I’ve got another email from My NCBI (Subject: What’s new for ‘BioAssay – Limits: Protein 3D Structure). It was about AID: 2353 – qHTS Assay for Inhibitors of RecQ-Like Dna Helicase 1 with 23 active and 1272 tested compounds. There are 2 Links for Protein Structure corresponding to open and closed conformations. I run virtual screening for both of them, which produced similar results.

This looks more like an ROC curve you’ll see in publications. In contrast to my previous results, this has fewer active compounds. One would think that AutoDock did a better job here since ROC curves are above the diagonal. However, as you can see from the plots on the left, lowest binding energies are coming from inactive compounds. The image below shows molecular surface for 2WWY (chain A) in green and lowest binding energy conformation for CID: 5328760 (-6.03 kcal/mol) and CID: 11957460 (-10.37 kcal/mol). The first one being the most active in the assay shows a weaker (virtual) binding compared to the second one, which although has the best computed binding energy is not active in the assay. The favourable binding energy is partally because of the size; CID: 11957460 is one of the largest in this assay. So the question is: what kind of changes needs to be done to virtual screening to make it agree more with experiment?