Silver Nanoparticles for the Adsorption of Manganese from Biological Samples

In this study, silver nanoparticles were prepared and used for separation and preconcentration of manganese from biological samples. The technical feasibility of silver nanoparticles for manganese removal was investigated under batch studies. The effects of different parameters such as pH of solution, time (t), amounts of PAN (E), and silver nanoparticles (N) on the adsorption of manganese by silver nanoparticle were investigated using factorial design and response surface methodology based on Box–Behnken design. Thermodynamic parameters indicate the adsorption process to be exothermic. The limit of detection of the proposed method followed by inductively coupled plasma was found to be 0.08?µg L^?1. The method was applied to determine of manganese in biological samples.     

Role of Hsp70 ATPase Domain Intrinsic Dynamics and Sequence Evolution in Enabling its Functional Interactions with NEFs

Catalysis of ADP-ATP exchange by nucleotide exchange factors (NEFs) is central to the activity of Hsp70 molecular chaperones. Yet, the mechanism of interaction of this family of chaperones with NEFs is not well understood in the context of the sequence evolution and structural dynamics of Hsp70 ATPase domains. We studied the interactions of Hsp70 ATPase domains with four different NEFs on the basis of the evolutionary trace and co-evolution of the ATPase domain sequence, combined with elastic network modeling of the collective dynamics of the complexes. Our study reveals a subtle balance between the intrinsic (to the ATPase domain) and specific (to interactions with NEFs) mechanisms shared by the four complexes. Two classes of key residues are distinguished in the Hsp70 ATPase domain: (i) highly conserved residues, involved in nucleotide binding, which mediate, via a global hinge-bending, the ATPase domain opening irrespective of NEF binding, and (ii) not-conserved but co-evolved and highly mobile residues, engaged in specific interactions with NEFs (e.g., N57, R258, R262, E283, D285). The observed interplay between these respective intrinsic (pre-existing, structure-encoded) and specific (co-evolved, sequence-dependent) interactions provides us with insights into the allosteric dynamics and functional evolution of the modular Hsp70 ATPase domain.     

Insecticides and soil microorganisms. III. Fate of 14C-labelled Dipterex as affected by two nodule-forming rhizobium spp. and roots of their respective leguminous host plants.

Chromatographic analysis led to the identification of monomethyl- and dimethyl-phosphates as metabolites resulting from the enzymatic degradation of 14C-labelled Dipterex in the buffer solutions and root tissues of broad bean and clover plants, as well as in the culture media of rhizobium leguminosarum and Rhizobium trifolii. The formation of 14CO2 from rhizobial cultures containing radioactive Dipterex suggests that some of the liberated methanol groups (during breakdown of Dipterex) are oxidatively degraded by the two Rhizobium spp.     

Two novel loci underlie natural differences in Caenorhabditis elegans abamectin responses

Parasitic nematodes cause a massive worldwide burden on human health along with a loss of livestock and agriculture productivity. Anthelmintics have been widely successful in treating parasitic nematodes. However, resistance is increasing, and little is known about the molecular and genetic causes of resistance for most of these drugs. The free-living roundworm Caenorhabditis elegans provides a tractable model to identify genes that underlie resistance. Unlike parasitic nematodes, C. elegans is easy to maintain in the laboratory, has a complete and well annotated genome, and has many genetic tools. Using a combination of wild isolates and a panel of recombinant inbred lines constructed from crosses of two genetically and phenotypically divergent strains, we identified three genomic regions on chromosome V that underlie natural differences in response to the macrocyclic lactone (ML) abamectin. One locus was identified previously and encodes an alpha subunit of a glutamate-gated chloride channel (glc-1). Here, we validate and narrow two novel loci using near-isogenic lines. Additionally, we generate a list of prioritized candidate genes identified in C. elegans and in the parasite Haemonchus contortus by comparison of ML resistance loci. These genes could represent previously unidentified resistance genes shared across nematode species and should be evaluated in the future. Our work highlights the advantages of using C. elegans as a model to better understand ML resistance in parasitic nematodes.     

Contribution of the mesophilic fungi of different spices in Egypt

Thirty-eight genera and 81 species of fungi were isolated and identified from 120 samples of 24 kinds of spices collected from different places at Assiut Governorate, Egypt. Predominant genera wereAspergillus (25 species) andPenicillium (7 species) of whichA. flavus, A. niger, A. ochraceus, A. fumigatus, A. flavus var.columnaris, A. terreus, P. chrysogenum andP. corylophilum were the most commonly occurring.     

Conjugative transfer functions of broad-host-range plasmid RK2 are coregulated with vegetative replication

The kilB locus (which is unclonable in the absence of korB) of broad-host-range plasmid RK2 (60 kb) lies between the trfA operon (co-ordinates 16.4 to 18.2 kb), which encodes a protein essential for vegetative replication, and the Tra2 block of conjugative transfer genes (co-ordinates 20.0 to 27.0 kb). Promoter probe studies indicated that kilB is transcribed clockwise from a region containing closely spaced divergent promoters, one of which is the trfA promoter. The repression of both promoters by korB suggested that kilB may also play a role in stable maintenance of RK2. We have sequenced the region containing kilB and analysed it by deletion and insertion mutagenesis. Loss of the KilB+ phenotype does not result in decreased stability of mini RK2 plasmids. However insertion in ORFI (kilBI) of the region analysed results in a Tra- phenotype in plasmids which are otherwise competent for transfer, demonstrating that this locus is essential for transfer and is probably the first gene of the Tra2 region. From the kilBI DNA sequence KilBI is predicted to be 34995 Da, in line with M(r) = 36,000 observed by sodium dodecyl sulphate/polyacrylamide gel electrophoresis, and contains a type I ATP-binding motif. The purified product was used to raise antibody which allowed the level of KilBI produced from RK2 to be estimated at approximately 2000 molecules per bacterium. Protein sequence comparisons showed the highest homology score with VirB11, which is essential for the transfer of the Agrobacterium tumefaciens Ti plasmid DNA from bacteria to plant cells. The sequence similarity of both KilBI and VirB11 to a family of protein export functions suggested that KilBI may be involved in assembly of the surface-associated Tra functions. The data presented in this paper provide the first demonstration of coregulation of genes required for vegetative replication and conjugative transfer on a bacterial plasmid.     

Asplenetin,a flavone and its glycoside from Launaea asplenifolia

A new flavone, asplenetin, has been isolated from Launea asplenifolia and characterized as 5,7,3′,4′,5′-pentahydroxy-3-(3-methylbutyl)flavone. Its glycoside, asplenetin 5-O-neohesperidoside, is also reported.     

A Simple and Widely Applicable Method for Preparing Homogeneous and Stable Quality Control Samples in Water Microbiology

Test strains suspended in skim milk, quickly frozen in dry ice-ethanol, and stored at - 70°C can be used as quality control samples that are immediately available by quickly thawing at 37°C. The samples remain homogeneous and stable for at least 1 year, except for Aeromonas hydrophila, which decreases 20 to 30% in 1 year.