Table 2. Helix-helix interactions in parallel coiled coils.

	GCN4 leucine-zipper variant*
Parameter	Dimer	Trimer	Tetramer	COMP* pentamer	Trp-14 pentamer
Superhelix
Supercoil radius, Ro, Å	4.9	6.7	7.6	8.6	9.7
Residues per supercoil turn, ωo	100	118	139	140	190
Supercoil pitch, Å	148	175	205	204	277
Radius of curvature, Å	118	124	149	—	211
Superhelix crossing angle, χ °	−11.7	−13.4	−13.0	—	−12.4
Position a orientation angle, φ, °	21.6	20.4	19.8	19.5	2.0
α-Helix
Residues per α-helix turn, n	3.62	3.60	3.59	3.58	3.60
Rise per residue, d, Å	1.51	1.53	1.52	1.52	1.49
α-Helix radius (Cα), R1, Å	2.28	2.24	2.26	2.20	2.06
Pairwise helix-crossing angle, Ω, °	23.4	23.2	18.3	18.5	14.0
Pairwise interhelix distance, D, Å	9.8	11.5	10.6	10.2	11.2

—, not provided.

^*Values for the leucine-zipper peptide variants and the COMP pentamer were from refs. 25 and 26, respectively.