Before revision:  In order to describe such `higher-order' secondary structure in a compact way , we introduce here a means of describing regions on the Ramachandran plot in terms of a single  Ramachandran number , {R}, which is a structurally meaningful combination of \phi and \psi.
After revision:  In order to describe such `higher-order' secondary structure in a compact way we introduce here a means of describing regions on the Ramachandran plot in terms of a single  Ramachandran number , {R}, which is a structurally meaningful combination of \phi and \psi.