in modeling the position vectors of atoms in macromolecules it is often necessary to convert from cartesian coordinates (x,y,z) to generalized coordinates. the flory convention for defining the variables involved is usually employed. for an example, a peptide bond can be described by the x,y,z positions of every atom in this bond or the flory convention can be used. here one must know the bond lengths formula_1, bond angles formula_2, and the dihedral angles formula_3. a three-dimensional structure can be described using the flory convention by applying a vector conversion from the cartesian coordinates to the generalized coordinates.