New unsymmetric dinuclear Cu(II)Cu(II) complexes and their relevance to copper(II) containing metalloenzymes and DNA cleavage

The new homodinuclear complexes, [Cu(2)(II)(HLdtb)(mu-OCH(3))](ClO(4))(2) (1) and [Cu(2)(II)(Ldtb)(mu-OCH(3))](BPh(4)) (2), with the unsymmetrical N(5)O(2) donor ligand (H(2)Ldtb) - {2-[N,N-Bis(2-pyridylmethyl)aminomethyl]-6-[N',N'-(3,5-di-tert-butylbenzyl-2-hydroxy)(2-pyridylmethyl)]aminomethyl}-4-methylphenol have been synthesized and characterized in the solid state by X-ray crystallography.In both cases the structure reveals that the complexes have a common {Cu(II)(mu-phenoxo)(mu-OCH(3))Cu(II)} structural unit.Magnetic susceptibility studies of 1 and 2 reveal J values of -38.3 cm(-1) and -2.02 cm(-1), respectively, and that the degree of antiferromagnetic coupling is strongly dependent on the coordination geometries of the copper centers within the dinuclear {Cu(II)(mu-OCH(3))(mu-phenolate)Cu(II)} structural unit.Solution studies in dichloromethane, using UV-Visible spectroscopy and electrochemistry, indicate that under these experimental conditions the first coordination spheres of the Cu(II) centers are maintained as observed in the solid state structures, and that both forms can be brought into equilibrium ([Cu(2)(HLdtb)(mu-OCH(3))](2+)=[Cu(2)(Ldtb)(mu-OCH(3))](+)+H(+)) by adjusting the pH with Et(3)N (Ldtb(2-) is the deprotonated form of the ligand).On the other hand, potentiometric titration studies of 1 in an ethanol/water mixture (70:30 V/V; I=0.1M KCl) show three titrable protons, indicating the dissociation of the bridging CH(3)O(-) group.The catecholase activity of 1 and 2 in methanol/water buffer (30:1 V/V) demonstrates that the deprotonated form is the active species in the oxidation of 3,5-di-tert-butylcatechol and that the reaction follows Michaelis-Menten behavior with k(cat)=5.33 x 10(-3)s(-1) and K(M)=3.96 x 10(-3)M. Interestingly, 2 can be electrochemically oxidized with E(1/2)=0.27 V vs.Fc(+)/Fc (Fc(+)/Fc is the redox pair ferrocinium/ferrocene), a redox potential which is believed to be related to the formation of a phenoxyl radical.Since these complexes are redox active species, we analyzed their activity toward the nucleic acid DNA, a macromolecule prone to oxidative damage.Interestingly these complexes promoted DNA cleavage following an oxygen dependent pathway.     

Auxin metabolism and rooting in young and mature clones of Sequoia sempervirens

The capacity of young and mature Sequoia sempervirens clones to produce roots in vitro was studied after wounding and indole-3-butyric acid (IBA) treatments. Rooting was not observed in mature or in young cuttings cultivated for 30 days in medium without IBA. The presence of 25 μ M IBA in the medium resulted in the appearance of roots at the base of the cuttings. More roots appeared and grew faster on cuttings of the young than on the mature clone. This difference in rooting capacity between young and mature cuttings may be related to differences in the hormone levels at the base of the 5 mm long cuttings during the first 4 days of the root inductive period. After HPLC fractionation. IAA. IBA and related compounds, including indole-3-aspartic acid (IAAsp) and IBA-glucose ester (IBA-GE), were determined by MS and MS-MS and their levels measured by ELISA. Another immunoreactive compound was also found and determined to be N,N-dimethyltryptophan (DMT), a compound previously reported to inhibit auxin-enhanced ethylene production. Wounding of the stem without IBA treatment revealed a transient increase in IAA, IAAsp and DMT levels in young cuttings while a dramatic increase in the levels of DMT was observed in mature cuttings. Following IBA treatment. IAA levels increased in both clones, but higher levels were measured in the young than in the mature clone. IBA and IBA-GE were also found but in higher levels in the mature clone. Thus, the difficult-to-root mature clone differs from the young clone in its auxin metabolism.     

