On 3/22/12 8:08 AM, Valerio Lupperger wrote: > I use MODELLER (9.10) in a c-program like in > http://salilab.org/modeller/manual/node456.html. As input I have one > structure and its restraints. Is it possible to calculate energy for the > given structure with MODELLER's C API and derivative with respect to all > coordinates (x,y,z)? And if so, how is it possible?

If you can do it in a Python script, you can generally do it with the C API (most of the Python interface to Modeller is simply calling the C API underneath, in the _modeller module). So you can write the equivalent Python code, and then look at Modeller's Python interface to see what the equivalent C API functions are that it's calling. For example, to calculate the energy you would call the energy() method in the selection class; if you look at modlib/modeller/selection.py you'll see that that method calls the C API mod_energy() function. In C you will have to manually keep track of memory and handle errors, of course, which is done automatically for you by the Python interface.

Ben Webb, Modeller Caretaker