Database Processing
The most common application of dock is to process a database of molecules to find potential inhibitors or ligands of a target macromolecule. However, with the new separation of components in version 4.0, the database processing tools can be combined with other tasks, like stand-alone Scoring , Score Optimization , or Chemical Screen .
Database processing is signalled with the multiple_ligands parameter. A subset of the database may be processed using the ligands_maximum , initial_skip , and interval_skip reading parameters and the heavy_atoms_minimum and heavy_atoms_maximum size-selection parameters. If scoring has been selected, then molecules can be output as a ranked list using the rank_ligands parameter. When comparing molecules, the score of large molecules may be penalized using the contact_size_penalty parameter and so on for each scoring function. If ligands are not ranked, then all orientations recorded for each molecule are written (see Orientation Search on page 28 for how multiple orientations are recorded). When no orientation search is performed (i.e. stand-alone scoring), then molecules are written if they pass a score cutoff set by the contact_maximum parameter and so on for each scoring function.
Database jobs produce two output files in addition to the molecule output files. The restart_file parameter specifies the file which stores the current rank_ligands list. If the job is terminated prematurely, then it may be restarted with the -r flag (see Command-line Arguments on page 53 ) and the run is initialized with information in the existing restart file. The frequency at which the restart file is updated is specified with the restart_interval parameter. In addition, the info_file parameter specifies the file which stores information about the current progress of the run.
Database jobs may also be interacted with during execution via the presence of two input files. The dump_file parameter specifies a file whose presence will trigger the job to write out the current results to the info file, the restart file and the molecule output files. The user may create this file at any time to inspect the current results. The dock job will automatically delete the dump file after a dump has taken place. In addition, the quit_file parameter specifies a file whose presence will trigger the job to write out results (like a dump request) and also terminate execution. This parameter is useful for gently terminating a job without loss of information for restart at a later time. The presence of either of these files is only checked in between processing molecules, so it may take up to a minute for such a file to be noticed.