in approximation of backbone regular conformations for the case of c2 symmetry ( the symmetry axis is perpendicular to s-s bridges and passes through their midpoint ) on the basis of total analysis of ring geometry possibilities and estimation of steric conditions , the existence of two conformations with n = 3 ( 3 ( 10 ) helix type and polyproline ii type ) was inferred .
C0037949
backbone
C0004457
axis