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Technical Briefs |
Departments of1 Laboratory Medicine and Pathology and3 Medicine, Mayo Clinic, Rochester, MN;2 Idaho Technology Inc., Salt Lake City, UT
aaddress correspondence to this author at: Endocrine Laboratory, Hilton 730C, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905; fax 507-284-9758, e-mail grebs@mayo.edu
| The first 300 words of the full text of this article appear below. |
During the last decade, research and clinical use of real-time PCR applications has continued to grow in importance (1). Many laboratories that use real-time PCR with fluorescent probes experience an unexplained loss of probe fluorescence at some stage, in particular with pairs of fluorescence resonance energy transfer (FRET) probes. Photobleaching is often assumed to be the cause. Structural integrity of the oligonucleotides is also a major factor, and its loss has been shown to correlate with repeated freezethaw cycles (2). Laboratories guard against these two problems by aliquoting probes and protecting them from light. Despite these precautions, inexplicable FRET probe failures are still observed. In one recent such case, we were able to determine an additional mechanism for FRET probe failure: loss of the phosphate cap from the 3' end of a probe. To our knowledge, this has not been described previously. Our studies revealed that this may be a common and important problem, intrinsic to 3'-phosphate-blocking chemistry. We also found that alternative terminating groups may be a preferable option to 3'-phosphate blocking.
A 3-nmol/L synthesis-scale LightCyclerTM hybridization probe set was purchased from Idaho Technology Inc. Biochem in April 2003. As is common practice, the manufacturer produced a large-scale synthesis and, after shipping our order, archived the remainder for a possible future reorder. The first half of the batch (
-probe set) was sent immediately, whereas the second half (ß-probe set) was stored lyophilized for 6 months at 20 °C and then shipped with our next order.
Oligonucleotides from the first shipment were used in PCR reactions in a LightCycler with satisfactory results. PCR conditions were as follows: 1x LightCycler FastStart DNA Master Hybridization Probe Mix (Roche Diagnostics), MgCl2 (final concentration, 3.5 mM), 0.5 µM each of the forward (5'-GGCCTTTCTGAAGCAAG-3') and reverse (5'-GACGATTTCTTATTTCACAGCTCC-3') primers, 0.2
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C. N. Gundry, S. F. Dobrowolski, Y. R. Martin, T. C. Robbins, L. M. Nay, N. Boyd, T. Coyne, M. D. Wall, C. T. Wittwer, and D. H.-F. Teng Base-pair neutral homozygotes can be discriminated by calibrated high-resolution melting of small amplicons Nucleic Acids Res., June 1, 2008; 36(10): 3401 - 3408. [Abstract] [Full Text] [PDF] |
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S. Dames, R. L. Margraf, D. C. Pattison, C. T. Wittwer, and K. V. Voelkerding Characterization of Aberrant Melting Peaks in Unlabeled Probe Assays J. Mol. Diagn., July 1, 2007; 9(3): 290 - 296. [Abstract] [Full Text] [PDF] |
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M. T. Seipp, J. D. Durtschi, M. A. Liew, J. Williams, K. Damjanovich, G. Pont-Kingdon, E. Lyon, K. V. Voelkerding, and C. T. Wittwer Unlabeled Oligonucleotides as Internal Temperature Controls for Genotyping by Amplicon Melting J. Mol. Diagn., July 1, 2007; 9(3): 284 - 289. [Abstract] [Full Text] [PDF] |
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