Consequently, the angle between the two bonds (bond angle) also remains constant. Thus, B(D min , D max ) becomes a set of structures with bond lengths and angles equal to those of the reference structure, while weak constraints exclude structures with excessively small or large interatomic distances from the bottom. Next, we investigate the properties of the merged FB-ENM. If an atom pair i, j is strongly constrained in all reference structures, the interatomic distance of this atom pair in the merged FB-ENM is also strongly constrained within the range of fluctuations among the reference structures. Eqs 7, 8, and 11 give