Tork - Conformational search method

Tork [1] is a powerful and flexible conformational search application which processes drug-like compounds and chemical host-guest complexes with arbitrary initial conformations. The method can efficiently generate low energy conformations of the compounds. Tork can be considered as a molecular level eigenvector-following technique [2,3]. However, it has several new features to accelerate the search, and is highly efficient for cyclic, acyclic, and mixed single molecules, as well as for host-guest complexes. Tork computes normal modes in key torsional coordinates, distorts the molecule along these modes singly and in various combinations, and then energy-minimizes the distorted conformations to yield new low-energy conformations. Normal modes are useful because they represent concerted "natural" motions that tend to lead to new low-energy structures.  The use of torsional, rather than Cartesian, coordinates markedly speeds the search because torsional coordinates generate more extensive bond rotations. Moreover, Tork has been implemented into Vconf, a conformational search software for drug-like compounds launched by Verachem, LLC

What is normal mode?