 Solution

A complete bivalent antibody could show greater apparent avidity, provided both protein binding sites can engage suitably spaced antigens on the particle. Dissociation of one arm then need not release the antibody because the other arm retains it nearby. The observed release can consequently be slower than for an isolated monovalent domain.

This does not imply that the intrinsic single-site antibody affinity has improved. Geometry, accessibility and the antibody context could prevent bivalent engagement or even impair the isolated domain's interaction. Thus an altered apparent binding strength is plausible, but its direction and size cannot be inferred solely from conversion to a full antibody.