However, because 310 helices are much more common in the tertiary structures of proteins than pi helices, extension of the Lifson–Roig model to accommodate 310 helices - resulting in a 9x9 transfer matrix when capping is included - has found a greater range of application. Analogous extensions of the Zimm–Bragg model have been put forth but have not accommodated mixed helical conformations.
On the other hand, because 310 helices are much more frequent in protein tertiary structures than pi helices, the Lifson–Roig model has been expanded to include 310 helices - leading to a 9x9 transfer matrix when capping is taken into account - and this extension has proven useful in a wider variety of applications. Similar extensions of the Zimm–Bragg model have been suggested but have not successfully incorporated mixed helical conformations.