Patent ID: 7642056

Claim:
A method of detecting a target protein in a sample, comprising the steps of: 1) forming a DNA duplex consisting of(a) a DNA aptamer comprising a sequence needed for target binding and a sequence extended from the 5′-end of the target binding sequence (“5′-extended region”) and (b) a single stranded DNA (“G-DNA”) complementary to a region of the DNA aptamer that includes the 5′-extended region; 2) mixing the sample with the DNA duplex of step 1); 3) mixing the mixture obtained in step 2) with RNase H and a single-stranded RNA complementary to the G-DNA, wherein a fluorophore and a quencher are labeled at the 5′- and 3′-ends, respectively, of the single-stranded RNA and wherein the length of the single-stranded RNA is not longer than that of the single-stranded DNA; and 4) measuring the fluorescence intensity of the mixture obtained in step 3) to determine the presence or amount of the target protein in the sample.