Bert Sakmann and his patch clamp technique
Along with Erwin Neher, Bert Sakmann developed the patch clamp technique to record the small ionic currents
(only a few picoamperes) that flow through a single ion channel in neuronal membranes. In 1976 Sakmann and
Neher made the first recordings of single ion channel currents in nicotinic acetylcholine receptors from muscle.
They were awarded the Nobel Prize for this work in 1991.
Current work in Professor Sakmann's group is focused on understanding fast signaling in neurons, including biophysical
and molecular mechanisms underlying synaptic transmission.
NATIVE CHANNELS Recorded with the PATCH CLAMP
The first recordings of native ion channels in biological membranes were made
by Bert Sakmann and Erwin Neher using an innovative modification of the
voltage-clamp method. Rather than penetrating the cell with a sharp electrode
as was traditionally done in voltage-clamp experiments, Neher and Sakmann
fabricated blunt-tipped glass pipettes that, when pressed gently against the
membrane of a cell would isolate a small area of membrane (diameter = 1 mm).
In this way they were able to trap or isolate one or a few ion channels in
the membrane. They used this method, now called the patch-clamp method, to
make the first single channel recordings of muscle nicotinic acetylcholine
receptors in 1976.
Typically, a single ion channel conducts about 10 million ions per second.
The corresponding current, however, is not as impressive; only a few picoamperes.
The primary difficulty for Sakmann and Neher in their development of the patch
clamp method was noise. Transistors used to make the amplifier, and thermal
noise associated with a low resistance seal between the glass pipette and the
membrane often obscured the rectangular-shaped currents arising from opening
of single channels.
In the years following the introduction of their method,
two improvements were made to compensate for these problems. New low-noise
transistors were used in the construction of high quality amplifiers
(Fred Sigworth made significant contributions here). Also, in 1981 the
"gigaseal" modification of the method was introduced by Owen Hamill in
Sakmann's group. Seals exceeding 10 GW were subsequently reported, and
impressive low-noise recordings could be made without difficulty.
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