The simplest way to run SPRUCE is by passing in an input biomolecular structure file (PDB or mmCIF) as the only argument.
prompt> spruce -in 3fly.pdb
Here, SPRUCE will correctly split and prepare 3fly.pdb with the -in parameter and the standard set of default options. The output will be a set of OEDesignUnit (.oedu) files.
There are also many options that can be invoked from SPRUCE on the command line. For instance, several options are available to help SPRUCE determine the ligand based on molecular features like the number of residues in a peptidic ligand:
So for example:
prompt> spruce -in 4obd.pdb -max_lig_residues 20
will correctly split and prepare 4obd.pdb, based on the -max_lig_residues which sets the maximum number of residues that can still be considered a ligand (required for larger, peptidic ligands like those in 4OBD).
Alternatively, one may want to prepare a biomolecular structure file based on the structure of a similar reference system. For instance, one may construct an OEDesignUnit with a set of site residues defined using a reference that includes a ligand:
prompt> spruce -ref 4OBD.oedu -in 1hhp.cif
Here, an mmCIF file (1hhp.cif) is prepared using the site defined in the output OEDesignUnit file prepared using the -ref option and an output .oedu file from the example above.
To calculate the Iridium classification as a metric of structure quality, one must provide the map file that corresponds to experiment from which the biomolecular structure was derived:
prompt> spruce -map 3rox.mtz -in 3rox.pdb
Here a set of OEDesignUnit files will be produced from 3rox.pdb, where each oedu file will include its own Iridium score taken from a calculation on the density passed in through the -map option (3rox.mtz). The Iridium score can be extracted from any OEDesignUnit file using the spruce TK API, but it will also be reported in the spruce application’s output.
Several options in SPRUCE are available to help control how the system is prepared. For instance by default, spruce calculates partial charges and adds any hydrogen atoms missing from the experimental structure. However, if you have a have a downstream application that does not require certain time-consuming computations, like calculating partial charges or adding missing hydrogen atoms, you can tell SPRUCE to turn these features off:
prompt> spruce -protonate false -charge_radii false -in 3tpp.pdb
Here, SPRUCE will not add partial charges or hydrogen atoms to the output structures during the preparation process of 3tpp.pdb by using the boolean options -protonate and -charge_radii, both of which are set to true by default.
To prevent continually over-writing output files, the -prefix input parameter. allows you to give unique names to these files.
prompt> spruce -in 4icl.pdb -prefix FOO_
will write the output structures into a files named FOO_4ICL_AB__DU__14N_A-607.oedu and FOO_4ICL_AB__DU__T27_A-601.oedu, each identifying separate binding sites.
Finally, to help spruce identify ligands in the biomolecular structure file, use the -ligand_names flag as in this example with 3b3n.pdb.
prompt> spruce -ligand_names JI2 -in 3b3n.pdb