FORME: an interactive package for protein backbone deformation.

The FORME package presented herein is designed for modeling purposes: It allows interactive deformation of the protein backbone. General formalism on transformations is introduced and the operators of stretching inside an "acceptance area" and stretching with end-block invariance (i.e., governed by a translational moving) are described. A discussion is presented on the choice of strategy to achieve an interactive deformation tool. Perspectives about complex transformations are presented.