Patent ID: 8679742

Claim:
A method for determining whether a sample contains an enzyme comprising: contacting the sample with a recombinant tandem fluorescent protein construct comprising: a polypeptide chain having a donor fluorescent protein moiety, an acceptor fluorescent protein moiety, and a peptide linker moiety that couples the donor and acceptor moieties, wherein the donor and acceptor moieties exhibit fluorescence resonance energy transfer when the donor moiety is excited, wherein the donor moiety and acceptor moiety are Aequorea fluorescent protein moieties, wherein the linker moiety consists of between 5 amino acids and 50 amino acids, wherein the donor and acceptor Aequorea fluorescent protein moieties together have a contiguous sequence of 150 amino acids with at least 85% sequence identity with a contiguous amino acid sequence of 150 amino acids from the wild type Aequorea green fluorescent protein of SEQ ID NO:2, wherein at least one of the donor and acceptor protein moieties comprises a mutation selected from the group consisting of F64L, S65G, V68L, S72A, N149K, I167T, T203I, and T203Y, and wherein said linker moiety does not substantially emit light to excite said donor fluorescent protein moiety; exciting the donor moiety; and determining the degree of fluorescence resonance energy transfer in the sample, whereby a degree of fluorescence resonance energy transfer that is lower than an expected amount indicates the presence of an enzyme.