Figure 3
(a) The stacking of hydrophobic groups of (I) along the regular fourfold axis. A wire-frame representation is used to emphasize the steric conflict leading to the 1:1 disorder described in the text. Some prohibitively short distances (in Å) are indicated by dashed lines (red in the electronic version of the paper). (b) The hydrogen bonding (dashed lines) along the 42 screw axis. A right-handed hydrogen-bonded chain formed by the –OH groups of component 1 has been highlighted. The directly opposing amino acid must have a different conformation; the sequence shown here (3–3–2–2–3–2 from the top) is just a random example. The colour coding is as in Fig. 1. |