TABLE 1.

Amino acid	ΔGi (kcal/mol)
I	−2.6
L	−2.6
F	−1.5
V	−1.2
A	−0.2
G	0.0
C	+0.4
S	+0.8
T	+1.1
M	+1.3
W	+1.3
P	+2.8
Y	+4.3
Q	+5.4
H	+6.8
K	+7.4
N	+7.7
E	+9.5
D	+11.5
R	+19.8
N–H	+1.8
C=O	+2.5

A hydrophobicity scale representing free energies of transfer of each of the 20 amino acids from water into the center of the hydrocarbon region of a model lipid bilayer (Δg_i). The scale was computationally derived, as described in Kessel and Ben-Tal (2002). The amino acid residues are presented using a single letter code. The values include the free-energy penalty due to the transfer of the backbone hydrogen bond from water into the membrane. The last two rows present an extra free-energy penalty associated with the transfer of unsatisfied backbone N–H and C=O hydrogen bonds from water to the membrane. This penalty was added to the water-to-membrane transfer free energy of amino acids in conformations that are incompatible with hydrogen-bond formation.