Nanopore readers for DNA sequencing
17 May 2012 by qmcqmmjcbp.d qmcqmmjcbp.d
A nanoscale sensor able to electronically read the sequence of a single DNA molecule could lead to affordable personalised medicine, potentially revealing predispositions for afflictions such as cancer, diabetes or addiction.
Researchers from University of Washington previously reported creating a nanopore by genetically engineering a protein pore from a myobacteria. To make this work as a reader, they placed it in a membrane surrounded by potassium-chloride solution with a small voltage applied to create an ion channel flowing through the nanopore. The electrical signature varies depending on the type of nucleotide passing through the nanopore – each type of DNA nucleotide produces a distinctive signature.
"There is a clear path to a workable, easily produced sequencing platform," said Jens Gundlach, a physics professor who led the research team. "We augmented a protein nanopore we developed for this purpose with a molecular motor that moves a DNA strand through the pore a nucleotide at a time."
In a new research paper – published in Nature Biotechnology – researchers report the successful demonstration of the new technique using six different strands of DNA. The sequences of DNA – which had readable regions of 42 to 53 nucleotides long – were already known.
“The motor pulls the strand through the pore at a manageable speed of tens of milliseconds per nucleotide, which is slow enough to be able to read the current signals,” said Gundlach.
Gundlach says the nanopore technique can also be used to identify how DNA is modified in any given individual. Such modifications – epigenetic DNA modifications – take place as chemical reactions within cells and are the underlying causes of various conditions.
"Epigenetic modifications are rather important for things like cancer," he said. Being able to provide DNA sequencing that can identify epigenetic changes "is one of the charms of the nanopore sequencing method."
