Molecular modeling on pyruvate phosphate dikinase of Entamoeba histolytica and in silico virtual screening for novel inhibitors

Pyruvate phosphate dikinase (PPDK) is the key enzyme essential for the glycolytic pathway in most common and perilous parasite Entamoeba histolytica. Inhibiting the function of this enzyme could control the wide spread of intestinal infections caused by Entamoeba histolytica in humans. With this objective, we modeled the three dimensional structure of the PPDK protein. We used templates with 51% identity and 67% similarity to employ homology-modeling approach. Stereo chemical quality of protein structure was validated by protein structure validation program PROCHECK and VERIFY3D. Experimental proof available in literature along with the in silico studies indicated Lys21, Arg91, Asp323, Glu325 and Gln337 to be the probable active sites in the target protein. Virtual screening was carried out using the genetic docking algorithm GOLD and a consensus scoring function X-Score to substantiate the prediction. The small molecule libraries (ChemDivision database, Diversity dataset, Kinase inhibitor database) were used for screening process. Along with the high scoring results, the interaction studies provided promising ligands for future experimental screening to inhibit the function of PPDK in Entamoeba histolytica. Further, the phylogeny study was carried out to assess the possibility of using the proposed ligands as inhibitors in related pathogens.     

A comparative study on the growth and characterization of nonlinear optical amino acid crystals: L-alanine (LA) and L-alanine alaninium nitrate (LAAN)

A comparative study on the properties of L-alanine and LAAN crystals has been made and discussed. It may be concluded that the protonation of the amino group in the L-alanine molecule is the key factor in increasing the relative SHG efficiency of LAAN. The protonation is justified by the crystal structure analysis, FTIR and photoluminescence studies. The factor group vibrations are compared and found that there is an increase in vibrational modes of LA when reacted with nitric acid forming LAAN.     

Synthesis and evaluation of urea and thiourea derivatives of oxazolidinones as antibacterial agents

Urea and thiourea derivatives of oxazolidinones were synthesized and their inhibitory activity (MIC) was determined on the bacterial strains which includes clinical isolates and quality control organisms. The structure activity relationships were studied and a 3D-QSAR model was built using Genetic Function Approximation. Interestingly found that electron withdrawing groups at the ortho position of the phenyl ring enhances the activity.     

Design,synthesis, and evaluation of novel combretastatin A-4 based chalcone derivatives as anticancer agents

A series of combretastatin A-4 based chalcones ( 14a-l ) were designed, synthesized and these compounds examined for inhibitory effects on the proliferation of human lung (A549), breast (MCF-7), melanoma (A375), and colon (HT-29) carcinoma cells. Compounds 14b , 14c , 14e , 14h , and 14i (tri/dimethoxy, methyl, and mono/dinitro derivatives) have exhibited the most potent antiproliferative activity with IC₅₀ < 2 μM and the hexa methoxy derivative 14b , the most promising one, which displayed the potent inhibitory activities in MCF-7 (IC₅₀: 10 nM), A375 (IC₅₀: 12 nM), and A549 (IC₅₀: 65 nM) cell lines, and is 18 times more potent than the CA-4. Compound 14b represents a new scaffold and the results provide insights into further development of anticancer agents.     

Intramolecular charge transfer and Z-scan studies of a semiorganic nonlinear optical material sodium acid phthalate hemihydrate: a vibrational spectroscopic study

FT-IR and Raman spectra of the nonlinear optical material sodium acid phthalate hemihydrate crystal have been recorded and analyzed. The equilibrium geometry, bonding features, and harmonic vibrational wavenumbers have been investigated with the help of the B3LYP density functional theory method. A detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. The natural bond orbital analysis confirms the occurrence of strong intermolecular hydrogen bonding in the molecule. Nonlinear optical absorption of the sample has been studied at 532 nm using single 5 ns laser pulses, employing the open-aperture Z-scan technique. It is found that the NaAPH molecule is a potential candidate for optical limiting applications.     

Synthesis,growth and optical properties of semi organic non linear optical single crystal: l-Arginine acetate

In the recent past, nonlinear optical materials are getting attention in the field fibre optic communication and optical signal processing. In the present study, the title compound was successfully synthesized by conventional chemical reaction and then the single crystal was grown by slow evaporation solution growth technique. l-Arginine acetate (LAA) is semi organic non linear optical single crystal and crystallizes in noncentrosymmetric space group. The grown good quality single crystals have been analyzed by different characterization analyses such as powder X-ray diffraction, high resolution X-ray diffraction (HRXRD), Raman spectroscopy, photoluminescence, SEM, micro-hardness, thermal and birefringence analyses.     

Dielectric measurements on urea added ZTS single crystals

Pure and urea added zinc tris(thiourea)sulphate (ZTS) single crystals were grown by the solvent evaporation method from aqueous solutions. The grown crystals were characterized by X-ray powder diffraction, Fourier transform infrared, second harmonic generation and density measurements. The observed results show that the small amount of urea molecules were incorporated in the crystalline matrix of ZTS crystals. Dielectric measurements were carried out along a-, b- and c-directions of the grown crystals at various temperatures by the conventional parallel plate capacitor method with a fixed frequency of 1 kHz. The present study shows that the dielectric parameters (viz. dielectric constant, dielectric loss and a.c. conductivity) increases with the increase in temperature for all the grown crystals. Activation energies were also determined.     

Characterization of melt grown phthalic anhydride single crystal

The bulk organic single crystal of phthalic anhydride (PA) was grown by vertical Bridgman technique. The structural perfection of the grown crystal was analysed by high resolution X‐ray diffraction (Multicrystal X‐ray diffractometry) studies. The thermal and mechanical properties have been studied. The second harmonic generation relative efficiency of Phthalic anhydride crystal is compared with KDP crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)