Characterization of plant-growth promoting diazotrophic bacteria isolated from field grown Chinese cabbage under different fertilization conditions

Diazotrophic bacteria isolated from the rhizosphere of Chinese cabbage were assessed for other plant growth promoting characteristics viz., production of IAA, ethylene, ACC deaminase, phosphate solubilization, and gnotobiotic root elongation. Their effect on inoculation to Chinese cabbage was also observed under growth chamber conditions. A total of 19 strains that showed higher nitrogenase activity identified by 16S rRNA gene sequence analysis were found to be the members of the genera Pseudomonas and Agrobacterium belonging to α- and γ-Proteobacteria groups. These strains were also efficient in producing IAA and ACC deaminase though they produced low levels of ethylene and no phosphate solubilization. In addition, inoculation of selected diazotrophic bacterial strains significantly increased seedling length, dry weight, and total nitrogen when compared to uninoculated control. The colonization of crop plants by diazotrophic bacteria can be affected by many biotic and abiotic factors, and further studies are oriented towards investigating the factors that could influence the establishment of a selected bacterial community.     

Production of lactic acid from hemicellulose extracts by <Emphasis Type="Italic">Bacillus coagulans</Emphasis> MXL-9

Bacillus coagulans MXL-9 was found capable of growing on pre-pulping hemicellulose extracts, utilizing all of the principle monosugars found in woody biomass. This organism is a moderate thermophile isolated from compost for its pentose-utilizing capabilities. It was found to have high tolerance for inhibitors such as acetic acid and sodium, which are present in pre-pulping hemicellulose extracts. Fermentation of 20 g/l xylose in the presence of 30 g/l acetic acid required a longer lag phase but overall lactic acid yield was not diminished. Similarly, fermentation of xylose in the presence of 20 g/l sodium increased the lag time but did not affect overall product yield, though 30 g/l sodium proved completely inhibitory. Fermentation of hot water-extracted Siberian larch containing 45 g/l total monosaccharides, mainly galactose and arabinose, produced 33 g/l lactic acid in 60 h and completely consumed all sugars. Small amounts of co-products were formed, including acetic acid, formic acid, and ethanol. Hemicellulose extract formed during autohydrolysis of mixed hardwoods contained mainly xylose and was converted into lactic acid with a 94% yield. Green liquor-extracted hardwood hemicellulose containing 10 g/l acetic acid and 6 g/l sodium was also completely converted into lactic acid at a 72% yield. The Bacillus coagulans MXL-9 strain was found to be well suited to production of lactic acid from lignocellulosic biomass due to its compatibility with conditions favorable to industrial enzymes and its ability to withstand inhibitors while rapidly consuming all pentose and hexose sugars of interest at high product yields.     

Enhancement of production and activity of alkaline zinc metalloprotease from <Emphasis Type="Italic">Salinivibrio proteolyticus</Emphasis> using low intensity direct electric current and zinc nanoparticles

Objectives

To improve the production and activity of an alkaline zinc metalloprotease from Salinivibrio proteolyticus in response to ZnSO₄ (ionic and nanoparticle forms) and low intensity direct electric current (LIDC).

Results

A DC of 50 µA for 10 min increased enzyme production from 35 to 53 U ml^?1 when applied to the stationary phase bacterial cells. Zn²⁺ improved enzyme production better than zinc nanoparticles (52 vs. 43.5 U ml^?1). Zinc nanoparticles (0.5 mM) added to an enzyme reaction mixture containing casein (0.65 %) and 20 mM Tris/HCl buffer (pH 8) improved enzyme activity more than Zn²⁺ (42 vs. 36 U ml^?1).

Conclusion

LIDC exposure (50 µA, 10 min) to the stationary phase bacterial cells increases metalloprotease production in Salinivibrio. A low concentration of zinc nanoparticles (0.5 mM) increases maximum enzyme activity.

     

Altered Platelet Monoamine Oxidase-B Activity in Idiopathic Parkinson’s Disease

A case-control study was undertaken to investigate the status of platelet monoamine oxidase-B (MAO-B) activity in Indian cases of idiopathic Parkinson’s disease. A significant increase in the activity of platelet MAO-B was observed in Parkinson’s cases (n = 26) as compared to controls (n = 26). No significant change in the activity of the enzyme was observed while the data was analysed with respect to age, sex and duration of disease. A trend of decrease in platelet MAO-B activity was observed in Parkinson’s cases with respect to stage although the change was not significant. No correlation in platelet MAO-B activity was observed with respect to age and sex in the control subjects. Parkinson’s cases treated with L-DOPA and MAO-B inhibitor exhibited decreased platelet MAO-B activity as compared to drug naive cases and those treated with L-DOPA alone. Interestingly, Parkinson’s cases treated with L-DOPA and amantadine also had lower platelet MAO-B activity as compared to drug naive cases and those treated with L-DOPA alone. Activity of platelet MAO-B in Parkinson’s patients was increased in naive cases and those treated with L-DOPA alone or in combination with other drugs compared to controls. The results of the present study indicate that phenotypic activity of platelet MAO-B is high in Indian Parkinson’s cases. Further, action mechanism of drugs used in the treatment of Parkinson’s disease could be understood by assay of platelet MAO-B activity. It is an interesting observation and may be looked further in large number of cases.     

