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Stabilization of an amorphous solid against devitrification can be achieved using additives that interact specifically with the parent molecule, and restrain it from rearranging into a crystal lattice. The amorphous form of celecoxib (CEL) was stabilized by poly(vinylpyrrolidone) (PVP), both in the solid state and during dissolution. A comprehensive characterization of CEL-PVP binary amorphous systems by thermal, spectroscopic, and computer simulation techniques provided greater insight into the molecular interaction between the two species. PVP antiplasticized the amorphous CEL, thus raising its glass transition temperature (T(g)) and restricting the molecular mobility. The T(g)()mix values for CEL-PVP binary amorphous systems of varying composition showed positive deviation from those predicted through the Gordon-Taylor/ Kelley-Bueche equation, thus indicating a molecular interaction between CEL and PVP. This was further substantiated by shifts observed in DSC melting endotherms of CEL, and FTIR bands for C=O stretching vibrations in PVP for CEL-PVP binary amorphous systems. Computer simulation showed stronger H-bonds between amido protons of CEL and carbonyl O of a monomeric unit of PVP, compared to those observed in pure amorphous CEL. These molecular interactions between CEL and PVP supported the stabilizing action of PVP for the amorphous form of CEL.

Small Interfering RNAs (siRNAs) are one of the valuable tools to investigate the functions of genes, and are also used for gene silencing. It has a wide scope in drug discovery through in vivo target validation. siRNA therapeutics are not optimal drug-like molecules due to poor bioavailability, immunogenic and off-target effects. In order to overcome the challenges associated with siRNA therapeutics, identification of appropriate chemical modifications that improves the stability, specificity and potency of siRNA is essential. This review focuses on the various chemical modifications and their implications in siRNA therapy.

The accuracy of ligand-protein docking may be affected by the presence of water molecules on the surface of the protein. Cross-docking simulations have been performed on a number of ligand-protein complexes for various proteins whose crystal structures contain water molecules in their binding sites. Only common sets of water molecules found in the binding site of the proteins were considered. A statistically significant overall increase in accuracy was observed when water molecules were included in cross-docking simulations. These results confirm the importance of including water molecules whenever possible in ligand-protein docking simulations.