mTagBFP2(11) is a split fluorescent protein fragment derived from mTagBFP2; it is a small fragment encoding the 11th strand of the mTagBFP2 β-barrel structure. If the mTagBFP2(11) split fluorescent fragment is brought together with a complementary split fluorescent fragment (e.g. mTagBFP2(1-10)) in vivo, a functional fluorescent protein may be reconstituted.