Table 1. Possible binding positions of two arms from a single IgG.

n, n + 1 not possible; beyond maximum reach
n, n + 2 not possible; beyond maximum reach
n, n + 3 maybe steric hindrance
n, n + 4 unlikely, maximum stretch of tether
n, n + 5 not possible; beyond maximum reach
n, n + 6 unlikely, maximum stretch of tether
n, n + 7 most likely, part of top sticks out
n, n + 8 not possible; beyond maximum reach