Influence of Soil Salinity on Selected Element Contents in Different Brassica Species

Climate changes in coastal regions cause increased soil salinity, a well-known type of environmental stress for a high number of agricultural crop species, including Brassicaceae, whose growth and development, and consequently the crop quality and yield, are affected by salinity stress. The aim of the present study is to investigate the effect of salt stress on micro- and macro-element homeostasis in different Brassica crops. Kale (Brassica oleracea var. acephala), white cabbage (B. oleracea var. capitata) and Chinese cabbage (B. rapa ssp. pekinensis) were grown hydroponically and treated with 200 mmol/L sodium chloride for 24 h to mimic short-term salt stress. The contents of Al, Ca, K, Mg, Na, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V and Zn were determined in the roots and leaves of the salt-treated plants and corresponding controls by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. While Al, Ca, K, Mg and Na were determined in the mg/g range, the contents of the other elements were found at the µg/g level. A statistical analysis of the obtained data showed that the applied salt treatment significantly influenced the single-element contents in different plant parts. The major elements Ca, K and Mg were mainly unaffected in the more-salt-tolerant kale and white cabbage under salinity stress, while K and Mg were significantly decreased in the more-sensitive Chinese cabbage. The levels of micro-elements were found to be species/variety specific. In general, potentially toxic elements were accumulated in the roots of salt-treated plants to a higher extent than in the corresponding controls.     

New cyclic aminals derived from rac-trans-1,2-diaminocyclohexane: synthesis and crystal structure of racemic 1,8,10,12-tetraazatetracyclo[8.3.1.1.8,1202,7] pentadecane and a route to its enantiomerically pure (R,R) and (S,S) isomers

New enantiomerically pure macrocyclic aminals (2R,7R)- and (2S,7S)-1,8,10,12-tetraazatetracyclo[8.3.1.1.^8,120^2,7]pentadecane (4a and 4b) were obtained by a three component reaction between their respective pure enantiomer of trans-1,2-diaminocyclohexane, ammonia, and formaldehyde. Additionally, the X-ray structure of the racemic compound 4 and the specific rotations of the racemic and optically pure compounds were determined. To further understand the synthetic utilities of enantiomers 4a and 4b, Mannich-type reactions with 1H-benzotriazole were performed, affording (3aR,7aR)- and (3aS,7aS)-1,1′-{[2,3,3a,4,5,6,7,7a-octahydro-1H-1,3-benzimidazole-1,3-diyl]bis(methylene)}bis-1H-benzotriazole (9 and 10) and allowing for new possibilities related to the preparation of chiral ligands for asymmetric catalysis.     

Strategies for the asymmetric synthesis of H-phosphinate esters

Access to P-chiral H-phosphinates via desymmetrization of hypophosphite esters was investigated. The use of chiral auxiliaries, chiral catalysts, and of a bulky prochiral group that could lead to kinetic resolution was explored. A chiral NMR assay for enantiomeric excess determination of H-phosphinates was developed. An asymmetric route to C-chiral H-phosphinates is also examined and an assay was developed.     

Solution and solid-state properties of highly fluorescent dithieno[3,2-b:2',3'-d]pyrrole-based oligothiophenes

Dithieno[3,2-b:2',3'-d]pyrrole-based terthiophene and quaterthiophene analogues have been prepared from N-functionalized dithieno[3,2-b:2',3'-d]pyrroles (DTPs) via Stille coupling. In order to thoroughly study the structure-function property relationships within these DTP-based oligothiophenes, an oligomer series was prepared that allows for the investigation of a number of structural effects including chain length, thiophene functionalization, and pyrrole N-functionalization. As pyrrole N-functionalization allows the incorporation of solubilizing side chains without the unwanted steric interactions that typically reduce backbone planarity, the effect of the bulk of these side chains on the optical properties in both solution and the solid state has been carefully investigated. The DTP-based quaterthiophene, N-tert-butyl-2,6-bis(2'-thienyl)dithieno[3,2-b:2',3'-d]pyrrole was characterized via X-ray crystallography and was found to crystallize in the monoclinic space group P2(1)/c with a = 17.489(4) ?, b = 7.8855(16) ?, c = 14.540(3) ?, β = 108.37(3)°, and Z = 4. The effect of side chains on the solid-state packing of the DTP-based quaterthiophenes was further investigated through X-ray diffraction of solution processed thin films. In comparison to the parent oligothiophenes, the resulting DTP-based systems exhibit enhanced fluorescence efficiencies in solution (up to 66%) and measurable solid-state emission from thin films.     

