Helix radial projection

Figure 7-6 (A) Heterologous bonding of subunits to form a helix. (B) Radial projection of subunits arranged as in helix A. Different bonding regions of the subunit are designated a, b, c, j, k, and l.

Fig. 14.—Antiparallel packing arrangement of extended, 4-fold, 2,3,6-tri-O-ethylamylose (12) helices, (a) Stereo view of two unit cells approximately normal to the lie-plane. The helix at the center (filled bonds) is antiparallel to the two helices (open bonds) at the comers in the back. There is no intra- or inter-chain hydrogen bond, and only van der Waals forces stabilize the helices, (b) A e-axis projection of the unit cell shows that the ethyl groups extend into the medium in radial directions. 

As shown above all external angles () are the same, as are the chords (C ) between atoms, and the radial distance (r) of atoms from the helix axis. Even though the bond distances (d) are the same, those for the projected figure will be different if the dihedral angles around bonds a and b (ya and yt>) are different. We wish now to determine values for... 

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