Another nanopore design for DNA sequencing
The DNA sequence was determined using nanopores
The work (Kumar et al., PEG-Labelled Nucleotides and Nanopore Detection for Single Molecule DNA Sequencing by Synthesis) is published in the journal Scientific Reports, and its summary is provided on the Columbia University website: Researchers Report Novel Approach for Single Molecule Electronic DNA Sequencing.
The DNA sequence is determined in a microscopic chamber divided into two parts by means of a membrane. There is a nanopore in the membrane – a hole through which ions can pass, creating an electric current. A single–stranded nucleic acid molecule is placed in the part of the chamber where the enzyme DNA polymerase is fixed in the immediate vicinity of the nanopore. He is able to complete the second chain of single-stranded DNA. In this case, the polymerase uses nucleotides – "beads", which make up the nucleic acid chain.
When a nucleotide participates in a reaction, it splits into two parts: the main part becomes a link on the synthesized DNA, and the second one gets into the nanopore under the action of the current. Sequence determination is based on the fact that the nucleotides used for DNA synthesis are not ordinary, but chemically modified in a special way. Moreover, each of the nucleotides – A, T, G and C is modified in its own way.
Getting into the nanopore, they "plug" its hole and do not allow other ions to pass through. The current between the membrane-separated parts of the chamber drops sharply. The depth and duration of this fall is determined by the size and charge of those chemical modifications that scientists have introduced into different nucleotides. By recording the changes in the current strength between the parts of the chamber, it is possible to determine which nucleotides passed through the nanopore and, accordingly, what is their sequence on the matrix DNA.
The developed technology potentially makes it possible to determine the sequence of a single nucleic acid molecule entirely and at a very high speed. Unlike other "next generation" sequencing technologies that read DNA in small pieces of 20-50 nucleotides, it does not require a long and time-consuming assembly of the "molecular puzzle".
The new method is not the first of those where nanopores are used. Earlier, another group of researchers from Oxford Nanopore developed a technology where the sequence of nucleic acid was determined by directly dragging the molecule through the pore. In February 2012, scientists demonstrated the first complete genome (bacteriophage genome) determined using this method. Representatives of the company showed a portable device running on this technology and capable, according to them, of sequencing the human genome in 15 minutes.
Portal "Eternal youth" http://vechnayamolodost.ru24.09.2012