Table 1.

Thermodynamic propensity of different amino acid residues at the helical positions

Amino acid residue	ΔΔG(X32)	ΔΔG(X28)	ΔΔG(X28/V5A)	ΔΔG(P&S)	ΔΔG(PHD)/Pg(C2)
A	0.0 ± 0.2	0.0 ± 0.2	0.0 ± 0.2	0.0 ± 0.5	0.0/1.46
F	−2.4 ± 0.4	—	—	−2.3 ± 0.5	−1.7/0.74
G	−4.3 ± 0.4	−4.4 ± 0.3	−4.2 ± 0.1	−4.2 ± 0.5	−4.1/0.28
I	−0.9 ± 0.2	−1.0 ± 0.2	−1.0 ± 0.2	−1.7 ± 0.5	−0.7/1.12
L	−0.6 ± 0.2	—	—	−0.9 ± 0.2	−0.3/1.31
M	−0.4 ± 0.1	—	—	−1.0 ± 0.3	−0.4/1.24
N	−2.8 ± 0.3	—	—	−2.7 ± 0.4	−2.2/0.60
Q	0.1 ± 0.1 (−0.4 ± 0.1)a	—	—	−1.6 ± 0.4	−0.3/1.29
S	−2.0 ± 0.1	−2.7 ± 0.3	−2.3 ± 0.1	−2.1 ± 0.3	−1.8/0.71
T	−2.5 ± 0.1	—	—	−2.8 ± 0.4	−1.9/0.69
V	−1.7 ± 0.4	−2.0 ± 0.1	−1.7 ± 01	−2.6 ± 0.5	−1.2/0.89

All ΔΔG values are relative to alanine and are in kilojoules per mole. ΔΔG(PHD) = −R • T • ln[P_g(X)/P_g(A)], where the normalized frequency for individual amino acid residues in position C2 of α-helices, P_g, was calculated from the data reported in Penel et al. (1999a,^b); ΔΔG(P&S) values of helical propensity for the middle of α-helix are taken from Pace and Scholtz (1998).

^a Changes in ΔΔG relative to A32 in the background of A28 variant.