Patent ID: 7329494

Claim:
A method for detecting and quantifying cGMP, which comprises: (1) introducing a polynucleotide expressing a cGMP-visualizing probe into cells, whereby the cGMP-visualizing probe is expressed and made to coexist with cGMP, wherein the cGMP-visualizing probe comprises: (a) a polypeptide that binds specifically to cGMP and is obtained by deleting amino acids 1 to 47 of cGMP-dependent protein kinase Iα (PKG Iα), and (b) two chromophores with different fluorescence wavelengths, one of which is linked to the N-terminal and the other of which is linked to the C-terminal of the polypeptide, wherein the chromophores are capable of exhibiting fluorescence resonance energy transfer (FRET); and (2) measuring the change in fluorescence wavelength.