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. Author manuscript; available in PMC: 2014 Jul 15.
Published in final edited form as: Biochemistry. 2008 Aug 26;47(38):9987–9999. doi: 10.1021/bi800746p

Figure 1.

Figure 1

Overview of the exponential amplification reaction (EXPAR), which rapidly and isothermally amplifies trigger X, a short oligonucleotide serving as the analyte. (a) Trigger X transiently binds to the complementary recognition sequence at the 3′-end of the amplification template. (b) The trigger sequence is extended by the DNA polymerase, forming the double-stranded nicking enzyme recognition site 5′-GAGTCNNNN-3′ on the top strand. (c) The top strand is cleaved through the nicking endonuclease Nt.BstNBI. (d) At the temperature of the reaction (55 °C), the newly formed trigger is released from the amplification template. The trigger-producing form of the template re-enters the linear amplification cycle, and new trigger oligonucleotides are generated through duplex extension, nicking, and release. (e) The newly formed trigger oligonucleotides activate additional template sequences, giving rise to exponential amplification of trigger X.