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Nanopore sequencing is a method under development since 1995 for determining the order in which nucleotides occur on a strand of DNA. A nanopore is simply a small hole with an internal diameter of the order of 1 nanometer. Certain porous transmembrane cellular proteins act as nanopores, and nanopores have also been made by etching a somewhat larger hole (several tens of nanometers) in a piece of silicon, and then gradually filling it in using ion-beam sculpting methods which results in a much smaller diameter hole: the nanopore. Graphene is also being explored as a synthetic substrate for solid-state nanopores. The theory behind nanopore sequencing is that when a nanopore is immersed in a conducting fluid and a potential (voltage) is applied across it, an electric current due to conduction of ions through the nanopore can be observed. The amount of current is very sensitive to the size and shape of the nanopore. If single nucleotides (bases), strands of DNA or other molecules pass through or near the nanopore, this can create a characteristic change in the magnitude of the current through the nanopore. ==Background== DNA could be passed through the nanopore for various reasons. For example, electrophoresis might attract the DNA towards the nanopore, and it might eventually pass through it. Or, enzymes attached to the nanopore might guide DNA towards the nanopore. The scale of the nanopore means that the DNA may be forced through the hole as a long string, one base at a time, rather like threading through the eye of a needle. As it does so, each nucleotide on the DNA molecule may obstruct the nanopore to a different, characteristic degree. The amount of current which can pass through the nanopore at any given moment therefore varies depending on whether the nanopore is blocked by an A, a C, a G or a T or a section of DNA that includes more than one of these bases (kmer). The change in the current through the nanopore as the DNA molecule passes through the nanopore represents a direct reading of the DNA sequence. Alternatively, a nanopore might be used to identify individual DNA bases as they pass through the nanopore in the correct order - this approach was published but not commercially developed by Oxford Nanopore Technologies and Professor Hagan Bayley. Using Nanopore sequencing, a single molecule of DNA can be sequenced directly (using a nanopore ), without the need for an intervening PCR amplification step or a chemical labelling step or the need for optical instrumentation to identify the chemical label. The versatility of the nanopore concept is underlined by the fact that it has also been proposed for detection of life on other planets, since it is not necessarily restricted to the detection of the genetic information carrier DNA, but in general can be applied to sequence chain-like genetic information carriers without knowing the exact structure of their building blocks. Nanopore-based DNA analysis techniques are being industrially developed by Oxford Nanopore Technologies (developing strand sequencing using protein nanopores, and solid-state sequencing through internal R&D and collaborations with academic institutions). As of June 2015, the MinION device from Oxford Nanopore has now been used by a number of participants in the MinION Access Programme. Publications on the method outline its use in rapid identification of (viral pathogens ), (monitoring ebola ), (environmental monitoring ), (food safety monitoring ), monitoring (of antibiotic resistance ), (haplotyping ) and (other applications ). Other companies have noted that they have Nanopore programmes, NabSys (using a library of DNA probes and using nanopores to detect where these probes have hybridized to single stranded DNA) and NobleGen (using nanopores in combination with fluorescent labels). IBM has noted research projects on computer simulations of translocation of a DNA strand through a solid-state nanopore, but not projects on identifying the DNA bases on that strand. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Nanopore sequencing」の詳細全文を読む スポンサード リンク
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