Abstract: The invention pertains to the field of structural biology and relates to a process to compare various three-dimensional (3D) structures and to identify functional similarities among them. The process of comparison of 3D atomic structures of the invention is based on the comparisons of defined chemical groups onto the 3D atomic structures and allows the detection of local similarities even when neither the fold nor sequence for example aminoacid sequences for polypeptides sequences or nucleotide sequences for nucleic acid sequences are conserved. This process requires the attribution of selected physico-chemical parameters to each atom of a 3D atomic structure, then the representation of each 3D atomic structure by a graph of chemical groups.