Pb contaminated soil from a lead-acid battery plant immobilized by municipal sludge and raw clay.

Soil heavy metal pollution poses a serious threat to the eco-environment. Municipal sludge-based passivators and clay minerals have been widely applied to immobilize heavy metal contamination in soils. However, little is known about the immobilization effect and mechanisms of raw municipal sludge and clay in reducing the mobility and bioavailability of heavy metals in soils. Here, municipal sludge, raw clay and mixtures of thereof were used to remediate Pb-contaminated soil from a Pb-acid battery factory. The remediation performance was evaluated through acid leaching, sequential extraction, and plant assay. Results showed that the leachable Pb content in the soil decreased from 5.0 mg kg-1 to 4.8, 4.8 and 4.4 mg kg-1 after 30 d of remediation with MS and RC added at equal weights to give total dosage of 20, 40 wt% and 60 wt %, respectively. The leachable Pb further decreased to 1.7, 2.0 and 1.7 mg kg-1 after 180 d of remediation. Speciation analysis of the soil Pb indicated that the exchangeable and Fe-Mn oxide-bound Pb were transformed into residual Pb in the early stage of remediation, and the carbonate-bound Pb and organic matter-bound Pb were transformed into residual Pb in the later stage of remediation. As a result, Pb accumulation in mung beans decreased by 78.5%, 81.1% and 83.4% after 180 days of remediation. These results indicate that the leaching toxicity and phytotoxicity of Pb in remediated soils were significantly reduced, presenting a better and low-cost method for soil remediation.

Exploration of biguanido-oxovanadium complexes as potent and selective inhibitors of protein tyrosine phosphatases.

The inhibitory effects of three biguanido-oxovanadium complexes ([VO(L(1-3))(2)]·nH(2)O: HL(1) = metformin, HL(2) = phenformin, HL(3) = moroxydine) against four protein tyrosine phosphatases (PTPs) and an alkaline phosphatase (ALP) were investigated. The complexes display strong inhibition against PTP1B and TCPTP (IC(50), 80-160 nM), a bit weaker inhibition against HePTP (IC(50), 190-410 nM) and SHP-1(IC(50), 0.8-3.3 µM) and much weaker inhibition against ALP (IC(50), 17-35 µM). Complex 3 is about twofold less potent against PTP1B, TCPTP and HePTP than complexes 1 and 2, while complex 2 inhibits SHP-1 more strongly (about three to fourfold) than the other two complexes. These results suggest that the structures of the ligands slightly influence the potency and selectivity against PTPs. The complexes inhibit PTP1B and ALP with a typical competitive type.

Inhibition protein tyrosine phosphatases by an oxovanadium glutamate complex, Na2[VO(Glu)2(CH3OH)](Glu = glutamate).

The insulin-sensitizing effect of vanadium complexes has been linked to their ability to inhibit protein tyrosine phosphatases (PTPs). Considering that vanadium complexes may exchange in vivo with amino acids, forming in situ vanadium-amino acid complexes, we have synthesized and characterized an oxovanadium glutamate complex, Na(2)[V(IV)O(Glu)(2)(CH(3)OH)]H(2)O (1·H(2)O). The complex showed potent inhibition against four human PTPs (PTP1B, TCPTP, HePTP, and SHP-1) with IC(50) in the 0.21-0.37 µM ranges. Fluorescence titration studies suggest that the complex binds to PTP1B with the formation of a 2:1 complex. Enzyme kinetics analysis using Lineweaver-Burk plots indicates a typical competitive inhibition mode.

Hexakis(dimethyl-ammonium) di-µ(6)-oxido-tetra-µ(3)-oxido-tetra-deca-µ(2)-oxido-octa-oxidodeca-vanadate(V) monohydrate.

