Patent ID: 8013119

Claim:
A fluorescent protein comprising: a donor fluorescent protein fused via a linker sequence to an acceptor fluorescent protein, wherein the donor fluorescent protein and the acceptor fluorescent protein have fluorescence wavelengths that are different from each other; and wherein the fused fluorescent protein is configured to allow intramolecular fluorescence resonance energy transfer (FRET) to occur between the donor fluorescent protein and the acceptor fluorescent protein as a result of (a) photoactivation/photoconversion of the acceptor fluorescent protein with ultraviolet light or violet light of 400 or 405 nm, and (b) irradiation of the donor fluorescent protein with excitation light, wherein the donor fluorescent protein is a cyan fluorescent protein (CFP) mutant, the acceptor fluorescent protein is a photoactivatable green fluorescent protein (PA-GFP) mutant, and the fluorescent protein has either one of the following amino acid sequences: (i) the amino acid sequence shown in SEQ ID NO: 2; or (ii) the amino acid sequence shown in SEQ ID NO: 2 in which one to ten amino acids have been deleted, substituted, and/or added.