The present invention provides an isolated nucleic acid sequence encoding a non-oligomerizing Clavularia teal fluorescent protein (mTFP) variant having a tyrosine-derived chromophore, as well as fragments and derivatives thereof. Also provided is a method for engineering the nucleic acid sequence, a vector comprising the nucleic acid sequence, a host cell comprising the vector, and use of the vector in a method for expressing the nucleic acid sequence. The present invention further provides an isolated nucleic acid, or mimetic or complement thereof, that hybridizes under stringent conditions to the nucleic acid sequence. Additionally, the present invention provides a non-oligomerizing mTFP variant encoded by the nucleic acid sequence, as well as derivatives, fragments, and homologues thereof. Also provided is an antibody that specifically binds to the mTFP variant. The present invention further provides a tandem dimer comprising two mTFP dimers, operatively linked by a peptide linker.