Nanostructure on taro leaves resists fouling by colloids and bacteria under submerged conditions

The antifouling and self-cleaning properties of plants such as Nelumbo nucifera (lotus) and Colocasia esculenta (taro) have been attributed to the superhydrophobicity resulting from the hierarchical surface structure of the leaf and the air trapped between the nanosized epicuticular wax crystals. The reported study showed that the nanostructures on the taro leaf surfaces were also highly resistant to particle and bacterial adhesion under completely wetted conditions. Adhesion force measurements using atomic force microscopy revealed that the adhesion force on top of the papilla as well as the area around it was markedly lower than that on the edge of an epidermal cell. The decreased adhesion force and the resistance to particle and bacterial adhesion were attributed to the dense nanostructures found on the epidermal papilla and the area surrounding it. These results suggest that engineered surfaces with properly designed nanoscale topographic structures could potentially reduce or prevent particle/bacterial fouling under submerged conditions.     

Anion-free bambus[6]uril and its supramolecular properties

Methods for the preparation of anion-free bambus[6]uril (BU6) are presented. They are based on the oxidation of iodide anion, which is bound inside the macrocycle, utilizing dark oxidation by hydrogen peroxide or photooxidation in the presence of titanium dioxide. Anion-free BU6 was found to be insoluble in any of the investigated solvents; however, it dissolves in methanol/chloroform (1:1) or acetonitrile/water (1:1) mixtures in the presence of the tetrabutylammonium salt of a suitable anion. The association constants with halide ions, BF(4)(-), NO(3)(-), and CN(-), were measured by (1)H NMR spectroscopy. The highest association constant (8.9×10(5) M(-1)) was found for the 1:1 complex of BU6 with I(-) in acetonitrile/water mixture. A number of crystal structures of BU6 complexes with various anions were obtained. The influence of the anion size on the macrocycle diameter is discussed together with an unusual arrangement of the macrocycles into separate layers.     

Structural features of muscimol, a potent GABAA receptor agonist, crystal structure and quantum chemicalab initio calculations

Muscimol, a constituent of the mushroomAmanita muscaria, is a semirigid analogue of the inhibitory neurotransmitter 4-aminobutyric acid (GABA). X-ray structure determinations and quantum chemicalab initio calculations (HF/6-31G^*) have been carried out on the muscimol zwitterion. The solid-state conformations of the muscimol zwitterion are calculated to be 1.6–2.2 kcal/mol higher in energy than that of the calculated minimum energy structurein vacuo. A comparison of the calculated and experimental structures indicates that the hydrogen bonding network in the solid state significantly affects the geometry of the molecular structure. This conclusion is supported by results ofab initio calculations on binary complexes between muscimol and an ammonium ion and between muscimol and a methoxide anion, simulating observed hydrogen bonding in the crystal structures.     

A novel approach to phosphonic acids from hypophosphorous acid

A novel access to phosphonic acids via Pd-catalyzed tandem carbon-phosphorus bond formation-oxidation processes was developed. The procedures involve atom-economical and environmentally friendly functionalization reactions of hypophosphorous acid (H₃PO₂) and H-phosphinic acids [RP(O)(OH)(H)].     

Ideal extensions of graph algebras

Let A and B be graph algebras. In this paper we present the notion of an ideal in a graph algebra and prove that an ideal extension of A by B always exists. We describe (up to isomorphism) all such extensions.