Fig. 3 in Spirornatas A-C from brown alga Turbinaria ornata: Anti-hypertensive spiroketals attenuate angiotensin-I converting enzyme

Fig. 3. Molecular docking interactions of spirornata A and standard antihypertensive agent captopril with ACE-I. Nearer view of molecular binding interfaces of spirornata A (A) and captopril (B) in the catalytic domain (together with WPD loop) of ACE-I. The dotted lines designated the H-bonding connections with the active site of ACE-I. The studied compounds were drawn in ACD/ChemSketch, and saved as MDL-molfiles (ver-2000), which were changed to PDB layout using Open Babel (GUI ver-2.4.1.) software. The macromolecule was assigned for polar hydrogens with added kollman charge of +7.75. The grid box was built by the method of hit and miss, wherein grid box for ACE-I was taken as x = 57, y = 42, z = 38 (54 Å, 33 Å, 55 Å). The binding site was additionally corroborated by keeping the zinc ion in the optimized protein file. Cygwin-I terminal was applied to run the docking algorithm, and after autodocking experiment, RMSD (Root-Mean-Square Deviation) was evaluated, and Cygwin-II was used for further optimization.