This is an implementation of the analytical loop closure algorithm as described in

A Kinematic View of Loop Closure,
E. A. Coutsias, C. Seok, M. P. Jacobson, and K. A. Dill,
Journal of Computational Chemistry,
Volume 25, Issue 4, Pages 510 - 528 (2004),

which solves a polynomial equation to find loop closure solutions. This is a generalization of the algorithm of Wedemeyer and Scheraga in that any rigid segments are allowed between the pairs of torsion angles. The bond angle perturbation schemes described in the paper are not included in this distribution.

This program can be used to find loop structures involving six backbone torsion angles given the position of the two atoms before the loop and two atoms after the loop. For example, in the case of protein, possible structures for a three residue gap can be found given the coordinates of the N and CA atoms of the first residue and the CA ans C atoms of the third residue. Multiple conformations are generated in general.

Contact Chaok Seok at chaok@snu.ac.kr for any questions.