Curtius Rearrangement Using Ultrasonication: Isolation of Isocyanates of Fmoc-Amino Acids and Their Utility for the Synthesis of Dipeptidyl Ureas

An efficient conversion of N^α-[(9–fluorenylmethyl)oxy]carbonyl (Fmoc) amino acid azides to the corresponding isocyanates using ultrasound is described. The Curtius rearrangement was accomplished using acid azides in toluene solution as well as solid powder at room temperature. All isocyanates synthesized have been obtained as crystalline solids and were characterized. Coupling of isocyanates with amino acid methyl ester hydrochloride salts in presence of N-methylmorpholine (NMM) resulted in Fmoc-protected dipeptidyl urea esters, which have been well characterized by ¹H NMR, ¹³C NMR and mass spectrometry.     

Protective effect of supplemental low intensity white light on ultraviolet-B exposure-induced impairment in cyanobacterium <Emphasis Type="Italic">Spirulina platensis</Emphasis>: formation of air vacuoles as a possible protective measure

Nitric oxide (NO) is a diffusible, very reactive gas that is involved in the regulation of many processes in plants. Several enzymatic sources of NO production have been identified in recent years. Nitrate reductase (NR) is one of them and it has been shown that this well-known plant protein, apart from its role in nitrate reduction and assimilation, can also catalyse the reduction of nitrite to NO. This reaction can produce large amounts of NO, or at least more than is needed for signalling, as some escape of NO to the outside medium can be detected after NR activation. A role for NO and NR in stomata functioning in response to abscisic acid has also been proposed. The question that remains is whether this NR-derived NO is a signalling molecule or the mere product of an enzymatic side reaction like the products generated by the oxygenase activity of RuBisCO.     

Copper alone, but not oxidative stress, induces copper-metallothionein gene in Neurospora crassa

Two metal response elements, flanking an antioxidant response element, were identified in regions upstream (-3730 bp) to copper metallothionein (CuMT) gene of Neurospora crassa. Presence of copper in culture media, but not of pro-oxidants like H2O2 or menadione, induced CuMT gene expression that could not be completely abolished by antioxidants such as N-acetyl cysteine and ascorbic acid. Gel shift assays revealed the ability of nuclear extracts from copper induced cultures to bind PCR-amplified metal response or antioxidant response elements. Similar observations could not be made with cultures exposed either to pro-oxidants or antioxidants. These results differentiate between CuMT gene induction by copper from antioxidant functions associated with the identified upstream elements.     

Influence of zinc on cardiac and serum biochemical parameters in rabbits

The pattern of lipid profiles and organic constituents of cardiac and serum tissues of rabbits were studied on treatment with cholesterol, zinc and zinc + cholesterol. Total carbohydrate and total protein levels were decreased with elevated lipid levels in cholesterol fed rabbits. However, the zinc and cholesterol + zinc fed rabbits showed decreased lipid fractions in cardiac and serum tissues leading to reduced atherosclerotic process in rabbits. These results suggest that the zinc is acting as a hypolipidaemic and anti atherogenic agent in experimental rabbits.     

The slow S to M rise of chlorophyll a fluorescence reflects transition from state 2 to state 1 in the green alga Chlamydomonas reinhardtii

Photosynthesis Research - The green alga Chlamydomonas (C.) reinhardtii is a model organism for photosynthesis research. State transitions regulate redistribution of excitation energy between...     

Agrobacterium-mediated transformation of the medicinal plant Podophyllum hexandrum Royle (syn. P. emodi Wall. ex Hook.f. & Thomas)

An efficient Agrobacterium-mediated genetic transformation method has been developed for the medicinal plant Podophyllum hexandrum Royle, an important source of the anticancer agent podophyllotoxin. Highly proliferating embryogenic cells were infected with Agrobacterium tumefaciens harbouring pCAMBIA 2301, which contains npt II and gusA as selection marker and reporter genes, respectively. The transformed somatic embryos and plantlets were selected on Murashige and Skoog (MS) basal medium containing kanamycin and germination medium, respectively. GUS histochemical analysis, polymerase chain reaction and Southern blot hybridisation confirmed that gusA was successfully integrated and expressed in the P. hexandrum genome. Compared with cefotaxime, 200 mg l^?1 timentin completely arrested Agrobacterium growth and favoured somatic embryo development from embryogenic cells. Among the different Agrobacterium strains, acetosyringone concentrations and co-cultivation durations tested, embryogenic callus infected with A. tumefaciens EHA 105 and co-cultivated for 3 days on MS basal medium containing 100 μM acetosyringone proved to be optimal and produced a transformation efficiency of 29.64 % with respect to germinated GUS-positive plantlets. The Agrobacterium-mediated genetic transformation method developed in the present study facilitates the transference of desirable genes into P. hexandrum to improve the podophyllotoxin content and to enhance other useful traits.     

