The data provided by the challenge was prepared by Prof. Dr. Mabel Loza and Dr. Jose Brea from the University of Santiago de Compostela. To create a predictive model that is applicable to a wide range of chemical space, the hosts of the online challenge selected and experimentally measured 101,017 small molecules. Compounds were dispensed into 384-well assay plates using 50 nL from a 10 mM solution in the polar aprotic solvent DMSO. Subsequently, 50 μL of PBS (pH=7.4) were added to each well to achieve a constant pH value of 7.4. The final concentration of the substance was 10 μM, and the mixture also contained 0.1% of DMSO as a residue of the first solution. The plates were sealed and stirred at 37°C for two hours. After that time, the plates were centrifuged for 20 seconds at 200 xg, and the amount of undissolved sediment was measured with a nephelometer. Each small molecule was measured at least twice, with the substance being dissolved each time on a different plate but in the same position. On each plate, some wells were used for blank measurements (background noise) and for the control compounds Amiodarone and Phenytoin.