YFP(2) corresponds to a C-terminal portion (amino acids 159-239) of the YFP fluorescent protein. If the YFP(2) split fluorescent fragment is brought together with a complementary split fluorescent fragment in vivo, a functional fluorescent protein may be reconstituted. YFP(2) is designed for use in a fluorescent protein fragment complementation assay, which is used to study protein-protein interactions in vivo (PMID:15048128).