Scheme 1. Size of a fluorescent nanobody compared to nanobodies labeled with a fluorescent protein, termed chromobody. Bulky fluorescent proteins (>25 kDa) triple the size of the nanobody (≈13 kDa). In comparison, the minimal size of fluorophores (<1 kDa) is unlikely to disturb the nanobody and offers a higher quantum yield as well as photostability.
