Water balance of N2-fixing root nodules: Can phloem and xylem transport explain it?

Abstract Analysis of nodule inputs via the phloem and outputs via the xylem leads to the conclusion that water fluxes along those conduits alone would give a xylem sap osmolality in excess of that of sieve tubes and would thus plasmolyse the latter unless N₂ fixation involved a very high respiratory consumption of organic C entering in the phloem, or there is significant water influx from soil through the nodule surface. Whether N₂ fixation by attached nodules not in contact with an external water supply is energetically inefficient (and hence also, at a whole plant level, inefficient in terms of water-use) is as yet untested. However, the hypothesis which we prefer involves the shortfall in water entry via the phloem being made up the parenchymatic water flux from the root to the nodule.     

The synthesis of cyclic imidates from amides of glucuronic acid and investigation of glycosidation reactions

The synthesis of novel cyclic glycosyl imidates and an investigation of their potential as donors in glycosidation reactions is described. The results show that 1,2-cis glycosides obtained from the reactions of glycosyl acetates or cyclic imidates, each derived from amides of glucuronic acid, result from the anomerisation of initially formed 1,2-trans glycosides.     

Diverse amide analogs of sulindac for cancer treatment and prevention

Sulindac is a non-steroidal anti-inflammatory drug (NSAID) that has shown significant anticancer activity. Sulindac sulfide amide (1) possessing greatly reduced COX-related inhibition relative to sulindac displayed in vivo antitumor activity that was comparable to sulindac in a human colon tumor xenograft model. Inspired by these observations, a panel of diverse sulindac amide derivatives have been synthesized and their activity probed against three cancer cell lines (prostate, colon and breast). A neutral analog, compound 79 was identified with comparable potency relative to lead 1 and activity against a panel of lymphoblastic leukemia cell lines. Several new series also show good activity relative to the parent (1), including five analogs that also possess nanomolar inhibitory potencies against acute lymphoblastic leukemia cells. Several new analogs identified may serve as anticancer lead candidates for further development.     

New amides from the roots of Anisodus tanguticus

Two new amides (1 and 2) and four known analogues (3–6) were isolated from the roots of Anisodus tanguticus (Maxim.) Pascher. Their structures were determined by extensive spectroscopic analyses. The absolute configuration of compound 1 was determined by comparison of the calculated optical rotation (OR) value with the experimental OR value. All known amides were isolated from the genus Anisodus for the first time, of which compounds 3, 5, and 6 were first reported from the family Solanaceae. Furthermore, the chemotaxonomic significance of these secondary metabolites is discussed.     

N,N,N′,N′-Tetramethylethylendiamine adducts of amido calcium bases - Synthesis of monomeric [(tmeda)Ca{N(SiMe3)2}2], [(tmeda)Ca{NiPr2}2], and dimeric Hauser base-type [(tmeda)Ca(tmp)(μ-I)]2 (tmp = 2,2,6,6-tetramethylpiperidide)

The metathetical reaction of calcium diiodide with KNR₂ in the presence of N,N,N′,N′-tetramethylethylendiamine yields the corresponding amido calcium bases [(tmeda)Ca(tmp)₂] (1), [(tmeda)Ca{N(SiMe₃)₂}₂] (3), and [(tmeda)Ca(NiPr₂)₂] (4) regardless of the stoichiometric ratio of the starting compounds. All compounds are highly air and moisture sensitive. Only in the case of NR₂ being a tmp group very few crystals of the Hauser base-type dimeric derivative [(tmeda)Ca(tmp)(μ-I)]₂ (2) with bridging iodide ions can be isolated. In all these calcium complexes the amides are bound terminally and contain planarily coordinated nitrogen atoms. The calcium complex [(tmeda)Ca(NiPr₂)₂] (4) is much more reactive than the lighter magnesium congener and therefore, it has to be stored below 0 °C in order to avoid decomposition reactions.     

Synthesis of novel benzothiazole amides: Evaluation of PPAR activity and anti-proliferative effects in paraganglioma,pancreatic and colorectal cancer cell lines

The reduced activation of PPARs has a positive impact on cancer cell growth and viability in multiple preclinical tumor models, suggesting a new therapeutic potential for PPAR antagonists. In the present study, the benzothiazole amides 2a-g were synthesized and their activities on PPARs were investigated. Transactivation assay showed a moderate activity of the novel compounds as PPARα antagonists. Notably, in cellular assays they exhibited cytotoxicity in pancreatic, colorectal and paraganglioma cancer cells overexpressing PPARα. In particular, compound 2b showed the most remarkable inhibition of viability (greater than 90%) in two paraganglioma cell lines, with IC₅₀ values in the low micromolar range. In addition, 2b markedly impaired colony formation capacity in the same cells. Taken together, these results show a relevant anti-proliferative potential of compound 2b, which appears particularly effective in paraganglioma, a rare tumor poorly responsive to chemotherapy.     

