Crotonic,cynnamic, and propiolic acids motifs in the synthesis of thiopyrano[2,3-d][1,3]thiazoles via hetero-Diels–Alder reaction and related tandem processes

Various novel thiopyrano[2,3-d][1,3]thiazol-2-one-6-carboxylic acids derivatives were synthesized in 54–86% yields via hetero-Diels–Alder reactions and related acylation-based tandem processes of 5-arylidene-4-thioxo-2-thiazolidinones with crotonic, propiolic, and cynnamic acids derivatives. Stereo- and regioselectivity of cycloaddition were investigated.     

The acclimative response of the main light-harvesting chlorophyll a/b-protein complex of photosystem II (LHCII) to elevated irradiances at the level of trimeric subunits

The changes in structural organization of the major light-harvesting chlorophyll a/b–protein complex of photosystem II (LHC II) at the level of trimeric subcomplexes were studied in spinach plants grown under low light conditions (50 μmol quanta m⁻² s⁻¹) and then acclimated to elevated irradiances. By monitoring photochemical quenching of fluorescence yield (q_P), photosystem II (PS II) functional status was assessed in leaves of plants acclimated to a range of elevated irradiances. Three separate acclimative irradiances were selected for the experiments, reflecting: limiting light conditions (150 μmol quanta m⁻² s⁻¹), near to the inflexion point on the irradiance curve conditions (300 μmol quanta m⁻² s⁻¹) and an excessive light, causing a moderate stress in the form of down regulation of PS II (450 μmol quanta m⁻² s⁻¹). An immunoblot analysis showed that there was a clear decline in an abundance on chlorophyll basis of Lhcb1-3 apoproteins as an acclimative irradiance increased from 50 to 450 μmol quanta m⁻² s⁻¹, with Lhcb1 decreasing to a lesser extent than Lhcb2 and Lhcb3 (only at excessive irradiance). When analyzed by non-denaturing isoelectric focusing BBY membrane fragments (PSII-enriched, stacked thylakoid membranes) isolated from low light-grown plants were resolved into nine fractions, seven of which (labelled 3–9) were established by us previously [Jackowski and Pielucha, J. Photochem. Photobiol. B: Biol. 64 (2001) 45] to be LHC II subcomplexes representing mixed populations of closely similar trimers, comprising permutations of Lhcb1 and Lhcb2 (subcomplexes 3–7) or Lhcb1-3 (subcomplexes 8 and 9). A heterogeneity with regard to accumulation behaviour of LHC II subcomplexes in response to elevated irradiances was revealed. The subcomplexes 5 and 6 were accumulating at similar level, regardless of the light irradiance experienced. Another group consisting of the subcomplexes 3 and 4 (the most basic ones) showed a progressive increase in relative abundance with increasing an irradiance intensity whereas the subcomplexes 7–9 (the most acidic ones) exhibited a progressive decline in their relative abundance during an acclimation of spinach plants to elevated irradiances thus they may collectively represent an elevated irradiance-responsive subunit of LHCII.     

Factorization of symmetric matrices over polynomial rings with involution

We find necessary and sufficient conditions for the existence of a factorization of symmetric matrices over polynomial rings with involution.Translated fromMatematichni Metodi ta Fiziko-Mekhanichni Polya, Vol. 40, No. 4, 1997, pp. 91–95.     

On the study of the decomposition of matrix polynomials into factors

We present a survey of studies of questions on the decomposition of matrix polynomials into factors. The main attention is devoted to results obtained by P. S. Kazimirs 'kii on a method of solving the problem of determining the regular factors of a matrix polynomial over an algebraically closed field of characteristic zero. Translated fromMatematichni Metody i Fiziko-Mekhanichni Polya, Vol. 38, 1995.     

trans-Aconitic acid-based hetero-Diels-Alder reaction in the synthesis of thiopyrano[2,3-d][1,3]thiazole derivatives

The hetero-Diels-Alder reaction of 5-arylideneisorhodanines with trans-aconitic acid proceeds as a regio- and diastereoselective process with spontaneous decarboxylation of the [4+2]-adduct to furnish thiopyrano[2,3-d][1,3]thiazole (2) and chromeno[4′,3′:4,5]thiopyrano[2,3-d]thiazole (3) derivatives analogously to the use of itaconic acid as a dienophile. Conversely, the one-pot, three-component reaction of 5-arylideneisorhodanines, trans-aconitic acid and anilines proceeded without decarboxylation, leading to novel rel-(5′R,6′R,7′R)-5′-carboxy-7′-aryl-1-aryl-3′,7′-dihydro-2H,2′H,5H-spiro[pyrrolidin-3,6′-thiopyrano[2,3-d]thiazol]-2,2′,5-triones 4. Interestingly, the use of trans-aconitic acid trimethyl ester led to the opposite regioselectivity, yielding rel-(5R,6S,7S)-5-methyloxycarbonylmethyl-2-oxo-7-aryl-3,5,6,7-tetrahydro-2H-thiopyrano[2,3-d]thiazol-5,6-dicarboxylates 5. Selected compounds were examined for trypanocide activity against the bloodstream forms of Trypanosoma brucei where compound 4e showed the highest activity (IC₅₀ = 6.74 μM).     

Delivery of both active enzyme and bleach from water-in-silicone oil (D(4)) emulsions

Advanced cleaning formulations, such as liquid laundry packages, consist of many components that require a complex mixture of interfacial actives including silicones for foam control, bleach for brightening, and enzymes for stain removal. Many of these ingredients are mutually incompatible, particularly in liquid formulations where they can be in intimate contact over extended periods of time. Solid dispersions of a prototypical bleach, NaBO3, in silicone polyether surfactants were shown to be very stable over time, even in the presence of water-in-silicone (D(4)) emulsions containing the enzyme alpha-chymotrypsin. Normally, perborates undergo rapid decomposition on contact with water. The rate of denaturation of the enzyme in the emulsion was similarly unaffected by the presence of the bleach until the emulsion was broken, unlike the case where the polyether surfactant was not present. The polyether surfactant thus protects the perborate from hydration and the enzyme from denaturing on contact with silicone oil until excess water and high shear are applied to the emulsion; protective mechanisms are discussed.     

Poly-albumen: Bio-derived structural polymer from polymerized egg white

Bio-derived materials could play an important role in future sustainable green and health technologies. This work reports the synthesis of a unique egg white-based bio-derived material showing excellent stiffness and ductility by polymerizing it with primary amine-based chemical compounds to form strong covalent bonds. As shown by both experiments and theoretical simulations, the amine-based molecules introduce strong bonds between amine ends and carboxylic ends of albumen amino acids resulting in an elastic modulus of ～4 GPa, a fracture strength of ～2 MPa and a high ductility of 40%. The distributed and interconnected network of interfaces between the hard albumen and the soft amine compounds gives the structure its unique combination of high stiffness and plasticity. A range of in-situ local and bulk mechanical tests as well as molecular dynamics (MD) simulations, reveal a significant interfacial stretching during deformation and a micro-crack diversion leading to an increased in ductility and toughness. The structure also shows a self-stiffening behavior under dynamic loading and a strength-induced aging suggesting adaptive mechanical behavior. This egg white-derived material could also be developed for bio-compatible and bio-medical applications.     

On the Mean Values of the Dirichlet Series

For Dirichlet series with arbitrary abscissa of absolute convergence, we investigate the relationhip between the increase in the maximum term and , q ∈ (0,+∞).__________Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 56, No. 11, pp. 1501–1512, November, 2004.