• Evans Coutinho

      Articles written in Journal of Chemical Sciences

    • Quantum mechanical calculations on dopamine D2-receptor antagonists: Conformation of remoxipride, eticlopride and NCQ 115

      Anil Saran Evans Coutinho

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      The quantum mechanical PCILO method has been used to study the conformation of three selective dopamine D2-receptor antagonists: remoxipride, eticlopride and NCQ 115. The calculations were done for both the protonated and ‘free base’ forms of the antagonists. The protonated antagonists all have folded structures due to intramolecular hydrogen bonding between the carbonyl of the amide moiety and the hydrogen on the pyrrolidine nitrogen. The ‘free bases’ on the other hand are characterised by extended structures. An interaction model for these molecules with the dopamine receptor has been proposed.

    • Influence of nature of side chain on conformation of alternatingl- andd-stereo oligopeptides

      Shantaram Kamath Evans Coutinho

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      Peptides containing residues with alternatingd- andl-stereochemistry in the backbone have been studied for their single-strand helix-forming capability by molecular dynamics (MD) simulations. The influence of the nature of the side chain such as steric, branching and polarity on helix forming ability has been probed by studyingt-Boc-(l-Ala-d-Ala)4-OMe (small hydrophobic side chain),t-Boc-(l-Phe-d-Phe)4-OMe (bulky hydrophobic side chain),t-Boc-(l-Val-d-Val)4-OMe (β-branch in side chain),t-Boc-(d-allolle-l-Ile)3-OMe (γ-branch in side chain), andt-Boc-(l-Ala-d-Ser)4-OMe (hydrophobic and hydrophilic side chains). Besides this, the effect of unsymmetricalα,α-disubstitution with alternatingd- andl-stereochemistry and Cα carbons on helix stability has also been investigated. The results show that such peptides, with the exception of those withα,α-disubstitution, have a unique ability to formβ-helices.

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