In the title compound, (C(2)H(8)N)(6)[V(10)O(28)]·H(2)O, the [V(10)O(28)](6-) polymetalate anion has crystallographic mirror symmetry with six V atoms and 12 O atoms lying on the mirror plane. Each of the V(V) atoms adopts a distorted octa-hedral geometry. Eight terminal O atoms are bonded to V(V) atoms with double bonds and the others act as bridging atoms. In the crystal structure, a network of N-H⋯O and O-H⋯O hydrogen bonds helps to establish the packing.

[Differential effect of temperature on Plt and PCA synthesis in a rsmA inactivated mutant strain of Pseudomonas sp. M-18].

Rsm (repressor of secondary metabolite) A is an mRNA binding protein which functions as a global repressor to control multiple genes at the posttranscriptional level. Using homologous recombination technique a chromosomal rsmA inactivated mutant strain M-18R was constructed in Pseudomonas sp. M-18, a strain of plant-growth-promoting rhizobacteria, which could inhibit several soilborn phytopathogens by producing secondary metabolites including phenazine-1-carboxylic acid (PCA) and pyoluteorin (Plt) in one single strain. To further study the effect of RsmA on the synthesis of Plt and PCA in the wild type strain M-18, the dynamic curves of Plt and PCA produced respectively by M-18 and M-18R were measured in KMB medium under different temperature conditions such as 37 degrees C constant, 28 degrees C constant and nonconstant (37 degrees C 4 hours at first and then 28 degrees C constant) cultivation. The synthesis of both Plt and PCA were almost inhibited in the cultures under the condition of 37 degrees C. At 28 degrees C, however, compared with the wild type strain M-18, the mutant strain produced tenfold amount of Plt, while the production of PCA decreased only about 50%. When cultivated under the nonconstant condition, the amount of Plt produced by M-18R could reach 400 microg/mL while the PCA production was not significantly affected, but in the wild type strain M-18, the amount of Plt production decreased obviously while the PCA production was not affected in comparison with the results at 28 degrees C constant. These results suggest that a temperature sensitive factor exists to function as an activator independent of RsmA to promote the synthesis of Plt in the rsmA mutant strain M-18R while it may bind with RsmA to repress the synthesis of Plt in the wild type strain M-18. But this factor did not exert any affect on the synthesis of PCA.

Phenazine-1-carboxylic acid is negatively regulated and pyoluteorin positively regulated by gacA in Pseudomonas sp. M18.

The biosynthesis of antimicrobial metabolites is controlled by the GacS/GacA two-component regulatory system in Pseudomonas species. The production of phenazine-1-carboxylic acid and pyoluteorin is differentially regulated by GacA in Pseudomonas sp. M18. Pyoluteorin was reduced to nondetectable level in culture of the gacA insertional mutant strain M18G grown in King's medium B broth, whereas phenazine-1-carboxylic acid production was increased 30-fold over that of the wild-type strain. Production of both antibiotics was restored to wild-type levels after complementation in trans with the wild-type gacA gene. Expression of the translational fusions phzA'-'lacZ and pltA'-'lacZ confirmed the effect of GacA on both biosynthetic operons.

[Differential regulation of phenazine-1-carboxylic acid and pyoluteorin production mediated by inactivated gacA in Pseudomonas sp. M18].

Pseudomonas sp. M18 is one of the plant-growth-promoting rhizobacteria, which can produce fungicides: phenazine-1-carboxylic acid (PCA) and pyoluteorin (Plt). The chromosomally gacA inactivated mutant named M18G was constructed and its PCA production was enhanced 31-fold and Plt production was almost blocked completely in KMB medium. To assess the mutual influence of two antibiotics, the plt gene cluster mutant M18T and the phz gene cluster mutant M18GA were then constructed. Non-Plt-producing M18T could synthesize the same amount of PCA as wild type strain. Plt could not be detected in M18GA while PCA production was inhibited dramatically in it. Results indicate that promotion of PCA and inhibition of Plt production in M18G do result from the inactivation of gacA gene. It suggests that the production of antibiotics in strain M18 is differentially mediated by the gacA.