The Pivotal Role of Astrocytes in the Metabolism of Iron in the Brain

Iron is essential for the normal functioning of cells but since it is also capable of generating toxic reactive oxygen species, the metabolism of iron is tightly regulated. The present article advances the view that astrocytes are largely responsible for distributing iron in the brain. Capillary endothelial cells are separated from the neuropil by the endfeet of astrocytes, so astrocytes are ideally positioned to regulate the transport of iron to other brain cells and to protect them if iron breaches the blood-brain barrier. Astrocytes do not appear to have a high metabolic requirement for iron yet they possess transporters for transferrin, haemin and non-transferrin-bound iron. They store iron efficiently in ferritin and can export iron by a mechanism that involves ferroportin and ceruloplasmin. Since astrocytes are a common site of abnormal iron accumulation in ageing and neurodegenerative disorders, they may represent a new therapeutic target for the treatment of iron-mediated oxidative stress.     

Survival and growth of two heterotrophic hydrothermal vent archaea, <Emphasis Type="Italic">Pyrococcus</Emphasis> strain GB-D and <Emphasis Type="Italic">Thermococcus fumicolans</Emphasis>, under low pH and high sulfide concentrations in combination with high temperature and pressure regimes

Growth and survival of hyperthermophilic archaea in their extreme hydrothermal vent and subsurface environments are controlled by chemical and physical key parameters. This study examined the effects of elevated sulfide concentrations, temperature, and acidic pH on growth and survival of two hydrothermal vent archaea (Pyrococcus strain GB-D and Thermococcus fumicolans) under high temperature and pressure regimes. These two strains are members of the Thermococcales, a family of hyperthermophilic, heterotrophic, sulfur-reducing archaea that occur in high densities at vent sites. As actively growing cells, these two strains tolerated regimes of pH, pressure, and temperature that were in most cases not tolerated under severe substrate limitation. A moderate pH of 5.5–7 extends their survival and growth range over a wider range of sulfide concentrations, temperature and pressure, relative to lower pH conditions. T. fumicolans and Pyrococcus strain GB-D grew under very high pressures that exceeded in-situ pressures typical of hydrothermal vent depths, and included deep subsurface pressures. However, under the same conditions, but in the absence of carbon substrates and electron acceptors, survival was generally lower, and decreased rapidly when low pH stress was combined with high pressure and high temperature. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Influence of habitat complexity and landscape configuration on pollination and seed-dispersal interactions of wild cherry trees

Land-use intensification is a major cause for the decline in species diversity in human-modified landscapes. The loss of functionally important species can reduce a variety of ecosystem functions, such as pollination and seed dispersal, but the intricate relationships between land-use intensity, biodiversity and ecosystem functioning are still contentious. Along a gradient from forest to intensively used farmland, we quantified bee species richness, visitation rates of bees and pollination success of wild cherry trees (Prunus avium). We analysed the effects of structural habitat diversity at a local scale and of the proportion of suitable habitat around each tree at a landscape scale. We compared these findings with those from previous studies of seed-dispersing birds and mammals in the same model system and along the same land-use gradient. Bee species richness and visitation rates were found to be highest in structurally simple habitats, whereas bird species richness—but not their visitation rates—were highest in structurally complex habitats. Mammal visitation rates were only influenced at the landscape scale. These results show that different functional groups of animals respond idiosyncratically to gradients in habitat and landscape structure. Despite strong effects on bees and birds, pollination success and bird seed removal did not differ along the land-use gradient at both spatial scales. These results suggest that mobile organisms, such as bees and birds, move over long distances in intensively used landscapes and thereby buffer pollination and seed-dispersal interactions. We conclude that measures of species richness and interaction frequencies are not sufficient on their own to understand the ultimate consequences of land-use intensification on ecosystem functioning.