Patch-Clamping
Patch clamping is a widely applied electrophysiological technique for
the study of ion channels and membrane proteins that regulate the flow
of ions across cellular membranes and therefore influence the physiology
of all cells.
The patch-clamp technique was developed by Neher and Sak-mann in 1976
to be able to study the tiny ion currents through single channels in cell
membranes which are in the range of pico-Amperes (10-12 A). That was,
at that time, an almost unbelievable achievement, awarded the Noble Prize
in 1992.
The principle of the patch-clamp technique is that a small piece of a
cell membrane, is electrically isolated by the thin tip of a glass pipette
(~1µm diameter), which is pressed towards the membrane surface.
By application of a small negative pressure in the pipette, a very tight
seal between the membrane and the pipette is created. The resistance between
the two surfaces can have a resistance in the range of 109
Ohm (GOhm, which is then called the giga-seal.
Because of the tightness of this seal, different recording con-figurations
can be made. The four most common variants include on-cell patch, inside-out
patch, outside-out patch, and whole-cell clamp.
Patch-clamp methods are commonly used to voltage clamp, that is control
the voltage across the membrane and measure current flow, but current-clamp
methods, in which the current is controlled and the voltage is measured,
are also used. These variations in the technique allow a diverse investigation
of ion channels.
The patch-clamp technique is the ‘gold standard’ of cellular
electrophysiological methods, and is heavily relied upon by re-searchers
in both academia in pharmaceutical industry. Especially with the latter,
there is a need for a patch clamp device compatible with high-throughput
screening (HTS) applications, in which many cells can be rapidly patched
and measured in series or in parallel.
17.01.2002, Elke Guenther
Patch-clamp equipment
- electronic instrumentation for use in the life sciences
http://www.npielectronic.com - reference list on single electrode amplifiers
http://npielectronic.com/content/downloads/SEClit.pdf
