To narrow down the calculated descriptors to only the most significant ones, we employed attribute selection from WEKA, an open-source machine learning software. The descriptors were ranked by the Information Gain Attribute Evaluation (InfoGain) function, an unsupervised machine-learning algorithm, that measures how important each descriptor is in determining whether a given molecule is an inhibitor or not. Only the most significant descriptors were selected to be used by the machine-learning algorithm in order to reduce noise. Figure