Nanopore Topics

• lipid bilayer
• dna molecules
• molecule analysis
• electron beams
• cause interruptions
• protein channel
• electrolyte solution
• rapid dna
• langerhans cells
• pancreatic cells
• dna sequencing
• immunoglobins
• molecular dimensions
• protein interactions
• hemolysin
• immunosuppressants
• ion beam
• human skin
• islets

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Nanopore, Nanopore

It can be a biological protein channel in a lipid bilayer or a pore in a solid-state membrane. The detection principle is based on monitoring the ionic current of an electrolyte solution passing through the nanopore as a voltage is applied across the membrane. When the nanopore is of molecular dimensions, passage of molecules (e.g., DNA) cause interruptions of the "open" current level, leading to a "translocation event" pulse. The passage of RNA or single-stranded DNA molecules through the membrane-embedded alpha-hemolysin channel (1.5 nm diameter), for example, causes a ~90% blockage of the current (measured at 1 M KCl solution) . The observation that a passing strand of RNA containing different bases results in different blocking levels has led to the nanopore sequencing hypothesis. Such sequencing, if successful, could revolutionize the field of genomics, as sequencing could be carried out in a matter of seconds. Apart from rapid DNA sequencing, other applications include separation of single stranded and double stranded DNA in solution, and the determination of length of polymers. At this stage, nanopores are making contributions to the understanding of polymer biophysics, as well as to single-molecule analysis of DNA-protein interactions.

Solid-state nanopores can be manufactured with several techniques including ion-beam sculpting and electron beams.

These pores allow small molecules like oxygen, glucose and insulin to pass however they prevent large immune system molecules like immunoglobins to leave the cell. This way rat pancreatic cells are microencapsulated, they receive nutrients and release insulin through nanopores being totally isolated from their neighboring environment i.e foreign cells. This knowledge can help to replace nonfunctional islets of Langerhans cells in the liver (responsible for producing insulin), by harvested piglet cells. They can be implanted underneath the human skin without the need of immunosuppressants which put diabetic patients at a risk of infection.

Unlike the fragile lipid-bilayer membrane in which most natural ion channels are embedded, this synthetic film is mechanically and chemically robust. Even though ion channels in living organisms have been studied by a mimic method using synthetic nanopores during the past several decades, how to endow these synthetic nanopores with intelligence is still a challenging task. Prof. Lei Jiang and his colleagues extend the function of molecule - nanopore systems by using G-quadruplex DNA. In their biomimetic nanochannel system, there is an ion concentration effect, which is a very important phenomenon in a living body and other systems do not have. Their novel biomimetic nanochannel system was responsive to potassium ion within a certain concentration range and simulated these processes in a pH-neutral environment as in a natural organism. In their work, the situation of the grafting G-quadruplex DNA on a single nanopore can closely imitate the in vivo condition because the G-rich telomere overhang is attached to the chromosome. Therefore, their artificial system could promote a potential to conveniently study biomolecule conformational change in confined space by the current measurement, which is significantly different from the nanopore sequencing. Moreover, such a system may also potentially spark further experimental and theoretical efforts to simulate the process of ion transport in living organisms and can be further generalized to other more complicated functional molecules for the exploitation of novel bioinspired intelligent nanopore machines.

Source: Wikipedia > Nanopore