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. 2013 Oct 28;110(47):18904–18909. doi: 10.1073/pnas.1310240110

Fig. 2.

Fig. 2.

Methylation detection. (A and B) Segments of raw current traces. Ion current changes as DNA passes through the pore in single-nucleotide steps. Average current values for each current level are shown in black or red. The traces shown in A and B are for DNA with identical nucleotide sequence. The current trace shown in A contains a single unmethylated CpG site, whereas the trace in B contains a single mCpG. (C) Extracted average current values from each level in A in black and B in red. The stochastic duration of current levels has been removed so that the DNA base sequence can be aligned to the observed current levels. The DNA sequence is shown below with the modified C indicated in red. (D) Current difference plot. The current levels obtained with methylated DNA were subtracted from the current levels obtained with unmethylated DNA. The effect of a single mCpG causes an ion current increase that persists over approximately four steps of the DNA through the pore. The magnitude and shape of the current difference is determined by the nucleotides adjacent to the methylated C (Figs. 3 and 4).