Discrete differential geometry of proteins: a new method for encoding   three-dimensional structures of proteins
  In nature the three-dimensional structure of a protein is encoded in the corresponding gene. In this paper we describe a new method for encoding the three-dimensional structure of a protein into a binary sequence. The feature of the method is the correspondence between protein-folding and ``integration''. A protein is approximated by a folded tetrahedron sequence. And the binary code of a protein is obtained as the ``second derivative'' of the shape of the folded tetrahedron sequence. With this method at hand, we can extract static structural information of a protein from its gene. And we can describe the distribution of three-dimensional structures of proteins without any subjective hierarchical classification. 
Naoto Morikawa