Speed read: Recording channels
Many important tasks in living cells like muscle contraction and nerve impulse transmission are driven by electrical power, generated by positively and negatively charged atoms, or ions, flowing into and out of cells. It was assumed that this ion transport is regulated by tunnel-like channels nestled within the cell’s outer boundary, yet for decades it had been impossible to study these channels individually. The 1991 Nobel Prize in Physiology or Medicine rewarded two scientists for creating the experimental measuring device that conclusively proved the existence and function of these ion channels.
Erwin Neher and Bert Sakmann’s patch-clamp technique is based on an exquisitely simple idea. An extremely fine glass pipette with a very small opening is used to make contact with a tiny area, or patch, of the cell’s outer membrane that, with some luck, will contain only a single ion channel. Applying a small amount of suction through the pipette forms a seal tight enough such that ions can only flow from the channel into the pipette. By fitting the pipette with a highly sensitive electrode, Neher and Sakmann could record every minute change in current produced as ions flow through the clamped channel into the pipette. With their recording device, they showed how these channels function by opening up and closing in nerve cell membranes to allow certain ions through one at a time.
The patch clamp technique allowed key features of these channels to be defined with fine precision. Specifically altering the genes that encode ion channels and studying the consequences in cells allowed Neher and Sakmann to pinpoint the parts of the channel that open or close and that select which ions can pass through. In the latter case, some channels are shaped to fit the diameters of specific ions, while other channels contain rings of molecules that act as a filter, allowing only ions with the opposite charge to pass through. The patch clamp technique soon became an essential tool for scientists studying the activity and behaviour of a host of ion channels in many types of cell, and also for understanding how defective regulation of ion channels underlie a host of diseases, including diabetes and cystic fibrosis.
By Sophie Petit-Zeman, for Nobelprize.org
This Speed read is an element of the multimedia production “Nerve Signaling”. “Nerve Signaling” is a part of the AstraZeneca Nobel Medicine Initiative.
First published 16 September 2009
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