A. Intersected α9 dimer: the structural model on the left depicts one monomer with Gly179 in sphere form, and the other monomer with Phe176, Gly179 and Val180 that have van der Waals' contacts with the first Gly179 in stick form. The same model is shown on the right, except that the two Gly179 are changed to isoleucine (G179I), which results in steric clashes between the Ile179 in one monomer and the Phe176, Ile179 and Val180 in the other monomer, and vice versa.Parallel α9 dimer: the structural model on the left depicts the two interfacial Thr182 that have van der Waals' contacts in sphere or stick form. The same model is shown on the right, except that the two Thr182 are changed to isoleucine (T182I), which results in a steric clash with each other. 