Biological process of arsenic removal using selected microalgae

In the present investigation, growth of the organisms was reduced due to presence of arsenic (III) and (V) in the culture medium. In comparison to arsenic (V), arsenic (III) had more toxic effect on microalgae. Among the different algal strains, blue green algal species Oscillatoria-Lyngbya mixed culture showed maximum efficiency in removing arsenic (64%) after 21 days of incubation and the same algal species could remove arsenic (III), but 60% after 21 days when incubated in 0.1 mg/l arsenic (III) containing medium. Maximum removal was observed at their exponential growth phase and also so sometime extended to the stationary phase.     

A novel motif in the yeast mitochondrial dynamin Dnm1 is essential for adaptor binding and membrane recruitment

To initiate mitochondrial fission, dynamin-related proteins (DRPs) must bind specific adaptors on the outer mitochondrial membrane. The structural features underlying this interaction are poorly understood. Using yeast as a model, we show that the Insert B domain of the Dnm1 guanosine triphosphatase (a DRP) contains a novel motif required for association with the mitochondrial adaptor Mdv1. Mutation of this conserved motif specifically disrupted Dnm1–Mdv1 interactions, blocking Dnm1 recruitment and mitochondrial fission. Suppressor mutations in Mdv1 that restored Dnm1–Mdv1 interactions and fission identified potential protein-binding interfaces on the Mdv1 β-propeller domain. These results define the first known function for Insert B in DRP–adaptor interactions. Based on the variability of Insert B sequences and adaptor proteins, we propose that Insert B domains and mitochondrial adaptors have coevolved to meet the unique requirements for mitochondrial fission of different organisms.     

Dimeric Dnm1-G385D interacts with Mdv1 on mitochondria and can be stimulated to assemble into fission complexes containing Mdv1 and Fis1

Interactions between yeast Dnm1p, Mdv1p, and Fis1p are required to form fission complexes that catalyze division of the mitochondrial compartment. During the formation of mitochondrial fission complexes, the Dnm1p GTPase self-assembles into large multimeric complexes on the outer mitochondrial membrane that are visualized as punctate structures by fluorescent labeling. Although it is clear that Fis1p.Mdv1p complexes on mitochondria are required for the initial recruitment of Dnm1p, it is not clear whether Dnm1p puncta assemble before or after this recruitment step. Here we show that the minimum oligomeric form of cytoplasmic Dnm1p is a dimer. The middle domain mutant protein Dnm1G385Dp forms dimers in vivo but fails to assemble into punctate structures. However, this dimeric mutant stably interacts with Mdv1p on the outer mitochondrial membrane, demonstrating that assembly of stable Dnm1p multimers is not required for Dnm1p-Mdv1p association or for mitochondrial recruitment of Dnm1p. Dnm1G385Dp is reported to be a terminal dimer in vitro. We describe conditions that allow assembly of Dnm1G385Dp into functional fission complexes on mitochondria in vivo. Using these conditions, we demonstrate that multimerization of Dnm1p is required to promote reorganization of Mdv1p from a uniform mitochondrial localization into punctate fission complexes. Our studies also reveal that Fis1p is present in these assembled fission complexes. Based on our results, we propose that Dnm1p dimers are initially recruited to the membrane via interaction with Mdv1p.Fis1p complexes. These dimers then assemble into multimers that subsequently promote the reorganization of Mdv1p into punctate fission complexes.     

Improvement on the Performance of InP/CdS Solar Cells with the Inclusion of Plasmonic Layer of Silver Nanoparticles

The effect of nano-Ag (n-Ag) plasmonic layer in InP/CdS solar cell structure was examined. An enhancement of short circuit current improving the overall cell efficiency was observed in InP/n-Ag/CdS cells. Location of the plasmonic layer in the above cell structure has been analyzed critically. The effect of introducing plasmonic layer on the overall performance of the cell has been studied in terms of the morphology, particle size distribution, optical absorption, I–V, C–V characteristics, and lifetime of the photo-generated carriers. Secondary ion mass spectroscopy (SIMS) studies were carried out for investigating possible interface alloying.     

Syntheses, structures and magnetic properties of μ1,5 dicyanamide bridged coordination polymers of copper(II) and nickel(II) containing a tetradentate N-donor Schiff base

One neutral [Cu₂(enbzpy)(dca)₄]_n (1) and one polycationic [Ni(enbzpy)(dca)]_n(ClO₄)_n (2) [enbzpy = N,N′-(bis-(pyridin-2-yl)benzylidene)ethane-1,2-diamine; dca = dicyanamide] 1D coordination polymers are synthesized and characterized. X-ray structural analyses reveal each copper(II) center in 1 to adopt a distorted square pyramidal geometry with a CuN₅ chromophore coordinated through two N atoms of the Schiff base behaving as a binucleting bis(bidentate) ligand and three nitrile N atoms of one terminal and two single μ_1,5 dca units leading to a 1D ladder structure. In 2, each nickel(II) center has a distorted octahedral coordination environment with an NiN₆ chromophore bound by four N atoms of enbzpy through tetradentate chelation and two nitrile N atoms of two different single bridged μ_1,5 dca units; the latter connects other neighboring metal centers in a non-ending fashion affording a 1D chain. Variable-temperature magnetic susceptibility measurements of 1 and 2 show weak antiferromagnetic interactions among the metal centers through μ_1,5 dca bridges.     

Nuclear pool of phosphatidylinositol 4 phosphate 5 kinase 1α is modified by polySUMO-2 during apoptosis

Phosphatidylinositol 4 phosphate 5 kinase 1α (PIP5K) is mainly localized in the cytosol and plasma membrane. Studies have also indicated its prominent association with nuclear speckles. The exact nature of this nuclear pool of PIP5K is not clear. Using biochemical and microscopic techniques, we have demonstrated that the nuclear pool of PIP5K is modified by SUMO-1 in HEK-293 cells stably expressing PIP5K. Moreover, this SUMOylated pool of PIP5K increased during apoptosis. PolySUMO-2 chain conjugated PIP5K was detected by pull-down experiment using affinity-tagged RNF4, a polySUMO-2 binding protein, during late apoptosis.     

Syntheses, structures and magnetic properties of μ1,5-dicyanamide bridged di- and polynuclear manganese(II) complexes containing neutral N-donor Schiff bases: Control of coordination number and nuclearity by varying denticity

Two hexacoordinated dinuclear compounds [Mn(L1)(dca)]₂(ClO₄/PF₆)₂·CH₃OH (1/2) and two heptacoordinated coordination polymers [Mn(L2)(dca)]_n(ClO₄/PF₆)_n (3/4) [L1 = N,N′-(bis-(pyridin-2-yl)benzylidene)-1,3-propanediamine; L2 = N,N′-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine; dca = dicyanamide] are synthesized and characterized. Structures of 1-3 have been solved by X-ray diffraction measurements. Each manganese(II) center in 1/2 is located in a distorted octahedral environment with an MnN₆ chromophore coordinated by the four N atoms of L1 and two nitrile N atoms of bibridged μ_1,5 dca. Interestingly, the coordination polymer 3 forms a 1D chain through single Mn-(NCNCN)-Mn units in which each manganese(II) center adopts a pentagonal bipyramidal geometry with an MnN₇ chromophore occupied with five N atoms of L2 and two nitrile N atoms of monobridged μ_1,5 dca. Magnetic susceptibility measurements of 1-3 in the 2-300 K temperature range reveal weak antiferromagnetic interactions.