Published online 5 July 2006
© 2006 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commerical use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Molecular Zipper: a fluorescent probe for real-time isothermal DNA amplification
Department of Pathology, Mount Sinai School of Medicine, New York University One Gustave L. Levy Place, New York, NY 10029, USA
*To whom correspondence should be addressed at Department of Pathology, Mount Sinai School of Medicine, New York University, One Gustave L. Levy Place, New York, NY 10029, USA. Tel: +1 212 659 8173; Fax: +1 212 427 2082; Email: david.zhang{at}mssm.edu
Received October 17, 2005. Revised November 21, 2005. Accepted March 31, 2006.
Rolling-circle amplification (RCA) and ramification amplification (RAM, also known as hyperbranched RCA) are isothermal nucleic acid amplification technologies that have gained a great application in in situ signal amplification, DNA and protein microarray assays, single nucleotide polymorphism detection, as well as clinical diagnosis. Real-time detection of RCA or RAM products has been a challenge because of most real-time detection systems, including Taqman and Molecular Beacon, are designed for thermal cycling-based DNA amplification technology. In the present study, we describe a novel fluorescent probe construct, termed molecular zipper, which is specially designed for quantifying target DNA by real-time monitoring RAM reactions. Our results showed that the molecular zipper has very low background fluorescence due to the strong interaction between two strands. Once it is incorporated into the RAM products its double strand region is opened by displacement, therefore, its fluorophore releases a fluorescent signal. Applying the molecular zipper in RAM assay, we were able to detect as few as 10 molecules within 90 min reaction. A linear relationship was observed between initial input of targets and threshold time (R2 = 0.985). These results indicate that molecular zipper can be applied to real-time monitoring and qualification of RAM reaction, implying an amenable method for automatic RAM-based diagnostic assays.
Present address: Jizu Yi, BD-Diagnostics, One Becton Drive, Franklin Lakes, NJ 07417, USA
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