Patent ID: 8426127

Claim:
A method for detecting a target nucleic acid sequence, which comprises: hybridizing to a target nucleic acid sequence, (i) a first nucleic acid probe having a nucleic acid sequence complementary to a region of a portion of the target nucleic acid sequence, which is labeled with a nonfluorescent molecule having an azido group represented by the following formula (1A) or (2A): wherein R 1 represents an amino group, or an amide group optionally having a protecting group or a substituent, wherein said nonfluorescent molecule becomes capable of emitting fluorescence when the azido group of the nonfluorescent molecule is reduced to an amino group, and (ii) a second nucleic acid probe having a nucleic acid sequence complementary to a region of another portion of the target nucleic acid sequence, which is labeled with a molecule capable of reducing the azido group of the nonfluorescent molecule in the first nucleic acid probe to an amino group, wherein said molecule capable of reducing the azido group is dithiothreitol or a trivalent phosphorus compound, and is covalently linked to the second nucleic acid probe; and detecting a fluorescence produced by reducing the azido group of the nonfluorescent molecule in the first nucleic acid probe to an amino group.