Nucleic Acids Research Advance Access published online on July 15, 2008
Nucleic Acids Research, doi:10.1093/nar/gkn436
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Methods Online |
Electrical detection of the temperature induced melting transition of a DNA hairpin covalently attached to gold interdigitated microelectrodes
1Portland Bioscience, Inc., Portland, OR 97201, 2Department of Electrical & Computer Engineering, Portland State University, 3SHARP Laboratories of America, Inc., Camas, WA 98607, 4Department of Physics and 5Department of Chemistry, Portland State University, Portland, OR 97207, USA
*To whom correspondence should be addressed. Tel: +503 725 2350; Fax: +503 725 2305; Email: gbrewood{at}pdxbio.com
Received October 10, 2007. Revised June 24, 2008. Accepted June 24, 2008.
The temperature induced melting transition of a self-complementary DNA strand covalently attached at the 5' end to the surface of a gold interdigitated microelectrode (GIME) was monitored in a novel, label-free, manner. The structural state of the hairpin was assessed by measuring four different electronic properties of the GIME (capacitance, impedance, dissipation factor and phase angle) as a function of temperature from 25°C to 80°C. Consistent changes in all four electronic properties of the GIME were observed over this temperature range, and attributed to the transition of the attached single-stranded DNA (ssDNA) from an intramolecular, folded hairpin structure to a melted ssDNA. The melting curve of the self-complementary single strand was also measured in solution using differential scanning calorimetry (DSC) and UV absorbance spectroscopy. Temperature dependent electronic measurements on the surface and absorbance versus temperature values measured in solution experiments were analyzed assuming a two-state process. The model analysis provided estimates of the thermodynamic transition parameters of the hairpin on the surface. Two-state analyses of optical melting data and DSC measurements provided evaluations of the thermodynamic transition parameters of the hairpin in solution. Comparison of surface and solution measurements provided quantitative evaluation of the effect of the surface on the thermodynamics of the melting transition of the DNA hairpin.