PATSEE is a public domain program for location of a fragment of known geometry by integrated Patterson, packing, and direct methods (Egert, E., Sheldrick, G.M.; Acta Crystallographica, A41, 262-268, 1985).
The program attempts to combine the merits of both Patterson and direct methods in order to position a fragment of known geometry in the unit cell. It is valid for all space groups in all settings.
The rotation search can find the orientation of a search model of any size and allows one torsional degree of freedom. (Searching for two independent fragments simultaneously would be very time consuming because a large number of combinations of orientations would have to be considered.) The translation search may locate up to two independent fragments of any size (including single atoms) taking into account known atoms at fixed positions, if any.
PATSEE has proved to be rather powerful for small molecule structures, and the program is now being extended to solve larger structures, e.g. small proteins and nucleic acids.
The program runs on any 486 (or higher) IBM compatible PC with at least 4 MB memory and on VAX or SGI computers. PATSEE is available as source code or as an precompiled executable. To compile the program a FORTRAN 77 compiler is necessary.