The first paper in this series (see previous article) described structure-activity studies of carboxamide analogues of zanamivir binding to influenza virus sialidase types A and B and showed that inhibitory activity of these compounds was much greater against influenza A enzyme. To understand the large differences in affinities, a number of protein-ligand complexes have been investigated using crystallography and molecular dynamics. The crystallographic studies show that the binding of ligands containing tertiary amide groups is accompanied by the formation of an intramolecular planar salt bridge between two amino acid residues in the active site of the enzyme. It is proposed that the unexpected strong binding of these inhibitors is a result of the burial of hydrophobic surface area and salt-bridge formation in an environment of low dielectric. In sialidase from type A virus, binding of the carboxamide moeity and salt-bridge formation have only a minor effect on the positions of the surrounding residues, whereas in type B enzyme, significant distortion of the protein is observed. The results suggest that the decreased affinity in enzyme from influenza B is directly correlated with the small changes that occur in the amino acid residue interactions accompanying ligand binding. Molecular dynamics calculations have shown that the tendency for salt-bridge formation is greater in influenza A sialidase than influenza B sialidase and that this tendency is a useful descriptor for the prediction of inhibitor potency.

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The publisher apologises for an error in the fourth named author of this article. The author's name should be 'Omkar' only, NOT 'Omkar Singh' as published.

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Worldwide depletion of fossil fuel due to its greater utilization is causing a serious threat to the environment. This has drawn global attention to its conservation, and the search for an alternative to fossil fuel driven engines. Compressed air is a potential working fluid for generating shaft work, and it can be a viable alternative to run light motor vehicles with reasonably small inbuilt compressed air tanks. In this article, the details of the development of a small air turbine with vaned-type rotor are presented. The proposed air turbine has been developed, and is in the process of being tested. Results based on its testing are presented here.