Oxford Nanopores: GridION

GridION uses unique pores made of the protein α-hemolysin from the bacteria Staphylococcal to sequence DNA by threading DNA through the pores. These pores are embedded in a lipid bilayer. Many of these pore-complexes can then be used in an array of microwells. (34)

The diagram above explain the theory behind nanopores. When each different sized molecule is placed across the nanopore,  each molecule blocks the current in a particular way, resulting in a unique current drop for each molecule which can be measured.

1. The GridION pore is actually made of the protein α-hemolysin (that's the Greek letter alpha) from the bacteria Staphylococcal, and it is embedded in a lipid bilayer. Many pores can be embedded in an array of microwells.
2. An ionic current is set to flow across the pore by causing a voltage difference across the membrane.
3. Then, DNA is threaded across the nanopore at a rate of about one nucleotide per millisecond.
4. As each nucleotide crosses the nanopore, each nucleotide partially obstructs the current, causing a measurable drop in the current, and each nucleotide causes a different current drop. If you don't understand this, think of the current as water flowing across the nanopore, and the nucleotides as four different-sized rocks. When a rock is placed near the nanopore, it will block part of the water flowing and cause the amount of water entering to drop. Since each rock is a different size, each rock will cause the water flow to drop by a different amount. (34)

Since these protein nanopores can be unstable and hard to use, new solid-state, or artificial, nanopores are being developed by Oxford Nanopore. In collaboration with several labs from Harvard University, researchers are developing new nanopores made from graphene, a one-atom layer of carbon which forms the thinnest known membrane. (37)

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