Paritosh Shukla

Structure-based drug design of novel Aurora kinase A inhibitors: structural basis for potency and specificity.

Aurora kinases have emerged as attractive targets for the design of anticancer drugs. Through structure-based virtual screening, novel pyrazole hit 8a was identified as Aurora kinase A inhibitor (IC(50) = 15.1 microM). X-ray cocrystal structure of 8a in complex with Aurora A protein revealed the C-4 position ethyl carboxylate side chain as a possible modification site for improving the potency. On the basis of this insight, bioisosteric replacement of the ester with amide linkage and changing the ethyl substituent to hydrophobic 3-acetamidophenyl ring led to the identification of 12w with a approximately 450-fold improved Aurora kinase A inhibition potency (IC(50) = 33 nM), compared to 8a. Compound 12w showed selective inhibition of Aurora A kinase over Aurora B/C, which might be due to the presence of a unique H-bond interaction between the 3-acetamido group and the Aurora A nonconserved Thr217 residue, which in Aurora B/C is Glu and found to sterically clash with the 3-acetamido group in modeling studies.

Diazapentacene Derivatives as Thin-Film Transistor Materials: Morphology Control in Realizing High-Field-Effect Mobility

5,7,12,14-Tetrachloro-6,13-diaza-6,13-dihydropentacene (TCDAHP) and 5,7,12,14-tetrachloro-6,13-diazapentacene (TCDAP) were synthesized and assessed as the active channel materials for thin-film transistor applications. Analyses of the crystal structures of these molecules revealed that both exhibited slipped pi-pi stacking of the long and fused aromatic moiety. Although the packing features of the two compounds are basically identical, their highest occupied molecular orbitals, which are relevant to hole transport, are very different. Better mobility was predicted for TCDAHP over TCDAP based on the dimeric structure in the X-ray coordinates. The morphologies of thin films of TCDAHP and TCDAP prepared by thermal evaporation depend critically on the substrate on which the molecules were deposited: from the amorphous state on a SiO(2)/Si surface to the crystalline state on a pentacene buffer layer surface. The performance of thin-film transistors prepared on various substrate surfaces was studied. While no field-effect mobility was observed for these films deposited on SiO(2)/Si, a high mobility of 1.4 cm(2)/(V s) for the TCDAHP film was achieved when deposited on a pentacene buffer layer prepared on a rubbed monolayer of n-nonyltrichlorosilane on a SiO(2)/Si surface. A similar device prepared from TCDAP gave a mobility of 0.13 cm(2)/(V s).

Scaffold-hopping strategy: Synthesis and biological evaluation of 5,6-fused bicyclic heteroaromatics to identify orally bioavailable anticancer agents

Utilizing scaffold-hopping drug-design strategy, we sought to identify a backup drug candidate for BPR0L075 (1), an indole-based anticancer agent. For this purpose, 5,6-fused bicyclic heteroaromatic scaffolds were designed and synthesized through shuffling of the nitrogen from the N-1 position or by insertion of one or two nitrogen atoms into the indole core of 1. Among these, 7-azaindole core 12 showed potent in vitro anticancer activity and improved oral bioavailability (F = 35%) compared with 1 (F < 10%).

Developments and challenges in biodiesel production from microalgae: A review

The imminent depletion of fossil fuels and the surging global demand for renewable energy have led to the search for nonconventional energy sources. After a few decades of trial and error, the world is now testing the sources of the third generation of fossil fuels, which contain for most parts microalgae. With more than 80% oil content, being adaptable in growth parameters and highly versatile, microalgae are highly promising sources of biofuels in the present time. The present article makes a sweeping attempt to highlight the various methods employed for cultivation of microalgae, techniques to harvest and extract biomass from huge algal cultures, as well as their downstream production and processing procedures. The advantages, limitations, and challenges faced by each of them have been described to some extent. Major concerns pertaining to biofuels are supposed to be their environmental sustainability and economic viability along with their cost effectiveness. This would require a great deal of empirical data on existing systems and a great deal of optimization to generate a more robust one. We have concluded our article with a SWOT analysis of using algae for biodiesel production in a tabulated form.

Sensing of contaminants in potable water using TiO2 functional film

The piezoelectric based quartz crystal microbalance is employed for sensing contaminants in potable water. A spin coated thin layer of TiO2 nanoparticles was formed at the sensing area of a 5 MHz AT-cut quartz wafer. The thin film of TiO2 nanoparticles forms a mesoporous functional layer for the trapping of water borne contaminants. The morphology of the thin film of TiO2 nanoparticles was studied using field emission scanning electron microscope (FESEM). The surface morphology of the TiO2 nanoparticles reveals the mesoporous structures indicating large number of defects and porous sites. Such film was employed for the detection of water borne contaminants by detecting the piezoelectric response from a quartz crystal microbalance. We found the film to be very sensitive to the contaminants. The minimum detection limit was found to be 330 ppb. The effect of surface recharging was also studied by altering the physical conditions so that the film can be used for repetitive usage.

Synthesis of functionalized pyrazolopyran derivatives: comparison of two-step vs. one-step vs. microwave-assisted protocol and X-ray crystallographic analysis of 6-amino-1,4-dihydro-3-methyl-4-phenylpyrano[2,3-c]pyrazole-5-carbonitrile

A library of pyrazolopyran heterocycles was synthesized first by the traditional heating techniques using two-step and one-step procedures and then by microwave-assisted (MWA) multicomponent condensation of ethyl acetoacetate, hydrazine, malonodinitrile and a variety of substituted aldehydes. A comparison of the foregoing methods was first done based on the yields and then based on the time taken for the completion of the reactions. It was found that although the traditional methods gave slightly better yields, the MWA syntheses lead to substantial reduction in reaction timings. The title compound crystallizes in the triclinic crystal system with space group P–1. The crystal structure as elucidated by X-ray diffraction methods shows the presence of different intermolecular interactions, and the nature and energetics associated with these interactions have been characterized using PIXEL software.