TABLE 1.

Classification of intersubunit contacts, H bonds, and ionic pairs between central subunit A and neighbor subunits^a

Virus genotype	Total no./specific type
	Contactsb	H bondsc	Ionic pairsd
WT	48/13R (6s, 7w), 19L (10s, 9w), 8D (4s, 4w), 6U (2s, 4w), 2T (2s)	18/2R (2w), 10L (3s, 3m, 4w), 4D (1s, 3w), 2U (1m, 1w)	6/3R (3.30, 3.46, 3.82), 3L (3.30, 3.46, 3.82)
M138N	32/12R (4s, 8w), 18L (7s, 11w), 1U (1s), 1E (1w)	10/2R (1s, 1w), 6L (1s, 2m, 3w), 1T (1m)	6/3R (3.36, 3.42, 3.91), 3L (3.36, 3.42, 3.91)
A86G	50/22R (14s, 8w), 18L (10s, 8w), 5U (2s, 3w), 1C (1s), 4E (1s, 3w)	17/6R (4m, 2w), 7L (1s, 4m, 2w), 2U (1m, 1w), 2C (1m, 1w)	8/2R (3.40, 3.75), 2L (3.40, 3.75), 2U (3.37, 3.57), 2C (3.37, 3.57)
L13F+G66V	53/19R (13s, 6w), 15L (12s, 3w), 2D (1s, 1w), 6U (3s, 3w), 3T (2s, w), 8E (4s, 4w)	16/5R (4s, 1m), 2L (1s, 1m), 4D (1s, 3w), 4U (1s, 1m, 2w), 1E (1m)	0
T43K+D50G	54/15R (8s, 7w), 28L (13s, 15w), 2D (2w), 5U (2s, 3w), 3T (3s), 1E (1w)	24/8R (1s, 5m, 2w), 10L (1s, 6m, 3w), 2D (1s, 1m), 3U (2s, 1m), 1T (1m)	10/5R (2.55, 3.00, 3.28 3.60, 3.66), 5L (2.55, 3.00, 3.28 3.60, 3.66)
T43K	54/15R (8s, 7w), 28L (13s, 15w), 2D (2w), 5U (2s, 3w), 3T (3s), 1E (1w)	24/8R (1s, 5m, 2w), 10L (1s, 6m, 3w), 2D (1s, 1m), 3U (2s, 1m), 1T (1m)	11/5R (2.55, 3.00, 3.28, 3.60, 3.66), 5L (2.55, 3.00, 3.28, 3.60, 3.66), 1T (3.11)
D50G	45/14R (9s, 5w), 23L (12s, 11w), 2D (2w), 3U (1s, 2w), 3T (3s)	24/8R (1s, 5m, 2w), 10L (1s, 6m, 3w), 2D (2m), 4U (3m, 1w)	4/2R (3.00, 3.28), 2L (3.00, 3.28)

^aThe neighbor subunits are T, U, V, L, R, C, D, and E, as labeled in Fig. 3B.

^bContacts are considered strong (s) if the interatomic distance d is ≤3.2 Å and weak (w) if d is >3.2 Å.

^cThe strength of A-H—B hydrogen bonds is classified in terms of the d(A—B) distance as strong (s) if d = 2.2 to 2.5 Å, moderate (m) if d = 2.5 to 3.2 Å, and weak (w) if d = 3.2 to 3.7 Å.

^dAttraction energy in ionic pairs is inversely proportional to the interatomic distance; values in parentheses are in angstroms.