Protection of rice against Nilaparvata lugens by direct toxicity of sodium selenate

Nilaparvata lugens is one of the most notorious pest insects of cultured rice, and outbreaks of N. lugens cause high economic losses each year. While pest control by chemical pesticides is still the standard procedure for treating N. lugens infections, excessive use of these insecticides has led to the emergence of resistant strains and high pesticide residues in plants for human consumption and the environment. Therefore, novel and environment-friendly pest control strategies are needed. In previous studies, selenium was shown to protect selenium-accumulating plants from biotic stress. However, studies on nonaccumulator (crop) plants are lacking. In this study, rice plants (Oryza sativa, Nipponbare) were treated with sodium selenate by seed priming and foliar spray and then infested with N. lugens. Brown planthoppers feeding on these plants showed increased mortality compared to those feeding on control plants. Treatment of the plants with sodium selenate did not affect the enzymes involved in the biosynthesis of the plant stress hormones jasmonic acid and salicylic acid, suggesting that the observed insect mortality cannot be attributed to the activation of these hormonal plant defenses. Feeding assays using an artificial diet supplemented with sodium selenate revealed direct toxicity toward N. lugens. With a low concentration of 6.5 ± 1.5 µM sodium selenate, half of the insects were killed after 3 days. In summary, sodium selenate treatment of plants can be used as a potential alternative pest management strategy to protect rice against N. lugens infestation through direct toxicity.     

Pulmonary and systemic vasodilator responses to the soluble guanylyl cyclase activator, BAY 60-2770, are not dependent on endogenous nitric oxide or reduced heme

4-({(4-Carboxybutyl)[2-(5-fluoro-2-{[4'-(trifluoromethyl)biphenyl-4-yl]methoxy}phenyl)ethyl]amino}methyl)benzoic acid (BAY 60-2770) is a nitric oxide (NO)-independent activator of soluble guanylyl cyclase (sGC) that increases the catalytic activity of the heme-oxidized or heme-free form of the enzyme. In this study, responses to intravenous injections of the sGC activator BAY 60-2770 were investigated under baseline and elevated tone conditions induced by the thromboxane mimic U-46619 when NO synthesis was inhibited by N(ω)-nitro-L-arginine methyl ester hydrochloride (L-NAME), when sGC activity was inhibited by 1H-[1,2,4]-oxadizaolo[4,3]quinoxaline-1-one (ODQ), an agent that oxidizes sGC, and in animals with monocrotaline-induced pulmonary hypertension. The intravenous injections of BAY 60-2770 under baseline conditions caused small decreases in pulmonary arterial pressure, larger decreases in systemic arterial pressure, and no change or small increases in cardiac output. Under elevated tone conditions during infusion of U-46619, intravenous injections of BAY 60-2770 caused larger decreases in pulmonary arterial pressure, smaller decreases in systemic arterial pressure, and increases in cardiac output. Pulmonary vasodilator responses to BAY 60-2770 were enhanced by L-NAME or by ODQ in a dose that attenuated responses to the NO donor sodium nitroprusside. ODQ had no significant effect on baseline pressures and attenuated pulmonary and systemic vasodilator responses to the sGC stimulator BAY 41-8543 2-{1-[2-(fluorophenyl)methyl]-1H-pyrazolo[3,4-b]pyridin-3-yl}-5(4-morpholinyl)-4,6-pyrimidinediamine. BAY 60-2770 and sodium nitroprusside decreased pulmonary and systemic arterial pressures in monocrotaline-treated rats in a nonselective manner. The present data show that BAY 60-2770 has vasodilator activity in the pulmonary and systemic vascular beds that is enhanced by ODQ and NOS inhibition, suggesting that the heme-oxidized form of sGC can be activated in vivo in an NO-independent manner to promote vasodilation. These results show that BAY 60-2770 and sodium nitroprusside decreased pulmonary and systemic arterial pressures in monocrotaline-treated rats, suggesting that BAY 60-2770 does not have selective pulmonary vasodilator activity in animals with monocrotaline-induced pulmonary hypertension.     

The catalase activity of diiron adenine deaminase

Adenine deaminase (ADE) from the amidohydrolase superfamily (AHS) of enzymes catalyzes the conversion of adenine to hypoxanthine and ammonia. Enzyme isolated from Escherichia coli was largely inactive toward the deamination of adenine. Molecular weight determinations by mass spectrometry provided evidence that multiple histidine and methionine residues were oxygenated. When iron was sequestered with a metal chelator and the growth medium supplemented with Mn²⁺ before induction, the post-translational modifications disappeared. Enzyme expressed and purified under these conditions was substantially more active for adenine deamination. Apo-enzyme was prepared and reconstituted with two equivalents of FeSO₄. Inductively coupled plasma mass spectrometry and Mössbauer spectroscopy demonstrated that this protein contained two high-spin ferrous ions per monomer of ADE. In addition to the adenine deaminase activity, [Fe^II/Fe^II]-ADE catalyzed the conversion of H₂O₂ to O₂ and H₂O. The values of k_cat and k_cat/K_m for the catalase activity are 200 s⁻¹ and 2.4 × 10⁴ M⁻¹ s⁻¹, respectively. [Fe^II/Fe^II]-ADE underwent more than 100 turnovers with H₂O₂ before the enzyme was inactivated due to oxygenation of histidine residues critical for metal binding. The iron in the inactive enzyme was high-spin ferric with g_ave = 4.3 EPR signal and no evidence of anti-ferromagnetic spin-coupling. A model is proposed for the disproportionation of H₂O₂ by [Fe^II/Fe^II]-ADE that involves the cycling of the binuclear metal center between the di-ferric and di-ferrous oxidation states. Oxygenation of active site residues occurs via release of hydroxyl radicals. These findings represent the first report of redox reaction catalysis by any member of the AHS.