The general goal of constraint generation is to obtain a file of constraints that can be used in one of several structure calculatin program. You can export the restraints displayed in the table to appropriately formatted files. Select the File → Write Constraints... menu item from the menu bar of the Constraint Table to get the following dialog. There are two items to select in the dialog. One is the format of the constraint file, which can be that used by XPLOR or that used by CYANA. The other is whether or not to use Constraint Combination. This is a method used within the CYANA program. By providing a similar capability here one can generate constraint files that already have combined constraints and use the appropriately formatted one in CYANA or XPLOR. Constraint combination is a way to minimize the effect of erroneous assignments. It works because if an erroneous constraint is combined into an ambigous constraint with a valid constraint the erroneous constraint will have little impact on the calculated structure. If you randomly combine constraints, and a minority of them are erroneous it is likely that most of the erroneous constraints will be found in combination with a valid constraint. Having selected the two output options, click the Write button. A File Dialog will appear in which you can select the output file name.

Figure 14.13. Distance Constraint Table Filtering

Constraints can also be imported from the files formatted for XPLOR and the output files of ARIA. Use the File → Read XPLOR Constraints menu item of the Constraint Table to read XPLOR distance constraints. Use the File → Read ARIA XML Output menu item of the Constraint Table to read the output of an ARIA run. In both cases you will be prompted for the file to open.