Tailor-made hollow silver nanoparticle cages assembled with silver nanoparticles: an efficient catalyst for epoxidation.

A novel approach toward the synthesis of hollow silver nanoparticle (NP) cages built with building blocks of silver NPs by layer-by-layer (LbL) assembly is demonstrated. The size of the NP cage depends on the size of template used for the LbL assembly. The microcages showed a uniform distribution of spherical silver nanoparticles with an average diameter of 20 ± 5 nm, which increased to 40 ± 5 nm when the AgNO3 concentration was increased from 25 to 50 mM. Heat treatment of the polyelectrolyte capsules at 80 °C near their pKa values yielded intact nano/micro cages. These cages produced a higher conversion for the epoxidation of olefins and maintained their catalytic activity even after four successive uses. The nanocages exhibited unique and attractive characteristics for metal catalytic systems, thus offering the scope for further development as heterogeneous catalysts.

Fabrication and characterisation of high performance polypyrrole modified microarray sensor for ascorbic acid determination.

In this study, gold microelectrode array (Au/MEA) with electrode of 12 µm diameter was fabricated by photolithography technique. Subsequently, polypyrrole (Ppy) modified gold microarrays sensor (Ppy/Au/MEA) was prepared by cyclic voltammetry technique. The deposition potential range and number of cycles were optimised in order to get optimum thickness of Ppy film. Scanning Electron Microscope and Atomic Force Microscope investigations reveal that Ppy coating formed at 3 cycles is porous with thickness of 1.5 µm which exhibiting high catalytic current for ascorbic acid (AA) in square wave technique (SWV). In contrast to earlier sensors designs, these Ppy/Au/MEA sensors exhibits lower detection limit (LOD) of 10 nm towards AA at physiological conditions. It also exhibits enhanced sensitivity (2.5 mA cm(-2) mM(-1)) and long range of linear detection limit from 10 nm to 2.8 mM. In the same way, polypyrrole modified macro Au (Ppy/Au/MA) biosensor was also fabricated and its electro catalytic property towards AA was compared with that of Ppy/Au/MEA. The Ppy/Au/MA exhibits sensitivity of only 0.27 mA cm(-2) mM(-1), LOD of 5 µM and linear range of 10 µM to 2.2mM. Hence, our investigations indicate that the Ppy/Au/MEA could serve as highly sensitive sensor for AA than any of the earlier designs. So, the Ppy/Au/MEA electrode was utilised for determination AA in a wide variety of real samples.

Combining structure-based pharmacophore and in silico approaches to discover novel selective serotonin reuptake inhibitors.

Inhibition of human serotonin transporter (hSERT) has been reported to be a potent strategy for the treatment for depression. To discover novel selective serotonin reuptake inhibitors (SSRIs), a structure-based pharmacophore model (SBPM) was developed using the docked conformations of six highly active SSRIs. The best SBPM, consisting of four chemical features: two ring aromatics (RAs), one hydrophobic (HY), and one positive ionizable (PI), was further validated using Gunner-Henry (GH) scoring and receiver operating characteristic (ROC) curve methods. This well-validated SBPM was then used as a 3D-query in virtual screening to identify potential hits from National Cancer Institute (NCI) database. These hits were subsequently filtered by absorption, distribution, metabolism, excretion, and toxicity (ADMET) prediction and molecular docking, and their binding stabilities were validated by 20-ns MD simulations. Finally, only two compounds (NSC175176 and NSC705841) were identified as potential leads, which exhibited higher binding affinities in comparison with the paroxetine. Our results also suggest that cation-π interaction plays a crucial role in stabilizing the hSERT-inhibitor complex. To our knowledge, the present work is the first structure-based virtual screening study for new SSRI discovery, which should be a useful guide for the rapid identification of novel therapeutic agents from chemical database.