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Direct calibration of microarray probes. Making a “DNA-meter”. Alex Pozhitkov, Peter A. Noble, Diethard Tautz, Ploen Workshop, 2011. Conundrum. Signal intensity vs. GC Signal intensity vs. D G 0 Sense vs. antisense (same genomic loci) R 2 =0.37. Confirms:
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Direct calibration of microarray probes Making a “DNA-meter” Alex Pozhitkov, Peter A. Noble, Diethard Tautz, Ploen Workshop, 2011.
Conundrum • Signal intensity vs. GC • Signal intensity vs. DG0 • Sense vs. antisense (same genomic loci) R2=0.37 Confirms: Pozhitkov, et al (2006). Tests of rRNA hybridization … cannot be predicted. NAR 34, e66-e6
Melting study • Overhangs • Buffer composition • Tm Sense vs. Tm antisense • Tm vs. Signal Intensity on the array
Tm Antisense (0C) Tm Sense (0C) Melting Temperatures
Microarray is an Instrument Instruments require calibration
800 5000 5000 4000 600 3000 400 2000 200 1000 8 6 2 0 4 8 6 2 0 4 “Good”, “Bad” and Noise Signal Intensity Concentration Individual replicas Averages
Freundlich isotherm!y=axb Langmuir isotherm is not the only possible isotherm: Pozhitkov et al. (2010) Beyond Affymetrix arrays: … NAR 38, e28.
DNA and RNA y=axb+c
Measurements and Errors Single probe replicate Average over 10 replicates
CNV detection CNV expected: 1
Sample prep variability $ loci
Acknowledgements • Max Planck Society • Alabama State University