has a canonical set of representatives, C ₀ L, consisting of those sets between J and L which intersect each of the intervals I _j =[j ,j ] (jJ), where j and j denote the greatest element of L less than, respectively, not greater than j. The complete lattices in C ₀ L form a closure system C L, consisting of all Dedekind–MacNeille completions of posets in C ₀ L. We describe explicitly those L for which C ₀ L, respectively, C L is a (complete atomic) Boolean lattice, and similarly, those for which C L is distributive (or modular). Analogous results are obtained for C L, the closure system of all posets in C ₀ L that are closed under meets of less than elements (where is any cardinal number).