Biosynthesis of colloidal gold nanoparticles by <i style="mso-bidi-font-style:normal">Streptomyces</i> sp. NK52 and its anti-lipid peroxidation activity

969-972Gold nanoparticles (Au-NPs) were synthesized from chloroauric acid using cell free supernatant of <i style="mso-bidi-font-style: normal">Streptomyces sp. NK52 grown in nutrient broth. These nanoparticles were synthesized by varying pH and temperature of the reaction mixture and chloroauric acid concentration. The nanoparticles were characterized by spectrometry, X-ray diffraction, Scanning electron microscopy and energy dispersive spectrometry. Au-NP ranged from 10-100 nm in size and exhibited a polydispersive nature with various shapes like rods, hexagons, triangles, spheres. The diffraction peaks at 2θ = 38.1◦ and 44.5◦ could be assigned to the (1 1 1) and (2 0 0) planes of a faced centre cubic (fcc) lattice of gold. Au-NP showed 47% inhibition of lipid peroxidation in vitro. To the best of our knowledge, this is the first report on the rapid biosynthesis of Au-NP using cell free supernatant of Streptomyces sp. and its evaluation for anti-lipid peroxidation

Crystallization and preliminary X-ray diffraction analysis of human seminal plasma protein PSP94

The human seminal plasma protein PSP94 has been purified from human seminal plasma and crystallized

Observation of a tetrahedral reaction intermediate in the HIV-1 protease–substrate complex

HIV-1 protease is an effective target for the design of drugs against AIDS. To help this process of drug design, three-dimensional structures have been determined of complexes between HIV-1 protease and a variety of transition-state analogue inhibitors. The true transition state, however, has not been structurally characterized. The crystal structure of the C95M/C1095A HIV-1 protease tethered dimer shows a distinctive feature in which the two flaps of the enzyme are in a ‘closed conformation’ even in the unliganded state. This unique feature has been utilized here to study the structure of HIV-1 protease complexed to an oligopeptide substrate of amino acid sequence His-Lys-Ala-Arg-Val-Leu*NPhe-Glu-Ala-Nle-Ser (where* denotes the cleavage site, and NPhe and Nle denote p-nitrophenylalanine and norleucine residues respectively). The X-ray structure of the complex refined against 2.03 Å (0.203 nm) resolution synchrotron data shows that the substrate is trapped as a tetrahedral reaction intermediate in the crystal. The hydrogen-bonding interactions between the reaction intermediate and the catalytic aspartates are different from those observed previously using transition-state analogues. The reaction intermediate did not dissociate to release the products, possibly due to the inflexibility introduced in the flaps when the enzyme is packed inside crystals