“…In efforts to detect novel bioactive ligands, ligand-based techniques, including properties-based and pharmacophore-based tools, are being used more and more for modeling the bioactivity of molecules and for the virtual screening of large chemical databases [ 35 , 36 , 37 , 38 ]. Ligand-based modeling tools use optimization algorithms such as Monte Carlo simulations (MCs), simulated annealing (SA) [ 39 ], genetic algorithms (Gas) [ 40 ], neural networks (NNs) [ 41 ], support vector machines (SVM) [ 42 ], the k-nearest neighbor algorithm (kNN) [ 43 , 44 ], Bayesian classifiers and some combinations thereof (Monte Carlo/ simulated annealing algorithm, MCSA) [ 45 , 46 , 47 , 48 , 49 ]. Distinguishing between active and inactive ligands that are useful for treating a certain disease may be accomplished by using sets of active and inactive chemicals and certain optimization techniques [ 50 , 51 , 52 ].…”