  DNA methylation plays a pivotal role in the genetic evolution of both
embryonic and adult cells. For adult somatic cells, location and dynamics of
methylation has been very precisely pinned down with the 5-cytosine markers on
cytosinephosphate- guanine (CpG) units. Unusual methylation on CpG islands are
identified as one of the prime causes for silencing the tumor suppressant
genes. Early detection of such methylation can diagnose the potentially harmful
oncogenic evolution of cells, and provide a promising guideline for cancer
prevention. With this motivation, we propose a cytosine methylation detection
technique.Our hypothesis is that electronic signatures of DNA acquired as a
molecule translocates through a nanopore, would be significantly different for
methylated and non-methylated bases. This difference in electronic fingerprints
would allow for reliable real-time differentiations of methylated DNA. We
calculate transport currents through a punctured graphene membrane while the
cytosine and methylated cytosine translocate through the nanopore. We also
calculate the transport properties for uracil and cyanocytosine for comparison.
Our calculations of transmission, current, and tunneling conductance show
distinct signatures in their spectrum for each molecular type. Thus, in this
work, we provide a theoretical analysis that points to a viability of our
hypothesis.
