Scientists at the Federal Polytechnic School in Lausanne city found a way to significantly improve the accuracy of reading DNA by pulling through the nanopore. The gain in the precision able to obtain by using a special kind of solvents, in which DNA is moving considerably slower than in ordinary water.
DNA sequencing of the dragging through the pore is as follows.
- Single-stranded nucleic acid is placed in the solution, separated by a thin membrane into two parts. The membrane has a pore into which DNA enters due to the fact that different parts of the solution applied voltage (in solution DNA is negatively charged and move toward the anode). Passing through the pore different bases in DNA differently it is closed. Because of this, in the circuit falls different amperage: varying depth and time of the voltage drop. Observing this drop, it is possible, theoretically, to restore the sequence of the nucleic acid.
- The problem is that the required voltage DNA moves too fast for one millisecond time through the “fly” is usually three to 50 thousand bases. Because of this, in practice, the accuracy of determining the sequence appears to be very low. Reduce tensions that speed can not be lower: in this case is proportional to the amplitude of the signal decreases.
In New York, scientists decided to use DNA to slow fundamentally different type of solvent.
- It is of ionic liquids-organic substances which are in liquid form composed entirely of ions. Unlike the conventional aqueous solution of ionic liquids were better suited for this type of sequencing. They are able to slow down the movement of the DNA (about a thousand times) while providing an electrical current through the pore sufficient amplitude to determine the base sequence. Note that the novelty of the method lies not only in the use of ionic liquids, but in the application of a new type of membranes of molybdenum sulfide (MoS2). Unlike graphite (which had previously been tried to use for sequencing, but not too successful), the material does not adsorb to the DNA itself, which significantly simplifies the whole process.
New technology relates to the class reading DNA techniques where used as the pore openings in inorganic substances.
For quite a long time developing parallel sequencing technology, where the pores are used natural biological channels. In these methods, there is no problem of too rapid prostaskivaniya DNA through hole (contrary). The main difficulty with these techniques due to the fact that the protein complexes rather wear out quickly and require frequent replacement and maintenance. The membranes and pores, similar to that used in the present study, these disadvantages do not have – they are “virtually forever.”