Two views of S6 (17), showing the ΦC-values of different mutated residues, calculated according to Eq. 3. Residues 8,9, 26, 33, 40, 48, 88, and 90 (blue) have Φ-values around 0.6 whereas residues 6, 21, 30, 37, 60, 65, 67, 75, and 79 (red) have Φ-values below 0.2. Residues 22, 35, and 85 (green) have negative Φ-values (see text).