ADMET Predictor™ is designed to run on Pentium-class Windows NT, XP,2000, or Windows 98 personal computers. The program can also successfully run on Windows Vista in the XP compatibility mode. See the User Manual regarding installation issuses on Windows Vista. A minimum of 128 MB of RAM and screen resolution of at least 600x800 pixels is recommended for optimal performance.
There is no set limit on the total number of records the program can process in one session. In the batch mode the only limit is the available disk space. Our internal tests showed that as many as 300,000 compounds could be processed that way without interruption. The interactive mode, however, is restricted by the spreadsheet display of all records at a time. In turn, the spreadsheet is limited by the RAM. Tentatively, running on a freshly restarted notebook computer with 256 MB RAM and Windows 98 operating system, ADMET Predictor was able to process up to 68,000 records in the interactive mode. On a WindowsXP notebook with 2GB RAM the program was successfully opening files with over 90,000 records.
Most modern Intel machines should be able to run ADMET Predictor with reasonable speed. Unlike previous versions of the program, performance of the present ADMET Predictor is almost entirely determined by the built-in multiprotic pKa model. In prediction of ionization constants the number of operations per molecule increases exponentially with the number of ionizable groups. The processing speed is no longer a simple function of the number of molecules supplied on input. Instead, it strongly depends on molecular complexity. Using a 2.4 GHz notebook computer with 512 MB of RAM, we have run several benchmark tests on inputs of varying complexity. In the first test, 1450 molecules with no more than 7 ionizable groups per compound were processed in 21 seconds (2D mode) and 23 seconds (3D mode). This translates to average processing rates of 248,571 and 226,956 molecules per hour, respectively. In the second test, 9658 molecules with no more than 11 ionizable groups per compound were processed in 2 minutes 56 seconds (3D mode). These results correspond to an average rate of 197,550 compounds per hour. As the two tests illustrate, average processing rate drops with the maximum number of ionization centers per molecule. Moreover, the processing difference between 2D and 3D inputs, strongly pronounced in previous versions of the program, is washed out by the CPU time needed by the pKa routine.The third benchmark test, perhaps the most illustrative of all, used only 3D input consisting of 238 very complex compounds. Several of these had relatively high number of ionization centers - up to 16. With all ionizable groups detected, this set was processed in as long as 4 minutes 50 seconds. In the fourth test we have used one of the pKa accelerator options to skip molecules with more than 12 ionizable groups - only 5 compounds were skipped. This resulted in the running time for the remaining 233 molecules equal to only 24 seconds! Hence, the 5 complex molecules in the third test, 2.1% of data set, required 91.7% of the CPU time! The default pKa accelerator option skips aliphatic OH and isolated aliphatic amide groups without limiting the total number of groups; this shortened the run time to only 13 seconds.
In all of the above benchmark tests, "one molecule" means calculation of all descriptors and all ADMET properties.