The biochemistry of drug metabolism--an introduction: part 3. Reactions of hydrolysis and their enzymes

This review continues a general presentation of the metabolism of drugs and other xenobiotics begun in two recent issues of Chemistry & Biodiversity. This Part presents some of the numerous hydrolases involved, their nomenclature, relevant biochemical properties, catalytic mechanisms, and the many reactions of hydrolysis they catalyze. A number of medicinally, environmentally, and toxicologically relevant examples are presented and discussed. The reactions examined include the hydrolysis of carboxylic esters, amides and peptides, lactones, and other labile rings, and esters of inorganic acids. The hydration of epoxides and its enzymology are treated separately.     

Secondary metabolites from endophytic Streptomyces sp. Lz531

From the branch tissue of Maytenus hookeri, the endophytic strain Lz531 was isolated, and determined to belong to Streptomyces, according to its 16S rRNA sequence. From the extracts of the fermentation broth of Streptomyces sp. Lz531, two new and four known compounds were isolated. The two new compounds were identified as cyclo(L-Pro-L-Val-L-Val) (1) and 13-methyl-N-(2-phenylethyl)tetradecanamide (2).     

Ternary copper(II) complexes involving 2-(aminomethyl)-benzimidazole and some bio-relevant ligands. Equilibrium studies and kinetics of hydrolysis for glycine methyl ester under complex formation

Formation equilibria of copper(II) complexes of 2-(aminomethyl)-benzimidazole (AMBI) and the ternary complexes Cu(AMBI)L (L = amino acid, amide, dicarboxylic acid or DNA constituents) have been investigated. Ternary complexes of amino acids or amides are formed by a simultaneous mechanism. Amino acids form the complex Cu(AMBI)L, whereas amides form two complex species Cu(AMBI)L and Cu(AMBI)(LH₋₁). The ternary complexes of copper(II) with AMBI and dicarboxylic acids or DNA units are formed by a stepwise mechanism, whereby binding of copper(II) to AMBI is followed by ligation of the dicarboxylic acids or DNA components. The values of Δ log K indicate that the ternary complexes containing aromatic amino acids are significantly more stable than the complexes containing alkyl- and hydroxyalkyl-substituted amino acids. This may be taken as an evidence for a stacking interaction between the aromatic moiety of AMBI and the aromatic side chains of the bio-active ligands. The solid complexes Cu(AMBI)L where L = 1,1-cyclobutanedicarboxylic acid (CBDCA) and malonic acid were separated and identified by elemental analysis and infrared spectroscopy and magnetic moment. The decomposition course and steps for the isolated complexes were analyzed and the kinetic parameters of the non-isothermal decomposition were calculated. The hydrolysis of glycine methyl ester (MeGly) is catalyzed by the Cu(AMBI)²⁺ complex. The kinetic data is fitted assuming that the hydrolysis reaction proceeds in two steps. The first step, involving coordination of the amino acid ester by the amino and carbonyl groups, is followed by rate-determining attack by OH⁻ ion. The second step involves the equilibrium formation of the hydroxo-complex Cu(AMBI)(MeGly)(OH) followed by intramolecular OH⁻ attack.     

Nitrile hydratases (NHases): At the interface of academia and industry

Nitrile hydratase (NHase, EC 4.2.1.84) is one of the key enzymes of nitrile metabolism in a large number of microbes that catalyses the hydration of nitriles to corresponding amides, and has been successfully adopted in chemical industry for production of acrylamide, nicotinamide and 5-cyanovaleramide. However, NHase is still under active consideration of enzymologists to expand its potential for synthesis of various amides. Most of the NHases have been reported for their limited substrates acceptability, low enantioselectivity and thermostability and therefore a considerable improvement is required for developing as robust biocatalyst for synthesis of a range of organic amides. Studies on biochemical properties, gene configuration, active-site chemical models and site-directed mutagenesis have given the insight into the structural and functional characteristics of NHase. Keeping in view, the present review critically describes the available information on natural sources (based on activity and phylogenetic analysis), biochemical properties, catalysis–structure relationship, molecular expression and potential applications of this enzyme.